No description available.

<p> The microwave spectra were measured in the 4&ndash;15 GHz regime for cyclopropanecarboxylic acid, 1,2-cyclohexanedione, maleimide, phthalimide, and 4a,8a-azaboranaphthalene. Doubly hydrogen bonded dimers formed with formic acid were also measured with the molecules cyclopropanecarboxylic acid, 1,2-cyclohexanedione, maleimide, and tropolone. Measurements were made using a pulsed beam Fourier transform microwave spectrometer. Rotational and centrifugal distortion constants were determined from the microwave spectra. In the case of the systems that exhibit electric quadrupole coupling interactions, the electric quadrupole coupling strengths were also determined from the analysis of the hyperfine structure in the spectra, yielding additional electronic structure information for the molecules studied. The spectra were also measured for a number of unique, singly substituted isotopologues under natural abundance concentrations. This isotopologue data is crucial in order to obtain key gas phase molecular structure parameters of the molecules and complexes studied. Many theoretical computations, using <i>ab initio</i> and DFT methods, were also performed to obtain optimized electronic structures of the systems studied. These computations aid in the search and assignments of the rotational transitions measured. Comparisons between the theory and the experimental results are described in greater detail in the respective chapters for those systems. The experimental results for the organic systems studied agreed well (within a few percent) with the gas phase optimization computations performed.</p><p>

No description available.

No description available.

An infra-red study was made of the molecular complex of hexafluorobenzene (HFB) in benzene solutions. Interactions between HFB and benzene lead to a frequency shift and a broadening of the band arising from the out of plane C-F bending vibration It is deduced that the intermolecular interactions are short lived, stochastic, are not simple polar interactions, and that the resulting forces are directed perpendicular to the ring plane. The band contours of the vibrational Raman band of chlorine in benzene/tetrachloromethane solution mixtures have been studied. Band fitting analysis of the complexed chlorine band using two Lorentzians, each with their isotopic sub bands, produced good simulations of the observed spectra. The consistency of the relative intensities suggests that they arise from complexes of the samestoichiometry. It is concluded that chlorine forms a 1:2 complex with benzene, with an equilibrium constant K = .095 elm mol . Entropy imply that there is a large molecular ordering compatible with the idea of specific structure of the complex. The vibrational Raman band of liquid chlorine was studied to shifts of 130 cm from the band centre. The second moment of the anisotropic component is about 15 above the theoretical value. Good exponential decays of the second order orientational correlation function are observed from t > 0.2 ps. The resulting relaxation times are well reproduced by a microviscosity equation. The results are in reasonable accord with n.m.r. relaxation times. Absolute intensity measurements have been made on the fundamental vibrations of methyl iodide, by integrating the optical density over the absorption band. Exact band fitting of the theoretical spectra, to the experimental spectra was not possible, no explanation can be offered. The intensity measurements were analysed in terms of the dipole moment derivatives with respect to symmetry coordinates, using three formulations of the vibrational angular momentum correction. Gribov's formulation is considered superior to the earlier Crawford hypothetical isotope method. Barrow and Crawford also derived a formulation similar to Gribov's.

Physical interaction between two bulk media occurs mainly at the surface interface. The surface properties of materials therefore dictate how a system will respond to different influences, while being just a fraction of the entire volume. Alteration of a surface can therefore have a significant effect on a system. In this thesis the functionalization of surfaces via covalent attachment of short chained molecules was undertaken to manipulate surface-surface interactions for different outcomes. The separation and purification of bulk media of impurities has always been undertaken. Many different processes exist, however the removal of impurities from dynamic or open systems remains a problem. The use of filtration technologies remains the best option in this type of system. In filtration technology membranes are employed to selectively remove one or more elements from another generally under a driving force. The selectivity of a membrane has either traditionally relied on either physical attributes such as pore size or chemical attributes such as charge, van der Waals etc. In this thesis we propose the use of organically functionalized ceramic nanoparticles alumoxanes to act as a coating of the side walls of the fibers of a base bulk fabric material Nomex © . The side chain of cysteic acid has been found to be extremely hydrophilic due in part to its Zwitter ionic properties. The use of hydrophilic cysteic acid alumoxane was used as part of a composite membrane to screening hydrocarbons. Doping of this membrane with cysteic acid ferroxane the iron analogue of alumoxane was used as a membrane to screen MS2 bacteriophage.

Thesis (Ph. D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-04, Section: B, page: 2081. Adviser: Hiten D. Madhani.

Thesis (Ph. D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-04, Section: B, page: 2082. Adviser: Robert J. Fletterick.

