Protein-surfactant interactions

Protein-surfactant interactions in aqueous media have been investigated. The globular proteins lysozyme and bovine serum albumin (BSA) served as model proteins. Several ionic and non-ionic surfactants were used.Fluorescence probe measurements showed that at low sodium dodecyl sulfate (SDS) concentration (< 0.1 M) one micelle-like SDS cluster is bound to lysozyme. From dynamic light scattering (DLS) results it was observed that lysozyme in the complex does not correspond to the fully unfolded protein. At high SDS concentration (> 0.1 M) one compact and one more extended lysozyme-SDS complex coexist.The influence of surfactant alkyl chain length and headgroup on BSA-surfactant complex formation was investigated. In these studies, binding isotherms were determined by nuclear magnetic resonance (NMR), DLS was used to measure the hydrodynamic radii of the complexes and the size of the micelle-like aggregates on BSA was determined using fluorescence probe methods.
It was observed from fluorescence measurements that the number of bound SDS molecules does not depend on the presence of the disulfide bridges. Reduced proteins wrap more efficiently around the micelle-like structures, resulting in somewhat smaller complexes, as observed with DLS…


1 Introduction
1.1 Self-Assembly of Surfactants
1.2 Proteins
1.2.1 Protein Structure
1.2.2 Unfolding of Proteins
1.2.3 Lysozyme
1.2.4 BSA
1.3 Protein-Surfactant Interactions
1.3.1 Binding Isotherms
1.3.2 Structure of Protein-Surfactant Complexes
2 Experimental Techniques
2.1 Light Scattering
2.1.1 Light Scattering Apparatus
2.1.2 Dynamic Light Scattering
2.1.3 Static Light Scattering
2.1.4 Light Scattering on Gels
2.2 Fluorescence Probe Methods
2.3 Nuclear Magnetic Resonance
3 Results and Discussion
3.1 The Lysozyme-SDS System
3.2 The BSA-SDS System
3.3 BSA-Surfactant; The Influence of the Surfactant Headgroup on Complex Formation
3.4 BSA-Surfactant; The Influence of the Surfactant Chain
Length on Complex Formation
3.5 Reduced Protein-SDS Systems
3.6 Ternary Phase Diagram: BSA-SDS-3.1 mM NaN3
3.7 Heat-Set BSA-SDS Gels
3.7.1 Heat-Induced Aggregation of BSA-SDS Complexes
3.7.2 Structure of Heat-Set BSA-SDS Gels
4 Concluding Remarks and Future Outlook

Author: Valstar, Ank

Source: Uppsala University Library

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