(188ck) Effect of Methanol and Glycerol on the Structure of Plasma Protein Solutions

Small angle scattering (SAS) is an important tool to study the structural properties and interactions of biological macromolecules. Numerous studies have been published about the effect of organic solvents on intramolecular protein interactions. However, little attention has been paid to the effect of organic solvents on both intra and inter molecular interactions in protein solutions. The solution behavior of major plasma proteins like human serum albumin (HSA), immunoglobulin G (IgG), thrombin and fibrinogen in the presence of methanol and glycerol was studied by small angle neutron scattering (SANS). Experiments covering a wide range of protein, salt, and cosolvent concentrations at 5, 25, and 45 °C were performed. The radius of gyration (R_g), molecular weight and surface area were obtained by curve fitting the experimental data. A comprehensive analysis of the effect of these cosolvents on the structure showed that methanol shortens the range of the intermolecular forces. Low resolution solution structures of the plasma proteins were obtained using ab initio shape reconstruction by ATSAS 2.8 package. Simulated annealing implemented either using DAMMIN which uses a dummy atom model or GASBOR which uses a chain-like ensemble of dummy residues was employed to find a configuration that fits the data while minimizing the interfacial area. Pairwise distribution function (P(r)) profiles were used to deduce the particle shape using GNOM. Theoretical scattering curves predicted from the models fits well with the experimental data. The models obtained closely resemble the shape of known high resolution crystallographic structures.