@phdthesis{Messer2002, author = {Messer, Kim Sven}, title = {Isolierung, Strukturaufkl{\"a}rung und Beitr{\"a}ge zur Synthese von Naturstoffen aus tropischen Heilpflanzen sowie Etablierung chiraler On-line-Analytik}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-3774}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2002}, abstract = {Die Natur er{\"o}ffnet mit der strukturellen Vielfalt ihrer Sekund{\"a}rmetaboliten einen nahezu unersch{\"o}pflichen Pool in der Leit- und Wirkstoffsuche nach pharmazeutisch wirksamen Substanzen. Insbesondere die Alkaloide zeichnen sich durch ihre biologischen Wirksamkeiten aus. Eine noch junge, sehr vielversprechende Substanzklasse stellen die sogenannten Naphthylisochinolin-Alkaloide dar, die bislang ausschließlich in den beiden Pflanzenfamilien der Ancistrocladaceae und Dioncophyllaceae gefunden wurden. Im Rahmen dieser Arbeit wurden Extrakte von Ancistrocladus congolensis (A.c.), Triphyophyllum peltatum (T.p.) und Dioncophyllum thollonii (D.t.) untersucht. Hierbei gelang die Isolation und Strukturaufkl{\"a}rung des bereits bekannten Korupensamin A (A.c.) sowie von sechs bislang unbekannten Alkaloiden: Ancistrocongolin A-D (A.c.), Habropetalin A (T.p.) und Dioncophyllin E (D.t.). Zu dem letztgenannten wurde ein synthetischer Zugang evaluiert. Alle neu isolierten Naturstoffe wurden einer biologischen Aktivit{\"a}tstestung zugef{\"u}hrt. Im analytischen Bereich der Arbeit gelang die vollst{\"a}ndige Strukturzuordnung des bereits seit mehreren Jahren bekannten Tetralons Isoshinanolon, was somit nun ein einfache Analytik f{\"u}r die Bestimmung der absoluten Konfiguration an die Hand gibt. Des Weiteren wurde die HPLC-CD-Kopplung als schnelle und praktikable chirale on-line-Analytik an mehreren Beispielen (Phyllin, TaClo, Murrastifolin F, Cyclorocaglamid, Thalidomid) sowohl im phytochemischen als auch synthetischen Bereich eingef{\"u}hrt und etabliert.}, subject = {Naphthylisochinolinalkaloide}, language = {de} } @article{MessiNdjokoIosetHertleinAmslingeretal.2012, author = {Messi, Bernadette Biloa and Ndjoko-Ioset, Karine and Hertlein-Amslinger, Barbara and Lannang, Alain Meli and Nkengfack, Augustin E. and Wolfender, Jean-Luc and Hostettmann, Kurt and Bringmann, Gerhard}, title = {Preussianone, a New Flavanone-Chromone Biflavonoid from Garcinia preussii Engl.}, series = {Molecules}, volume = {17}, journal = {Molecules}, number = {5}, doi = {10.3390/molecules17056114}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-130881}, pages = {6114 - 6125}, year = {2012}, abstract = {A new flavanone-chromone biflavonoid, preussianone (1), has been isolated from the leaves of Garcinia preussii, along with four known biflavonoids. The absolute stereostructures were elucidated by chemical, spectroscopic, and chiroptical methods. The biological properties of the new biflavonoid against several bacterial strains were evaluated.}, language = {en} } @article{MetropoulosEngelsPeyerimhoff1993, author = {Metropoulos, B. and Engels, Bernd and Peyerimhoff, S.D.}, title = {On the chemi-ionization reaction O + CH ----> HCO\(^+\)+ e\(^-\). Coollinear O-CH Approach}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58963}, year = {1993}, abstract = {We have investigated theoretically the importance of the O(\(^3\)P)+CH(a\(^4\sum^-\)) and the O(\(^3\)P)+CH(X\(^2\Pi\)) channels in the collinear chemi-ionization reaction O+CH->HCO\(^+\) +e\(^-\). We have found that both channels may lead to chemi-ionization via favorable Franck-Condon overlaps with the states ofthe ionic species.}, subject = {Organische Chemie}, language = {en} } @phdthesis{MezaChincha2021, author = {Meza Chincha, Ana Lucia}, title = {Catalytic Water Oxidation with Functionalized Ruthenium Macrocycles}, doi = {10.25972/OPUS-20962}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-209620}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {In light of the rapidly increasing global demand of energy and the negative effects of climate change, innovative solutions that allow an efficient transition to a carbon-neutral economy are urgently needed. In this context, artificial photosynthesis is emerging as a promising technology to enable the storage of the fluctuating energy of sunlight in chemical bonds of transportable "solar fuels". Thus, in recent years much efforts have been devoted to the development of robust water oxidation catalysts (WOCs) leading to the discovery of the highly reactive Ru(bda) (bda: 2,2'-bipyridine-6,6'-dicarboxylic acid) catalyst family. The aim of this thesis was the study of chemical and photocatalytic water oxidation with functionalized Ruthenium macrocycles to explore the impact of substituents on molecular properties and catalytic activities of trinuclear macrocyclic Ru(bda) catalysts. A further objective of this thesis comprises the elucidation of factors that influence the light-driven water oxidation process with this novel class of supramolecular WOCs.}, subject = {Rutheniumkomplexe}, language = {en} } @article{MezaChinchaLindnerSchindleretal.2020, author = {Meza-Chincha, Ana-Lucia and Lindner, Joachim O. and Schindler, Dorothee and Schmidt, David and Krause, Ana-Maria and R{\"o}hr, Merle I. S. and Mitrić, Roland and W{\"u}rthner, Frank}, title = {Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation}, issn = {2041-6539}, doi = {10.1039/d0sc01097a}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204653}, year = {2020}, abstract = {Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites.}, language = {en} } @phdthesis{Michail2021, author = {Michail, Evripidis}, title = {Design and Development of a Two-Photon Absorption Induced Fluorescence Spectrometer and the Investigation of Nonlinear Optical Properties of Organic Chromophores}, doi = {10.25972/OPUS-24218}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-242185}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Main objectives of the present dissertation can be divided in two parts. The first part deals with setting up a spectroscopic technique for reliable and accurate measurements of the two-photon absorption (2PA) cross section spectra. In the second part, this firmly established experimental technique together with conventional spectroscopic characterization, quantum-chemical computations and theoretical modelling calculations was combined and therefore used as a tool to gain information for the so-called structure-property relationship through several molecular compounds.}, subject = {Nonlinear Optical Properties of Organic Materials}, language = {en} } @article{MieczkowskiSteinmetzgerBessietal.2021, author = {Mieczkowski, Mateusz and Steinmetzger, Christian and Bessi, Irene and Lenz, Ann-Kathrin and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Pena, Vladimir and H{\"o}bartner, Claudia}, title = {Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine}, series = {Nature Communications}, volume = {12}, journal = {Nature Communications}, doi = {10.1038/s41467-021-23932-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-270274}, year = {2021}, abstract = {Fluorogenic RNA aptamers are synthetic functional RNAs that specifically bind and activate conditional fluorophores. The Chili RNA aptamer mimics large Stokes shift fluorescent proteins and exhibits high affinity for 3,5-dimethoxy-4-hydroxybenzylidene imidazolone (DMHBI) derivatives to elicit green or red fluorescence emission. Here, we elucidate the structural and mechanistic basis of fluorescence activation by crystallography and time-resolved optical spectroscopy. Two co-crystal structures of the Chili RNA with positively charged DMHBO+ and DMHBI+ ligands revealed a G-quadruplex and a trans-sugar-sugar edge G:G base pair that immobilize the ligand by π-π stacking. A Watson-Crick G:C base pair in the fluorophore binding site establishes a short hydrogen bond between the N7 of guanine and the phenolic OH of the ligand. Ultrafast excited state proton transfer (ESPT) from the neutral chromophore to the RNA was found with a time constant of 130 fs and revealed the mode of action of the large Stokes shift fluorogenic RNA aptamer.}, language = {en} } @article{MieczkowskiSteinmetzgerBessietal.2021, author = {Mieczkowski, Mateusz and Steinmetzger, Christian and Bessi, Irene and Lenz, Ann-Kathrin and Schmiedel, Alexander and Holzapfel, Marco and Lambert, Christoph and Pena, Vladimir and H{\"o}bartner, Claudia}, title = {Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine}, series = {Nature Communications}, volume = {12}, journal = {Nature Communications}, doi = {10.1038/s41467-021-23932-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254527}, pages = {3549}, year = {2021}, abstract = {Fluorogenic RNA aptamers are synthetic functional RNAs that specifically bind and activate conditional fluorophores. The Chili RNA aptamer mimics large Stokes shift fluorescent proteins and exhibits high affinity for 3,5-dimethoxy-4-hydroxybenzylidene imidazolone (DMHBI) derivatives to elicit green or red fluorescence emission. Here, we elucidate the structural and mechanistic basis of fluorescence activation by crystallography and time-resolved optical spectroscopy. Two co-crystal structures of the Chili RNA with positively charged DMHBO+ and DMHBI+ ligands revealed a G-quadruplex and a trans-sugar-sugar edge G:G base pair that immobilize the ligand by π-π stacking. A Watson-Crick G:C base pair in the fluorophore binding site establishes a short hydrogen bond between the N7 of guanine and the phenolic OH of the ligand. Ultrafast excited state proton transfer (ESPT) from the neutral chromophore to the RNA was found with a time constant of 130 fs and revealed the mode of action of the large Stokes shift fluorogenic RNA aptamer.}, language = {en} } @phdthesis{Mims2023, author = {Mims, David}, title = {Einblicke in die Spinchemie durch Untersuchung des Magnetfeldeffektes in rigide gebundenen Radikalionenpaaren}, doi = {10.25972/OPUS-30354}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-303547}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Synthese starrer Donor-Akzeptor-Verbindungen und Untersuchung des Magnetfeldeffektes auf Lebenszeit resultierender Biradikale mittels optischer Spektroskopie.}, subject = {Magnetfeldeffekt}, language = {de} } @phdthesis{Mladenovic2008, author = {Mladenovic, Milena}, title = {Theoretical Investigation into the Inhibition of Cystein Proteases}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-25763}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {Although known about and investigated since the late 1970's, the picture of the basic principles governing inhibitor strengths and the structure-activity relationships of the cysteine protease inhibition mechanism is still very incomplete. Computational approaches can be a very useful tool for investigating such questions, as they allow the inspection of single, specific effects in isolation from all others, in a manner very difficult to achieve experimentally. The ab initio treatments of such large systems like proteins are still not feasible. However, there is a vast number of computational approaches capable of dealing with protein structures with reasonable accuracy. This work presents a summary of theoretical investigations into cysteine protease cathepsin B using a range of methods. We have concentrated on the investigation of cysteine protease inhibition by epoxide- and aziridine-based inhibitors in order to obtain better insight into these important topics. Various model systems are simulated by means of pure quantum mechanical methods and by hybrid (QM/MM) methods. Both approaches provide a static picture. Dynamical effects are then accounted for by additional molecular dynamics (MD) simulations, using both classical and QM/MM MD approaches. The quantum mechanical approach was used to study very small model systems consisting only of the electrophilic warhead of the inhibitor (both substitituted and not) and molecular moieties simulating a very simplified protein active site (methylthiolate instead of Cys29 and methylimidazolium instead of His199 