Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. / Includes bibliographical references (leaves 180-195). Also available on microfiche.

X-ray crystallography is extensively deployed to determine the structure of proteins, both unbound and bound to different molecules. Crystallography has the power to visually reveal the binding of small molecules, assisting in their development in structure-based lead design. Currently, however, the methods used to detect binding, and the subjectivity of inexperienced modellers, are a weak-point in the field. Existing methods for ligand identification are fundamentally flawed when identifying partially-occupied states in crystallographic datasets; the ambiguity of conventional electron density maps, which present a superposition of multiple states, prevents robust ligand identification. In this thesis, I present novel methods to clearly identify bound ligands and other changed states in the case where multiple crystallographic datasets are available, such as in crystallographic fragment screening experiments. By applying statistical methods to signal identification, more crystallographic binders are detected than by state-of-the-art conventional approaches. Standard modelling practice is further challenged regarding the modelling of multiple chemical states in crystallography. The pervading modelling approach is to model only the bound state of the protein; I show that modelling an ensemble of bound and unbound states leads to better models. I conclude with a discussion of possible future applications of multi-datasets methods in X-ray crystallography, including the robust identification of conformational heterogeneity in protein structures.

In his programmatic article More Is Different (1972), Nobel laureate P. W. Anderson captured the fundamental interest in quantum matter in a nutshell. The central motive in this field is emergence. In the inaugural volume of the homonymous journal, J. Goldstein defined this as "the arising of novel and coherent structures, patterns and properties during the process of self-organization in complex systems". Famously, the idea that the "the whole is greater than the sum of its parts" goes back to Aristotle's metaphysics, and it has served as a stimulating concept in 19th century biology, economics and philosophy. The study of emergence in condensed matter physics is unique in that the underlying complex systems are sufficiently "simple" to be modelled from first principles. Notably, the emergent phenomena discovered in this field, such as high-temperature superconductivity, giant magnetoresistance, and strong permanent magnetism have had an enormous impact on technology, and thus, society. Historically, there has been a distinction between materials with localized, strongly interacting (or correlated) electrons - and non-interacting, itinerant electronic states. In the last decade, several new states of matter have been discovered, which emerge not from correlations, but from peculiar symmetries (or topology) of itinerant electronic states. The term quantum materials has therefore become popular to subsume these two strands of condensed matter physics: Electronic correlations and topology. In this thesis, I report investigations of four quantum materials which each illustrate present key interests in the field: The mechanism of high temperature superconductivity, the search for materials that combine both electronic correlations and non-trivial topology and novel emergent phenomena that arise from the synergy of electronic correlations and a strong coupling of spin- and orbital degrees of freedom. The common factor and potential key to understanding these materials is magnetism. My experimental work is focused on neutron and x-ray scattering techniques, which are able to determine both order and dynamics of magnetic states at the atomic scale. I illustrate the full scope of these methods with experimental studies at neutron and synchrotron radiation facilities. This includes both diffraction and spectroscopy, of either single- or polycrystalline samples. My in-depth analysis of each dataset is aided by structural, magnetic and charge transport experiments. Thus, I provide a quantitative characterization of magnetic fluctuations in an iron-based superconductor and in two Dirac materials, and determine the magnetic order in a Dirac semimetal candidate and a complex oxide. As a whole, these results demonstrate the elegant complementarity of modern scattering techniques. Although such methods have a venerable history, they are presently developing at a rapid pace. Several results of this thesis have only been enabled by very recent instrumental advances.

Thesis (Ph.D.)--Boston University / Lutetium oxide doped with europium oxide (Lu20 3:Eu3+) has been established to be a bright, dense scintillator materi al with vast potential in both medical and high resolution X-ray imaging applications. Unfortunately its commercial viability has been restricted due to the manufacturing and post treatment costs associated with device fabrication. This research was aimed at the development of two vapor deposition techniques; chemical and physical vapor deposition (CVD and PVD), to produce coatings of Lu203:Eu3+ for various X-ray imaging applications. A customized CVD process to codeposit Lu20 3 and Eu20 3 was developed using lutetium and europium chloride (LuCb and EuCI3) precursors and reacting with carbon dioxide (C02) and hydrogen (H2) . An in depth study was performed by systematically varying the process parameters to explore the deposition kinetics and identify the rate limiting steps and their effects on the growth morphology using both cold and hot wall CVD reactors. The activation energy for the kinetically limited deposition of Lu20 3 from the LuCI3 - Ar - C02 - H2 system was identified to be approximately 170 kJ/mol , which is significantly lower than expected. The predominant growth orientations were identified to be { 111} and { 100} , depending on the deposition conditions. As the temperature is increased, the growth orientation preference decreases to produce a randomly oriented growth at 1150°C. The scintillation and X-ray imaging characteristics of a co-deposited Lu203:Eu3+ thin film with a {100} orientation were measured, confirming the feasibility and applicability of the CVD system to produce thick scintillator x-ray imaging devices. A fundamental study of the PVD process was performed by sputtering of Lu203:Eu3+ using a single target magnetron sputtering gun. Systematic vatiations of the deposition parameters were used to understand the effect of the ejected flux kinetic energies and deposition rate on the deposit density, stress, optical and scintillation properties. The deposition system was subsequently optimized for rapid, dense growth of a 10 um thick Lu203:Eu3+ coating at elevated temperatures. The X-ray imaging properties were measured and the results yielded an X-ray imaging resolution slightly better than 1 um with the potential for 0.5 um with further optimization, a level never before attained.

