Protein-protein interactions in ovalbumin solutions studied by small angle scattering: effect of ionic strength, and the chemical nature of cations

Luca Ianselli, Fajun Zhang, Maximilian W. A. Skoda, Robert M. J. Jacobs, Richard Martin, Shirley Callow, Sylvain Prévost, Frank Schreiber

Research output: Contribution to journalArticle

Abstract

The influence of ionic strength and of the chemical nature of cations on the protein-protein interactions in ovalbumin solution was studied using small-angle X-ray and neutron scattering (SAXS/SANS). The globular protein ovalbumin is found in dimeric form in solutions as suggested by SANS/SAXS experiments. Due to the negative charge of the proteins at neutral pH, the protein-protein interactions without any salt addition are dominated by electrostatic repulsion. A structure factor related to screened Coulombic interactions together with an ellipsoid form factor was used to fit the scattering intensity. A monovalent salt (NaCl) and a trivalent salt (YCl3) were used to study the effect of the chemical nature of cations on the interaction in protein solutions. Upon addition of NaCl, with ionic strength below that of physiological conditions (150 mM), the effective interactions are still dominated by the surface charge of the proteins and the scattering data can be understood using the same model. When yttrium chloride was used, a reentrant condensation behavior, i.e., aggregation and subsequent redissolution of proteins with increasing salt concentration, was observed. SAXS measurements reveal a transition from effective repulsion to attraction with increasing salt concentration. The solutions in the reentrant regime become unstable after long times (several days). The results are discussed and compared with those from bovine serum albumin (BSA) in solutions.
Original languageEnglish
Pages (from-to)3776-3783
Number of pages8
JournalJournal of Physical Chemistry: Part B
Volume114
Issue number11
DOIs
Publication statusPublished - 25 Mar 2010

Keywords

  • cations
  • protein−protein interactions
  • ovalbumin solution
  • screened Coulombic interactions
  • ellipsoid form factor
  • monovalent salt
  • trivalent salt
  • bovine serum albumin

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