Role of hydrophobic and polar interactions for BSA-amphiphile composites

To evaluate the role of hydrophobic and electrostatic or other polar interactions for protein-ligand binding, we have studied the interactions of bovine serum albumin (BSA) with 2-alkylmalonic acid and 2-alkylbenzimidazole amphiphiles having different head group and alkyl chain length. The binding affinity for the protein-amphiphile interactions is found to depend predominantly on the length of hydrocarbon chain, suggesting the crucial role of hydrophobic forces, supported by polar interactions at the protein surface. The BSA fluorescence exhibits appreciable hypsochromic shift along with a reduction in fluorescence intensity and mean lifetime upon binding with 2-alkylmalonic acid. UV-visible, steady state and time-resolved fluorescence measurements were performed to compare the effects of amphiphiles on BSA as a function of the amphiphiles head group and alkyl chain length.