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Konformasie-analise van 'n tetrapeptiedfragment van Erabutoksien B

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dc.contributor.author Du Toit A en
dc.date.accessioned 2016-09-26T06:26:43Z
dc.date.available 2016-09-26T06:26:43Z
dc.date.submitted 1992 en
dc.identifier.uri http://hdl.handle.net/20.500.11892/174000
dc.description.abstract In order to explain the activity of proteins on a molecular basis it is necessary to study the conformation of the protein. Since there is evidence that certain peptides are responsible for specific activities, the study of the conformation space of these peptides can continue to give significant information on the spacial structure of active proteins. The aim of this study is to visualize the spatial conformation of the tetra-peptide His-Ser-Ser-Gln (HSSQ), by making use of theoretical (molecular mechanics), experimental (nuclear magnetic resonance spectroscopy) and molecular graphical (interactive molecular graphics) methods. This tetra-peptide is found in the &beta;-turn of the first loop of the short chain neurotoxins. Since the &beta;-turn is able to bind to a receptor, it is the aim of this study to determine the preferred conformations of HSSQ, so that more information can be obtained about the receptor conformation and therefore also to better understand this activity. The conformation space of HSSQ was investigated by using rigid-geometry force-field calculations. The Build-up method was used to calculate the minimum energy conformations (MEC). In the dipeptide, the two central Ser residues in the tetrapeptide already show a Type III &beta;-turn. After all the data had been sorted, it was found that all the MEC of HSSQ did indeed stabilise a Type III &beta;-turn. It was essensially the presence of hydrogen bonds between the backbone and side chain atoms that stabilise the &beta;-turn conformations. Molecular modelling studies were done on the MEC of HSSQ by means of interactive molecular graphics. Spatial relationships were observed between these conformations, which elucidate the activity and selectivity of the peptides. In the NMR studies on the synthetic tetrapeptide HSSQ, two polar solvents, namely D<sub>2</sub>O and DMSO-d<sub>6</sub>, were used. The peptide assumes random coil conformations in D<sub>2</sub>O, while small populations of non-random conformations occur in DMSO-d<sub>6</sub>. The NO-effect (Nuclear Overhauser Enhancement Effects) between HisC<sup>&alpha;</sup>H and GlnN<sup>&alpha;</sup>H that is observed on the ROESY spectrum, further confirms the presence of &beta;-turn conformations in the tetrapeptide. en
dc.language Afrikaans en
dc.subject Chemistry en
dc.title Konformasie-analise van 'n tetrapeptiedfragment van Erabutoksien B en
dc.type Masters degree en
dc.description.degree MSc en

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