Binding of Cationic Single-Chain and Dimeric Surfactants to Bovine Serum Albumin

The interactions between bovine serum albumin (BSA) and the single-chain surfactants N-benzyl-N,N-dimethyl-N-(1-dodecyl)ammonium bromide (PH12) and N-cyclohexylmethyl-N,N-dimethyl-N-(1-dodecyl)ammonium bromide (CH12) and their two dimeric counterparts, N,N'-[1,3-phenylenebis(methylene)]bis[N,N-dimethyl-N-(1-dodecyl)]ammonium dibromide (12PH12) and N,N'-[cyclohexane-1,3-diylbis(methylene)]bis [N,N-dimethyl-N-(1-dodecyl)]ammonium dibromide (12CH12), respectively, have been investigated by surface tension, fluorescence, circular dichroism, zeta potential, and atomic force microscopy. The results obtained permit the examination of the way an increase in the number of hydrophobic chains and the substitution of a cyclohexyl ring by a phenyl ring, either in the headgroup of single-chain surfactants or in the spacer of dimeric surfactants, affect BSA-surfactant interactions. The comparison of the fluorescence results with those obtained by zeta potential measurements shows that the sites of binding of the surfactants with aromatic rings to the BSA are somewhat different from those of the surfactants with no aromatic rings.