Modification of interactions among proteins with the lowering of solution pD toward the isoelectric point in presence of different valent ions

Bovine serum albumins show a short-range attraction and a long-range electrostatic repulsion among them and these interactions are modified depending upon the solution pD and different dissolved counterions in the solution. Small angle neutron scattering study shows that for equal mono-valent (Na+) and di-valent (Ni2+) ion concentrations, both the attractive and repulsive interaction decreases with lowering the solution pD toward the protein isoelectric point, however for the tri-valent (Fe3+) ion attractive interaction increases and repulsive interaction decreases. Interaction variation for the equal ionic strength of the three different valent ions becomes prominent as the pD decreases toward the isoelectric point.