@article{VenjakobLeonhardtKlein2020,
  author    = {Venjakob, Christine and Leonhardt, Sara and Klein, Alexandra-Maria},
  title     = {Inter-individual nectar chemistry changes of field scabious, Knautia arvensis},
  series = {Insects},
  volume    = {11},
  journal   = {Insects},
  number    = {2},
  issn      = {2075-4450},
  doi       = {10.3390/insects11020075},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200866},
  year      = {2020},
  abstract  = {Nectar is crucial to maintain plant-pollinator mutualism. Nectar quality (nutritional composition) can vary strongly between individuals of the same plant species. The factors driving such inter-individual variation have however not been investigated closer. We investigated nectar quality of field scabious, Knautia arvensis in different grassland plant communities varying in species composition and richness to assess whether nectar quality can be affected by the surrounding plant community. We analyzed (with high performance liquid chromatography) the content of carbohydrates, overall amino acids, and essential amino acids. Amino acid and carbohydrate concentrations and proportions varied among plant individuals and with the surrounding plant community but were not related to the surrounding plant species richness. Total and individual carbohydrate concentrations were lowest, while proportions of the essential amino acids, valine, isoleucine, leucine (all phagostimulatory), and lysine were highest in plant species communities of the highest diversity. Our results show that K. arvensis nectar chemistry varies with the composition of the surrounding plant community, which may alter the taste and nutritional value and thus affect the plant's visitor spectrum and visitation rate. However, the strong inter-individual variation in nectar quality requires additional studies (e.g., in semi-field studies) to disentangle different biotic and abiotic factors contributing to inter-individual nectar chemistry in a plant-community context.},
  language  = {en}
}
@phdthesis{Meyer2015,
  author    = {Meyer, Frank},
  title     = {Soft X-ray Spectroscopic Study of Amino Acid and Salt Solutions},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-124295},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {This thesis focuses on the investigation of the electronic structure of amino acids and salts in aqueous solution using X-ray spectroscopic methods. Both material groups are of fundamental importance with regards to many physiological reactions, especially for the Hofmeister effect which describes the solubility of proteins in salt solutions. Hence, the investigation of the electronic structure of amino acids and the influence of ions on the hydrogen bonding network of liquid water are important milestones to a deeper understanding of the Hofmeister series. Besides investigating the electronic structure of amino acids in aqueous solution, the spectra were used to develop a building block model of the spectral fingerprints of the functional groups and were compared to spectral signatures of suitable reference molecules. In the framework of this thesis, it is shown that the building block approach is a useful tool with allows the interpretation of spectral signatures of considerably more complex molecules In this work, the focus lies on the investigation of the occupied and unoccupied electronic states of molecules in solid state, as well as in aqueous solution. Hereby, different X-ray spectroscopic methods were applied. X-ray emission spectroscopy (XES) was used to probe the occupied electronic structure of the solution, while the unoccupied electronic structure was addressed by using X-ray absorption spectroscopy (XAS). Finally, resonant inelastic X-ray scattering (RIXS) as a combination of XAS and XES measurements provides the combined information about the unoccupied and occupied molecular levels. The element specific character of the three measurement methods is a feature which allows the investigation of the local electronic structure of a single functional group. With RIXS, also non-equivalent atoms of the same element can be addressed separately. Within this thesis firstly, a library of the XE spectra of all 20 proteinogenic amino