Interactions of proteins in aqueous ammonium-sulfate solutions:Mixtures of lysozyme and ovalbumin

Abstract

Fluorescence anisotropy was used to determine lysozyme-ovalbumin interactions in 20-mM sodium-phosphate buffer at pH 7 and 25 o C over an ammonium-sulfate ionic-strength range 0.0 to 7.5 M. At pH 7, the net charge on lysozyme is +8 while that on ovalbumin is -12. The association constant calculated from fluorescence-anisotropy data in salt-free buffer solution was interactions at these moderate ionic strengths. At high ionic strength, the cross-and selfinteractions are greater because of increasing hydrophobic attraction, and both self-interactions are more attractive than the cross-interaction of lysozyme and ovalbumin.