residue) and solvent surroundings (two waters or two ammonium ions, in combination with a continuum solvent model). Although simple, such a system provides a good description of the most important interactions involved in the inhibition reaction. It also allows investigation of the influence of the properties of the electrophilic warhead on the reaction rate. Beside the properties of the electrophilic warhead, the protein and solvent environment is also an important factor in the irreversible deactivation of the enzyme active site by the inhibitor. The non-covalent interactions of the inhibitor with the oxyanion hole and other subsites of the enzyme, as well as its interaction with the solvent molecules, need to be explicitly taken into account in the calculations, because of their possible impact on the reaction profile. As molecular modeling methods allow the treatment of such large systems, but lack the possibility of describing covalent interactions, our method of choice was the combined quantum mechanics/molecular modeling approach. By splitting the system into a smaller part that undergoes the bond cleavage/formation process and must be treated quantum mechanically, and a larger part, comprised of the rest of the protein, which could be treated using force fields, we managed to simulate the system at the desired precision. Our investigations concentrated on the role of His199 in the inhibition mechanism as well as on the structure-reactivity relationships between cysteine protease and various inhibitors, yielding new insight into the kinetics, regio- and stereospecificity of the inhibition. In particular, our calculations provide the following insights: i.) an explanation for the regioselectivity of the reaction, and original insight into which interactions affect the stereoselectivity; ii.) a clear model which explains the known structure-activity relationships and connects these effects with the pH-dependency of the inhibition; iii.) our computations question the generally accepted two-step model by showing that substituent effects accelerate the irreversible step to such an extent that the achievement of an equilibrium in the first step is doubtful; iv.) by way of theoretical characterizations of aziridine models, the reasons for similarities and differences in the mode of action of epoxide- and aziridine-based inhibitors are elucidated; and finally, v.) combining our results with experimental knowledge will allow rational design of new inhibitors. To account for dynamical effects as well, molecular dynamics (MD) computations were also performed. In these calculations the potential energy was computed at the force field level. The results not only supported and clarified the QM/MM results, but comparison with previous X-ray structures helped correct existing errors in the available geometrical models and resolved inconsistencies in the weighting of various factors governing the inhibition. In the work the first QM/MM MD calculations on the active site of the cysteine proteases are presented. In contrast to the MD simulations, these calculations used potential energies computed at the QM/MM-level. With the help of these computations we sought to address strongly disputed questions about the reasons for the existence of the active site ion pair and its role in the high activity of the enzyme.}, subject = {Quantenchemie}, language = {en} } @phdthesis{Mohrschladt2003, author = {Mohrschladt, Christian J.}, title = {Synthese und Untersuchung der photochemischen und photophysikalischen Eigenschaften Donor-Akzeptor-substituierter Anthracenderivate}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-8486}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2003}, abstract = {In der vorliegenden Arbeit wurde gezeigt, dass Donor-Akzeptor-substituierte Anthracen- und Ethenoanthracenderivate bemerkenswerte photophysikalische und photochemische Eigenschaften aufweisen. So bieten derartige Anthracenderivate eine interessante Grundlage sowohl zur Entwicklung von Fluoreszenzsonden beispielsweise f{\"u}r Schwermetallionen wie auch zur Entwicklung von molekularen Schaltern f{\"u}r die Datenverarbeitung. Weiterhin stellen die untersuchten Anthracene und Ethenoanthracene hervorragende Systeme zur systematischen Untersuchung von Substituenteneinfl{\"u}ssen auf Photoreaktionen dar.}, subject = {Anthracenderivate}, language = {de} } @article{MuellerLuettigMalyetal.2019, author = {Mueller, Stefan and L{\"u}ttig, Julian and Mal{\´y}, Pavel and Ji, Lei and Han, Jie and Moos, Michael and Marder, Todd B. and Bunz, Uwe H. F. and Dreuw, Andreas and Lambert, Christoph and Brixner, Tobias}, title = {Rapid multiple-quantum three-dimensional fluorescence spectroscopy disentangles quantum pathways}, series = {Nature Communications}, volume = {10}, journal = {Nature Communications}, doi = {10.1038/s41467-019-12602-x}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-202529}, pages = {4735}, year = {2019}, abstract = {Coherent two-dimensional spectroscopy is a powerful tool for probing ultrafast quantum dynamics in complex systems. Several variants offer different types of information but typically require distinct beam geometries. Here we introduce population-based three-dimensional (3D) electronic spectroscopy and demonstrate the extraction of all fourth- and multiple sixth-order nonlinear signal contributions by employing 125-fold (1⨯5⨯5⨯5) phase cycling of a four-pulse sequence. Utilizing fluorescence detection and shot-to-shot pulse shaping in single-beam geometry, we obtain various 3D spectra of the dianion of TIPS-tetraazapentacene, a fluorophore with limited stability at ambient conditions. From this, we recover previously unknown characteristics of its electronic two-photon state. Rephasing and nonrephasing sixth-order contributions are measured without additional phasing that hampered previous attempts using noncollinear geometries. We systematically resolve all nonlinear signals from the same dataset that can be acquired in 8 min. The approach is generalizable to other incoherent observables such as external photoelectrons, photocurrents, or photoions.}, language = {en} } @article{MufusamaFeineisMudogoetal.2019, author = {Mufusama, Jean-Pierre and Feineis, Doris and Mudogo, Virima and Kaiser, Marcel and Brun, Reto and Bringmann, Gerhard}, title = {Antiprotozoal dimeric naphthylisoquinolines, mbandakamines B\(_3\) and B\(_4\), and related 5,8′-coupled monomeric alkaloids, ikelacongolines A-D, from a Congolese Ancistrocladus liana}, series = {RSC Advances}, volume = {9}, journal = {RSC Advances}, number = {21}, doi = {10.1039/C9RA01784D}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201141}, pages = {12034-12046}, year = {2019}, abstract = {From the leaves of a botanically and phytochemically as yet unexplored Ancistrocladus liana discovered in the rainforests of the Central region of the Democratic Republic of the Congo in the vicinity of the town of Ikela, six new naphthylisoquinoline alkaloids were isolated, viz., two constitutionally unsymmetric dimers, the mbandakamines B\(_3\) (3) and B\(_4\) (4), and four related 5,8′-linked monomeric alkaloids, named ikelacongolines A-D (5a, 5b, 6, and 7). The dimers 3 and 4 are structurally unusual quateraryls comprising two 5,8′-coupled monomers linked via a sterically strongly constrained 6′,1′′-connection between their naphthalene units. These compounds contain seven elements of chirality, four stereogenic centers and three consecutive chiral axes. They were identified along with two known related compounds, the mbandakamines A (1) and B\(_2\) (2), which had so far only been detected in two Ancistrocladus species indigenous to the Northwestern Congo Basin. In addition, five known monomeric alkaloids, previously found in related Central African Ancistrocladus species, were isolated from the here investigated Congolese liana, three of them belonging to the subclass of 5,8′-coupled naphthylisoquinoline alkaloids, whereas two compounds exhibited a less frequently occurring 7,8′-biaryl linkage. The stereostructures of the new alkaloids were established by spectroscopic (in particular HRESIMS, 1D and 2D NMR), chemical (oxidative degradation), and chiroptical (electronic circular dichroism) methods. The mbandakamines B\(_3\) (3) and B\(_4\) (4) displayed pronounced activities in vitro against the malaria parasite Plasmodium falciparum and the pathogen of African sleeping sickness, Trypanosoma brucei rhodesiense.}, language = {en} } @phdthesis{MufusamaKoySita2019, author = {Mufusama Koy Sita, Jean-Pierre}, title = {Quality Assessment of Antimalarial Medicines Sold in the Democratic Republic of the Congo and Phytochemical Investigations on a Congolese Ancistrocladus Liana}, doi = {10.25972/OPUS-19238}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-192382}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2019}, abstract = {Nowadays, the management of infectious diseases is especially threatened by the rapid emergence of drug resistance. It has been suggested that the medicine quality assurance combined with good medication adherence may help to reduce this impendence. Moreover, the search for new antimicrobial agents from medicinal plants is strongly encouraged for the exploration of alternatives to existing therapies. In this context, the present work focused on both the quality evaluation of commercialized antimalarial medicines from the Democratic Republic of the Congo and on the phytochemical investigations of a Congolese Ancistrocladus species.}, subject = {Antimalariamittel}, language = {en} } @phdthesis{Musch2003, author = {Musch, Patrick}, title = {Large-Scale Applications of Multi-Reference Methods in Chemistry and Development of a Multi-Reference Moller-Plesset Perturbation Theory Program}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-7741}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2003}, abstract = {The first part of this work focuses on the characterization of systems which complex electronic structures require the application of multi-reference methods. The anti-tumor efficacy of the natural product Neocarzinostatin is based on the formation of diradicals and causes DNA cleavage and finally cytolysis. Computations on model systems performed in the present work show the influence of structural features on the mode of action and the efficacy of this antitumor-antibiotic. The cyclization of systems related to the enyne-cumulene framework like the enyne-allenes was investigated earlier and relations to the more unusual class of enyne-ketenes are analyzed. The class of enyne-ketenes (and also the enyne-allenes) show a broad spectrum of possible intermediates (diradicals, zwitterions, allenes). The electronic structures of these intermediates are also possible for the (heteroatom substituted) 1,2,4-cyclohexatriene and a model for their energetic sequence based on high-level multi-reference computations is proposed. In all three projects the application of multi-reference approaches is necessary to obtain a comprehensive picture of the reactivity and electronic structure but also shows up the limits inherently existing in the currently available programs with respect to the size of the molecules. In the second part, algorithms for a multi-reference Moller-Plesset perturbation theory (MR-MP2) program, designed to perform large-scale computations, were developed and implemented. The MR-MP2 approach represents the most cost-effective multireference ansatz and requires an efficient evaluation of the Hamilton matrix for which an algorithm is designed to instantly recognize only non-vanishing matrix elements and to employ the recurring interaction patterns of the Hamilton matrix. The direct construction of the Hamilton matrix is additionally parallelized to work on cluster environments.