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University, Diss., 2007--Frankfurt (Main). / Zsfassung in engl. und dt. Sprache.

Würzburg, Univ., Diss., 2005. / Erscheinungsjahr an der Haupttitelstelle: 2004

The work in this thesis can be divided into two sections, namely the study of delicious peptide, a food flavour and the antimicrobial peptide lactofenicin B. The main interest in these compounds is in terms of structure and conformation adopted in solution and how this relates to their mode of action. Delicious peptide was studied initially by 1H NMR spectroscopy for evidence of a specific solution structure. Results show that delicious peptide does not adopt a regular conformation in solution. Molecular dynamics simulations of this peptide show the flexibility of the peptide structure in solution. Quenched molecular dynamics simulations were used to search for low energy conformers of the peptide. The results suggest that the flavour of the peptide is produced by interaction of basic and acidic regions in the peptide. The work was extended to examine delicious peptide analogues with similar flavour characteristics. The results obtained suggest that similar interactions of basic and acidic regions occur for these peptides to produce a savoury flavour. The antimicrobial peptide Lactofemcin B was synthesised by Fmoc poly-amide synthesis. Problems with the synthesis occurred due to the protecting groups used for the five arginine residues present in the sequence. Predictive modelling studies on Lactofenicin B peptide, derived from bovine lactofenicin protein suggest that the peptide adopts a region of alpha-helical conformation in solution. The flexibility of the peptide was studied by molecular dynamics in solution and simulations of other environmental conditions were carried out by variation of electrostatic interactions using dielectric constants for membrane, TFE and water environments. The results suggest the beta-helical conformation is most stable in an environment such as trifluoroethanol, the peptide showing more flexibility in aqueous solution. Experimental results for the peptide confirm the flexibility of the peptide in solution. CD results show that lactofenicin B has no specific conformation in solution, although an beta-helical conformation is adopted in trifluoroethanol. The peptide also adopts a beta-sheet conformation in low concentrations of SDS micelle and therefore its conformation is dependant on environmental conditions. NMR studies show that the peptide, although flexible in solution, shows short-range NOE interactions that suggest a local beta-helical conformation may be present. However the overall conformation for the peptide is a flexible one.

No description available.

Die Beobachtung von Neutrinomassen und Leptonenmischungen haben gezeigt, dass das Standard-Modell unvollständig ist. Im Zuge dieser Entdeckung tauchen neue Fragestellungen auf: warum sind die Neutrinomassen so klein, wie sieht ihre Massenhierarchie aus, warum sind die Mischungen im Quark- und Leptonen-Sektor so unterschiedlich oder welche Form hat der Higgs-Sektor. Um diese Fragen zu beantworten und um zukünftige experimentelle Daten vorherzusagen, werden verschiedene Ansätze betrachtet. Besonders interessant sind Grand Unified Theories, wie SU(5) oder SO(10). GUTs sind vertikale Symmetrien, da sie die SM-Teilchen in Multipletts vereinheitlichen und üblicherweise neue Elementarteilchen vorhersagen, die durch den Seesaw-Mechanismus, auf natürliche Weise die Kleinheit der Neutrinomassen erklären. Darüberhinaus sind auch horizontale Symmetrien, d.h. Flavor-Symmetrien, welche auf den Generationen-Raum der SM-Teilchen wirken, interessant. Sie können die Quark- und Leptonen-Massenhierarchien, sowie die unterschiedlichen Quark- und Leptonenmischungen, erklären. Ausserdem beeinflussen Flavor-Symmetrien massgeblich den Higgs-Sektor und sagen bestimmte Formen von Massenmatrizen vorher. Diese hohe Vorhersagekraft machen GUTs und Flavor-Symmetrien sowohl für Theoretiker, als auch für Experimentalphysiker interessant. Solche Erweiterungen des SM können mit weiteren Konzepten wie Supersymmetrie oder extra Dimensionen kombiniert werden. Hinzu kommt, dass sie für gewöhnlich Auswirkungen auf die beobachtete Materie-Antimaterie Asymmetrie des Universums haben und einen dunkle Materie Kandidaten beinhalten können. Im Allgemeinen sagen sie auch die seltene Leptonenzahl verletzenden Zerfälle mu -> e gamma, tau -> mu gamma und tau -> e gamma vorher, die stark von Experimenten eingeschränkt sind, aber möglicherweise in der Zukunft beobachtet werden. In dieser Arbeit kombinieren wir all diese Zugänge, d.h. GUTs, den Seesaw-Mechanismus und Flavor-Symmetrien. Drüber hinaus ist unser Anliegen einen systematischen Zugang zum Modellbau zu entwickeln und durchzuführen, sowie die Suche nach phänomenologischen Implikationen. Dies stellt eine neue Sichtweise im Modellbau dar, da es uns erlaubt bestimmte Modelle durch ihre theoretischen und phänomenologischen Vorhersagen zu filtern. D.h. wir können weitere Einschränkungen an Modelle fordern, um ein bestimmtes auszuwählen. Die Ergebnisse unserer Herangehensweise sind zum Beispiel mannigfaltige Leptonen-Flavor- und GUT-Modelle, ein systematischer Scan von Leptonenzahl verletzenden Prozessen, neue Massenmatrizen, eine neues Veständnis der Leptonenmischungswinkel, eine Verallgemeinerung der Idee der Quark-Leptonen-Komplementarität theta_12=pi/4-epsilon/sqrt{2} und zum ersten Mal die QLC-Relation in einer SU(5) GUT. / The observation of neutrino masses and lepton mixing has highlighted the incompleteness of the Standard Model of particle physics. In conjunction with this discovery, new questions arise: why are the neutrino masses so small, which form has their mass hierarchy, why is the mixing in the quark and lepton sectors so different or what is the structure of the Higgs sector. In order to address these issues and to predict future experimental results, different approaches are considered. One particularly interesting possibility, are Grand Unified Theories such as SU(5) or SO(10). GUTs are vertical symmetries since they unify the SM particles into multiplets and usually predict new particles which can naturally explain the smallness of the neutrino masses via the seesaw mechanism. On the other hand, also horizontal symmetries, i.e., flavor symmetries, acting on the generation space of the SM particles, are promising. They can serve as an explanation for the quark and lepton mass hierarchies as well as for the different mixings in the quark and lepton sectors. In addition, flavor symmetries are significantly involved in the Higgs sector and predict certain forms of mass matrices. This high predictivity makes GUTs and flavor symmetries interesting for both, theorists and experimentalists. These extensions of the SM can be also combined with theories such as supersymmetry or extra dimensions. In addition, they usually have implications on the observed matter-antimatter asymmetry of the universe or can provide a dark matter candidate. In general, they also predict the lepton flavor violating rare decays mu -> e gamma, tau -> mu gamma and tau -> e gamma which are strongly bounded by experiments but might be observed in the future. In this thesis, we combine all of these approaches, i.e., GUTs, the seesaw mechanism and flavor symmetries. Moreover, our request is to develop and perform a systematic model building approach with flavor symmetries and to search for phenomenological implications. This provides a new perspective in model building since it allows us to screen models by its predictions on the theoretical and phenomenological side, i.e., we can apply further model constraints to single out a desired model. The results of our approach are, e.g., diverse lepton flavor and GUT models, a systematic scan of lepton flavor violation, new mass matrices, a new understanding of lepton mixing angles, a general extension of the idea of quark-lepton complementarity theta_12=pi/4-epsilon/sqrt{2} and for the first time the QLC relation in an SU(5) GUT.

