Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M. Med. Sc.)--University of Hong Kong, 2006.

3C-like protease (3CLpro) of severe acute respiratory syndrome-coronavirus (SARS-CoV) is required for autoprocessing of the polyproteins 1a and 1ab, and is a potential target for treating coronaviral infection. To obtain a thorough understanding of its substrate preference, we created a substrate library of 19 x 8 variants by performing saturation mutagenesis on the autocleavage sequence at P5 to P3' positions. The substrate sequences were inserted between cyan and yellow fluorescent proteins so that the cleavage rates were monitored by in vitro fluorescence resonance energy transfer (FRET). The relative cleavage rate for different substrate sequences was correlated with various structural properties. P5 and P3 positions prefer residues with high beta-sheet propensity P4 prefers small hydrophobic residues: P2 prefers hydrophobic residues without beta-branch. Gln is the best residue at P1 position, but observable cleavage can be detected with His and Met substitutions. P1' position prefers small residues, while P2' and P3' positions have no strong preference on residue substitutions. Noteworthy, solvent exposed sites such as P5, P3 and P3' positions favour positively charged residues over negatively charged one, suggesting that electrostatic interactions may play a role in catalysis. A super-active substrate, which combined the preferred residues at P5 to P1 positions, was found to have 2.8 fold higher activity than the wild-type sequence. / Inhibition of SARS-CoV 3CLpro proteolytic activity suppresses virion replication and virus-induced cytopathic effects. Peptidomimetic inhibitors with nitrile warheads, which inhibit Cys protease activity, have been applied for clinical therapy. To investigate whether the nitrile group can target 3CLpro, a series of nitrile-based peptidomimetic inhibitors with various protective groups, peptide length and peptide sequences were synthesized. Inhibitor potency in terms of IC50 and Ki values was determined by FRET assay. Most of these nitrile-based inhibitors in micromolar range can significantly reduce 3CLpro activity. The most potent inhibitor is the tetrapeptidomimetie inhibitor linked with carbobenzyloxy (cbz) group 'cbz-AVLQ-CN' with IC50 and Ki values of 5.9 +/- 0.6 muM and 0.62 +/- 0.11 muM respectively. Crystal structures of 3CLpro-inhibitor complexes demonstrated that nitrite warhead covalently bonded to Cys145, while P1 -- P4 residues interacted with 3CLpro as substrate bound. The cbz group in 'cbz-AVLQ-CN' flipped into a cavity of Gu166 -- Pro168, providing an extra binding force to enhance inhibitor potency. In conclusion, the nitrile-based peptidomimetic inhibitor with cbz group is a convincing model for drug development. / Substrate specificities of various 3CLpro were further investigated by using the substrate library of SARS-CoV 3CLpro. Among various viral strains, the proteases of HCoV-NL63, HCoV-OC43 and infectious bronchitis virus (IBV) were selected from group I, IIa and III respectively for specificity profiling. Their proteolytic rates against 19 x 8 variants were obtained by FRET assay, and correlated with structural properties of substituting residues. Like SARS-CoV 3CLpro in group IIb, these 3CLpro consistently prefer small hydrophobic P4 residues, positively charged P3 residues, hydrophobic P2 residues without beta-branch, P1-Gln and small P1' residues. These proteases also tend to accommodate P5 and P3' residues with positive charge, and P2' residues with small size. In contrast, their preferences on secondary structure are diverse. Correlation was found between IBV 3Clpro activity and beta-sheet propensity at P5 position, while no strong correlation with secondary structure propensities was observed in HCoV-NL63 and HCoV-0C43. Collectively, all 3CLpro share universal preferences on charge, side chain volume and hydrophobicity, but not secondary structure. Their relative activities against universal and specific super-active substrates were elevated to 1.4 -- 4.3, showing synergetic effects by combining preferred residues. These substrates were examined by group I HCoV-229E and group IIa HCoV-HKU1 in parallel. Their activities were highly comparable to those of other group members. / Chuck, Chi Pang. / Adviser: Chi-Cheong Wan. / Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves [179]-187). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

published_or_final_version / abstract / Medicine / Master / Doctor of Medicine

Thesis (M. Med. Sc.)--University of Hong Kong, 2005.

Objetive: To describe the prevention and control practices for the infection to SARS-COV2 in the Peruvian population. Material and Methods: Observational descriptive study. We evaluated a non-probabilistic sample of adult residents in some departments of Peru. Preventive practices were evaluated in people without a history of COVID-19 and control practices in people who had suffered it. Results: We evaluated 3630 Peruvians (mean age 25.4 ± 9.5), of that 3231 don't have a history of COVID-19 and 399 who had suffered it. The prevention and control practices that were realized often or always, with more frequencies, was the use of a mask when they go out home (97.9% vs 87.7), cover their nose or mouth when they sneeze (95.4% vs 89.9%), save the distance to other people in the street (91.4% vs 74.7%), wash their hands when they came home (92.5% vs 88.7%), and disinfect the objects and personal places (82.6% vs 77.4%). The 22.1% and 83.7%, the 59.7% and 80.2, and the 8.0% and 16.8% consumed some type of medicine, medicinal plant, and chlorine dioxide to prevent and control the infection, respectively. Conclusion: In general, less than 50% of the participants performed prevention and control practices against COVID-19 often or always. / Revisión por pares

Cellular defense and metabolism are important biological processes in living cells. In this study, these two biological processes were investigated in two selected disease models: diabetes mellitus (DM) and severe acute respiratory syndrome associated coronavirus (SARS-CoV) infection by two-dimensional gel electrophoresis (2DE) coupled with Matrix-Assisted Laser Desorption Ionisation Time-Of-Flight Mass Spectrometry (MALDI-TOF MS)-based proteomic approaches. The major findings are summarized as follows: / Our results on DM investigation can help to better understand the pathophysiological changes in patients with DM and the pathogenesis of hyperglycemia-caused complications. Data obtained from SARS-CoV studies provided novel insights into the molecular basis of the host cell response upon viral infection. / Protein profile of streptozotocin (STZ)-induced diabetic animal tissues, including mice liver, kidney and eye, and rats sera, indicated that DM has an impaired cellular defense system. These include the impairment in reactive oxygen species scavenging and the impairment in activation of complement system and innate immunity, and the enhancement in blood coagulation reaction. Our results also demonstrated that glycolysis and gluconeogenesis did not alter significantly in the liver of STZ-diabetic mice, while fatty acid oxidation and TCA cycle were attenuated under the same conditions. Moreover, we also detected other abnormal metabolism in aldehyde and amino acid, especially glutamate metabolism and the urea cycle. Abnormalities were also detected in lipid transport and metabolism. Besides, protein profile of mouse liver c37 cells indicated that high glucose may induce apoptosis in these cells, and this apoptotic effect may be mediated via the mitochondrial pathway. Furthermore, the proteomic results from the in vivo and in vitro diabetic models have prompted us to look for glucose responsive element on the promoters of these up-regulated hepatic genes. We found that the mouse aldolase 2 gene has glucose responsiveness in c37 cells treated with high glucose by semi-quantitative RT-PCR and promoter transfection assay. Finally, protein profile of Vero E6 cells strongly implicated that SARS-CoV can induce anti-apoptosis. This effect may be mediated via the mitochondrial pathway. Our data also suggested that the anti-apoptotic activity may be required for viral replication at the early stage of infection. While under the condition of long-term infection, this may be needed for viral survival. / Zhong Mingqi. / "October 2005." / Advisers: Sai Ming Ngai; Hon Ki Cheng. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6217. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 223-248). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

Thesis (Ph.D. in Microbiology) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 168-210). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;