INTERACTION OF LOCAL-ANESTHETIC HEPTACAINE HOMOLOGS WITH PHOSPHATIDYLCHOLINE BILAYERS - SPIN-LABEL ESR STUDY

Local anesthetic monohydrochlorides of [2-(alkoxy)phenyl]-2-(1-piperid inyl)ethy esters of carbamic acid (CnA, n = 2, 3, 4, 6, 8, 10, 12 is t he number of carbon atoms in the alkyloxy substituent) increase the pr obability of formation of gauche isomers p(g) and decrease the effecti ve energy difference between gauche and trans conformation E-g in egg yolk phosphatidylcholine (EYPC) acyl chains, as determined by electron spin resonance spectroscopy using dipalmitoylphosphatidylcholines lab eled with the paramagnetic dimethyloxazolidinyl group on the 12-th or 16-th carbon atoms of their sn-2 acyl chain, and oriented EYPC bilayer s hydrated at 81% relative water vapour pressure. CnAs also increase t he hydration of EYPC in non-oriented bilayers at the same relative wat er vapour pressure. At the molar ratio of CnA:EYPC = 0.4:1, the maximu m effect on p(g), E-g and hydration has been observed for intermediate alkyloxy chain lengths n approximate to 4 divided by 6.