本論文中我們將介紹一種新穎且便利的利用微波的固相多肽合成方法，以及在此方法協助下對一組混合肽之間相互作用的研究。與傳統的多肽合成相比，微波輻射幫助提高耦合過程的效率，從而大大縮短了合成時間，以及提高了反應效率。家庭用和實驗室用微波爐的比較表明，家用微波爐在實驗室條件下足以勝任微波輔助固相多肽合成。在第二部分，我們利用微波固相多肽合成合成了一組多肽用以探究其之間相互作用。一對在之前文獻報導的，通過庫篩選得到的結合肽被用來與另一組捲曲肽組合構成混合肽，期望得到強而且具特異性的相互作用以用作蛋白的標記。然而文獻報導的這對多肽並未達到預期的相互作用，因此我們需要在後續實驗中重新設計混合肽。 / This thesis summarizes an investigation into a novel solid-phase peptide synthesis protocol assisted by microwave irradiation, as well as an attempt to design hybrid peptides for enhanced binding properties. Compared with conventional peptide synthesis, a brief microwave irradiation during coupling and deprotection was shown to significantly reduce the time for peptide synthesis, at the same time yielding satisfactory product purity. A comparison of a domestic and a laboratory microwave oven indicated that the former could be easily adapted for conducting microwave-assisted solid phase peptide synthesis in a research laboratory, a facile and budget-efficient solution for enhanced efficiency in solid phase synthesis. In the second part of the research, we utilized the developed protocol to synthesize a set of peptides to investigate peptide-peptide interaction. A pair of binding peptides previously identified through library screening and genetic selection reported in literature was fused with designed coiled coil peptides to afford hybrid peptides, which was expected to result in exceptionally strong interaction and enhanced specificity. These hybrid peptide pairs could find applications in protein labeling, immunoblotting, and purification. However, the peptide pair did not demonstrate the claimed binding affinity in the literature. Therefore, the current design is flawed, and we shall re-design hybrid peptides based on other binding pairs in the following research. / Detailed summary in vernacular field only. / Zhang, Han. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Abstracts also in Chinese. / 摘要 --- p.I / ABSTRACT --- p.II / TABLE OF CONTENTS --- p.III / ACKNOWLEDGEMENT --- p.V / ABBREVIATION --- p.VI / Chapter Chapter 1 --- Microwave -assisted synthesis of a defensin peptide: a comparison of domestic and laboratory microwaves --- p.1 / Chapter 1. --- INTRODUCTION --- p.1 / Chapter 1.1. --- Defensins --- p.1 / Chapter 1.2. --- Solid-phase peptide synthesis (SPPS) --- p.5 / Chapter 1.3. --- Microwave (MW) heating in organic synthesis --- p.6 / Chapter 1.4. --- Microwave (MW) heating assisted solid phase peptide synthesis --- p.7 / Chapter 2. --- METHODS --- p.8 / Chapter 2.1. --- General synthetic approach of SPPS --- p.8 / Chapter 2.2. --- Microwave-assisted SPPS --- p.9 / Chapter 2.3. --- Analysis and characterization of the product --- p.12 / Chapter 3. --- RESULT AND DISCUSSION --- p.12 / Chapter 3.1. --- Exploring the coupling step under microwaving --- p.12 / Chapter 3.2. --- Nαdeprotection under microwave heating --- p.14 / Chapter 3.3. --- Synthesis of the target peptide --- p.16 / Chapter 3.4. --- SPPS in laboratory MW reactor --- p.18 / Chapter 3.5. --- SPPS by standard conventional method --- p.20 / Chapter 3.6. --- Comparison of the three methods --- p.21 / Chapter 3.6.1. --- Product p Product p urity --- p.21 / Chapter 3.6.2. --- Time and cost --- p.24 / Chapter 3.6.3 --- Sc alabiltiy of SPPS --- p.24 / Chapter 4. --- Exploration of the mechanism of microwave-assisted SPPS: thermal or nonthermal effect? --- p.25 / Chapter 5. --- CONCLUSION --- p.29 / REFERENCE --- p.30 / Chapter Chapter 2 --- Hybrid peptides with enhanced affinity and specificity for protein labeling --- p.33 / Chapter 1. --- INTRODUCTION --- p.33 / Chapter 1.1. --- Protein labeling --- p.33 / Chapter 1.2. --- Hybrid peptides sequences --- p.35 / Chapter 2. --- EXPERIMENTAL SECTION --- p.36 / Chapter 2.1. --- HPLC result --- p.37 / REFERENCE --- p.48

