TY - JOUR
A1 - Krahfuss, Mirjam J.
A1 - Radius, Udo
T1 - N‐Heterocyclic Silylene Main Group Element Chemistry: Adduct Formation, Insertion into E−X Bonds and Cyclization of Organoazides
JF - European Journal of Inorganic Chemistry
N2 - Investigations concerning the reactivity of the N‐heterocyclic silylene Dipp\(_{2}\)NHSi (1, 1,3‐bis(2,6‐diisopropylphenyl)‐1,3‐diaza‐2‐silacyclopent‐4‐en‐2‐ylidene) towards selected alanes and boranes, elemental halides X\(_{2}\) (X=Br, I), selected halide containing substrates such as tin chlorides and halocarbons, as well as organoazides are presented. The NHSi adducts Dipp\(_{2}\)NHSi⋅AlI\(_{3}\) (2), Dipp\(_{2}\)NHSi⋅Al(C\(_{6}\)F\(_{5}\))\(_{3}\) (3), and Dipp\(_{2}\)NHSi⋅B(C\(_{6}\)F\(_{5}\))\(_{3}\) (4) were formed by the reaction of Dipp\(_{2}\)NHSi with the corresponding Lewis acids AlI\(_{3}\), Al(C\(_{6}\)F\(_{6}\))\(_{3}\) and B(C\(_{6}\)F\(_{5}\))\(_{3}\). Adducts 3 and 4 were tested with respect to their ability to activate small organic molecules, but no frustrated Lewis pair reactivity was observed. Reactions of Dipp\(_{2}\)NHSi with Br\(_{2}\), I\(_{2}\), Ph\(_{2}\)SnCl\(_{2}\) and Me\(_{3}\)SnCl led to formation of Dipp\(_{2}\)NHSiBr\(_{2}\) (5), Dipp\(_{2}\)NHSiI\(_{2}\) (6), Dipp\(_{2}\)NHSiCl\(_{2}\) (7) and {(Me\(_{3}\)Sn)N(Dipp)CH}\(_{2}\) (8), respectively. The reaction with the halocarbons methyl iodide, benzyl chloride, and benzyl bromide afforded the insertion products Dipp\(_{2}\)NHSi(I)(CH\(_{3}\)) (9), Dipp\(_{2}\)NHSi(Cl)(CH\(_{2}\)Ph) (10) and Dipp\(_{2}\)NHSi(Br)(CH\(_{2}\)Ph) (11). Reaction of Dipp\(_{2}\)NHSi with the organoazides Ad‐N\(_{3}\) (Ad=adamantyl) and TMS‐N\(_{3}\) (TMS=trimethylsilyl) led to the formation of 1‐Dipp\(_{2}\)NHSi‐2,5‐bis(adamantyl)‐tetrazoline (12) and bis(trimethylsilyl)amido azido silane (13), respectively. For 2,6‐(diphenyl)phenyl‐N\(_{3}\) C−H activation occurs and a cyclosilamine 14 was isolated.
KW - arbenes
KW - E−X bond activation
KW - acid/base adducts
KW - Organoazides
KW - Silylenes
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224507
VL - 2021
IS - 6
SP - 548
EP - 561
ER -
TY - JOUR
A1 - Renner, Rebecca
A1 - Mahlmeister, Bernhard
A1 - Anhalt, Olga
A1 - Stolte, Matthias
A1 - Würthner, Frank
T1 - Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area
JF - Chemistry - A European Journal
N2 - A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross-coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π-core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X-ray analyses of phenyl-, naphthyl- and pyrenyl-functionalized PBIs reveal interlocked π-π-stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol\(^{−1}\) for the tetraphenyl- and tetra-2-naphthyl-substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol\(^{−1}\). The redox and optical properties of these core-twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo-enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.
KW - Suzuki coupling
KW - perylenebisimide dyes
KW - circular polarized luminescence
KW - chirality
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-249070
VL - 27
IS - 46
SP - 11997
EP - 12006
ER -
TY - JOUR
A1 - Rupp, Mira T.
A1 - Auvray, Thomas
A1 - Hanan, Garry S.
A1 - Kurth, Dirk G.
