Solution effects and the order of the helix-coil transition in polyalanine

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A study was conducted on the helix-coil transition in two models of polyalanine that attempt to approximate the interaction of the molecule with the surrounding water by an implicit solvent. It was found that the helix-coil transition in these models was a true thermodynamic phase transition. Though, while polyalanine in gas phase critical exponents that were consistent with a (weak) first order phase transition, the results rather indicate for ASA and DDE solvent models a (weak) second order transition with critical exponents α and γ close to zero and dv close to two. This change in the strength was found to be consistent with the understanding of the protein-water interactions.

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Journal of Chemical Physics