Liposomal membrane. I. Chemical damage of liposomal membranes with functional detergent

The interaction and reaction between liposomal membrane and a functional detergent, N-hexadecyl-N-(imidazol-4-yl)methyl-N,N-dimethylammonium chloride hydroperchlorate (Im-I), have been investigated in conjunction with the leakage of bromothymol blue encapsulated as a marker in the bilayers of liposomes. Im-I carries an imidazole moiety and was expected to behave as a simple lipase model. The reaction with Im-I significantly enhanced the leakage of bromothymol blue encapsulated in the egg lecithin and dipalmitoyl phosphatidylcholine liposomes. During the course of reaction with Im-I, the formation of acyl-imidazole intermediate was clearly identified, which was certainly connected with the bromothymol blue release. From various kinetic results on bromothymol blue release and acyl-imidazole formation, it has been suggested that the bromothymol blue release from liposomal bilayer may be caused by the local and instantaneous decomposition of lipids when Im-I penetrates into the bilayer. However, it has also been demonstrated that the immediate reconstruction of liposomes retains the barrier function to protect against the further release of bromothymol blue.