The effect of light on polypeptide conformation was investigated by circular dichroism measurements on a series of copolymers composed of β-benzyl L-aspartate and β-(m-phenylazo)benzyl L-aspartate, dissolved in the mixed solvents of 1,2-dichloroethane (DCE) and trimethyl phosphate (TMP). The dark-adapted (trans) copolymers are all left-handed helices in DCE and undergo a conformational change from a left-handed helix to a right-handed helix with an increase in the amount of TMP in the solutions. Photoisomerization of the side-chain azobenzene moieties from trans to cis isomers also causes helix reversal in these copolymers at adequate solvent compositions. These copolymers exhibit CD bands in the regions of azobenzene n-π* and π-π* transitions which change their CD signs corresponding to the helix reversal.
ASJC Scopus subject areas
- Colloid and Surface Chemistry