acids in zwitterionic form is presented. From this sample-set XES fingerprints of the protonated alpha-amino group NH3+ and the deprotonated carboxylic group COO- were evaluated and used to identify the XES fingerprints of the nitrogen and oxygen containing functional groups of the side chains of the amino acids. The data is discussed based on a building block approach. Furthermore, the XE spectra of the functional groups of lysine and histidine, namely the NH2 group and the C3N2H4 ring structure, are both compared to XE spectra of suitable reference molecules (imidazole, ammonia and methylamine). It is found that the XE and RIXS spectra of the side chains of lysine and histidine show large similarities to the XE spectra of the reference molecules. This agreement in the XE and RIXS spectra allows a qualitative investigation of XE and RIXS spectra of more complex amino acids using the XE and RIXS spectra of suitable reference molecules. The chemical structure of histidine and proline is quite different from the structures of the other proteinogenic amino acids. Due to the unique chemical structure of the side chain which in both cases consists of a heterocyclic ring structure, these two amino acids were investigated in more detail. Zubavichus et al. [1] have shown that amino acids are decomposing while exposed to X-ray radiation of the experiment. The damage is irreversible and molecular fragments can adsorb on the membrane of the experimental setup. This contamination can also create a spectral signature which then overlaps with the signal of the solution and which complicates the interpretation of the data. To record spectra which are free from contributions of adsorbed molecular fragments on the membrane, the adsorption behavior was investigated. In contrast to the solid phase in which the amino acids are present as salts in one electronic conformation, the charge state of the amino acids can be manipulated in aqueous solution by tuning the pH-value. By doing this, all possible charge states are accessible (cation, anion, zwitterion). In this work it is shown that also the spectra of the different charge states can be modeled by the spectra of suitable reference molecules using the building block approach. The spectral changes occurring upon protonation and deprotonation of the functional groups are explored and verified by comparing them to theoretical calculations. The comparison with measurements of pyrrolidine show that the electronic structure which surrounds the nitrogen atom of proline is strongly influenced by the ring structure of the side chain. Furthermore, the proline, pyrrolidine, and histidine molecules are also degrading during the liquid sample measurements. This can be observed by the detection of a new spectral component which increases with the measurement time originating from the window membrane. In all cases, the speed of the agglomeration of molecular fragments at the membrane was observed to be highly sensitive to the pH value of the solution. To understand the Hofmeister series, also the impact of the salt ions have to be investigated. In this study the influence of potassium chloride (KCl) on the hydrogen bond network of water was studied by using non-resonantly excited XES as well as RIXS. A decreased dissociation of hydrogen molecules and changes in the molecular vibrations could be detected. These changes were interpreted with a molecular reorganization of the water molecules and a decreased number of hydrogen bonds.},
  subject      = {Aminos{\"a}uren},
  language  = {en}
}
@article{LapaWernerBluemeletal.2014,
  author    = {Lapa, Constantin and Werner, Rudolf A. and Bluemel, Christina and Lueckerath, Katharina and Muegge, Dirk O. and Strate, Alexander and Haenscheid, Heribert and Schirbel, Andreas and Allen-Auerbach, Martin S. and Bundschuh, Ralph A. and Buck, Andreas K. and Herrmann, Ken},
  title     = {Prediction of clinically relevant hyperkalemia in patients treated with peptide receptor radionuclide therapy},
  series = {EJNMMI Research},
  volume    = {4},
  journal   = {EJNMMI Research},
  number    = {74},
  doi       = {10.1186/s13550-014-0074-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-124963},
  year      = {2014},