}, language = {en} } @phdthesis{Mut2023, author = {Mut, J{\"u}rgen}, title = {Synthese komplexer funktionaler Mono- und Oligosaccharid-Bausteine zur Untersuchung und Modifikation von Membranoberfl{\"a}chen humaner mesenchymaler Stromazellen}, doi = {10.25972/OPUS-32065}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320654}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Bei der Biofabrikation werden Zellen mit einem Biomaterial versetzt (vereint werden diese als Biotinte definiert) und durch additive Fertigungsmethoden wie dem 3D-Druck zu hierarchischen Strukturen aufgebaut. Zur Herstellung von k{\"u}nstlichen Gewebe und zuk{\"u}nftig auch von funktionalen Organen ist ein detailliertes Zellverst{\"a}ndnis essentiell. Im Rahmen dieser Dissertation wurden Systeme generiert, um die Zellmembranen von mesenchymalen Stromazellen gezielt zu ver{\"a}ndern und um die Modifikationen zu charakterisieren. Durch Inkubation mit unnat{\"u}rlichen Zuckern werden diese von Zellen aufgenommen und in den Zellmetabolismus eingeschleust und auf die Glycoproteine {\"u}bertragen. Diese Methode ist als metabolic glycoengineering bekannt. Dazu wurden diverse humane Saccharid-Analoga mit bioorthogonalen Gruppen (Azid oder Alkin) synthetisiert. Alle in dieser Arbeit vorgestellten Molek{\"u}le wurden NMR-spektroskopisch als auch massenspektrometrisch charakterisiert. Die acetylierten Mannosamin-Derivate konnten {\"u}ber zwei Stufen und die Sialins{\"a}ure-Derivate {\"u}ber sechs Stufen synthetisiert werden. Sialins{\"a}uren sind die terminalen Zucker an Glycanketten von Proteinen mit wichtigen biologischen Funktionen. Im Rahmen des SFB TRR225 konnte in Kooperation mit der Gruppe von Prof. Dr. R. Ebert der Einbau der Saccharide in mesenchymalen Stromazellen durch Fluoreszenzmikroskopie evaluiert werden. Aufgrund des effizienteren Einbaus der Sialins{\"a}ure mit Alkingruppe gegen{\"u}ber der mit Azidgruppe, wurde dieser in den folgenden massenspektrometrischen Analysen eingesetzt. Die Messungen der markierten Glycoproteine wurden von Dr. Marc Driessen durchgef{\"u}hrt und der metabolische Einbau von SiaNAl und Ac4ManNAl in den Stromazellen gegen{\"u}bergestellt. 55 Glycoproteine konnten durch SiaNAl und 94 durch Ac4ManNAl charakterisiert werden. Ein Abgleich der Proteindatenbanken eine Anreicherung von Proteine durch F{\"u}tterung von SiaNAl die in Signaltransduktion, Zellkontakte und Differenzierung involviert sind, womit metabolic glycoengineering prinzipiell zur Optimierung von Biofabrikationsprozessen genutzt werden kann.}, subject = {Glykane}, language = {de} } @phdthesis{Muzha2022, author = {Muzha, Andreas}, title = {Herstellung und Charakterisierung kolloidaler L{\"o}sungen diamantbasierter und verwandter Materialien}, doi = {10.25972/OPUS-29668}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-296685}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {In der vorliegenden Publikation wurden stabile kolloidale L{\"o}sungen aus CVD-Diamant, Detonationsdiamant sowie artverwandten Materialien hergestellt und charakterisiert Besonderes Augenmerk wurde bei der Zerkleinerung von CVD Diamant daraufgelegt, dass die nanoskaligen Partikel ihre materialspezifischen Eigenschaften auch bei Reduktion der Gr{\"o}ße beibehalten. Systematisch wurde die Zerkleinerung in einer Planetenm{\"u}hle analysiert. Es wurde sowohl die minimal erreichbare Partikelgr{\"o}ße, als auch die Menge an erzeugtem, nanoskaligem Material bewertet. Um die Vermahlung zu verbessern, wurden die Geschwindigkeit der M{\"u}hle, die Gr{\"o}ße der Mahlk{\"o}rper, die Dauer der Vermahlung, sowie die eingesetzten L{\"o}semittel variiert. Des Weiteren konnten durch die Vermahlung unterschiedlich hergestellter CVD Diamantfilme in einer Vibrationsm{\"u}hle die Einfl{\"u}sse von Schichtdicke und Korngr{\"o}ße der Diamantkristalle untersucht werden. Durch Bearbeitung von Detonationsdiamanten und Kohlenstoffnanozwiebeln wurden stabile kolloidale L{\"o}sungen hergestellt, mit Partikelgr{\"o}ßen im unteren Nanometerbereich. Diese sind im alkalischen pH-Bereich stabil sein, hierf{\"u}r wurde durch Luft und S{\"a}ureoxidation oxidierter Detonationsdiamant und oxidierte Kohlenstoffnanozwiebeln hergestellt. Mithilfe der thermogravimetrischen Analyse und Infrarotspektroskopie wurde die hierf{\"u}r optimale Temperatur und Dauer bestimmt.}, subject = {Diamant}, language = {de} } @phdthesis{Muehlbacher2003, author = {M{\"u}hlbacher, J{\"o}rg}, title = {Molecular Modelling und Chiralit{\"a}t: Aufkl{\"a}rung der absoluten Konfiguration von Natur- und Wirkstoffen mit ungew{\"o}hnlichem Circular-Dichroismus}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-6120}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2003}, abstract = {Der Einsatz von computerchemischen Verfahren zur Vorhersage, Best{\"a}tigung oder Erkl{\"a}rung von Molek{\"u}leigenschaften hat sich zu einem Wissenschaftszweig innerhalb der Chemie entwickelt, der sowohl im universit{\"a}ren Umfeld als auch in der Industrie eine unverzichtbare Rolle einnimmt. So hat die in unserem Arbeitskreis in Zusammenarbeit mit Prof. J. Fleischhauer entwickelte und immer wieder erweiterte Methode zur Berechnung des Circular-Dichroismus (CD) organischer Molek{\"u}le schon in vielen F{\"a}llen die Arbeit experimentell arbeitender Naturstoffchemiker unseres Arbeitskreises und die vieler Kooperationspartner erleichtert. Im Rahmen der Strukturaufkl{\"a}rung wurde die Methode als effizientes Verfahren zur eindeutigen Zuordnung der absoluten Konfiguration von neuartigen chiralen Natur- und Wirkstoffen eingesetzt. In der vorliegenden Arbeit wurde die zusammen mit Prof. J. Fleischhauer etablierte Molekulardynamik-Methodik (MD-Methodik) - neben der schon vorher angewandten Boltzmann-Methodik (BM-Methodik) - zur Untersuchung des Circular-Dichroismus flexibler Verbindungen eingesetzt. Begonnen wurden die Studien mit der Evaluierung des Verfahrens an besonders flexiblen Molek{\"u}len, um im Anschluß den Circular-Dichroismus von Substanzen untersuchen zu k{\"o}nnen, deren CD-Spektren auf den ersten Blick sehr ungew{\"o}hnlich erschienen oder nicht den g{\"a}ngigen Vorstellungen vom chiroptischen Verhalten organischer Molek{\"u}le entsprachen. Die Ergebnisse dieser Arbeit zeigen sehr deutlich, daß der Circular-Dichroismus komplexer organischer Verbindungen immer vorsichtig zu interpretieren ist. Zwar ist der einfachste Weg zur Aufkl{\"a}rung der Absolutkonfiguration eines Molek{\"u}ls derjenige, das CD-Spektrum der unbekannten Verbindung mit dem einer bereits aufgekl{\"a}rten Substanz sehr {\"a}hnlicher Konstitution zu vergleichen. Doch wie an den untersuchten Beispielen deutlich gezeigt wurde, kann trotz vermeintlich guter {\"U}bereinstimmung von CD-Spektren leicht eine falsche Zuordnung erfolgen. Einzig bei Enantiomeren oder sehr einfachen Derivaten enantiomerer Grundstruktur kann man durch den Vergleich experimenteller CD-Spektren eine sichere Aussage treffen. Sobald jedoch die CD-Spektren von Diastereomeren oder gar konstitutionell verschiedenen Substanzen verglichen werden sollen, ist immer {\"a}ußerste Vorsicht geboten.}, subject = {Naturstoff}, language = {de} } @article{MuehlhaeuserEngelsMarianetal.1994, author = {M{\"u}hlh{\"a}user, M. and Engels, Bernd and Marian, C. M. and Peyerimhoff, S. D. and Bruna, P. J. and Jansen, M.}, title = {Einfluß der Ladungsverteilung auf die Bindungsl{\"a}ngen im P\(_4\)O\(_6\) Ger{\"u}st bei Verbindungen des Typs P\(_4\)O\(_6\)X}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59034}, year = {1994}, abstract = {No abstract available}, subject = {Organische Chemie}, language = {de} } @article{MuehlhaeuserFroudakisZdetsisetal.1994, author = {M{\"u}hlh{\"a}user, M. and Froudakis, G. and Zdetsis, A. and Engels, Bernd and Flytzanis, N. and Peyerimhoff, S. D.}, title = {Ab initio investigation of the stability of Si\(_3\)C<\(_3\) clusters and their structural and bonding features}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-59060}, year = {1994}, abstract = {Various structural possibilities for Si\(_3\)C\(_3\) clusters are investigated by ab initio calculations employing basis sets of double- and triple-zeta quality augmented by d polarization functions. Correlation effects are included by a second-order Moeller Piesset perturbation treatment. For the two lowest-lying structures higher-order correlation corrections and multi-reference effects are also included. Bonding features are investigated by two different types of population analyses to obtain insight into the nature of chemical bonding. A total of 17 stationary points were investigated, 14 of which correspond to local minima and three being transition states. The energetically lowest-lying structures are: A "pyramidlike" structure with various multicenter bonds, followed by a es symmetric isomer closely related to the ground state Si6 structure. Planar structures, favoured in small carbon clusters, lie higher in energy and are transition states. The lowest-lying triplet system is found to be the linear nonsymmetric Si - C-C-C-Si -Si structure, which is calculated to lie about 38 kcalfmole above the singlet ground state. A building-up principle based on bonding criteria is suggested for the occurence of the various structural possibilities.}, subject = {Organische Chemie}, language = {en} } @phdthesis{Mueller2011, author = {M{\"u}ller, Christian}, title = {Physical Properties of Chromophore Functionalized Gold Nanoparticles}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57657}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2011}, abstract = {n this work the synthesis and analysis of chromophore functionalized spherical gold nanoparticles is presented. The optical, electrochemical and spectroelectrochemical properties of these hybrid materials are furthermore studied. The work therefore is divided into two parts. The first part deals with triarylamine and PCTM-radical functionalized gold nanoparticles. The focus thereby was on the synthesis and on the investigations of chromophore-chromophore interactions and gold core-chromophore interactions. The chromopores, especially triarylamines, were attached to the gold core via different bridging units and were studied with optical and electrochemical methods. The purity and dimensions of the nanoparticles was determined by 1H-NMR spectroscopy, diffusion ordered NMR spectroscopy (DOSY), TGA, XPS and STEM. Furthermore a cyclic voltammetry technique was used to determine the composition of the particles via the Randles-Sevcik equation. An analysis of these parameters led to a model of a sea urchin-shaped nanoparticle. Optical measurements of the particles revealed an anisotropic absorption behavior of the triarylamine units due to gold core-chromophore interaction. However this behavior depends strongly on the relative orientation of the transition dipole moment of the chromophore to the gold surface and the distance of the chromophore to the surface. Hence, the anisotropic behavior was exclusively detected in the spectra of the Au-Tara1 particles. The short and rigid pi-conjugated bridging unit thereby facilitates this gold core-chromophore interaction. It was shown from electrochemical investigations that the triarylamine units can be chemically reversibly oxidized to the triarylamine monoradical cation. Furthermore, the measurements revealed a strong interligand triarylamine-triarylamine interaction which was only seen for the Au-Tara1 particles. The long pi-conjugated bridging units of the Au-Tara2 and Au-Tara3 particles as well as the aliphatic bridging unit of Au-Tara4 prevent any detectable interligand interactions. One may conclude that both the gold core-chromophore and the interligand triarylamine-triarylamine interaction depend on the length and the rigidity of the bridging unit. The electron transfer behavior of the triarylamine units adsorbed onto the gold core was additionally studied via spectroelectrochemical (SEC) measurements which are able to reveal weaker interactions. The investigations of Au-Tara1 and Au-Tara2 revealed a significant strong coupling between neighboring triarylamine units which is due to through-space intervalence interactions. This behavior was not detected for Au-Tara3 or for Au-Tara4. The SEC analysis also revealed that these observed interligand interactions depend on the length and the rigidity of the bridging unit. Thus, the systematic variation of the bridging unit gave a basic insight in the optical and electrochemical properties of triarylamines, located in the vicinity of a gold nanoparticle. The second part of this work aimed at the synthesis of new molecules, denoted as SERS-markers, for immuno SERS applications. For this purpose, the SERS-markers were designed to have a Raman-active unit and a thiol group for chemisorptions to Au/Ag nanoshells. In cooperation with the group of Schl{\"u}cker (University of Osnabr{\"u}ck) the SERS-markers were absorbed onto Au/Ag nanoshells, denoted as SERS-labels, and characterized. The SERS spectra of the SERS-labels exhibited intense and characteristic SERS-signals for each marker. For immuno SERS investigations SEMA3 was functionalized with a hydrophilic end unit. This marker was adsorbed onto an Au/Ag nanoshell and encapsulated with silica. An anti-p63 antibody was bound to the silica surface in order to generate a SERS-labeled antibody for the detection of the tumor suppressor p63 in benign prostate. Immuno-SERS imaging of prostate tissue incubated with SERS-labeled anti-p63 antibodies demonstrated the selective detection of p63 in the basal epithelium. The results show the potential of the method for the detection of several biomolecules in a multiplexing SERS experiment.