Effect of Amino Acids and Glycyl Dipeptides on Micellization of Antibacterial Drug Domiphen Bromide

The effects of amino acids (glycine, l -alanine, l -valine, l -leucine) and glycyl dipeptides (glycylglycine, glycyl- l -valine, glycyl- l -leucine) on the micellization behaviour of antibacterial drug domiphen bromide in aqueous solution as a function of temperature were studied by both conductivity and fluorescence spectroscopy. Critical micellar concentration, degree of counterion dissociation ( α ), limiting molar conductivity ( Λ 0 ), and a series of thermodynamic parameters of micellization of domiphen bromide have been calculated from the specific conductivity data. The I 1 / I 3 ratios associated with pyrene fluorescence vibronic bands were used to interpret the variation of micropolarity caused by the interactions between domiphen bromide and amino acids/glycyl dipeptides. The mean aggregation number of domiphen bromide was determined by a fluorescence quenching method. Effects of temperature, concentration, and alkyl chain length of the amino acids/glycyl dipeptides on the above properties were examined. Amino acids and glycyl dipeptides effectively enhance the surface activity of domiphen bromide solution. The intensity of amino acid/dipeptide-domiphen bromide interaction increased with the hydrophobicity of the amino acid/glycyl dipeptide.