  abstract  = {Background Peptide receptor radionuclide therapy (PRRT) is applied in patients with advanced neuroendocrine tumors. Co-infused amino acids (AA) should prevent nephrotoxicity. The aims of this study were to correlate the incidence of AA-induced hyperkalemia (HK) (≥5.0 mmol/l) and to identify predictors of AA-induced severe HK (>6.0). Methods In 38 patients, standard activity of \(^{177}Lu\)-labelled somatostatin analogs was administered. Pre-therapeutic kidney function was assessed by renal scintigraphy and laboratory tests. For kidney protection, AA was co-infused. Biochemical parameters (potassium, glomerular filtration rate, creatinine, blood urea nitrogen (BUN), sodium, phosphate, chloride, and lactate dehydrogenase (LDH)) were obtained prior to 4 and 24 h after the AA infusion. Incidence of HK (≥5.0) was correlated with pre-therapeutic kidney function and serum parameters. Formulas for the prediction of severe hyperkalemia (>6.0) were computed and prospectively validated. Results At 4 h, HK (≥5.0) was present in 94.7\% with severe HK (>6.0) in 36.1\%. Values normalized after 24 h in 84.2\%. Pre-therapeutic kidney function did not correlate with the incidence of severe HK. Increases in K+ were significantly correlated with decreases in phosphate (r = -0.444, p < 0.005) and increases in BUN (r = 0.313, p = 0.056). A baseline BUN of >28 mg/dl had a sensitivity of 84.6\% and a specificity of 60.0\% (AUC = 0.75) in predicting severe HK of >6.0 (phosphate, AUC = 0.37). Computing of five standard serum parameters (potassium, BUN, sodium, phosphate, LDH) resulted in a sensitivity of 88.9\% and a specificity of 79.3\% for the prediction of severe HK >6.0 (accuracy = 81.6\%). Conclusions A combination of serum parameters predicted prospectively the occurrence of relevant HK with an accuracy of 81.6\% underlining its potential utility for identifying 'high-risk' patients prone to PRRT.},
  language  = {en}
}
@phdthesis{Cota2010,
  author    = {Cota, Smaranda},
  title     = {Contributions to the Chemistry of Higher-Coordinate Silicon: Synthesis, Structure, and Stereodynamics of New Penta- and Hexacoordinate Silicon(IV) Complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-52312},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {Im Vordergrund dieser Arbeit stand die Synthese und strukturelle Charakterisierung penta- und hexakoordinierter Silicium(IV)-Komplexe. Im Verlauf dieser Untersuchungen wurden die neutralen pentakoordinierten Silicium(IV)-Komplexe 38, 39, 43-48, 54 und 55 dargestellt. Weiterhin konnten die neutralen hexakoordinierten Silicium(IV)-Komplexe 33-36,49, 50, 52, 53, 56-62, 63, 64 und 65 synthetisiert werden. Die Charakterisierung aller Verbindungen erfolgte durch Elementaranalyse, NMR-Spektroskopie in L{\"o}sung (1H, 13C, 15N, 29Si) und im Festk{\"o}rper (13C, 15N, 29Si VACP/MAS NMR), sowie durch Kristallstrukturanalyse(außer 45, 47-49, 52, 53 und 63).},
  subject      = {Silicium},
  language  = {en}
}
@phdthesis{Blum2009,
  author    = {Blum, Monika},
  title     = {Electronic and Chemical Properties of Liquids and Solutions},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-43732},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {Die hier vorgelegte Doktorarbeit wurde der Untersuchung der elektronischen und chemischen Eigenschaften von Fl{\"u}ssigkeiten und L{\"o}sungen mittels weicher R{\"o}ntgenstrahlen gewidmet. Die verwendeten Photonen-rein-Photonen-raus Methoden, namentlich R{\"o}ntgenabsorptionsspektroskopie (XAS), R{\"o}ntgenemissionsspektroskopie (XES) und resonante inelatische R{\"o}ntgenstreuung (RIXS) stellten sich als exzellente Methoden heraus, diese Systeme zu untersuchen. Im Rahmen dieser Arbeit wurde eine experimentelle Anlage gebaut, welche notwendig ist um die genannten Messmethoden zur Untersuchung von Fl{\"u}ssigkeiten zu nutzen. Zentraler Teil dieser Anlage ist eine neuartige Durchflussnasszelle, die die Handhabung der Messungen im Vergleich zu {\"a}lteren Nasszellen vereinfacht. Dabei ist sie variabel genug, um sie zur Messung von Gasen oder Fl{\"u}ssig-Fest-Grenzfl{\"a}chen anzupassen. Mit der Zelle ist es m{\"o}glich, die zu untersuchenden Fl{\"u}ssigkeiten unter gut kontrollierten Bedingungen (Temperatur und Durchfluss) zu untersuchen. Die