}, subject = {Gold}, language = {en} } @article{MuellerBessiRichteretal.2021, author = {M{\"u}ller, Diana and Bessi, Irene and Richter, Christian and Schwalbe, Harald}, title = {The Folding Landscapes of Human Telomeric RNA and DNA G-Quadruplexes are Markedly Different}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {19}, doi = {10.1002/anie.202100280}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-238917}, pages = {10895 -- 10901}, year = {2021}, abstract = {We investigated the folding kinetics of G-quadruplex (G4) structures by comparing the K\(^{+}\)-induced folding of an RNA G4 derived from the human telomeric repeat-containing RNA (TERRA25) with a sequence homologous DNA G4 (wtTel25) using CD spectroscopy and real-time NMR spectroscopy. While DNA G4 folding is biphasic, reveals kinetic partitioning and involves kinetically favoured off-pathway intermediates, RNA G4 folding is faster and monophasic. The differences in kinetics are correlated to the differences in the folded conformations of RNA vs. DNA G4s, in particular with regard to the conformation around the glycosidic torsion angle χ that uniformly adopts anti conformations for RNA G4s and both, syn and anti conformation for DNA G4s. Modified DNA G4s with \(^{19}\)F bound to C2′ in arabino configuration adopt exclusively anti conformations for χ. These fluoro-modified DNA (antiTel25) reveal faster folding kinetics and monomorphic conformations similar to RNA G4s, suggesting the correlation between folding kinetics and pathways with differences in χ angle preferences in DNA and RNA, respectively.}, language = {en} } @phdthesis{Muenchbach2001, author = {M{\"u}nchbach, Miriam Birgit}, title = {Untersuchungen zur endogenen Bildung, Cytotoxizit{\"a}t und DNA-sch{\"a}digenden Wirkung des dopaminergen Neurotoxins TaClo}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-385}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2001}, abstract = {Die kausalen Ursachen, die zur Ausl{\"o}sung der neurodegenerativen Erkrankung Morbus Parkinson f{\"u}hren, sind noch immer unklar. Man nimmt heute an, daß das Absterben dopaminerger Neurone im Mittelhirn von Parkinsonpatienten multifaktoriell ausgel{\"o}st wird. Genetische Pr{\"a}disposition sowie endogene und exogene Umweltgifte wie etwa Substanzen, die strukturelle {\"A}hnlichkeit mit dem bekanntesten dopaminergen Neurotoxin MPTP (1-Methyl-4-phenyl-1,2,3,5-tetrahydropyridin) besitzen, werden als Hauptursachen f{\"u}r die Entstehung des Parkinsonsyndroms diskutiert. Diese Arbeit besch{\"a}ftigt sich mit einer neuen Klasse von neurotoxisch wirksamen Tetrahydro-b-carbolinen, die sich von Trichloracetaldehyd (Chloral) ableiten. Die wohl prominenteste Verbindung in dieser Reihe ist TaClo (1-Trichlormethyl-1,2,3,4-tetrahydro-b-carbolin), das im menschlichen K{\"o}rper nach Aufnahme des Schlafmittels Chloralhydrat durch Pictet-Spengler-Kondensation mit dem endogen vorhandenen Tryptamin gebildet wird. Zus{\"a}tzlich scheint die Bildung von TaClo aus dem Industriel{\"o}sungsmittel TRI (Trichlorethylen), das im Organismus zu Chloral metabolisiert wird, m{\"o}glich. Die {\"u}ber Chloral eingef{\"u}hrte große CCl3-Gruppe erh{\"o}ht die Lipophilie von TaClo, die Passage der Blut-Hirn-Schranke ist erleichtert. In der Tat haben zahlreiche Untersuchungen in vitro und in vivo gezeigt, daß TaClo toxische Prozesse in dopaminergen und serotonergen Systemen zu induzieren vermag. Ein wesentliches Ziel dieser Arbeit bestand darin, die in-vivo-Entstehung und Metabolisierung von TaClo im Menschen sowie den Einfluß dieses Neurotoxins auf die DNA herauszuarbeiten und n{\"a}her zu untersuchen. Im einzelnen wurden folgende Ergebnisse erzielt: TaClo sch{\"a}digt die DNA, wie Versuche an zellfreier DNA und in-vitro-Experimente an PC12-Zellen belegen. Die endogene Bildung von TaClo in Chloralhydrat-behandelten Patienten und die in-vitro-Entstehung von TaClo aus Trichlorethylen wurde mittels HPLC-ESI-MS-MS-Analytik eindeutig bewiesen. Außerdem wurden erste Hinweise auf eine Anreicherung des Neurotoxins im menschlichen K{\"o}rper erhalten. Stereostrukturelle Aspekte der Bildung und Verstoffwechslung von TaClo wurden aufgekl{\"a}rt und TaClo-Metabolite in in-vitro- und in-vivo-Proben identifiziert. Das Tetrahydro-b-carbolin entsteht in racemischer Form, wird also nicht enzymatisch sondern spontan durch Pictet-Spengler-Reaktion gebildet. Zus{\"a}tzlich wurden Hinweise auf eine enzymatische Metabolisierung von TaClo gefunden. Außerdem gelang es, eine etablierte Methode des oxidativen Abbaus zur Aufkl{\"a}rung der absoluten Konfiguration von Tetrahydropyridin-Heterocyclen [z.B. Eleagnin] auf Substanzen mit benzylischer Hydroxy- oder Metylether-Gruppe zu erweitern. Geringe Mengen (1-2 mg) an Substanzen, die in benzylischer Position eine chirale Sauerstoffunktion besitzen, wurden durch Ruthenium-katalysierte Oxidation zu GC-g{\"a}ngigen S{\"a}uren abgebaut, deren absolute Konfiguration nach Trennung an chiraler Phase durch Vergleich mit enantiomerenreinem Referenzmaterial bestimmt wurde. Diese Zuordnung erlaubte den R{\"u}ckschluß auf die absolute Konfiguration einer Reihe Ausgangsverbindungen.}, subject = {Parkinson-Krankheit}, language = {de} } @article{MuetzelFarrellShoyamaetal.2022, author = {M{\"u}tzel, Carina and Farrell, Jeffrey M. and Shoyama, Kazutaka and W{\"u}rthner, Frank}, title = {12b,24b-Diborahexabenzo[a,c,fg,l,n,qr]pentacene: A Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbon}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {8}, doi = {10.1002/anie.202115746}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318808}, year = {2022}, abstract = {Herein we devise and execute a new synthesis of a pristine boron-doped nanographene. Our target boron-doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B-doping arrangement. Our synthesis of this target, a doubly B-doped hexabenzopentacene (B\(_{2}\)-HBP), employs six net C-H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr\(_{3}\)/AlCl\(_{3}\)/2,6-dichloropyridine-mediated C-H borylation steps. As predicted by our calculations, B\(_{2}\)-HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o-dichlorobenzene solutions. Furthermore, B\(_{2}\)-HBP possesses a very low LUMO level, showing two reversible reductions at -1.00 V and -1.17 V vs. Fc\(^{+}\)/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B-doped polycyclic aromatic hydrocarbons.}, language = {en} } @phdthesis{Neitz2024, author = {Neitz, Hermann}, title = {Hydrophobic recognition motifs in functionalized DNA}, doi = {10.25972/OPUS-34838}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-348382}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2024}, abstract = {In w{\"a}ssriger Umgebung spielen hydrophobe Wechselwirkungen eine wichtige Rolle f{\"u}r die DNA. Die Einf{\"u}hrung von Modifikationen, die auf hydrophoben aromatischen Einheiten basieren, kann die Erkennung und Reaktivit{\"a}t von funktionellen Gruppen in der DNA steuern. Modifikationen k{\"o}nnen durch ein k{\"u}nstliches R{\"u}ckgrat oder in Form einer Erweiterung der Nukleobasen eingebracht werden und so zu zus{\"a}tzlichen Eigenschaften der DNA f{\"u}hren. Diese Dissertation befasst sich mit der Verwendung von hydrophoben Einheiten zur Funktionalisierung von DNA. Im ersten Teil der Arbeit wurde das Tolanmotiv (Diphenylacetylen) in Kombination mit dem acyclischen R{\"u}ckgrat von GNA und BuNA verwendet, um Erkennungseinheiten im DNA-Kontext zu erzeugen. Die gezielte Fluorierung der aromatischen Ringe des Tolan-Bausteins bildete die Grundlage f{\"u}r eine supramolekulare Sprache, die auf Aren-Fluoroaren-Wechselwirkungen basiert. Die spezifische Erkennung wurde mittels thermodynamischer, kinetischer und NMR-spektroskopischer Methoden untersucht. Im zweiten Teil der Arbeit wurden Desoxyuridin-Derivate mit einer hydrophoben aromatischen Modifikation hergestellt und in die DNA-Doppelhelix eingebaut. Die Bestrahlung mit UV-Licht f{\"u}hrte zu einer [2+2]-Cycloaddition zwischen zwei modifizierten Nukleosiden in der DNA. Das Reaktionsprodukt wurde strukturell charakterisiert und die Reaktion in verschiedenen biochemischen und nanotechnologischen DNA-Anwendungen eingesetzt.}, subject = {Supramolekulare Chemie}, language = {en} } @article{NeitzBessiKachleretal.2022, author = {Neitz, Hermann and Bessi, Irene and Kachler, Valentin and Michel, Manuela and H{\"o}bartner, Claudia}, title = {Tailored tolane-perfluorotolane assembly as supramolecular base pair replacement in DNA}, series = {Angewandte Chemie International Edition}, volume = {62}, journal = {Angewandte Chemie International Edition}, number = {1}, doi = {10.1002/anie.202214456}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312575}, year = {2022}, abstract = {Arene-fluoroarene interactions offer outstanding possibilities for engineering of supramolecular systems, including nucleic acids. Here, we implement the tolane-perfluorotolane interaction as base pair replacement in DNA. Tolane (THH) and perfluorotolane (TFF) moieties were connected to acyclic backbone units, comprising glycol nucleic acid (GNA) or butyl nucleic acid (BuNA) building blocks, that were incorporated via phosphoramidite chemistry at opposite positions in a DNA duplex. Thermodynamic analyses by UV thermal melting revealed a compelling stabilization by THH/TFF heteropairs only when connected to the BuNA backbone, but not with the shorter GNA linker. Detailed NMR studies confirmed the preference of the BuNA backbone for enhanced polar π-stacking. This work defines how orthogonal supramolecular interactions can be tailored by small constitutional changes in the DNA backbone, and it inspires future studies of arene-fluoroarene-programmed assembly of DNA.}, language = {en} } @unpublished{NeitzBessiKuperetal.2023, author = {Neitz, Hermann and Bessi, Irene and Kuper, Jochen and Kisker, Caroline and H{\"o}bartner, Claudia}, title = {Programmable DNA interstrand crosslinking by alkene-alkyne [2+2] photocycloaddition}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, edition = {submitted version}, doi = {10.1021/jacs.3c01611}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-311822}, year = {2023}, abstract = {Covalent crosslinking of DNA strands provides a useful tool for medical, biochemical and DNA nanotechnology applications. Here we present a light-induced interstrand DNA crosslinking reaction using the modified nucleoside 5-phenylethynyl-2'-deoxyuridine (\(^{Phe}\)dU). The crosslinking ability of \(^{Phe}\)dU was programmed by base pairing and by metal ion interaction at the Watson-Crick base pairing site. Rotation to intrahelical positions was favored by hydrophobic stacking and enabled an unexpected photochemical alkene-alkyne [2+2] cycloaddition within the DNA duplex, resulting in efficient formation of a \(^{Phe}\)dU-dimer after short irradiation times of a few seconds. A \(^{Phe}\)dU dimer-containing DNA was shown to efficiently bind a helicase complex, but the covalent crosslink completely prevented DNA unwinding, suggesting possible applications in biochemistry or structural biology.