Volume 88, Number 6, December 2009
Article Number 68004
Number of page(s) 5
Section Interdisciplinary Physics and Related Areas of Science and Technology
Published online 01 December 2009
EPL, 88 (2009) 68004
DOI: 10.1209/0295-5075/88/68004

Elastic energy of proteins and the stages of protein folding

J. Lei1 and K. Huang2

1   Zhou Pei-Yuan Center for Applied Mathematics, Tsinghua University - Beijing 100084, China
2   Physics Department, Massachusetts Institute of Technology - Cambridge, MA 02139, USA

received 18 July 2009; accepted in final form 22 November 2009; published December 2009
published online 22 December 2009

We propose a universal elastic energy for proteins, which depends only on the radius of gyration Rg and the residue number N. It is constructed using physical arguments based on the hydrophobic effect and hydrogen bonding. Adjustable parameters are fitted to data from the computer simulation of the folding of a set of proteins using the CSAW (conditioned self-avoiding walk) model. The elastic energy gives rise to scaling relations of the form $R_{g}\sim N^{\nu }$ in different regions. It shows three folding stages characterized by the progression with exponents $\nu =3/5, 3/7, 2/5$, which we identify as the unfolded stage, pre-globule, and molten globule, respectively. The pre-globule goes over to the molten globule via a break in behavior akin to a first-order phase transition, which is initiated by a sudden acceleration of hydrogen bonding.

PACS - Generic models (lattice, HP, etc.).
87.15.Cc - Folding: thermodynamics, statistical mechanics, models, and pathways. - Analytical theories.

© EPLA 2009