T1 - Electrochemical and photophysical study of homoleptic and heteroleptic methylated Ru(II) Bis-terpyridine complexes
JF - European Journal of Inorganic Chemistry
N2 - In this study, we investigate the impact of N-methylation on the electronic and photophysical properties of both homoleptic and heteroleptic Ru(II) bis-terpyridine complexes based on the recently reported ligand 4’-(4-bromophenyl)-4,4’’’: 4’’,4’’’’-dipyr-idinyl-2,2’ : 6’,2’’-terpyridine (Bipytpy), with pyridine substituents in the 4- and 4’’-position. The first reduction of the methylated complexes takes place at the pyridinium site and is observed as multi-electron process. Following N-methylation, the complexes exhibit higher luminescence quantum yields and longer excited-state lifetimes. Interestingly, the photophysical properties of the heteroleptic and homoleptic complexes are rather similar. TD-DFT calculations support the experimental results. Furthermore, the complexes are tested as photosensitizers for photocatalytic hydrogen production, as the parent complex 1[Ru(Bipytpy)(Tolyltpy)](PF \(_6\))\(_2\) (Tolyltpy: 4’-tolyl-2,2’: 6’,2’’-terpyri-dine) was recently shown to be active and highly stable underphotocatalytic conditions. However, the methylated complexes reported herein are inactive as photosensitizers under the chosen conditions, presumably due to loss of the methyl groups, converting them to the non-methylated parent complexes.
KW - Ruthenium
KW - Luminescence
KW - Electrochemistry
KW - Ligand effects
KW - Photocatalysis
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-248769
VL - 2021
IS - 28
SP - 2822
EP - 2829
ER -
TY - JOUR
A1 - Chen, Chunguang
A1 - Rawat, Divya
A1 - Samikannu, Balaji
A1 - Bender, Markus
A1 - Preissner, Klaus T.
A1 - Linn, Thomas
T1 - Platelet glycoprotein VI‐dependent thrombus stabilization is essential for the intraportal engraftment of pancreatic islets
JF - American Journal of Transplantation
N2 - Platelet activation and thrombus formation have been implicated to be detrimental for intraportal pancreatic islet transplants. The platelet‐specific collagen receptor glycoprotein VI (GPVI) plays a key role in thrombosis through cellular activation and the subsequent release of secondary mediators. In aggregometry and in a microfluidic dynamic assay system modeling flow in the portal vein, pancreatic islets promoted platelet aggregation and triggered thrombus formation, respectively. While platelet GPVI deficiency did not affect the initiation of these events, it was found to destabilize platelet aggregates and thrombi in this process. Interestingly, while no major difference was detected in early thrombus formation after intraportal islet transplantation, genetic GPVI deficiency or acute anti‐GPVI treatment led to an inferior graft survival and function in both syngeneic mouse islet transplantation and xenogeneic human islet transplantation models. These results demonstrate that platelet GPVI signaling is indispensable in stable thrombus formation induced by pancreatic islets. GPVI deficiency resulted in thrombus destabilization and inferior islet engraftment indicating that thrombus formation is necessary for a successful intraportal islet transplantation in which platelets are active modulators.
KW - basic (laboratory) research / science
KW - coagulation and hemostasis
KW - graft survival
KW - islet transplantation
KW - molecular biology
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224471
VL - 21
SP - 2079
EP - 2089
ER -
TY - JOUR
A1 - Cullmann, Katharina
A1 - Jahn, Magdalena
A1 - Spindler, Markus
A1 - Schenk, Franziska
A1 - Manukjan, Georgi
A1 - Mucci, Adele
A1 - Steinemann, Doris
A1 - Boller, Klaus
A1 - Schulze, Harald
A1 - Bender, Markus
A1 - Moritz, Thomas
A1 - Modlich, Ute
T1 - Forming megakaryocytes from murine‐induced pluripotent stem cells by the inducible overexpression of supporting factors
JF - Research and Practice in Thrombosis and Haemostasis
N2 - Background
Platelets are small anucleate cells that circulate in the blood in a resting state but can be activated by external cues. In case of need, platelets from blood donors can be transfused. As an alternative source, platelets can be produced from induced pluripotent stem cells (iPSCs); however, recovered numbers are low.
Objectives
To optimize megakaryocyte (MK) and platelet output from murine iPSCs, we investigated overexpression of the transcription factors GATA‐binding factor 1 (GATA1); nuclear factor, erythroid 2; and pre–B‐cell leukemia transcription factor 1 (Pbx1) and a hyperactive variant of the small guanosine triphosphatase RhoA (RhoAhc).