Soft-paste porcelain was produced in Britain in great quantities between the mid-18th and early 19th centuries. Due to industrial secrecy and the complexities of creating a product that would survive high-temperature firing, a range of paste recipes was employed by dozens of factories. This has resulted in an array of porcelains which vary in their elemental composition and mineralogy. This research carries out a meta-analysis of the published data for porcelain bodies and glazes and concludes that some discrimination can be achieved using the major and minor elemental composition of the bodies, and that for the glazes intra-factory variation is often greater than inter-factory variation in composition. A pilot investigation of the trace elemental composition of British porcelain is carried out using Laser Ablation Inductively Coupled Plasma Mass Spectroscopy, which finds compositional groups corresponding to different sources of clay and silica raw materials. In the interests of preserving intact objects, there is recognised a need for a non-destructive method for analysing British porcelain, in order to provenance and date objects. Such a method would rely on data from the surface of the object, which is typically covered by glaze and over-glaze coloured enamels, and this research demonstrates that the formulae used for the glaze and enamels are in some cases characteristic of the factory, or workshop, and period at which they were created. Hand-Held XRF analysis is used to analyse the glaze, underglaze blue and polychrome enamels on a selection of porcelain objects from different factories, and compositional traits are identified that allow some factories and periods to be distinguished. Glass standards are developed, which are representative of the glaze and enamel composition, and which could allow X-ray fluorescence (XRF) data to be calibrated for fully quantitative results.

Doctor of Philosophy / Department of Grain Science and Industry / Yong Cheng Shi / Wheat bran is a by-product of the wheat flour milling industry. The number of food products containing wheat bran is on the rise because it is a well-recognized good source of dietary fiber. Currently, bran is a low-value commodity used mostly in animal feed, but it has the potential for more extensive applications. To understand the functional and nutritional properties of wheat bran and better use wheat bran in food, it is critical to understand the physical structure of wheat bran. For the first time, solid-state ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance (¹³C CP/MAS NMR), X-ray diffraction (XRD), and small angle X-ray scattering (SAXS) were used to study the physical structure of wheat bran and its dissected layers. The XRD and Solid-State ¹³C CP/MAS NMR both confirmed the presence of crystalline cellulose in untreated bran, enzymatically treated bran, and dissected bran layers. Destarched and deproteinized wheat bran (DSDPB) was treated with a mixture of either 7 or 9% sodium hydroxide and 12% urea solvent and structure of the extracted polymers was investigated. Three and 6 cycle dissolution schemes, were examined involving the repeated cooling of the solvent bran mixture to -12.6 °C and then agitating it at 25 °C. When 7% NaOH/12% urea (6 cycle) was applied to DSDPB, 84.1% of the material was solubilized including 89.8% of the arabinoxylans (AX). This procedure recovered more wheat bran AX for characterization than any previous study using alkaline dissolution. Wheat bran was enzymatically and hydrothermally treated to maximize the soluble fraction. Unlike previous research, the starch and protein were kept and not removed before endoxylanase treatment. The retained protein and glucose polymers (starch, β-glucan, cellulose) could provide functional benefits in addition to the arabinoxylan and could make the process more economical. Wheat bran hydrolyzed with thermostable α-amylase, protease, and xylanase was the recommended treatment. The combined solubles had a viscosity of 23 cP (10% w/w solids) and ranged in estimated molecular weight from ~600 to 20,000. The percentage of untreated wheat bran AX that was solubilized was 50% and the percentage of AX in the solubles was 23%.

No description available.

Carboxylesterases are glycosylated general detoxification enzymes belonging to the serine esterase superfamily and play a critical role in the hydrolysis of numerous ester- and amide- containing molecules, including active metabolites, drugs and prodrugs. Three functionally active carboxyleterases have been identified in man (CES1-3), which all show differential tissue expression and critically overlapping, yet specific substrate selectivities. Elucidating the basis of their exact substrate preference would help facilitate the design of clinical prodrugs which are activated by carboxylesterases. Because of their widespread applications, carboxylesterases have attracted much attention in recent years, with CES1 being the most extensively studied human carboxylesterase to date. The work presented here addresses the structure-function relationship of the three human carboxylesterases using a combination of X-ray crystallography, kinetic analysis and biophysical techniques. Recombinant proteins were successfully produced using a mammalian expression system in high yield (5.0 – 84.0 mg/ L cell culture). Analytic ultracentrifugation and size-exclusion chromatography coupled to multi-angle laser light scattering were used to investigate the proteins in solution. These results showed CES1 exists primarily in a trimeric arrangement, whilst CES2 and CES3 are monomeric. Interestingly, atypical mechanisms of substrate inhibition, positive cooperativity and biphasic kinetics were observed for both CES1 and CES2. Three structures of CES1 were solved: wild type, an aglycosylated form and a catalytically inactive form, to 1.48, 1.86 and 2.01 Å respectively. The novel structure of CES2 was solved to 2.04 Å, which revealed that the enzyme forms a strand exchange dimer in contrast to the trimeric CES1. To summarise, this thesis documents a platform that has been generated for the production, characterisation and crystallization of human carboxylesterases. This will aid future structural work for protein ligand binding studies.

No description available.

The reaction of [MCl2(cod)] (M = Pt, Pd) with two equivalents of 2-(diphenylphosphinoamino)pyridine, Ph2PNHpy, in warm acetonitrile led to cationic complexes of the type cis-[MCl(Ph2PNHpy-P,N){Ph2PNHpy-P}][Cl] (M = Pt, Pd) which exhibit broad single 31P{1H} NMR resonances due to their dynamic pyridyl exchange behaviour in solution. A single crystal X-ray diffraction study of the platinum species confirmed the proposed structure and revealed that adjacent complex molecules were held together by hydrogen bonding to the same chloride counter-ion. The bromo- and iodo-cis[MX(Ph2PNHpy-P,N){Ph2PNHpy-P}][X] (M = Pt, Pd; X = Br, I) complexes were obtained by metathesis from the corresponding chloride complex.