Molecular dynamics simulations of helix-forming, amine-functionalized m-poly(phenyleneethynylene)s.

We present here the results of all-atom and united-atom molecular dynamics (MD) simulations that were used to examine the folding behavior of an amine-functionalized m-poly(phenyleneethynylene) (m-PPE) oligomer in aqueous environment. The parallelized GROMACS MD simulation code and OPLS force field were used for multiple MD simulations of m-PPE oligomers containing 24 phenyl rings in extended, coiled and helix conformations separately in water to determine the minimum energy conformation of the oligomer in aqueous solvent and what interactions are most important in determining this structure. Simulation results showed that the helix is the preferred minimum energy conformation of a single oligomer in water and that Lennard-Jones interactions are the dominant forces for the stabilization of the helix. In addition, these solvophobic interactions are strong enough to maintain the helix conformation at temperatures up to 523 K.