Methods
To avoid off‐target effects, we generated iPSCs carrying the reverse tetracycline‐responsive transactivator M2 (rtTA‐M2) in the Rosa26 locus and expressed the factors from Tet‐inducible gammaretroviral vectors. Differentiation of iPSCs was initiated by embryoid body (EB) formation. After EB dissociation, early hematopoietic progenitors were enriched and cocultivated on OP9 feeder cells with thrombopoietin and stem cell factor to induce megakaryocyte (MK) differentiation.
Results
Overexpression of GATA1 and Pbx1 increased MK output 2‐ to 2.5‐fold and allowed prolonged collection of MK. Cytologic and ultrastructural analyses identified typical MK with enlarged cells, multilobulated nuclei, granule structures, and an internal membrane system. However, GATA1 and Pbx1 expression did not improve MK maturation or platelet release, although in vitro–generated platelets were functional in spreading on fibrinogen or collagen‐related peptide.
Conclusion
We demonstrate that the use of rtTA‐M2 transgenic iPSCs transduced with Tet‐inducible retroviral vectors allowed for gene expression at later time points during differentiation. With this strategy we could identify factors that increased in vitro MK production.
KW - genetic modification
KW - iPS cells
KW - megakaryocytes
KW - retroviral vectors
KW - Tet‐inducible system
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224565
VL - 5
IS - 1
SP - 111
EP - 124
ER -
TY - JOUR
A1 - Boff, Samuel
A1 - Friedel, Anna
T1 - Dynamics of nest occupation and homing of solitary bees in painted trap nests
JF - Ecological Entomology
N2 - 1. The oil‐collecting bee Centris analis (Fabricius, 1804) is an important pollinator for the Neotropical region. The species can be attracted to nest in human‐made cavities. Such trap nests or insect hotels offer the opportunity to study the behaviour of populations in semifield conditions.
2. We studied a newly established trap nest aggregation of C. analis in Mato Grosso do Sul, Brazil and tested the effect that differentially painted nesting options have on the rate of nest foundation, and on the ability of relocating the nest when returning from a foraging trip (homing behaviour). Moreover, we tested if the duration of foraging trips decreased with time.
3. We found that females preferred to nest in painted nests compared to unpainted nests, with blue nests being the most occupied ones, followed by purple, yellow, white, and green. Furthermore, bees improved their homing behaviour with time, however, nest colour did not seem to have an effect on this process. Moreover, we found that bees reduce the duration of their foraging trips with time. This could be an indicator of improved foraging efficiency through learning.
4. These findings could inform a new and fruitful line of research on the behaviour and ecology of trap nesting solitary bees.
KW - foraging activities
KW - nesting ecology
KW - oil bees
KW - painted nest preference
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-224605
VL - 46
IS - 2
SP - 496
EP - 499
ER -
TY - JOUR
A1 - Welker, Armin
A1 - Kersten, Christian
A1 - Müller, Christin
A1 - Madhugiri, Ramakanth
A1 - Zimmer, Collin
A1 - Müller, Patrick
A1 - Zimmermann, Robert
A1 - Hammerschmidt, Stefan
A1 - Maus, Hannah
A1 - Ziebuhr, John
A1 - Sotriffer, Christoph
A1 - Schirmeister, Tanja
T1 - Structure‐Activity Relationships of Benzamides and Isoindolines Designed as SARS‐CoV Protease Inhibitors Effective against SARS‐CoV‐2
JF - ChemMedChem
N2 - Inhibition of coronavirus (CoV)‐encoded papain‐like cysteine proteases (PL\(^{pro}\)) represents an attractive strategy to treat infections by these important human pathogens. Herein we report on structure‐activity relationships (SAR) of the noncovalent active‐site directed inhibitor (R)‐5‐amino‐2‐methyl‐N‐(1‐(naphthalen‐1‐yl)ethyl) benzamide (2 b), which is known to bind into the S3 and S4 pockets of the SARS‐CoV PL\(^{pro}\). Moreover, we report the discovery of isoindolines as a new class of potent PL\(^{pro}\) inhibitors. The studies also provide a deeper understanding of the binding modes of this inhibitor class. Importantly, the inhibitors were also confirmed to inhibit SARS‐CoV‐2 replication in cell culture suggesting that, due to the high structural similarities of the target proteases, inhibitors identified against SARS‐CoV PL\(^{pro}\) are valuable starting points for the development of new pan‐coronaviral inhibitors.
KW - antiviral agents
KW - computational chemistry
KW - drug design
KW - protease inhibitors
KW - structure-activity relationships
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225700
VL - 16
IS - 2
SP - 340
EP - 354
ER -
TY - JOUR
A1 - Romero‐Olmedo, Addi J.