}, language = {en} } @unpublished{NeitzHoebartner2023, author = {Neitz, Hermann and H{\"o}bartner, Claudia}, title = {A tolane-modified 5-ethynyluridine as a universal and fluorogenic photochemical DNA crosslinker}, series = {Chemical Communications}, journal = {Chemical Communications}, edition = {submitted version}, doi = {10.1039/D3CC03796G}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-328255}, year = {2023}, abstract = {We report the fluorescent nucleoside ToldU and its application as a photoresponsive crosslinker in three different DNA architectures with enhanced fluorescence emission of the crosslinked products. The fluorogenic ToldU crosslinking reaction enables the assembly of DNA polymers in a hybridization chain reaction for the concentration-dependent detectio of a specific DNA sequence.}, language = {en} } @phdthesis{Noll2023, author = {Noll, Niklas}, title = {Second Coordination Sphere Engineering in Macrocyclic Ruthenium Water Oxidation Catalysts}, doi = {10.25972/OPUS-30533}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-305332}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {About 2.4 billion years ago, nature has fundamentally revolutionized life on earth by inventing the multi-subunit protein complex photosystem II, the only molecular machine in nature that catalyzes the thermodynamically demanding photosynthetic splitting of water into oxygen and reducing equivalents. Nature chose a distorted Mn4CaO5 cluster as catalyst, better known as oxygen-evolving complex (OEC), thus recognizing the need for transition metals to achieve high-performance catalysts. The curiosity has always driven mankind to mimic nature's achievements, but the performance of natural enzymes such as the oxygen-evolving complex in photosystem II remain commonly unmatched. An important role in fine-tuning and regulating the activity of natural enzymes is attributed to the surrounding protein domain, which facilitates substrate preorganization within well-defined nanoenvironments. In light of growing energy demands and the depletion of fossil fuels, the unparalleled efficiency of natural photosynthesis inspires chemists to artificially mimic its natural counterpart to generate hydrogen as a 'solar fuel' through the light-driven splitting of water. As a result, significant efforts have been devoted in recent decades to develop molecular water oxidation catalysts based on earth-abundant transition metals and the discovery of the Ru(bda) (bda: 2,2' bipyridine-6,6'-dicarboxylate) catalyst family enabled activities comparable to the natural OEC. Similar to the natural archetypes, the design of homogeneous catalysts that interplay judiciously with the second coordination sphere of the outer ligand framework proved to be a promising concept for catalyst design. In this present thesis, novel supramolecular design approaches for enzyme like activation of substrate water molecules for the challenging oxidative water splitting reaction were established via tailor-made engineering of the secondary ligand environment of macrocyclic Ru(bda) catalysts.}, subject = {Katalyse}, language = {en} } @article{NollGrossShoyamaetal.2023, author = {Noll, Niklas and Groß, Tobias and Shoyama, Kazutaka and Beuerle, Florian and W{\"u}rthner, Frank}, title = {Folding-Induced Promotion of Proton-Coupled Electron Transfers via Proximal Base for Light-Driven Water Oxidation}, series = {Angewandte Chemie International Edition}, volume = {62}, journal = {Angewandte Chemie International Edition}, number = {7}, doi = {10.1002/anie.202217745}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312020}, year = {2023}, abstract = {Proton-coupled electron-transfer (PCET) processes play a key role in biocatalytic energy conversion and storage, for example, photosynthesis or nitrogen fixation. Here, we report a series of bipyridine-containing di- to tetranuclear Ru(bda) macrocycles 2 C-4 C (bda: 2,2′-bipyridine-6,6′-dicarboxylate) to promote O-O bond formation. In photocatalytic water oxidation under neutral conditions, all complexes 2 C-4 C prevail in a folded conformation that support the water nucleophilic attack (WNA) pathway with remarkable turnover frequencies of up to 15.5 s\(^{-1}\) per Ru unit respectively. Single-crystal X-ray analysis revealed an increased tendency for intramolecular π-π stacking and preorganization of the proximal bases close to the active centers for the larger macrocycles. H/D kinetic isotope effect studies and electrochemical data demonstrate the key role of the proximal bipyridines as proton acceptors in lowering the activation barrier for the crucial nucleophilic attack of H\(_{2}\)O in the WNA mechanism.}, language = {en} } @article{NollKrauseBeuerleetal.2022, author = {Noll, Niklas and Krause, Ana-Maria and Beuerle, Florian and W{\"u}rthner, Frank}, title = {Enzyme-like water preorganization in a synthetic molecular cleft for homogeneous water oxidation catalysis}, series = {Nature Catalysis}, journal = {Nature Catalysis}, edition = {accepted version}, doi = {10.1038/s41929-022-00843-x}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-302897}, year = {2022}, abstract = {Inspired by the proficiency of natural enzymes, mimicking of nanoenvironments for precise substrate preorganisation is a promising strategy in catalyst design. However, artificial examples of enzyme-like activation of H\(_2\)O molecules for the challenging oxidative water splitting reaction are hardly explored. Here, we introduce a mononuclear Ru(bda) complex (M1, bda: 2,2'-bipyridine-6,6'-dicarboxylate) equipped with a bipyridine-functionalized ligand to preorganize H\(_2\)O molecules in front of the metal center as in enzymatic clefts. The confined pocket of M1 accelerates chemically driven water oxidation at pH 1 by facilitating a water nucleophilic attack pathway with a remarkable turnover frequency of 140 s\(^{-1}\) that is comparable to the oxygen-evolving complex of photosystem II. Single crystal X-ray analysis of M1 under catalytic conditions allowed the observation of a 7th H\(_2\)O ligand directly coordinated to a RuIII center. Via a well-defined hydrogen-bonding network, another H\(_2\)O substrate is preorganized for the crucial O-O bond formation via nucleophilic attack.}, language = {en} } @article{NollWuerthner2024, author = {Noll, Niklas and W{\"u}rthner, Frank}, title = {Bioinspired water preorganization in confined space for efficient water oxidation catalysis in metallosupramolecular ruthenium architectures}, series = {Accounts of Chemical Research}, volume = {57}, journal = {Accounts of Chemical Research}, number = {10}, issn = {0001-4842}, doi = {10.1021/acs.accounts.4c00148}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-361232}, pages = {1538-1549}, year = {2024}, abstract = {Conspectus Nature has established a sustainable way to maintain aerobic life on earth by inventing one of the most sophisticated biological processes, namely, natural photosynthesis, which delivers us with organic matter and molecular oxygen derived from the two abundant resources sunlight and water. The thermodynamically demanding photosynthetic water splitting is catalyzed by the oxygen-evolving complex in photosystem II (OEC-PSII), which comprises a distorted tetramanganese-calcium cluster (CaMn\(_4\)O\(_5\)) as catalytic core. As an ubiquitous concept for fine-tuning and regulating the reactivity of the active site of metalloenzymes, the surrounding protein domain creates a sophisticated environment that promotes substrate preorganization through secondary, noncovalent interactions such as hydrogen bonding or electrostatic interactions. Based on the high-resolution X-ray structure of PSII, several water channels were identified near the active site, which are filled with extensive hydrogen-bonding networks of preorganized water molecules, connecting the OEC with the protein surface. As an integral part of the outer coordination sphere of natural metalloenzymes, these channels control the substrate and product delivery, carefully regulate the proton flow by promoting pivotal proton-coupled electron transfer processes, and simultaneously stabilize short-lived oxidized intermediates, thus highlighting the importance of an ordered water network for the remarkable efficiency of the natural OEC. Transferring this concept from nature to the engineering of artificial metal catalysts for fuel production has fostered the fascinating field of metallosupramolecular chemistry by generating defined cavities that conceptually mimic enzymatic pockets. However, the application of supramolecular approaches to generate artificial water oxidation catalysts remained scarce prior to our initial reports, since such molecular design strategies for efficient activation of substrate water molecules in confined nanoenvironments were lacking. In this Account, we describe our research efforts on combining the state-of-the art Ru(bda) catalytic framework with structurally programmed ditopic ligands to guide the water oxidation process in defined metallosupramolecular assemblies in spatial proximity. We will elucidate the governing factors that control the quality of hydrogen-bonding water networks in multinuclear cavities of varying sizes and geometries to obtain high-performance, state-of-the-art water oxidation catalysts. Pushing the boundaries of artificial catalyst design, embedding a single catalytic Ru center into a well-defined molecular pocket enabled sophisticated water preorganization in front of the active site through an encoded basic recognition site, resulting in high catalytic rates comparable to those of the natural counterpart OEC-PSII. To fully explore their potential for solar fuel devices, the suitability of our metallosupramolecular assemblies was demonstrated under (electro)chemical and photocatalytic water oxidation conditions. In addition, testing the limits of structural diversity allowed the fabrication of self-assembled linear coordination oligomers as novel photocatalytic materials and long-range ordered covalent organic framework (COF) materials as recyclable and long-term stable solid-state materials for future applications.}, language = {en} } @phdthesis{Noll2006, author = {Noll, Torsten Frank}, title = {Aufkl{\"a}rung der Biosynthese und Faltungsmodi aromatischer Polyketide in pflanzlichen Gewebekulturen, Mikroorganismen und Insekten sowie Strukturaufkl{\"a}rung von entsprechenden Biosynthese-Intermediaten mittels HPLC-MS, NMR und CD}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-20187}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2006}, abstract = {Polyketide stellen aufgrund ihrer großen strukturellen Vielfalt nach wie vor Leit- und Wirkstoffe f{\"u}r die Pharma- und Pflanzenschutzforschung in den Industriel{\"a}ndern dar und bilden außerdem eine der wichtigsten Klassen von Naturstoffen (Sekund{\"a}rmetaboliten) {\"u}berhaupt. Besonders die Biosynthese aromatischer Polyketide und die hierbei involvierten Enzyme, die Polyketidsynthasen (PKS), wurden von Biosyntheseforschern als hervorragendes Modellsystem zur Untersuchung von Struktur-Funktions-Beziehungen von Multienzymkomplexen erkannt. F{\"u}r annelierte aromatische Polyketide existiert seit dem Jahr 2001 eine biosynthetische Klassifizierung auf Metabolitebene, das sogenannte Modus-F/S-System, mit dessen Hilfe man zwischen pro- und eukaryotischen Produzenten unterscheiden kann. Die Erforschung der detaillierten Biosynthese von aromatischen Polyketiden ist somit in mehrfacher Hinsicht ein lohnendes Ziel. In der vorliegenden Dissertation sollten die Biosynthese und die Faltungsmodi ausgew{\"a}hlter aromatischer Polyketide einschließlich der Charakterisierung potentieller Vorstufen in verschiedensten biologischen Systemen untersucht werden. Die dabei gewonnenen Resultate sind das Ergebnis interdisziplin{\"a}rer Zusammenarbeit.