Characterization of adsorbed layers of a disordered coil protein on polystyrene latex

Mackie, A.R. and Mingins, J. and North, A.N. (1991) Characterization of adsorbed layers of a disordered coil protein on polystyrene latex. Journal of the Chemical Society-Faraday Transactions, 87 (18). pp. 3043-3049. ISSN 0956-5000. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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The combined use of small-angle X-ray scattering (SAXS) and photon correlation spectroscopy (PCS) to characterise adsorbed layers of beta-casein at the solid/liquid interface is reported. The protein was adsorbed to polystyrene latex particles at room temperature, low ionic strength and neutral pH and adsorption densities assessed by a solution-depletion technique which showed a plateau in the adsorption. Results from the SAXS experiments were analysed to provide electron-density profiles. These were backed up with results from PCS which provided hydrodynamic thicknesses over the range of the adsorption isotherm. This information, together with calculated hydrophobicity and charge profiles for the protein, yielded a molecular model for the adsorbed layer. Although beta-casein in solution has a largely random coil conformation, it appears to adopt a much more compact form when it is adsorbed on polystyrene latex. Most of the protein lies close to the surface, leaving part of the chain extended into the aqueous phase. The most likely candidate for the extended chain is part of the highly charged sequence of 40 or so amino acids at the N terminus of the protein. The hydrodynamic thickness of the protein layers increases with adsorbed concentration of protein. The thicknesses reached are substantially greater than those predicted by theories of self-avoiding walks of the extended chain with volume exclusion interactions included and it is suggested that long-range electrostatic repulsive forces are involved.

Item Type: Article
Subjects: Q Science > QD Chemistry
Q Science > QC Physics
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: O.O. Odanye
Date Deposited: 08 Oct 2009 18:16
Last Modified: 08 Oct 2009 18:16
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