Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596931
Title: Heat-induced structure formation by β-lactoglobulin
Author: Bromley, Elizabeth Helen Claire
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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Abstract:
The heat-induced structure formation by the globular protein, b-lactoglobulin, has been studied over a wide range of solution conditions and heating regimes. The results are split into two main categories corresponding to the regimes in which b-lactoglobulin forms fine stranded and particulate gels. In the fine stranded regime (non-isoelectric pH), b-lactoglobulin was found to form highly ordered structures which bound the amyloid specific dyes Congo red and Thioflavin T. In the case of the pH 2.5 and no added NaCl, the X-ray fibre diffraction pattern was found to correspond well to that of amyloid. Higher order structures in the form of spherulites composed of assemblies of amyloid fibrils were also investigated. The kinetics of fibril formation in b-lactoglobulin was investigated and modelled using a theory based on a slow forwards reaction, generating an active species followed by a critical stable nucleus size dependent nucleation and growth. In the particulate regime (isoelectric pH), the gel structures were investigated using Environmental SEM, confocal microscopy and small angle X-ray scattering. The gels were found to comprise densely packed particles with fractal surfaces. The effects of ionic strength, pH, protein concentration and heating regime on the size of the particles were investigated. Increasing heating rate and holding temperature were found to decrease the particle size, with ionic strength increasing particle size. A peak in particle size was found as a function of pH as the isoelectric point was approached. These results were described in terms of two models. The first model, based on a temperature imposed equilibrium size, accounts well for the decrease in particle size with holding temperature. The second model based on a nucleation rate which is dependent on the temperature via the unfolding transition, was more successful at describing the heating rate dependence.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.596931  DOI: Not available
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