<p> Dehydrodopa/dopamine derivatives form an important group of biomolecules participating in sclerotization of all arthropod cuticles, gluing and cementing mussels and related organisms to solid surfaces, and defense reactions of countless marine and invertebrate organisms. Yet very little information is available on the biochemistry of these highly reactive and unstable molecules. To understand their physiological role, I conducted a thorough biochemical study on three representative compounds that cover the entire plethora of dehydrodopa/dopamine derivatives. Employing diode array UV-visible spectroscopy, HPLC, liquid chromatography-mass spectrometry, and electrospray ionization tandem mass spectrometry, I investigated the oxidation chemistry of 1,2-dehydro-N-acetyldopamine (dehydro NADA), 1,2-dehydro-N-acetyldopa and 1,2-dehydro-N-acetyldopa methyl ester. Tyrosinase converted dehydro NADA to a reactive quinone methide that formed oligomeric products with the parent compound. The sister enzyme laccase, produced semiquinone radicals that exhibited a novel coupling reaction producing just dimers. Nonenzymatic oxidation of dehydro NADA also produced semiquinone radicals that formed oligomeric products. Moreover, nonenzymatic oxidation resulted in the production of superoxide anions that could function in defense reactions. The nonenzymatic oxidation studies on dehydro NADA at mild alkaline conditions revealed the mechanisms of defense reactions and tunic formation in a vast array of tunicates. Oxidative transformations of 1,2-dehydro-N-acetyldopa indicated a new route for the biosynthesis of a vast array of bioactive marine molecules possessing dihydroxycoumarin skeleton. In addition, it revealed new transformations of coumarins to oligomeric products via highly reactive quinone methide intermediates. Biochemical studies on 1,2-dehydro-N-acetyldopa methyl ester revealed a new Diels Alder type condensation of its quinone with the parent compound. This reaction shed light on the mode of gluing of mussels and other bivalves to solid surfaces as well as the hardening reactions occurring in their periostracum. I also examined the oxidation chemistry of dehydro NADA with a model nucleophile, N-acetylcysteine and discovered yet another new addition reaction of dehydro NADA that has tremendous biological significance. Finally, I investigated the mechanism of dehydro NADA binding to insect cuticle using labeled compounds and established that they could uniquely produce ketocatecholic compound, arterenone upon hydrolysis. The biochemical significances of all these new reactions are discussed in the dissertation.</p>

<p> This work explores mechanisms of pathology in Huntington's Disease (HD) in an attempt to identify attractive therapeutic targets. By inserting the gene for human huntingtin (<i>HTT</i>) into the genome of the fruit fly <i>Drosophila melanogaster</i>, we have reproduced the main features of HD. Using this model, we sought to explore the inherent qualities of specific fragments of mutant huntingtin protein (mHtt), and the role of modifier genes on the progression of pathology in the context of an intact, living organism. These studies contribute to a basic understanding of the molecular basis of HD pathogenic progression as well as providing a guide to selection of targets of therapeutic value. </p><p> Flies expressing mutant huntingtin display a range of pathology, including developmental abnormalities, neurodegeneration, movement deficits, reduction in longevity, biochemically detectable accumulation of mutant huntingtin protein, and microscopically visible inclusion body formation. Previous research has established that the 3144 aa Htt protein is processed by various endogenous proteolytic enzymes, releasing a series of N-terminal fragments of the huntingtin protein. Many of these fragments have been studied, utilizing a variety of model systems, and it has been suggested that some fragments can play a critical role in HD pathology while others do not. In this work I have compared the most commonly studied fragments side-by-side in flies with a common genetic background to determine their intrinsic pathogenic potential and biophysical behavior. Our findings indicate that the exon 1 fragment is clearly the most toxic of the naturally occurring fragments. </p><p> Previous research has also suggested that the small ubiquitin-like modifying protein SUMO plays an important role in HD pathology. We pursued this by genetically modifying the activity of SUMO in flies. Our results suggest that while SUMO does play a role, it is not primarily in the direct modification of huntingtin, and that modulation of SUMO-specific isopeptidases is unlikely to be an attractive therapeutic strategy. </p><p> Our studies also led to the investigation of the SUMO-related protein NEDD8. We found that while the NEDD8 pathway may play a role in HD pathology, it also affects the mechanics of the GAL4/UAS transgenic expression system. This is an important caveat for future investigations of this nature. </p><p> Finally, to address the long-standing problem of quantifying the levels of Htt protein in the face of aggregation and anomalous effects on secondary structure, we compared a number of methods of quantifying the amount of huntingtin in our samples. We find that time-resolved fluorescence resonance energy transfer detects greater relative levels of monomeric small fragments compared to western blotting and immunostaining, raising important questions about what parameters influence measurements of Htt in the different methods.</p>