A1 - Schulz, Axel R.
A1 - Huber, Magdalena
A1 - Brehm, Corinna U.
A1 - Chang, Hyun‐Dong
A1 - Chiarolla, Cristina M.
A1 - Bopp, Tobias
A1 - Skevaki, Chrysanthi
A1 - Berberich‐Siebelt, Friederike
A1 - Radbruch, Andreas
A1 - Mei, Henrik E.
A1 - Lohoff, Michael
T1 - Deep phenotypical characterization of human CD3\(^{+}\)CD56\(^{+}\) T cells by mass cytometry
JF - European Journal of Immunology
N2 - CD56\(^{+}\) T cells are a group of pro‐inflammatory CD3\(^{+}\) lymphocytes with characteristics of natural killer cells, being involved in antimicrobial immune defense. Here, we performed deep phenotypic profiling of CD3\(^{+}\)CD56\(^{+}\) cells in peripheral blood of normal human donors and individuals sensitized to birch‐pollen or/and house dust mite by high‐dimensional mass cytometry combined with manual and computational data analysis. A co‐regulation between major conventional T‐cell subsets and their respective CD3\(^{+}\)CD56\(^{+}\) cell counterparts appeared restricted to CD8\(^{+}\), MAIT, and TCRγδ\(^{+}\) T‐cell compartments. Interestingly, we find a co‐regulation of several CD3\(^{+}\)CD56\(^{+}\) cell subsets in allergic but not in healthy individuals. Moreover, using FlowSOM, we distinguished a variety of CD56\(^{+}\) T‐cell phenotypes demonstrating a hitherto underestimated heterogeneity among these cells. The novel CD3\(^{+}\)CD56\(^{+}\) subset description comprises phenotypes superimposed with naive, memory, type 1, 2, and 17 differentiation stages, in part represented by a phenotypical continuum. Frequencies of two out of 19 CD3\(^{+}\)CD56\(^{+}\) FlowSOM clusters were significantly diminished in allergic individuals, demonstrating less frequent presence of cells with cytolytic, presumably protective, capacity in these donors consistent with defective expansion or their recruitment to the affected tissue. Our results contribute to defining specific cell populations to be targeted during therapy for allergic conditions.
KW - allergy
KW - CD56
KW - human
KW - mass cytometry
KW - T cells
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225699
VL - 51
IS - 3
SP - 672
EP - 681
ER -
TY - JOUR
A1 - Doryab, Ali
A1 - Taskin, Mehmet Berat
A1 - Stahlhut, Philipp
A1 - Schröppel, Andreas
A1 - Wagner, Darcy E.
A1 - Groll, Jürgen
A1 - Schmid, Otmar
T1 - A Biomimetic, Copolymeric Membrane for Cell‐Stretch Experiments with Pulmonary Epithelial Cells at the Air‐Liquid Interface
JF - Advanced Functional Materials
N2 - Chronic respiratory diseases are among the leading causes of death worldwide, but only symptomatic therapies are available for terminal illness. This in part reflects a lack of biomimetic in vitro models that can imitate the complex environment and physiology of the lung. Here, a copolymeric membrane consisting of poly(ε‐)caprolactone and gelatin with tunable properties, resembling the main characteristics of the alveolar basement membrane is introduced. The thin bioinspired membrane (≤5 μm) is stretchable (up to 25% linear strain) with appropriate surface wettability and porosity for culturing lung epithelial cells under air–liquid interface conditions. The unique biphasic concept of this membrane provides optimum characteristics for initial cell growth (phase I) and then switch to biomimetic properties for cyclic cell‐stretch experiments (phase II). It is showed that physiologic cyclic mechanical stretch improves formation of F‐actin cytoskeleton filaments and tight junctions while non‐physiologic over‐stretch induces cell apoptosis, activates inflammatory response (IL‐8), and impairs epithelial barrier integrity. It is also demonstrated that cyclic physiologic stretch can enhance the cellular uptake of nanoparticles. Since this membrane offers considerable advantages over currently used membranes, it may lead the way to more biomimetic in vitro models of the lung for translation of in vitro response studies into clinical outcome.
