A New Twist on the Helix-Coil Transition:  A Non-Biological Helix with Protein-Like Intermediates and Traps

All-atom computer simulations for the folding of a nonbiological helix, a 12-mer poly-phenylacetylene (pPA), are presented. We find that, unlike the classical helix-coil picture, pPA folds via on-pathway intermediate states and can also get trapped in misfolded states, much like that which one finds in simple models for proteins. Quantitative characterization of our pPA folding simulations finds a marked deviation from exponential kinetics, in agreement with experiment. Finally, we suggest how the helix-coil picture can be generalized to include these effects.