Interaction of local anesthetic heptacaine homologs with phosphatidylcholine bilayers: spin label ESR study

摘要

Local anesthetic monohydrochlorides of [2-(alkoxy)phenyl]-2-(1-piperidinyl)ethyl esters of carbamic acid (CnA, n=2, 3, 4, 6, 8, 10, 12 is the number of carbon atoms in the alkyloxy substituent) increase the probability of formation of gauche isomers pg and decrease the effective energy difference between gauche and trans conformation Eg in egg yolk phosphatidylcholine (EYPC) acyl chains, as determined by electron spin resonance spectroscopy using dipalmitoylphosphatidylcholines labeled with the paramagnetic dimethyloxazolidinyl group on the 12-th or 16-th carbon atoms of their sn-2 acyl chain, and oriented EYPC bilayers hydrated at 81% relative water vapour pressure. CnAs also increase the hydration of EYPC in non-oriented bilayers at the same relative water vapour pressure. At the molar ratio of CnA:EYPC=0.4:1, the maximum effect on pg, Eg and hydration has been observed for intermediate alkyloxy chain lengths n≈4÷6.