Durch-flussnasszelle ist Teil einer neuen Synchrotronendstation (SALSA). F{\"u}r die Messungen stehen dabei ein Elektronenanalysator und ein neuartiges hochaufl{\"o}sendes, hocheffizientes Weichr{\"o}ntgenspektrometer zur Verf{\"u}gung. Mit diesem Spektrometer ist es m{\"o}glich, zweidimensionale RIXS Karten in sehr kurzer Zeit (wenige Minuten) aufzunehmen, welche die vollst{\"a}ndige Information von R{\"o}ntgenabsorption und R{\"o}ntgenemission beinhalten. Mit Hilfe der neu entwickelten Instrumentierung war es m{\"o}glich, eine Reihe unterschiedlicher Fl{\"u}ssigkeiten und L{\"o}sungen zu untersuchen. Als erstes System wur-den w{\"a}ssrige NaOH bzw. NaOD L{\"o}sungen erforscht. Die nicht-resonanten Emissionsspektren sind stark von dem genutzten L{\"o}sungsmittel dominiert und haben daher {\"A}hnlichkeit mit den Spektren von Wasser und schwerem Wasser. Es war m{\"o}glich, eine Abh{\"a}ngigkeit der Spektren von der Ionenkonzentration festzustellen. Trotz der {\"A}hnlichkeit der Spektren zu Wasserspektren war es aufgrund eines OH- / OD- spezifischen Charakteristikums an der Absorptionskante m{\"o}glich, resonante Spektren von OH-/OD- ohne Beitrag des Spektrums von Wasser zu erhalten. Diese Spektren zeigten Anzei-chen f{\"u}r Protonendynamik auf der Zeitskala der Rumpflochlebensdauer. F{\"u}r die Emissionsspektren von NaOH im festen Zustand konnten an der hochenergetischen Hauptline eine niederenergetische und hochenergetische Schulter festgestellt werden. Diese Schultern sind das Ergebnis des Eigendissoziationsprozesses von OH- Ionen, bei welchem O2- Ionen und H2O gebildet werden. Weiterhin waren die Untersuchungen an Natronlauge von Interesse f{\"u}r die folgenden Aminos{\"a}urenmessungen, da Natronlauge genutzt wurde, um die gew{\"u}nschten pH-Wert {\"A}nderungen zu erreichen. Die zweite Gruppe von Fl{\"u}ssigkeiten, die in dieser Arbeit untersucht wurde, sind Aminos{\"a}uren. Aminos{\"a}uren sind die Bausteine f{\"u}r Peptide und Proteine und da-mit sehr wichtig f{\"u}r alle Biowissenschaften. Als Vertreter der Aminos{\"a}uren wurden Glycin - die kleinste Aminos{\"a}ure, und Lysin - eine Aminos{\"a}ure mit zwei Amingruppen - untersucht. Beide Aminos{\"a}uren reagieren sensibel auf {\"A}nderungen des pH-Wertes mit einer Deprotonierung/Protonierung der Amingruppe (NH2 \&\#8596; NH3+). In den experimentellen Spektren konnte ein deutlicher Einfluss dieser Prozesse gefunden werden. Die gemessenen Spektren der protonierten Aminos{\"a}uren zeigen deutliche An-zeichen f{\"u}r Dissoziationsprozesse. Erste DFT Rechnungen best{\"a}tigten diese Anzeichen und unterst{\"u}tzen das Dissoziationsmodell der Aminos{\"a}uren. Qualitativ l{\"a}sst sich sagen, dass sich die hochenergetische Linie in den N K XES Spektren auf die unprotonierten Amingruppen bezieht und der niederenergetische Bereich im Spektrum den protonierten Gruppen zugeordnet werden kann. Neben Aminos{\"a}uren sind auch Alkohole und organische S{\"a}uren von Bedeutung f{\"u}r biologische Prozesse. Daher wurden als Vertreter aus diesen Gruppen der einfachste Alkohol (Methanol) und die einfachste S{\"a}ure (Essigs{\"a}ure) untersucht. Die O K und C K XES Spektren von fl{\"u}ssigem Methanol stimmen hervorragend mit Gasphasen DFT Rechnungen {\"u}berein. Dies l{\"a}sst den Schluss zu, dass der Einfluss der Umgebung (Wasserstoffbr{\"u}ckenbindungen) auf die Spektren gering ist. Durch resonante Anregung in geeignete unbesetzte Orbitale war es m{\"o}glich, die zwei unterschiedlichen Sauerstoffatome der Essigs{\"a}ure zu unterscheiden und auch einen Anhaltspunkt f{\"u}r die Carboxylgruppen-spezifischen C K XES Spektren zu bekommen. An der Kohlenstoffkante zeigten die XAS Spektren große Unterschiede zu Gasphasenmessungen, was ein Hinweis auf den Einfluss der Wasserstoffbr{\"u}ckenbindungen ist. Die Untersuchung der elektronischen und chemischen Eigenschaften von Fl{\"u}ssigkeiten und L{\"o}sungen ist immer noch ein sehr junges Forschungsgebiet. Die Ergebnisse dieser Doktorarbeit zeigen, welch interessantes Forschungsgebiet dies ist. Die vorgestellten Ergebnisse k{\"o}nnen als die grundlegende Basis f{\"u}r alle weiteren Untersuchungen in diesem Forschungsfeld angesehen werden.},
  subject      = {R{\"o}ntgenspektroskopie},
  language  = {en}
}