}, subject = {Polyketide}, language = {de} } @phdthesis{Ojala2012, author = {Ojala, Antti}, title = {Merocyanine Dyes as Donor Materials in Vacuum-Deposited Organic Solar Cells: Insights into Structure-Property-Performance Relationships}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-70073}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2012}, abstract = {In this study, a double-donor concept is used to improve the performance of thermally evaporated merocyanine(s)/C60 bulk heterojunction (BHJ) solar cells. It is shown that the co-evaporation of two merocyanine dyes with absorption bands at ~ 500 nm (SW dye) and ~ 650 nm (LW dye), respectively, together with C60 fullerene results in an improvement of open-circuit voltage (VOC), short-circuit current (JSC) as well as total power conversion efficiency (PCE) compared to the best single-donor cell. The enhancement of JSC is attributed to a higher photon harvesting efficiency of the mixed-donor devices due to a better spectral coverage.}, subject = {Merocyanine}, language = {en} } @article{OkudaLenzSeitzetal.2023, author = {Okuda, Takumi and Lenz, Ann-Kathrin and Seitz, Florian and Vogel, J{\"o}rg and H{\"o}bartner, Claudia}, title = {A SAM analogue-utilizing ribozyme for site-specific RNA alkylation in living cells}, series = {Nature Chemistry}, journal = {Nature Chemistry}, doi = {10.1038/s41557-023-01320-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-328762}, year = {2023}, abstract = {Post-transcriptional RNA modification methods are in high demand for site-specific RNA labelling and analysis of RNA functions. In vitro-selected ribozymes are attractive tools for RNA research and have the potential to overcome some of the limitations of chemoenzymatic approaches with repurposed methyltransferases. Here we report an alkyltransferase ribozyme that uses a synthetic, stabilized S-adenosylmethionine (SAM) analogue and catalyses the transfer of a propargyl group to a specific adenosine in the target RNA. Almost quantitative conversion was achieved within 1 h under a wide range of reaction conditions in vitro, including physiological magnesium ion concentrations. A genetically encoded version of the SAM analogue-utilizing ribozyme (SAMURI) was expressed in HEK293T cells, and intracellular propargylation of the target adenosine was confirmed by specific fluorescent labelling. SAMURI is a general tool for the site-specific installation of the smallest tag for azide-alkyne click chemistry, which can be further functionalized with fluorophores, affinity tags or other functional probes.}, language = {en} } @phdthesis{OrtegaSchulte2003, author = {Ortega Schulte, Claudius M.}, title = {Der EPR-spektroskopisch ermittelte D-Parameter von Cyclopentan-1,3-diyl-Triplettdiradikalen als Sonde zur Bestimmung von elektronischen Effekten in Propargyl- und Heteropropargylradikalen und geminal substituierten Donor/Donor- und Akzeptor/Donor-Allylradikalen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-5752}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2003}, abstract = {In der vorliegenden Arbeit wurde die Spindelokalisation im Propargylradikal im Vergleich zu den Heteropropargylradikalen untersucht, sowie die elektronischen Einfl{\"u}sse, welche geminal gebundenen Substituenten auf die Spinverteilung in Allylradikalen verursachen bestimmt. Die Spindichte wurde mit Hilfe des D-Parameters von lokalisierten 1,3-Cyclopentandiyitriplettdiradikalen experimentell bestimmt (EPR-Spektroskopie).}, subject = {Propinolderivate}, language = {de} } @article{OrtizSotoSeibel2016, author = {Ortiz-Soto, Maria Elena and Seibel, J{\"u}rgen}, title = {Expression of Functional Human Sialyltransferases ST3Gal1 and ST6Gal1 in Escherichia coli}, series = {PLoS ONE}, volume = {11}, journal = {PLoS ONE}, number = {5}, doi = {10.1371/journal.pone.0155410}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-179807}, year = {2016}, abstract = {Sialyltransferases (STs) are disulfide-containing, type II transmembrane glycoproteins that catalyze the transfer of sialic acid to proteins and lipids and participate in the synthesis of the core structure oligosaccharides of human milk. Sialic acids are found at the outermost position of glycostructures, playing a key role in health and disease. Sialylation is also essential for the production of recombinant therapeutic proteins (RTPs). Despite their importance, availability of sialyltransferases is limited due to the low levels of stable, soluble and active protein produced in bacterial expression systems, which hampers biochemical and structural studies on these enzymes and restricts biotechnological applications. We report the successful expression of active human sialyltransferases ST3Gal1 and ST6Gal1 in commercial Escherichia coli strains designed for production of disulfide-containing proteins. Fusion of hST3Gal1 with different solubility enhancers and substitution of exposed hydrophobic amino acids by negatively charged residues (supercharging-like approach) were performed to promote solubility and folding. Co-expression of sialyltransferases with the chaperon/foldases sulfhydryl oxidase, protein disulfide isomerase and disulfide isomerase C was explored to improve the formation of native disulfide bonds. Active sialyltransferases fused with maltose binding protein (MBP) were obtained in sufficient amounts for biochemical and structural studies when expressed under oxidative conditions and co-expression of folding factors increased the yields of active and properly folded sialyltransferases by 20\%. Mutation of exposed hydrophobic amino acids increased recovery of active enzyme by 2.5-fold, yielding about 7 mg of purified protein per liter culture. Functionality of recombinant enzymes was evaluated in the synthesis of sialosides from the β-d-galactoside substrates lactose, N-acetyllactosamine and benzyl 2-acetamido-2-deoxy-3-O-(β-d-galactopyranosyl)-α-d-galactopyranoside.}, language = {en} } @phdthesis{Osswald2007, author = {Osswald, Peter Uwe}, title = {Perylene Bisimide Atropisomers : Synthesis and Optical and Chiroptical Properties}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-23248}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2007}, abstract = {Zur Herstellung von atropo-enantiomeren Perylenbisimiden wurde die kovalente Verkn{\"u}pfung von Aryloxysubstituenten durch Makrocyclisierung eingesetzt. Die Darstellung makrocyclischer Perylenbisimide erfolgte ausgehend von einem vierfach (3-Hydroxyphenoxy)-funktionalisierten Perylenbisimid mit achiralen 2,6-Diisopropylphenylsubstituenten an den Imidpositionen durch Williamsonsche Ethersynthese. Die Synthese konnte f{\"u}r vier unterschiedliche Oligoethylenglykol-Kettenl{\"a}ngen realisiert werden, wobei f{\"u}r jede Br{\"u}ckenl{\"a}nge jeweils zwei regioisomere Makrocyclen, n{\"a}mlich das diagonal verbr{\"u}ckte (1,7- und 6,12-Verk{\"u}pfung) und das seitlich verbr{\"u}ckte Isomer (1,12- und 6,7- Verkn{\"u}pfung), isoliert werden konnten. Die strukturelle Zuordnung der isolierten Makrocyclen zu einem der beiden Regioisomeren gelang zweifelsfrei anhand von R{\"o}ntgenstrukturanalysen f{\"u}r zwei Makrocyclen und 1H NMR-Spektroskopie f{\"u}r alle Isomere. Der konformative Einfluß der Aryloxy-Substituenten auf die funktionenellen Eigenschaften dieser Farbstoffklasse konnte durch Vergleich der optischen und elektrochemischen Eigenschaften aller isolierter Makrocyclen mit einer offenkettigen Referenzverbindung abgeleitet werden. Hierbei zeigte sich, dass die Aryloxy-Substituenten dieser Farbstoffe in L{\"o}sung bevorzugt in einer horizontalen Konformation vorliegen. Durch l{\"o}sungsmittelabh{\"a}ngige Fluoreszenzmessungen konnte gezeigt werden, dass ein photoinduzierter Elektronentransferprozess f{\"u}r die Fluoreszenzl{\"o}sung elektronenreicher Aryloxy-Substituenten von Bedeutung ist. Die Trennung der Atropo-Diastereomere konnte f{\"u}r eine diagonal {\"u}berbr{\"u}ckte makrocyclische Verbindung mit chiralen 2-(R)-Octylamin Imidsubstituenten und Diethyleneglykol als Br{\"u}ckenkette mittels semi-preparativer HPLC an einer chiralen station{\"a}ren Phase realisiert werden. Die chiroptischen Eigenschaften der isolierten epimerenreinen Makrocyclen wurden mittels CD-Spektroskopie untersucht. Die Zuordnung der absoluten Stereochemie konnte anhand der erhaltenen CD-Spektren durch Anwendung der „Theorie der excitonischen Kopplung" abgeleitet und durch quantenchemische Berechnung der CD-Spektren best{\"a}tigt werden. Dieses Synthesekonzept wurde auf 1,7-diaryloxy-substituierten Perylenbisimide erweitert. Die Struktur der erhaltenen diagonal verbr{\"u}ckten monocyclischen Verbindung konnte erneut durch NMR-Spektroskopie und R{\"o}ntgenstrukturanalyse eindeutig bestimmt werden. Die Trennung der Atropo-Enantiomere gelang mittels semi-preparativer HPLC an einer chiralen station{\"a}ren Phase. Die Zuordnung der Stereochemie konnte anhand des Vergleichs der CD-Spektren mit den zuvor f{\"u}r epimerenreine Bismakrocyclen erhaltenen CD-Spektren realisiert werden. Anhand der R{\"o}ntgenstrukturanalysen sowohl der racemischen Mischung als auch eines Atropo-Enantiomers ließen sich bedeutende Informationen {\"u}ber die p-Dimerisierung von Perylenbisimiden ableiten. Die Abh{\"a}ngigkeit der Razemisierungsbarriere von der Gr{\"o}ße der Bay-Substituenten wurde f{\"u}r vier halogensubstituierte Derivate untersucht. Die dynamischen Eigenschaften wurden mittels temperaturabh{\"a}ngiger NMR-Spektroskopie und kinetischer Messungen mittels CD-Spektroskopie bestimmt. Unter Anwendung des „Apparent Overlap"-Konzeptes konnte eine {\"u}berzeugende lineare Beziehung zwischen der Gr{\"o}ße der Substituenten und der Inversionsbarriere hergestellt werden. Dar{\"u}ber hinaus war es m{\"o}glich die Atropo-Diastereomere bzw. Enantiomere der tetrachlor- und tetrabrom-substituierten Derivate zu trennen, wobei vor allem das 1,6,7,12-tetrabrom-substituierte Perylenbisimid stabile Enantiomere bei Raumtemperatur lieferte. Die abgeleitete Struktur-Eigenschaftsbeziehung sollte zuk{\"u}nftig die Herstellung von stabilen Enantiomeren durch geeignete Wahl der Substituenten in den Bay-Positionen erm{\"o}glichen. Um die Reversibilit{\"a}t der Selbstorganisation zur quantitativen Synthese makrocyclischer Perylenbisimide ausn{\"u}tzen zu k{\"o}nnen, wurde ein tetra(zinkporphyrin)-funktionalisiertes Perylenbisimid synthetisiert. Die Ausbildung des angestrebten 1:2-Sandwichkomplexes aus Tetra-Zinkporphyrin-Perylenbisimid und Diazabicyclo-[2.2.2]-undecan wurde mittels UV/Vis und 1H NMR Spektroskopie untersucht und die makrocyclische Struktur des Komplexes konnte mittels diffusionsabh{\"a}ngiger NMR Spektroskopie (DOSY NMR) eindeutig bewiesen werden. Weiterhin konnte mittels rasterkraftmikroskopischer (AFM) Untersuchungen gezeigt werden, dass diese funktionellen makrocyclischen Verbindungen sehr geordnet auf einer Graphitoberfl{\"a}che (HOPG) abgeschieden werden k{\"o}nnen. Die Ausrichtung eines amino-funktionalsierten p-konjugierten Polymers durch Zugabe des bichromphoren Tetra-Zinkporphyrin-Perlyenbisimids wurde mittels UV/Vis-Spektroskopie und AFM-Messungen untersucht. Die Oberfl{\"a}chenanalyse mittels AFM zeigte, dass die bichromophore Verbindung die linearen p-konjugierten Polymere {\"u}ber weite Teile der Oberfl{\"a}che auszurichten vermag, so dass eine definierte Anordnung von drei p-Systemen auf der Graphitoberfl{\"a}che erm{\"o}glicht wurde.