Combined NMR and simulation study of carbohydrate linkage dynamics

Master Thesis


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University of Cape Town

Biomaterials have recently gained significance as a result of environmental pressures and their increased viability through crop engineering. Starch harvested from maize crops is one example of a cheap and abundant biopolymer, which could substitute conventional polymers such as polyethylene as a material in manufacturing. Its practical application, however, will depend on understanding its physical behaviour, so that intelligent modifications can be made to enhance its properties. The most effective way of changing a polymer's properties is by modification at the chemical level, since ultimately it is this which determines the macroscopic features, such as viscosity, plasticity and tensile strength. Since the origin of these features is difficult to study experimentally, this thesis will tackle the problem by means of computer simulation of small carbohydrate fragments. In particular, the two principal types of carbohydra te linkage (namely 0: (1--+4) and 0: (1--+6)) will be examined in this thesis, since these are the chief elements of conformational flexibility in these molecules. The 0(1--+4) and 0:(1--+6) linkages are studied both separately in the maltose and isomaltose molecules respectively and together in panose and the resultant water structuring and dynamic behaviour are studied. Although the computational approach provides insights not available experimentally, it is nonetheless important to compare the results obtained with an experimental reference as a check on their validity. N!vlR T1 relaxation measurements, which give indirect information on the atomic scale dynamics, have been measured for each of the model fragments and compared with values calculated directly from simulation.

Includes bibliographical references.