published_or_final_version / abstract / Computer Science / Doctoral / Doctor of Philosophy

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Computational studies have shown that cage skeletons (7) have the tendency to impose a 310-helix as well as an áL-helix on the polypepeptide chain. Residues such as 7 are the useful tools for study of the conformational preferences of peptide models, the design of peptide analogues with improved pharmacokinetics profiles and the development of pharmacophore models. Synthesis of pentacycloundecane amino acid analogue suitable for peptide synthesis would enable us to verify the computational predictions and to contribute to this very active field of research. The sterically hindered 8-amino-pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8-carboxylic acid (7) was synthesised by hydrolysis of the novel bis-Boc protected pentacycloundecane-hydantoin (30). Progress to incorporate 7 into a non-natural peptides is reported. A computational investigation on the regioselective acetylation of hydantoin derivatives which includes PCU hydantoin, 5.5-dimethylhydantoin and 5-methylhydantoin is also reported. The results of the computational investigation initiated the regioselective synthesis of the mono-Boc and bis-Boc derivatives of 5,5-dimethylhydantoin and 5-methylhydantoin. These compounds have not been reported before. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2005.

One of the key questions in the field of star formation is the role of stellar feedback on the subsequent star formation process. The W3 giant molecular cloud complex at the western border of the W4 super bubble is thought to be influenced by the massive stars in W4. This paper presents a study of the star formation activity within AFGL. 333, a similar to 104 M-circle dot cloud within W3, using deep JHK(s) photometry obtained from the NOAO Extremely Wide Field Infrared Imager combined with Spitzer IRAC and MIPS photometry. Based on the infrared excess, we identify 812 candidate young stellar objects (YSOs) in the complex, of which 99 are Class I and 713 are Class II sources. The stellar density analysis of YSOs reveals three major stellar aggregates within AFGL. 333, namely AFGL. 333 Main, AFGL. 333 NW1 and AFGL. 333 NW2. The disk fraction within AFGL. 333 is estimated to be similar to 50%-60%. We use the extinction map made from the H - K-s colors of the background stars and CO data to understand the cloud structure and to estimate the cloud mass. From the stellar and cloud mass associated with AFGL. 333, we infer that the region is currently forming stars with an efficiency of similar to 4.5% and at a rate of similar to 2-3M(circle dot) Myr(-1) pc(-2). In general, the star formation activity within AFGL. 333 is comparable to that of nearby low mass star-forming regions. We do not find any strong evidence to suggest that the stellar feedback from the massive stars of nearby W4 super bubble has affected the global star formation properties of the AFGL. 333 region.