From collapse to freezing in random heteropolymers
Facultad de Física, P. Universidad Católica de Chile - Casilla 306, Santiago 22, Chile
2 Institute of Physics, Norwegian University of Science and Technology, 7034 Trondheim, Norway
Accepted: 7 February 1997
We consider a two-letter self-avoiding (square) lattice heteropolymer model of NH (out of N) attracting sites. At zero temperature, permanent links are formed leading to collapse structures for any fraction . The average chain size scales as (d is the space dimension). As , with for d=2. Moreover, for , entropy per monomer approaches zero as (being finite for a homopolymer). An abrupt decrease in entropy occurs at the phase boundary between the swollen () and collapsed region. Scaling arguments predict different regimes depending on the ensemble of crosslinks. Some implications to the protein folding problem are discussed.
PACS: 05.70.Fh – Phase transitions: general aspects / 82.35.+t – Polymer reactions and polymerization / 61.41.+e – Polymers, elastomers, and plastics
© EDP Sciences, 1997