KW - alveolar‐capillary barrier
KW - cyclic mechanical stretch
KW - hybrid polymers
KW - in vitro cell‐stretch model
KW - tunable ultra‐thin biphasic membrane
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225645
VL - 31
IS - 10
ER -
TY - JOUR
A1 - Hanft, Anna
A1 - Radacki, Krzysztof
A1 - Lichtenberg, Crispin
T1 - Cationic Bismuth Aminotroponiminates: Charge Controls Redox Properties
JF - Chemistry – A European Journal
N2 - The behavior of the redox‐active aminotroponiminate (ATI) ligand in the coordination sphere of bismuth has been investigated in neutral and cationic compounds, [Bi(ATI)\(_{3}\)] and [Bi(ATI)\(_{2}\)L\(_{n}\)][A] (L=neutral ligand; n=0, 1; A=counteranion). Their coordination chemistry in solution and in the solid state has been analyzed through (variable‐temperature) NMR spectroscopy, line‐shape analysis, and single‐crystal X‐ray diffraction analyses, and their Lewis acidity has been evaluated by using the Gutmann–Beckett method (and modifications thereof). Cyclic voltammetry, in combination with DFT calculations, indicates that switching between ligand‐ and metal‐centered redox events is possible by altering the charge of the compounds from 0 in neutral species to +1 in cationic compounds. This adds important facets to the rich redox chemistry of ATIs and to the redox chemistry of bismuth compounds, which is, so far, largely unexplored.
KW - aminotroponiminates
KW - bismuth
KW - cationic species
KW - redox chemistry
KW - redox-active ligands
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225669
VL - 27
IS - 20
SP - 6230
EP - 6239
ER -
TY - JOUR
A1 - Budiman, Yudha P.
A1 - Lorenzen, Sabine
A1 - Liu, Zhiqiang
A1 - Radius, Udo
A1 - Marder, Todd B.
T1 - Base‐Free Pd‐Catalyzed C−Cl Borylation of Fluorinated Aryl Chlorides
JF - Chemistry – A European Journal
N2 - Catalytic C−X borylation of aryl halides containing two ortho‐fluorines has been found to be challenging, as most previous methods require stoichiometric amounts of base and the polyfluorinated aryl boronates suffer from protodeboronation, which is accelerated by ortho‐fluorine substituents. Herein, we report that a combination of Pd(dba)2 (dba=dibenzylideneacetone) with SPhos (2‐dicyclohexylphosphino‐2’,6’‐dimethoxybiphenyl) as a ligand is efficient to catalyze the C‐Cl borylation of aryl chlorides containing two ortho‐fluorine substituents. This method, conducted under base‐free conditions, is compatible with the resulting di‐ortho‐fluorinated aryl boronate products which are sensitive to base.
KW - boronate ester
KW - borylation
KW - cross-coupling
KW - fluoroarene
KW - palladium-catalyzed
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225687
VL - 27
IS - 11
SP - 3869
EP - 3874
ER -
TY - JOUR
A1 - Weich, Alexander
A1 - Werner, Rudolf A.
A1 - Buck, Andreas K.
A1 - Hartrampf, Philipp E.
A1 - Serfling, Sebastian E.
A1 - Scheurlen, Michael
A1 - Wester, Hans-Jürgen
A1 - Meining, Alexander
A1 - Kircher, Stefan
A1 - Higuchi, Takahiro
A1 - Pomper, Martin G.
A1 - Rowe, Steven P.
A1 - Lapa, Constantin
A1 - Kircher, Malte
T1 - CXCR4-Directed PET/CT in Patients with Newly Diagnosed Neuroendocrine Carcinomas
JF - Diagnostics
N2 - We aimed to elucidate the diagnostic potential of the C-X-C motif chemokine receptor 4 (CXCR4)-directed positron emission tomography (PET) tracer \(^{68}\)Ga-Pentixafor in patients with poorly differentiated neuroendocrine carcinomas (NEC), relative to the established reference standard \(^{18}\)F-FDG PET/computed tomography (CT). In our database, we retrospectively identified 11 treatment-naïve patients with histologically proven NEC, who underwent \(^{18}\)F-FDG and CXCR4-directed PET/CT for staging and therapy planning. The images were analyzed on a per-patient and per-lesion basis and compared to immunohistochemical staining (IHC) of CXCR4 from PET-guided biopsies. \(^{68}\)Ga-Pentixafor visualized tumor lesions in 10/11 subjects, while \(^{18}\)F-FDG revealed sites of disease in all 11 patients. Although weak to moderate CXCR4 expression could be corroborated by IHC in 10/11 cases, \(^{18}\)F-FDG PET/CT detected significantly more tumor lesions (102 vs. 42; total lesions, n = 107; p < 0.001). Semi-quantitative analysis revealed markedly higher 18F-FDG uptake as compared to \(^{68}\)Ga-Pentixafor (maximum and mean standardized uptake values (SUV) and tumor-to-background ratios (TBR) of cancerous lesions, SUVmax: 12.8 ± 9.8 vs. 5.2 ± 3.7; SUVmean: 7.4 ± 5.4 vs. 3.1 ± 3.2, p < 0.001; and, TBR 7.2 ± 7.9 vs. 3.4 ± 3.0, p < 0.001). Non-invasive imaging of CXCR4 expression in NEC is inferior to the reference standard \(^{18}\)F-FDG PET/CT.
