Hydrogen Bonds in Polymer Folding
  The thermodynamics of a homopolymeric chain with both Van der Waals and highly-directional hydrogen bond interaction is studied. The effect of hydrogen bonds is to reduce dramatically the entropy of low-lying states and to give raise to long-range order and to conformations displaying secondary structures. For compact polymers a transition is found between helix-rich states and low-entropy sheet-dominated states. The consequences of this transition for protein folding and, in particular, for the problem of prions are discussed. 
J. Borg, M. H. Jensen, K. Sneppen and G. Tiana (Niels Bohr Institute   and Nordita)