}, language = {en} } @article{OuyangRueheZhangetal.2022, author = {Ouyang, Guanghui and R{\"u}he, Jessica and Zhang, Yang and Lin, Mei-Jin and Liu, Minghua and W{\"u}rthner, Frank}, title = {Intramolecular Energy and Solvent-Dependent Chirality Transfer within a BINOL-Perylene Hetero-Cyclophane}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {31}, doi = {10.1002/anie.202206706}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318818}, year = {2022}, abstract = {Multichromophoric macrocycles and cyclophanes are important supramolecular architectures for the elucidation of interchromophoric interactions originating from precise spatial organization. Herein, by combining an axially chiral binaphthol bisimide (BBI) and a bay-substituted conformationally labile twisted perylene bisimide (PBI) within a cyclophane of well-defined geometry, we report a chiral PBI hetero-cyclophane (BBI-PBI) that shows intramolecular energy and solvent-regulated chirality transfer from the BBI to the PBI subunit. Excellent spectral overlap and spatial arrangement of BBI and PBI lead to efficient excitation energy transfer and subsequent PBI emission with high quantum yield (80-98 \%) in various solvents. In contrast, chirality transfer is strongly dependent on the respective solvent as revealed by circular dichroism (CD) spectroscopy. The combination of energy and chirality transfer affords a bright red circularly polarized luminescence (CPL) from the PBI chromophore by excitation of BBI.}, language = {en} } @phdthesis{Paasche2013, author = {Paasche, Alexander}, title = {Mechanistic Insights into SARS Coronavirus Main Protease by Computational Chemistry Methods}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-79029}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2013}, abstract = {The SARS virus is the etiological agent of the severe acute respiratory syndrome, a deadly disease that caused more than 700 causalities in 2003. One of its viral proteins, the SARS coronavirus main protease, is considered as a potential drug target and represents an important model system for other coronaviruses. Despite extensive knowledge about this enzyme, it still lacks an effective anti-viral drug. Furthermore, it possesses some unusual features related to its active-site region. This work gives atomistic insights into the SARS coronavirus main protease and tries to reveal mechanistic aspects that control catalysis and inhibition. Thereby, it applies state-of-the-art computational methods to develop models for this enzyme that are capable to reproduce and interpreting the experimental observations. The theoretical investigations are elaborated over four main fields that assess the accuracy of the used methods, and employ them to understand the function of the active-site region, the inhibition mechanism, and the ligand binding. The testing of different quantum chemical methods reveals that their performance depends partly on the employed model. This can be a gas phase description, a continuum solvent model, or a hybrid QM/MM approach. The latter represents the preferred method for the atomistic modeling of biochemical reactions. A benchmarking uncovers some serious problems for semi-empirical methods when applied in proton transfer reactions. To understand substrate cleavage and inhibition of SARS coronavirus main protease, proton transfer reactions between the Cys/His catalytic dyad are calculated. Results show that the switching between neutral and zwitterionic state plays a central role for both mechanisms. It is demonstrated that this electrostatic trigger is remarkably influenced by substrate binding. Whereas the occupation of the active-site by the substrate leads to a fostered zwitterion formation, the inhibitor binding does not mimic this effect for the employed example. The underlying reason is related to the coverage of the active-site by the ligand, which gives new implications for rational improvements of inhibitors. More detailed insights into reversible and irreversible inhibition are derived from in silico screenings for the class of Michael acceptors that follow a conjugated addition reaction. From the comparison of several substitution patterns it becomes obvious that different inhibitor warheads follow different mechanisms. Nevertheless, the initial formation of a zwitterionic catalytic dyad is found as a common precondition for all inhibition reactions. Finally, non-covalent inhibitor binding is investigated for the case of SARS coranavirus main protease in complex with the inhibitor TS174. A novel workflow is developed that includes an interplay between theory and experiment in terms of molecular dynamic simulation, tabu search, and X-ray structure refinement. The results show that inhibitor binding is possible for multiple poses and stereoisomers of TS174.}, subject = {SARS}, language = {en} } @phdthesis{Patrakov2010, author = {Patrakov, Anatoly}, title = {Anwendung der Clustern{\"a}herung zur quantenchemischen Charakterisierung der Struktur und Stabilit{\"a}t von II-VI Halbleitersystemen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-46283}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2010}, abstract = {Kaum ein Bereich der menschlichen T{\"a}tigkeit hat sich jemals so st{\"u}rmisch entwickelt, wie die Mikro- und Nanoelektronik in den letzten Jahrzehnten. Der rasche Fortschritt dieser Gebiete war m{\"o}glich, weil die Vorteile in der Anwendung der Mikroelektronik den gewaltigen Entwicklungs- und Forschungsaufwand rechtfertigten. Eine besondere Rolle spielt dabei die Herstellung von Halbleiterbauelementen durch Kristallz{\"u}chtungsmethoden. In dieser Arbeit wurden Prozesse untersucht, die sich auf der Kristalloberfl{\"a}che abspielen und somit das Wachstum von hochgeordneten Kristallstrukturen bestimmen. In den vergangenen Jahren wurden mehrere Methoden zur Untersuchung dieser Prozesse entwickelt, deren Pr{\"a}zision sich von Jahr zu Jahr unabl{\"a}ssig steigerte. In der Reihe der theoretischen Ans{\"a}tze stehen quantenchemische Methoden im Vordergrund. Eine von diesen Methoden, die Dichtefunktionaltheorie, ist aufgrund ihrer Anschaulichkeit und des relativ niedrigen Rechenaufwands das Hauptwerkzeug der vorliegenden Arbeit. Im ersten Teil dieser Arbeit wurden die Wanderungsm{\"o}glichkeiten eines Adsorbatatoms (Cd oder Te) auf der (001) Oberfl{\"a}che von CdTe (Substrat) auf DFT-Niveau im Rahmen der GGA-N{\"a}herung untersucht. Dies erforderte es, die Gesamtenergie des Systems Adsorbat-Kristall an verschiedenen Adsorptionsstellen zu berechnen. Dabei wurde nur ein Teil des Kristalls - das Adsorbat selbst und die n{\"a}chste Umgebung der Adsorptionsstelle (Quantencluster) - auf DFT-Niveau berechnet. Der Einfluss des {\"u}brigen Kristalls auf den Cluster wurde mit einem Gitter aus Punktladungen angen{\"a}hert, wobei die Te- und Cd-Atome die Ladungen \&\#8722;2 bzw. +2 trugen. Bei dem Einsatz dieses Modells ergab sich allerdings das Problem, dass es eigentlich nur auf Ionenkristalle anwendbar ist, die in guter N{\"a}herung volle Ionizit{\"a}t besitzen. CdTe stellt aber laut vielen experimentellen und theoretischen Untersuchungen eine Abstufung zwischen ionischen und kovalenten Kristallen dar, was eine gr{\"u}ndliche Analyse der Abh{\"a}ngigkeit unserer Ergebnisse von der Clustergr{\"o}ße und der Entfernung der Adsorptionsstelle von den Clusterr{\"a}ndern erforderte. Als Ergebnis wurde ein Modell entworfen, das dazu in der Lage ist, die Struktur der (2X1) Te-terminierten CdTe Oberfl{\"a}che mit ausreichender Genauigkeit wiederzugeben. Durch geeignete Wahl des Quantenclusters (ausreichende Gr{\"o}ße in den Richtungen parallel zur Oberfl{\"a}che und Platzierung der weniger polarisierbaren Cd-Kationen an den Außenfl{\"a}chen) gelang es, den Einfluss der Clusteroberfl{\"a}che auf die untersuchten Eigenschaften auf ein akzeptables Maß zu verringern. Die durchgef{\"u}hrten Berechnungen der Cd-Potentialenergiefl{\"a}che zeigen zwei Potentialt{\"o}pfe, mit den Tiefen 2.1 eV und 1.7 eV. Die Existenz dieser beiden Minima ist eng mit der Dimerisierung von Te-Atomen an der adsorbatfreien Te-Oberfl{\"a}che verbunden. Das erste, der Struktur =Te-Cdad-Te= entsprechende Minimum entsteht durch den Bruch einer Te-Te Dimerbindung beim Cd-Angriff an diese Stelle. Der zweite Potentialtopf kommt dadurch zustande, dass das Cd-Adsorbatatom mit zwei entlang der [110]-Richtung angeordneten Te2-Dimeren reagiert. Die Potentialenergiefl{\"a}che des Te-Adsorbats unterscheidet sich zwar wesentlich von der des Cd-Atoms, es gibt aber auch {\"A}hnlichkeiten. Das gilt vor allem f{\"u}r das der Struktur =Te-Tead-Te= entsprechende Minimum, das ungef{\"a}hr 2.8 eV tief ist. Wie im Fall der Cd-Adsorption entsteht diese Struktur infolge der Wechselwirkung eines adsorbierten Te-Atoms mit einem Te2-Dimer auf der Oberfl{\"a}che. Die Ergebnisse unserer Berechnungen best{\"a}tigen experimentelle Hinweise, gem{\"a}ß denen Te- und Cd-Atome aus dem Teilchenfluss, dem die (2X1)Te Oberfl{\"a}che w{\"a}hrend der MBE ausgesetzt ist, leicht adsorbiert werden. Außerdem wurden die relativ genauen Werte der Potentialbarrieren bekommen, die f{\"u}r ein besseres Verst{\"a}ndnis des Wachstumsprozesses zum Beispiel mit Hilfe von Monte-Carlo-Simulationen notwendig sind. Im Vordergrund des zweiten Teils der vorliegenden Arbeit stand die Strukturbestimmung von ZnO-Nanoclustern, die durch spezielle Kristallisationsprozesse erzeugt werden und wegen ihrer eigenartigen optischen und elektronischen Eigenschaften von großem Interesse sind. Zwei grunds{\"a}tzlich unterschiedliche Atomanordnungen wurden betrachtet, wobei festgestellt werden sollte, welche dieser Strukturen in Abh{\"a}ngigkeit von der Clustergr{\"o}ße und der Umgebung stabiler ist. Angenommen wurde dabei, dass diese Tendenz bei der weiteren Vergr{\"o}ßerung der Atomanzahl von Hundert bis mehreren Tausenden erhalten bleibt. Die Clustermodelle erster Art besaßen die f{\"u}r ZnO-Verbindungen typische Wurtzitstruktur, die anderen, sogenannten K{\"a}figcluster, bestanden aus Zn3O3- und (oder) Zn2O2-Ringen, die so verkn{\"u}pft sind, dass sie kugel- oder zylinderf{\"o}rmige Strukturen bilden. Charakteristisch f{\"u}r letztere Cluster ist eine Homogenit{\"a}t der Atomumgebung, da alle Zn- und O-Atome dreifach koordiniert sind, w{\"a}hrend sie in Wurtzitstrukturen im Wesentlichen vierfach koordiniert sind. Durch Kn{\"u}pfung zus{\"a}tzlicher Zn-O Bindungen konnte die Anzahl der in Frage kommenden Strukturen nennenswert vergr{\"o}ßert werden. Dabei entstehen vierfach koordinierten Atome und, laut den Berechnungen, deutlich stabilere Cluster. Die Rechnungen wurden sowohl im Vakuum als auch im Rahmen des COSMO Verfahrens (im „Wasser") durchgef{\"u}hrt. Sie ergaben, dass die Wurtzitstrukturen bei der Zunahme der Atomanzahl stabiler werden als ihre K{\"a}fig-Analoge. Dieses Ergebnis ist allerdings eher von theoretischem Interesse, da die experimentell in einer L{\"o}sung gez{\"u}chteten ZnO-Nanocluster an ihrer Oberfl{\"a}che mit Molek{\"u}len aus der L{\"o}sung bedeckt sind. Ein weiterer Schritt war daher, den Einfluss der Umgebung auf die Bildungsenergie durch die Abs{\"a}ttigung der Oberfl{\"a}che mit H+- und OH\&\#8722;-Ionen zu simulieren. Als Bezugspunkt f{\"u}r die Berechnung der Bildungsenergie der verschiedenen Cluster wurde der Molek{\"u}lkomplex Zn(OH)2(H2O)2 verwendet. Mit anderen Worten wurde angenommen, dass ein freies Zn2+-Ion in der L{\"o}sung von zwei OH\&\#8722;-Gruppen und zwei H2O-Molek{\"u}len umgeben ist. Die Ergebnisse zeigen, dass die Abs{\"a}ttigung einen starken Einfluss auf die Randbereiche der wurtzitartigen Cluster aus{\"u}bt. Bei fast allen Clustermodellen sind diese stark verformt, w{\"a}hrend bei den K{\"a}figstrukturen nur deutlich geringere Verzerrungen beobachtet werden. Ebenso stark ist der Einfluss auf die Bildungsenergie: Verglichen mit ihren unabges{\"a}ttigten Analogen werden alle abges{\"a}ttigte Strukturen erheblich stabiler, was auf die Tatsache zur{\"u}ckzuf{\"u}hren ist, dass durch die OH\&\#8722; -Gruppen und H+-Kationen die freien Valenzen an der Clusteroberfl{\"a}che abges{\"a}ttigt werden. Ansonsten lassen sich bei den abges{\"a}ttigten Strukturen dieselben Tendenzen erkennen, wie bei nicht abges{\"a}ttigten. So werden Wurtzitstrukturen mit zunehmender Clustergr{\"o}ße energetisch g{\"u}nstiger als K{\"a}figstrukturen mit der gleichen Anzahl an Atomen. Da es die im Rahmen dieser Arbeit festgestellten Regelm{\"a}ßigkeiten erm{\"o}glichen, die stabilsten ZnO-Atomanordnungen auf die hier Betrachteten einzuschr{\"a}nken, ergibt sich, dass die stabilste Struktur f{\"u}r Nanocluster wurtzitartig ist. Dies stimmt auch mit allen verf{\"u}gbaren experimentellen Daten {\"u}berein.