Control of molecular orientation of alpha-helix in the monolayer at air-water interface

Amphiphilic block copolymers of poly(6-leucine-co-ethylene glycol) (PLeu(m) -PEG(m)) having three different compositions, m:n = 80:23, 57:46, and 66:11 4, were prepared and spread at an air-water interface to form a stable mono layer. The alpha -helical conformation of PLeu segment in the monolayers wa s confirmed by FT-IR and circular dichroism measurements. The molecular ori entation of PLeu helix rods in the monolayer was estimated by surface press ure-area isotherm and FT-IR reflection absorption spectroscopy measurements . As a result, we confirmed that alpha -helix rod of PLeu segment oriented slightly normal to the membrane plane. Furthermore, it was indicated that e ach alpha -helical rod in the PLeu(57)-PEG(46) monolayer is effectively ori ented normal to the interface compared to that in the PLeu(80)-PEG(23) and PLeu(66)-PEG(114) monolayers.