Heat-induced formation of ordered structures of ovalbumin at low ionic strength studied by small angle X-ray scattering

Abstract Small angle X-ray scattering (SAXS) has been performed on native ovalbumin solutions and heated ovalbumin systems at neutral pH and low ionic strength. In native ovalbumin solutions there is a partial ordering, where the interparticle distance ( d max ) scales with the protein concentration ( C ) as d max  ∼  C −0.28 . This exponent indicates that the ovalbumin monomers behave as a uniform distribution of charged spheres in solution. The q -dependent scattering intensity of ovalbumin aggregates can be well described by a form factor of rods. The dependence of d max for aggregates on the protein concentration was found to be d max  ∼  C −0.51 , this scaling behavior is in good agreement with that theoretically derived for the distribution of spaces in a random network of straight fibers. The existence of a well-defined interparticle distance between aggregates is confirmed by cryo-TEM. The scattering profiles of native and aggregated ovalbumin were successfully fitted including both form factor and structure factor, using the preferred distance ( L ), a measure of disorder ( σ / L ), and the radius ( R or a ) as fitting parameters.