Stimuli-responsivity of secondary structures of glycopolypeptides derived from poly(L-glutamate-co-allylglycine).

Copolypeptides containing L-glutamate and various amounts of either D-/DL-/L-allylglycine or D-/DL-/L-(3-(β-D-glucopyranosyl)thio)propylglycine defect units were studied by circular dichroism (CD) and infrared (FT-IR) spectroscopy according to their secondary structures in dependence of pH and temperature. All samples adopt random coil conformation at high pH and α-helix at low pH without evidence for β-sheet formation. Folding into the α-helix structure is strongly affected by the number and configuration of allylglycine defects (which intrinsically stabilize β-sheets). Helix folding is facilitated upon the attachment of D-glucopyranose to the L- (but not the D-) allylglycine units, which is attributed to a different secondary structure preference of the L-(3-(β-D-glucopyranosyl)thio)propylglycine (L: random coil; D: β-sheet) and a majority rule effect.