  We study helix-coil transitions in an all-atom model of polyalanine.
Molecules of up to length 30 residues are investigated by multicanonical
simulations. Results from two implicit solvent models are compared with each
other and with that from simulations in gas phase. While the helix-coil
transition is in all three models a true thermodynamic phase transition, we
find that its strength is reduced by the protein-solvent interaction term. The
order of the helix-coil transition depends on the details of the solvation
term.
