The effect of gentamicin on the biophysical properties of phosphatidic acid liposomes is influenced by the O-C = O group of the lipid.
We previously reported that gentamicin binds to liposomes composed of anionic phospholipids and depresses glycerol permeability and raises the activation energy for glycerol permeation in these liposomes. We postulated that these changes in the glycerol permeability and in the activation energy (Ea) for glycerol permeation were due to hydrogen bonding between O-C = O groups in the hydrogen belt and one or more amino groups of gentamicin. To test this hypothesis, we examined the effects of gentamicin on the membrane surface potential, the glycerol permeability coefficient (p), the Ea for glycerol permeation, and the aggregation of liposomes composed of 1:1 phosphatidylcholine (PC) and phosphatidic acid with the acyl chains of phosphatidic acid in either an ester (PA) or an ether (PA*) linkage. Gentamicin depressed the membrane surface electrostatic potential, measured by the partitioning of methylene blue between the bulk solution and the liposomal membrane, to an equivalent degree in PC-PA and PC-PA* liposomes, which indicates that substitution of the ether for the ester linkage did not interfere with the electrostatic interaction between the cationic drug and the negatively charged phosphate head group. Gentamicin caused a temperature-dependent decrease of p and raised Ea for glycerol permeation from 17.7 +/- 0.3 to 21.6 +/- 0.4 kcal/mol in PC-PA liposomes but had little or no effect on these parameters in PC-PA* liposomes. In contrast, gentamicin induced a significantly greater degree of aggregation of PC-PA* liposomes compared to that of PC-PA liposomes.(ABSTRACT TRUNCATED AT 250 WORDS)
Ramsammy
L S
LS
Department of Medicine, State University of New York, Stony Brook 11794-8152.
Kaloyanides
G J
GJ
D055598:Chemical Phenomena; D002621:Chemistry; D005839:Gentamicins; D008081:Liposomes; D008564:Membrane Potentials; D008954:Models, Biological; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines
D005839:Gentamicins; D008081:Liposomes; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines