Thermodynamic Analysis for Cationic Surfactants Binding to Bovine Serum Albumin

Document Type : Research Paper


Department of Chemistry, Shahreza Branch, Islamic Azad University, Shahreza, Iran


In the present study, the binding isotherms for interaction of a homologous series
of n-alkyltrimethyl ammonium bromides with bovine serum albumin (BSA) have
been analyzed on basis of intrinsic thermodynamic quantities. In this regards, the
intrinsic Gibbs free energy of binding, AGb(i,)„ has been estimated at various
surfactant concentrations and its trend of variation for both binding sets have been
interpreted on basis of cooperativity and hydrophobicity of process. Subsequently,
the contribution of electrostatic and hydrophobic interactions in AG,, have been
estimated using a published method which has been previously introduced by us
for analysis of jack bean urease-cationic surfactant system. The results represent
the favoring predominate role of hydrophobic interactions and inhibiting rule of
electrostatic interaction in binding affinity of both sets. The predominate role of
hydrophobic interactions in the second binding set can be related to entropy
statistical effect, which arises from numerous number of binding sites in this set
but it may be referred to large amount of positive charge density and accessible
hydrophobic surface area of BSA in first binding set.