Influence of the medium conditions on the 1-anilino-8-naphthalene sulfonate-bovine serum albumin binding.

The effect of medium conditions on the binding of 1-anilino-8-naphthalene sulfonate (ANS) to bovine serum albumin (BSA) was studied. The intensity of binding was affected by the type of the monovalent salts used. While F- and Cl- decreased, SCN- and ClO4- promoted the binding. The relative order in which various anions influence the ANS binding to albumin process followed the lyotropic series. Some changes in the solvent structure affect the extent of binding. Urea exhibited two opposite effects. At low concentration urea induced the binding; at concentration above 1 M the binding was decreased. pH increase between 3 to 6 decreased dramatically primary and secondary sites. At pH higher than 6 only the secondary site affinity was increased. pH effect on the ANS binding to albumin is due to a participation of the acid and neutral conformational change of BSA.