Includes bibliographical references (leaves 205-227) A study of phase conjugation by stimulated Brillouin scattering is presented with emphasis on the limiting factors, such as aperture and polarization losses, spatial coherence and saturation of the incident wave on the quality of phase conjugation, as well as the application of stimulated Brillouin scattering to loop phase-cojugated mirror and intracavity-SBS-cell-phase-conjugated oscillator.

The next generation of nuclear safety analysis computer codes will require detailed modeling of two-phase fluid flow. The most complete and fundamental model used for these calculations is known as the two-fluid model. It is the most accurate of the two-phase models since it considers each phase independently and links the two phases together with six conservation equations. A major drawback is that the current two-fluid model, when area-averaged to create a one-dimensional model, becomes ill-posed as an initial value problem when the gas and liquid velocities are not equal. The importance of this research lies in obtaining a model that overcomes this difficulty. It is desired to develop a modified one-dimensional two-fluid model for horizontal flow that accounts for the pressure difference between the two phases, due to hydrostatic head, with the implementation of a void fraction distribution parameter. With proper improvement of the one-dimensional two-fluid model, the next generation of nuclear safety analysis computer codes will be able to predict, with greater precision, the key safety parameters of an accident scenario. As part of this research, an improved version of the one-dimensional two-fluid model for horizontal flows was developed. The model was developed from a theoretical point of view with the three original distribution parameters simplified down to a single parameter. The model was found to greatly enhance the numerical stability (hyperbolicity) of the solution method. With proper modeling of the phase distribution parameter, a wide range of flow regimes can be modeled. This parameter could also be used in the future to eliminate the more subjective flow regime maps that are currently implemented in today's multiphase computer codes. By incorporating the distribution parameter and eliminating the flow regime maps, a hyperbolic model is formed with smooth transitions between various flow regimes, eliminating the unphysical oscillations that may occur near transition boundaries in today's multiphase computer codes. / Graduation date:2006

Glycosylation of recombinant proteins can change during the culture of animal cells. Since lipid-linked oligosaccharides (LLOs) are the carbohydrate donors in N-linked glycosylation, their availability is postulated to influence the extent of glycosylation. To test this hypothesis, relative LLO and glycosylation levels in Chinese hamster ovary (CHO) cells were monitored over the course of batch culture for corresponding changes. Radiolabelling studies reveal that throughout the length of culture, intracellular LLO levels remained within a 2-fold range and overall CHO protein glycosylation varied by less than 30%. The implications of these results and hypotheses to explain the findings are discussed. / Singapore-MIT Alliance (SMA)

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves [101]-106). Also available in electronic version.

No description available.

Global phase diagrams of binary systems in pressure-temperature (PT) space are very useful. In this project the techniques to automatically develop global phase diagrams in PT space were created. The codes to compute different components of a global phase diagram in PT space were developed. These codes were then successfully incorporated into a single functional program. <p>To generate the binary PT phase diagram, the overall composition was varied from pure component 2, the least volatile component (LVC) to pure component 1, the most volatile component (MVC). The step size for changing mole fraction was varied in the calculation of different parts of a global phase diagram. When the points near the joining points between different parts were computed, the step size was set to a rather small value. The step size was then increased to twice of the last value for each subsequent point computed. When the MVC mole fraction was approaching one, the step size was set to a small value to obtain enough points needed to minimize the chances of missing important phenomena. <p>The techniques to set initial guesses for evaluation of different components of a global phase diagram were discussed. The code performance, including the number of iterations for different convergence criteria and the sensitivity of the algorithm were presented. Using the code developed, phase diagrams of type I, type II, type III and type V were generated using representative binary systems from the petroleum processing field. <p>The boundary states between different types of phase behaviour were also explored. It was observed that with the increase of the binary interaction parameters, the phase behaviour of the ethane + ethanol binary system changes from type I to type II to type III while the methane + n-hexane binary system changes from type V to type III. These conclusions matched the results of van Konynenburg and Scott (1980). It was also concluded that with the increase of the binary interaction parameter for a binary system, the system showed a trend to exhibit more liquid-liquid immiscibility.

