Photoresponsive peptide and polypeptide systems V: Reversible photochromism of azo aromatic pentapeptide in solvents

Abstract

The photochemical properties of azo aromatic pentapeptide were investigated by absorption and circular dichroism (CD) spectroscopy in water and in organic solvents. The absorption spectra of the azo peptide exhibited photoconversion on irradiation with light owing to the trans—cis photoisomerization of the azo aromatic moieties. The azo peptide in water exhibited three dichroic bands at 430 nm (negative), 315 nm (negative) and 202 nm (negative) in the dark. On irradiation at 360 nm for 20 min, the negative band at 430 nm became positive at 410 nm, while re-irradiation at 460 nm caused a reverse photoconversion. The change at 430 – 410 nm was reversible under irradiation conditions. The effect of the solvent on the photochromism in the visible dichroic band was examined and was classified into three patterns.