KW - CXCR4
KW - NET
KW - NEC
KW - 68Ga-Pentixafor
KW - 18F-FDG
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234231
SN - 2075-4418
VL - 11
IS - 4
ER -
TY - JOUR
A1 - Mönius, Katja
T1 - Eigenvalues of zero-divisor graphs of finite commutative rings
JF - Journal of Algebraic Combinatorics
N2 - We investigate eigenvalues of the zero-divisor graph Γ(R) of finite commutative rings R and study the interplay between these eigenvalues, the ring-theoretic properties of R and the graph-theoretic properties of Γ(R). The graph Γ(R) is defined as the graph with vertex set consisting of all nonzero zero-divisors of R and adjacent vertices x, y whenever xy=0. We provide formulas for the nullity of Γ(R), i.e., the multiplicity of the eigenvalue 0 of Γ(R). Moreover, we precisely determine the spectra of \(\Gamma ({\mathbb {Z}}_p \times {\mathbb {Z}}_p \times {\mathbb {Z}}_p)\) and \(\Gamma ({\mathbb {Z}}_p \times {\mathbb {Z}}_p \times {\mathbb {Z}}_p \times {\mathbb {Z}}_p)\) for a prime number p. We introduce a graph product ×Γ with the property that Γ(R)≅Γ(R\(_1\))×Γ⋯×ΓΓ(R\(_r\)) whenever R≅R\(_1\)×⋯×R\(_r\). With this product, we find relations between the number of vertices of the zero-divisor graph Γ(R), the compressed zero-divisor graph, the structure of the ring R and the eigenvalues of Γ(R).
KW - EJMA-D-19-00287
KW - Zero-divisor graphs
KW - Graph eigenvalues
KW - Graphnullity
KW - Graph products
KW - Local rings
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-232792
SN - 0925-9899
VL - 54
ER -
TY - JOUR
A1 - Grob, Robin
A1 - Tritscher, Clara
A1 - Grübel, Kornelia
A1 - Stigloher, Christian
A1 - Groh, Claudia
A1 - Fleischmann, Pauline N.
A1 - Rössler, Wolfgang
T1 - Johnston's organ and its central projections in Cataglyphis desert ants
JF - Journal of Comparative Neurology
N2 - The Johnston's organ (JO) in the insect antenna is a multisensory organ involved in several navigational tasks including wind‐compass orientation, flight control, graviception, and, possibly, magnetoreception. Here we investigate the three dimensional anatomy of the JO and its neuronal projections into the brain of the desert ant Cataglyphis, a marvelous long‐distance navigator. The JO of C. nodus workers consists of 40 scolopidia comprising three sensory neurons each. The numbers of scolopidia slightly vary between different sexes (female/male) and castes (worker/queen). Individual scolopidia attach to the intersegmental membrane between pedicel and flagellum of the antenna and line up in a ring‐like organization. Three JO nerves project along the two antennal nerve branches into the brain. Anterograde double staining of the antennal afferents revealed that JO receptor neurons project to several distinct neuropils in the central brain. The T5 tract projects into the antennal mechanosensory and motor center (AMMC), while the T6 tract bypasses the AMMC via the saddle and forms collaterals terminating in the posterior slope (PS) (T6I), the ventral complex (T6II), and the ventrolateral protocerebrum (T6III). Double labeling of JO and ocellar afferents revealed that input from the JO and visual information from the ocelli converge in tight apposition in the PS. The general JO anatomy and its central projection patterns resemble situations in honeybees and Drosophila. The multisensory nature of the JO together with its projections to multisensory neuropils in the ant brain likely serves synchronization and calibration of different sensory modalities during the ontogeny of navigation in Cataglyphis.