This thesis documents two searches for rare hadronic decays of B⁺ mesons with the LHCb experiment at the Large Hadron Collider. Both are performed using proton-proton collision data corresponding to an integrated luminosity of 4.8 fb^-1, collected at centre-of-mass energies of 7, 8 and 13 TeV during 2011-2016. The first is a search for B⁺ → D_s⁺K⁺K^- decays. A significant signal is observed for the first time and the branching fraction is determined to be B(B⁺ → D_s⁺K⁺K^-) = (7.1 ± 0.5 ± 0.6 ± 0.7) x 10^-6, where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fraction of the normalisation mode B⁺ → Ds⁺D⁰. The second search is performed for the rare pure annihilation decay B⁺ → D_s⁺φ. No significant signal is observed and a limit of B(B⁺ → D_s⁺φ) < 4.9 x 10^-7 is set on the branching fraction at 95% confidence level.

Consumers place a high level of importance on flavour when assessing the acceptability of food. The flavour of dairy products can be affected by heating both during processing and by consumers during food preparation. Of particular importance to the flavour of heated dairy products is the highly complex network of Maillard reactions. Previously, emphasis has been placed on undesirable flavours generated through the Maillard reaction in dairy products and efforts have been made to minimise the formation of these flavours. However, beneficial flavours are also formed by the Maillard reaction. Dairy products such as ghee are formed by heating and are characterised by their unique flavours; these flavours are generated by the Maillard reaction. The objective of this thesis was to unravel the factors that influence the Maillard and caramelisation reactions that occur during the cooking of ghee. Particular focus was placed on the impact that the structure of the cream had on the reaction, and how manipulation of these parameters could provide an avenue for the control of the Maillard reaction. The development and validation of model reaction systems for the Maillard and caramelisation reactions involved the variation of parameters including cooking time, temperature, pH, phosphate buffers and salt. A group of eleven compounds including acetic acid, furfural, 2-acetylfuran, butyrolactone, 2(5H)-furanone, furfuryl alcohol, maltol, 2- acetylpyrrole, hydroxymaltol, hydroxymethylfurfural (HMF) and dihydro-4-hydroxy-2(3H)- furanone (DHHF) were monitored to determine the impact of these parameter changes. These results provided a starting point to assess the impact of food structure on these reactions. To assess the impact of food structure a series of matrix structures were designed starting from an aqueous matrix. The first component that was added to the aqueous matrix was fat to generate a two phase structure. Emulsion structures were then formed from the two phase structure using emulsifiers and high pressure homogenisation. Analysis of the volatile compounds formed as the matrix structures were altered was carried out using headspace solid phase microextraction/ gas chromatography mass spectrometry (SPME/GCMS). Results indicated that fat is a key structural component in flavour generation via the Maillard reaction. This could have implications for low fat foods where the flavour developed during cooking is important. The addition of fat indicated a significant impact on the Maillard reaction with a less significant impact seen on the caramelisation reaction. The formation of two emulsions with inverted structures provided a means to alter the ratio of volatile compounds in the cooked samples. The oil in water emulsion generated a volatile compound profile similar to that of the fat containing matrix, whereas the water in oil emulsion produced a different ratio of these same compounds. The results reported in this thesis shed some light on the relationship between food structure and flavour formation during the cooking of milk fat emulsions. These structures will create future opportunities to manipulate the structure of food to control flavour formation.