Molecular interactions versus local conformational details: TFE effects on bovine serum albumin solutions

The intertwining between intermolecular protein interactions solvent mediated and protein conformational details i is of fundamental importance in the understanding of protein aggregation processes. Tri-Fluor-Ethanol (TFE) in solution can alter protein conformation, by interfering with hydrogen bonds and by enhancing the stability of the alpha helical secondary strutture. In order Io investigate the relation between intermolecular interaction and molecular conformation,we study the influence of TFE on the thermodynamic stability and on the conformational changes of a model protein, bovine serum albumin (bsa). Solvent mediateci pair-wise interactions are investigated by static and dynamic light scattering, which give a measure of the second virial coefìicient (b2) and of the hydrodynamic coeficient (h), respectively. F-UV and N-UV circular dichroism, steady-state fluorescence measurements from an intemal (Triptophan) and an extemal probe (8-anilino-l-naphthalenesulphonate,ANS), inform on the protein conformational changes at different TFE concentrations. Results show that moderate concentration of TFE (less than 10%) can alter the molecular conformation of bsa. At TFE concentrations higher than 15%, bsa conformation is further changed and an effective attractive interaction is turned on, as indicated by light scattering data