Today’s solid phase microextraction (SPME) is a well known technique that combines knowledge from different fields in an attractive, efficient, and economic way. The development of SPME has seen huge growth since its introduction as a new approach to sample preparation in the early 1990s. The applications of SPME are continuously expanding, and one of the most interesting current aspects consists of applying SPME for fast analysis of biological fluids, both in vitro and in vivo. In spite of this great potential, development of new bio-applications is considerably hindered by the lack of suitable SPME products. The goal of this study is to find SPME coatings that can be utilized for in vivo and in vitro extractions, in direct contact with a biological matrix such as blood or tissue. This thesis presents several effective ways of preparing SPME coatings based on biocompatible polymers and silica-based extractive phases, focusing on their biocompatibility as a must. After fabrication, the proposed coatings are tested for biocompatibility and analytical utility. Finally, some practical applications of the new coatings are presented, such as fast drug analysis and determination of drug plasma protein binding. Six test drugs with different physico-chemical properties are chosen for the investigation: diazepam, verapamil, lorazepam, warfarin, nordiazepam, and loperamide. It is shown that the application of these new SPME fibers for biological sample analysis greatly reduces the time required for sample preparation and limits the exposure of the analytical personnel to potentially infectious biofluids.

Various sizes of BaTiO3 and Cr3+-doped BaTiO3 nanocrystals were synthesized through hydrothermal and solvothermal methods. The applied solvents water, ethanol and benzyl alcohol lead to nanoparticles with average sizes of 200, 10 and 5 nm, respectively. The nanocrystals were treated with trioctylphosphine oxide to remove surface-bound dopant ions, and colloidal free-standing nanocrystals smaller than 10 nm were obtained by using oleic acid as a dispersant surfactant. The tetragonal-to-cubic phase transition at room temperature of undoped nanocrystalline BaTiO3 has been investigated by powder X-ray diffraction (XRD) and Raman spectroscopy. The size effect of nanoscale BaTiO3 is observed that the tetragonal phase becomes unstable with decreasing particle size. However, we found that ferroelectric tetragonal structure persists to some extent even for particles at 5 nm. The successful substitution of Ti4+ with Cr3+ in the host BaTiO3 lattice for all three sizes was achieved at different Cr3+/Ti4+ molar ratios. The dopant is found to significantly promote the phase transition, even dominate over the size effect. Ligand-field electronic absorption spectroscopy suggests a subtle change of the octahedral coordinated Cr3+ environments between particles at 5 and 10 nm, confirming the structural differences. Preliminary magnetic measurement indicates Cr3+ as isolated paramagnetic ions without any chromium clusters or oxides. The ability to rationally manipulate the ferroelectric properties of BaTiO3 by size and dopants, in combination with possible ferromagnetism induced by incorporating paramagnetic transition metal ions, opens up new opportunities for modern multiferroic materials in information storage technology.

Today’s solid phase microextraction (SPME) is a well known technique that combines knowledge from different fields in an attractive, efficient, and economic way. The development of SPME has seen huge growth since its introduction as a new approach to sample preparation in the early 1990s. The applications of SPME are continuously expanding, and one of the most interesting current aspects consists of applying SPME for fast analysis of biological fluids, both in vitro and in vivo. In spite of this great potential, development of new bio-applications is considerably hindered by the lack of suitable SPME products. The goal of this study is to find SPME coatings that can be utilized for in vivo and in vitro extractions, in direct contact with a biological matrix such as blood or tissue. This thesis presents several effective ways of preparing SPME coatings based on biocompatible polymers and silica-based extractive phases, focusing on their biocompatibility as a must. After fabrication, the proposed coatings are tested for biocompatibility and analytical utility. Finally, some practical applications of the new coatings are presented, such as fast drug analysis and determination of drug plasma protein binding. Six test drugs with different physico-chemical properties are chosen for the investigation: diazepam, verapamil, lorazepam, warfarin, nordiazepam, and loperamide. It is shown that the application of these new SPME fibers for biological sample analysis greatly reduces the time required for sample preparation and limits the exposure of the analytical personnel to potentially infectious biofluids.