KW - ant brain
KW - chordotonal organ
KW - graviception
KW - magnetic compass
KW - multisensory integration
KW - navigation
KW - wind compass
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225679
VL - 529
IS - 8
SP - 2138
EP - 2155
ER -
TY - JOUR
A1 - Full, Julian
A1 - Panchal, Santosh P.
A1 - Götz, Julian
A1 - Krause, Ana‐Maria
A1 - Nowak‐Król, Agnieszka
T1 - Modular Synthesis of Organoboron Helically Chiral Compounds: Cutouts from Extended Helices
JF - Angewandte Chemie International Edition
N2 - Two types of helically chiral compounds bearing one and two boron atoms were synthesized by a modular approach. Formation of the helical scaffolds was executed by the introduction of boron to flexible biaryl and triaryl derived from small achiral building blocks. All‐ortho‐fused azabora[7]helicenes feature exceptional configurational stability, blue or green fluorescence with quantum yields (Φ\(_{fl}\)) of 18–24 % in solution, green or yellow solid‐state emission (Φ\(_{fl}\) up to 23 %), and strong chiroptical response with large dissymmetry factors of up to 1.12×10\(^{-2}\). Azabora[9]helicenes consisting of angularly and linearly fused rings are blue emitters exhibiting Φ\(_{fl}\) of up to 47 % in CH\(_{2}\)Cl\(_{2}\) and 25 % in the solid state. As revealed by the DFT calculations, their P–M interconversion pathway is more complex than that of H1. Single‐crystal X‐ray analysis shows clear differences in the packing arrangement of methyl and phenyl derivatives. These molecules are proposed as primary structures of extended helices.
KW - chirality
KW - circular dichroism
KW - fluorescence
KW - helicene
KW - organoboron
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225775
VL - 60
IS - 8
SP - 4350
EP - 4357
ER -
TY - JOUR
A1 - Urlaub, Jonas
A1 - Kaiser, Reinhard P.
A1 - Scherf‐Clavel, Oliver
A1 - Bolm, Carsten
A1 - Holzgrabe, Ulrike
T1 - Investigation of isomerization of dexibuprofen in a ball mill using chiral capillary electrophoresis
JF - Electrophoresis
N2 - Besides the racemate, the S‐enantiomer of ibuprofen (Ibu) is used for the treatment of inflammation and pain. Since the configurational stability of S‐Ibu in solid state is of interest, it was studied by means of ball milling experiments. For the evaluation of the enantiomeric composition, a chiral CE method was developed and validated according to the ICH guideline Q2(R1). The addition of Mg\(^{2+}\), Ca\(^{2+}\), or Zn\(^{2+}\) ions to the background electrolyte (BGE) was found to improve Ibu enantioresolution. Chiral separation of Ibu enantiomers was achieved on a 60.2 cm (50.0 cm effective length) x 75 μm fused‐silica capillary using a background electrolyte (BGE) composed of 50 mM sodium acetate, 10 mM magnesium acetate tetrahydrate, and 35 mM heptakis‐(2,3,6‐tri‐O‐methyl)‐β‐cyclodextrin (TM‐β‐CD) as chiral selector. The quantification of R‐Ibu in the mixture was performed using the normalization procedure. Linearity was evaluated in the range of 0.68–5.49% R‐Ibu (R\(^{2}\) = 0.999), recovery was found to range between 97 and 103%, the RSD of intra‐ and interday precision below 2.5%, and the limit of quantification for R‐ in S‐Ibu was calculated to be 0.21% (extrapolated) and 0.15% (dilution of racemic ibuprofen), respectively. Isomerization of S‐Ibu was observed under basic conditions by applying long milling times and high milling frequencies.
KW - capillary electrophoresis
KW - chiral separation
KW - Ibuprofen
KW - isomerization
KW - validation
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225852
VL - 42
IS - 17-18
SP - 1790
EP - 1799
ER -
TY - JOUR
A1 - Zahoranová, Anna
A1 - Luxenhofer, Robert
T1 - Poly(2‐oxazoline)‐ and Poly(2‐oxazine)‐Based Self‐Assemblies, Polyplexes, and Drug Nanoformulations—An Update
JF - Advanced Healthcare Materials
N2 - For many decades, poly(2‐oxazoline)s and poly(2‐oxazine)s, two closely related families of polymers, have led the life of a rather obscure research topic with only a few research groups world‐wide working with them. This has changed in the last five to ten years, presumably triggered significantly by very promising clinical trials of the first poly(2‐oxazoline)‐based drug conjugate. The huge chemical and structural toolbox poly(2‐oxazoline)s and poly(2‐oxazine)s has been extended very significantly in the last few years, but their potential still remains largely untapped. Here, specifically, the developments in macromolecular self‐assemblies and non‐covalent drug delivery systems such as polyplexes and drug nanoformulations based on poly(2‐oxazoline)s and poly(2‐oxazine)s are reviewed. This highly dynamic field benefits particularly from the extensive synthetic toolbox poly(2‐oxazoline)s and poly(2‐oxazine)s offer and also may have the largest potential for a further development. It is expected that the research dynamics will remain high in the next few years, particularly as more about the safety and therapeutic potential of poly(2‐oxazoline)s and poly(2‐oxazine)s is learned.
