The orientational orders of poly(β-phenethyl l-aspartate) in two opposite α-helical form: a molecular dynamic simulation

For a poly(β-phenethyl l-aspartate) (PPLA) segment with 30 structural units, molecular dynamics (MD) simulation was carried out. The α-helical backbone of PPLA molecules undergoes torsional motion in the molecular dynamics equilibrium state. However, on the average, the backbone adheres to α-helical forms in the Amber force field. The geometrical structure of PPLA is slightly relaxed in the MD equilibrium state and has a potential about 4800 kJ/mol higher than that in the minimized energy structure. The quadrupolar splittings observed by the deuterium nuclear magnetic resonance technique in the lyotropic liquid-crystalline state have been reasonably reproduced by the simulation calculations. The large difference of observed ratio Δν_CD/Δν_N between the right- and left-handed PPLA has been explained by the geometrical architecture and verified by the simulation calculations. Graphical abstract: .