CHARACTERIZATION OF HELICAL SENSE TRANSITION FOR POLY(BETA-P-BENZYL L-ASPARTATE) CONSTRAINED TO THE AIR-WATER-INTERFACE

From external reflectance infrared spectra directly obtained at the ai r-water interface, the conformation of poly(beta-benzyl L-aspartate) i s established in monolayer films. It was found that a right-handed alp ha-helix, 4.0(13) omega-helix, and a left-handed alpha-helix can all e xist simultaneously at such an interface. The right-handed alpha-helix forms immediately when the film is cast on a surface of pure water, a nd these helices persist at all compressions in a Langmuir trough. An alternate conformation similar to the 4.0(13) omega-helix forms on add ition of small amounts of 2-propanol to the aqueous subphase and conve rts either to left-handed or right-handed alpha-helices depending on t he amount of 2-propanol added.