KW - block copolymers
KW - colloids
KW - cytotoxicity
KW - drug delivery
KW - micelles
KW - microphase separation
KW - thermogelling
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225833
VL - 10
IS - 6
ER -
TY - JOUR
A1 - Hojsgaard, Diego
A1 - Schartl, Manfred
T1 - Skipping sex: A nonrecombinant genomic assemblage of complementary reproductive modules
JF - BioEssays
N2 - The unusual occurrence and developmental diversity of asexual eukaryotes remain a puzzle. De novo formation of a functioning asexual genome requires a unique assembly of sets of genes or gene states to disrupt cellular mechanisms of meiosis and gametogenesis, and to affect discrete components of sexuality and produce clonal or hemiclonal offspring. We highlight two usually overlooked but essential conditions to understand the molecular nature of clonal organisms, that is, a nonrecombinant genomic assemblage retaining modifiers of the sexual program, and a complementation between altered reproductive components. These subtle conditions are the basis for physiologically viable and genetically balanced transitions between generations. Genomic and developmental evidence from asexual animals and plants indicates the lack of complementation of molecular changes in the sexual reproductive program is likely the main cause of asexuals' rarity, and can provide an explanatory frame for the developmental diversity and lability of developmental patterns in some asexuals as well as for the discordant time to extinction estimations.
KW - amphimixis
KW - apomixis
KW - automixis
KW - gynogenesis
KW - hybridogenesis
KW - parthenogenesis
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225818
VL - 43
IS - 1
ER -
TY - JOUR
A1 - Budiman, Yudha P.
A1 - Westcott, Stephen A.
A1 - Radius, Udo
A1 - Marder, Todd B.
T1 - Fluorinated Aryl Boronates as Building Blocks in Organic Synthesis
JF - Advanced Synthesis & Catalysis
N2 - Organoboron compounds are well known building blocks for many organic reactions. However, under basic conditions, polyfluorinated aryl boronic acid derivatives suffer from instability issues that are accelerated in compounds containing an ortho‐fluorine group, which result in the formation of the corresponding protodeboronation products. Therefore, a considerable amount of research has focused on novel methodologies to synthesize these valuable compounds while avoiding the protodeboronation issue. This review summarizes the latest developments in the synthesis of fluorinated aryl boronic acid derivatives and their applications in cross‐coupling reactions and other transformations.
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KW - homogeneous catalysis
KW - boron reagents
KW - boronates
KW - fluorine
KW - fluoroarene
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225908
VL - 363
IS - 9
SP - 2224
EP - 2255
ER -
TY - JOUR
A1 - Ravat, Prince
T1 - Carbo[n]helicenes Restricted to Enantiomerize: An Insight into the Design Process of Configurationally Stable Functional Chiral PAHs
JF - Chemistry – A European Journal
N2 - The most important stereodynamic feature of carbo[n]helicenes is the interconversion of their enantiomers. The Gibbs activation energy (ΔG≠(T)) of this process, which determines the rate of enantiomerization, dictates the configurational stability of [n]helicenes. High values of ΔG≠(T) are required for applications of functional chiral molecules incorporating [n]helicenes or helicene substructures. This minireview provides an overview of the mechanism, recent developments, and factors affecting the enantiomerization of [n]helicenes, which will accelerate the design process of configurationally stable functional chiral molecules based on helicene substructures. Additionally, this minireview addresses the misconception and irregularities in the recent literature on how the terms “racemization” and “enantiomerization” are used as well as how the activation parameters are calculated for [n]helicenes and related compounds.
KW - [n]helicenes
KW - configurational stability
KW - enantiomerization
KW - Gibbs activation energy
KW - racemization
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225871
VL - 27
IS - 12
SP - 3957
EP - 3967
ER -