(33g) Chiral Induction and Propagation in Oligomers

Chiral induction is a phenomenon where an oligomer comprising achiral monomers can be forced into a helical conformation of specific handedness. For instance, poly- hexyl isocyanates form equiprobable left- or right-handed helices that are dynamic in nature and capable of switching handedness. Alternately, interaction with a chiral solvent can induce chiral conformations in achiral PEO. In this work we have developed a general bead-spring simulation model to study the dynamics of chiral induction through both mechanisms. We employ a symmetric, 2-well torsional potential that allows each dihedral along the backbone to either follow a left- or right-handed conformation with equal probability. For a subset of parameters, there is no cooperativity. But upon certain parametrization, if one of the dihedral angles falls into a right-handed well, others simultaneously follow the same conformation until thermal fluctuations knock a dihedral into the opposite well. To mimic solvent-induced helical formation, the dihedral angle for a chosen nucleation site is restricted to a single well and the dynamics of folding are studied. We envision that this simple and versatile model can be used to study chiral induction in sequence-specific oligomers.