Complexation-Driven Mutarotation in Poly(L-proline) Block Copolypeptides.

Novel poly(L-lysine)-block-poly(L-proline) (PLL-b-PLP)-based materials with all PLP helical conformers, i.e., PLP II and the rare PLP I are here reported. Electrostatic supramolecular complexation of the adjacent cationic PLL with anionic molecules bearing DNA analogue H-bonding functionalities, such as deoxyguanosine monophosphate (dGMP), preserves the extended PLP II helix, and the complexed molecule is locked and held in position by orthogonal shape-persistent hydrogen-bonded dGMP ribbons and their extended π-stacking. The branched anionic surfactant dodecylbenzenesulfonic acid (DBSA) on the other hand, introduces periodicity frustration and interlayer plasticization, leading to a reversed mutarotation to the more compact PLP I helix by complexation, without external stimuli, and is here reported for the first time. We foresee that our findings can be used as a platform for novel molecularly adaptive functional materials, and could possibly give insight in many proline-related transmembrane biological functions.