Europhys. Lett.
Volume 73, Number 2, January 2006
Page(s) 299 - 305
Section Interdisciplinary physics and related areas of science and technology
Published online 16 December 2005
Europhys. Lett., 73 (2), pp. 299-305 (2006)
DOI: 10.1209/epl/i2005-10391-8

Iso-scattering points during heat-induced aggregation and gelation of globular proteins indicating micro-phase separation

T. Nicolai1, M. Pouzot1, D. Durand1, M. Weijers2 and R. W. Visschers2

1  Polymères, Colloïdes, Interfaces, UMR-CNRS 6120 - Université du Maine 72085 Le Mans Cedex 9, France
2  Wageningen Centre for Food Sciences and NIZO Food Research Kernhemseweg 2, 6718 ZB Ede, The Netherlands

received 4 April 2005; accepted in final form 25 November 2005
published online 16 December 2005

Small-angle X-ray scattering was done in situ during heat-induced aggregation and gelation of concentrated solutions of two globular proteins ($\beta$-lactoglobulin and ovalbumin) over a wide range of ionic strengths at pH 7. A well-defined iso-scattering point independent of heating time was observed in all cases, which is interpreted in terms of micro-phase separation between native proteins and aggregates. At high scattering wave vectors the structure factor is simply the weighted average of the initial state (native protein) and the final state (gel). In this q-range the relative variation of the scattering intensity is controlled by the depletion rate of native proteins.

87.14.Ee - Proteins.
82.70.Gg - Gels and sols.
78.70.Ck - X-ray scattering.

© EDP Sciences 2006