From collapse to freezing in random heteropolymers

C. J. Camacho; T. Schanke

doi:10.1209/epl/i1997-00197-2

All issues

Volume 37 / No 9 (March 1997)

Europhys. Lett., 37 9 (1997) 603-608

Abstract

Issue		Europhys. Lett. Volume 37, Number 9, March 1997


Page(s)		603 - 608
Section		General
DOI		https://doi.org/10.1209/epl/i1997-00197-2
Published online		01 September 2002

Europhys. Lett., 37 (9), pp. 603-608 (1997)

From collapse to freezing in random heteropolymers

C. J. Camacho¹ and T. Schanke²

¹ 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

Received: 11 October 1996
Accepted: 7 February 1997

Abstract

We consider a two-letter self-avoiding (square) lattice heteropolymer model of N_H (out of N) attracting sites. At zero temperature, permanent links are formed leading to collapse structures for any fraction $\rho_{\rm H}=N_{\rm H}/N$ . The average chain size scales as $R\simeq N^{1/d}F(\rho_{\rm H})$ (d is the space dimension). As $\rho_{\rm H}\rightarrow 0$ , $F(\rho_{\rm H})\sim \rho_{\rm H}^\zeta$ with $\zeta={1/d-\nu}=-1/4$ for d=2. Moreover, for $0<\rho_{\rm H}<1$ , entropy per monomer approaches zero as $N\rightarrow\infty$ (being finite for a homopolymer). An abrupt decrease in entropy occurs at the phase boundary between the swollen ( $R\sim N^\nu$ ) 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

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