Cold gelation behavior of BSA has been studied after gradual heating below gelation temperature and mixing with Fe+3 ions at pD approximate to 7.0. Structures and interactions are obtained from small angle neutron scattering (SANS) studies by varying the Fe+3 ion concentration. Fractal structure grows with the addition of salt (even for 10 mM Fe+3) for the heat treated BSA. Heat treated BSA without salt shows intermediate range electrostatic repulsion and long range attraction. Without heat treatment, same types of interactions exist among BSA for both low and high ion concentrations, but for the intermediate ion concentrations fractal structure forms. (c) 2013 Elsevier B.V. All rights reserved.