Kinetics of channel formation of gramicidins A and B in phospholipid vesicle membranes

The thermal incorporation and channel formation of gramicidins A and B into phosphatidylcholine/phosphatidylglycerol large unilamellar vesicle membranes was studied using 23Na NMR. Delta H and delta S of activation for channel formation for gramicidin A are 11.8 kcal/mol and -11 e.u., respectively. For gramicidin B, delta H and delta S of activation are 14.6 kcal/mol and -4 e.u., respectively. Possible reasons for the differences in delta H and delta S of activation between the two analogues are discussed