}, subject = {Zwei-Sechs-Halbleiter}, language = {de} } @phdthesis{PeethambaranNairSyamala2021, author = {Peethambaran Nair Syamala, Pradeep}, title = {Bolaamphiphilic Rylene Bisimides: Thermodynamics of Self-assembly and Stimuli-responsive Properties in Water}, doi = {10.25972/OPUS-21342}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-213424}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {The present thesis demonstrates how different thermodynamic aspects of self-assembly and stimuli-responsive properties in water can be encoded on the structure of π-amphiphiles, consisting of perylene or naphthalene bisimide cores. Initially, quantitative thermodynamic insights into the entropically-driven self-assembly was studied for a series of naphthalene bisimides with UV/Vis and ITC measurements, which demonstrated that their thermodynamic profile of aggregation is heavily influenced by the OEG side chains. Subsequently, a control over the bifurcated thermal response of entropically driven and commonly observed enthalpically driven self-assembly was achieved by the modulation of glycol chain orientation. Finally, Lower Critical Solution Temperature (LCST) phenomenon observed for these dyes was investigated as a precise control of this behavior is quintessential for self-assembly studies as well as to generate 'smart' materials. It could be shown that the onset of phase separation for these molecules can be encoded in their imide substituents, and they are primarily determined by the supramolecular packing, rather than the hydrophobicity of individual monomers.}, subject = {Supramolekulare Chemie}, language = {en} } @article{PericEngels1992, author = {Peric, M. and Engels, Bernd}, title = {Ab initio calculations of the vibronically averaged values for the hyperfine coupling constants in NH\(_2\), NHD and ND\(_2\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58941}, year = {1992}, abstract = {Vibronically averaged values for K =0 and K = 1 bending levels in the energy range between 0 and 25 000 cm\(^{-1}\) are computed for the \(^{14}\)N, H, and D atoms in NH\(_2\), NHD, and ND\(_2\) The pure ab initio electronic potentials, as well as those derived by fitting of experimentally observed band positions are employed. Effects of vibronic coupling and local perturbations of close-lying levels belanging to different electronic states are discussed.}, subject = {Organische Chemie}, language = {en} } @article{PericEngels1992, author = {Peric, M. and Engels, Bernd}, title = {Ab initio calculation of the vibronically averaged hyperfine coupling constants in the 1\(^2\)Π\(_u\) electronic state of CH\(_2 ^+\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58951}, year = {1992}, abstract = {The results of pure ab initio calculations of the hyperfine coupling constants for the 1 \(^2 \pi _u\) electronic state for various isotopomers of CHi in the energy range between 0 and 20 000 cm\(^{-1}\) are presented. Effects of vibronic and spin-orbit coupling are discussed.}, subject = {Organische Chemie}, language = {en} } @article{PericEngelsPeyerimhoff1991, author = {Peric, M. and Engels, Bernd and Peyerimhoff, S.D.}, title = {Ab initio investigation of the vibronic structure of the C\(_2\)H spectrum Calculation of the hyperfine coupling constants for the three lowest lying electronic states}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58901}, year = {1991}, abstract = {The hyperfine coupling constants (isotropic hfcc and four Cartesian components of the ani~ tropic tensor) are calculated for all three atoms of C\(_2\)H in its three lowest-lying electronic states at various molecu)ar geometries by means of the ab initio configuration interaction ( MRO.CI) method. The off-diagonal electronic matrix elements involving the two species ofthe A' symmetry are also computed. A diabatic transforrnation is perforrned Jeading to simple geometrical depen· dences of the hyperline coupling constants.}, subject = {Organische Chemie}, language = {en} } @article{PericEngelsPeyerimhoff1991, author = {Peric, M. and Engels, Bernd and Peyerimhoff, S.D.}, title = {Ab initio investigation of the vibronic structure of the C\(_2\)H spectrum Computation of the vibronically-averaged values for the Hyperfine Coupling Constants}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-58915}, year = {1991}, abstract = {The vibronically averaged values for tbe hyperfine coupling constants in the X\(^2 \sum\)-A\(^2 \Pi\) system of the ethynyl radical are computed by means of tbe ab initio metbod calculations. The results point at tbe importance of taking into account the coupling of a1l tbree electronic states in question ( I\(^2\)A', 2\(^2\)A', and 1\(^2\)A") for a reliable explanation of the available experimental findings. The mean values of the hfcc's for K = 0 and 1 levels in \(^{13}\)C\(_2\)H and \(^{13}\)C\(_2\)D in the energy range up to 6000 cm\(^{-1}\) are predicted.}, subject = {Organische Chemie}, language = {en} } @article{PetersKaiserFinketal.2021, author = {Peters, Simon and Kaiser, Lena and Fink, Julian and Schumacher, Fabian and Perschin, Veronika and Schlegel, Jan and Sauer, Markus and Stigloher, Christian and Kleuser, Burkhard and Seibel, Juergen and Schubert-Unkmeir, Alexandra}, title = {Click-correlative light and electron microscopy (click-AT-CLEM) for imaging and tracking azido-functionalized sphingolipids in bacteria}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-021-83813-w}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259147}, pages = {4300}, year = {2021}, abstract = {Sphingolipids, including ceramides, are a diverse group of structurally related lipids composed of a sphingoid base backbone coupled to a fatty acid side chain and modified terminal hydroxyl group. Recently, it has been shown that sphingolipids show antimicrobial activity against a broad range of pathogenic microorganisms. The antimicrobial mechanism, however, remains so far elusive. Here, we introduce 'click-AT-CLEM', a labeling technique for correlated light and electron microscopy (CLEM) based on the super-resolution array tomography (srAT) approach and bio-orthogonal click chemistry for imaging of azido-tagged sphingolipids to directly visualize their interaction with the model Gram-negative bacterium Neisseria meningitidis at subcellular level. We observed ultrastructural damage of bacteria and disruption of the bacterial outer membrane induced by two azido-modified sphingolipids by scanning electron microscopy and transmission electron microscopy. Click-AT-CLEM imaging and mass spectrometry clearly revealed efficient incorporation of azido-tagged sphingolipids into the outer membrane of Gram-negative bacteria as underlying cause of their antimicrobial activity.}, language = {en} } @phdthesis{Pfeifer2003, author = {Pfeifer, Robert-Michael}, title = {Synthese axialchiraler Liganden unter Verwendung des Lacton-Konzepts}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-6246}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2003}, abstract = {Das Ph{\"a}nomen der Axialchiralit{\"a}t von Biarylverbindungen wurde erstmalig 1922 beschrieben. Jedoch wurde die Suche nach stereoselektiven Zugangswegen zu dieser Stoffklasse lange Zeit vernachl{\"a}ssigt, obwohl derartige Verbindungen außergew{\"o}hnliche pharmakologische Aktivit{\"a}ten aufweisen und das Strukturelement der rotationsgehinderten Biarylachse in immer mehr chiralen Liganden, Auxiliaren und Reagenzien als stereogenes Element auftritt. Im Arbeitskreis Bringmann gelang durch die Entwicklung der 'Lacton-Methodik' ein konzeptionell v{\"o}llig neuartiger Zugang zu rotationsgehinderten und somit optisch aktiven Biarylen. Dieses Verfahren ist einzigartig, da es die beiden entscheidenden Reaktionsschritte, die Bildung der Biarylbindung sowie die Festlegung der Stereochemie, zeitlich voneinander separiert, was eine unabh{\"a}ngige Optimierung erlaubt. Die entscheidenden Schl{\"u}sselintermediate sind die konfigurativ noch nicht festgelegten Biaryllactone, welche nach Vorfixierung der beiden molekularen H{\"a}lften und mittels einer Esterbr{\"u}cke durch eine intramolekulare Kreuzkupplung erhalten werden. Diese Lactone sind nicht flach, sondern liegen in einem Gleichgewicht als racemische Mischung ihrer beiden atropisomeren Formen vor. Aus diesem Gleichgewicht ist es m{\"o}glich, mittels chiraler Nucleophile im Sinne einer dynamisch kinetischen Racematspaltung unter externer Stereoinduktion konfigurativ stabile Biaryle in atropisomerenreiner Form zu erhalten. In dieser Dissertation wurde das oben beschriebene Syntheseprinzip zur Synthese einer Reihe axialchiraler P,N- und Phosphinliganden genutzt. Des weiteren wurde die Etablierung von Zugangswegen zu dreifach axialchiralen tripodalen Liganden mit unterschiedlicher Topologie erreicht. Das katalytische Potential dieser verschiedenen Auxiliare wurde in einigen g{\"a}ngigen Testreaktionen wie Hydrosilylierungen, asymmetrischen Diethylzink-Additionen und atropselektiven Suzuki-Kupplungen evaluiert.}, subject = {Biaryle}, language = {de} } @article{PimentelElardoBubackGulderetal.2011, author = {Pimentel-Elardo, Sheila M. and Buback, Verena and Gulder, Tobias A. M. and Bugni, Tim S. and Reppart, Jason and Bringmann, Gerhard and Ireland, Chris M. and Schirmeister, Tanja and Hentschel, Ute}, title = {New Tetromycin Derivatives with Anti-Trypanosomal and Protease Inhibitory Activities}, series = {Marine drugs}, volume = {9}, journal = {Marine drugs}, number = {10}, doi = {10.3390/md9101682}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-141171}, pages = {1682-1697}, year = {2011}, abstract = {Four new tetromycin derivatives, tetromycins 1-4 and a previously known one, tetromycin B (5) were isolated from Streptomyces axinellae Pol001(T) cultivated from the Mediterranean sponge Axinella polypoides. Structures were assigned using extensive 1D and 2D NMR spectroscopy as well as HRESIMS analysis. The compounds were tested for antiparasitic activities against Leishmania major and Trypanosoma brucei, and for protease inhibition against several cysteine proteases such as falcipain, rhodesain, cathepsin L, cathepsin B, and viral proteases SARS-CoV M(pro), and PL(pro). The compounds showed antiparasitic activities against T. brucei and time-dependent inhibition of cathepsin L-like proteases with K(i) values in the low micromolar range.}, language = {en} } @article{PinznerKellerMutetal.2021, author = {Pinzner, Florian and Keller, Thorsten and Mut, J{\"u}rgen and Bechold, Julian and Seibel, J{\"u}rgen and Groll, J{\"u}rgen}, title = {Polyoxazolines with a vicinally double-bioactivated terminus for biomacromolecular affinity assessment}, series = {Sensors}, volume = {21}, journal = {Sensors}, number = {9}, issn = {1424-8220}, doi = {10.3390/s21093153}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-239530}, year = {2021}, abstract = {Interactions between proteins and carbohydrates with larger biomacromolecules, e.g., lectins, are usually examined using self-assembled monolayers on target gold surfaces as a simplified model measuring setup. However, most of those measuring setups are either limited to a single substrate or do not allow for control over ligand distance and spacing. Here, we develop a synthetic strategy, consisting of a cascade of a thioesterification, native chemical ligation (NCL) and thiol-ene reaction, in order to create three-component polymer conjugates with a defined double bioactivation at the chain end. The target architecture is the vicinal attachment of two biomolecule residues to the α telechelic end point of a polymer and a thioether group at the ω chain end for fixating the conjugate to a gold sensor chip surface. As proof-of-principle studies for affinity measurements, we demonstrate the interaction between covalently bound mannose and ConA in surface acoustic wave (SAW) and surface plasmon resonance (SPR) experiments.}, language = {en} }