Formation of unique structure in polypeptide chains. Theoretical investigation with the aid of a replica approach.
A replica approach analogous to that used in spin glass systems is implemented to study the configurational space of a heteropolymeric model of protein with a quenched, disordered sequence of links in the limit of a large number of link types. It is shown that there exists a threshold value of chain heterogeneity which separates two qualitatively different types of behavior. For a low degree of heterogeneity the protein globule is like a homopolymer in a collapsed state without definite chain folds: an exponentially large number of folds make a significant contribution to the partition function in this regime. After the threshold heterogeneity has been overcome, the chain freezes drastically but without latent heat; few (approx. 1) frozen states with definite chain folds are thermodynamically dominant in this state. The relation of these results to thermodynamic aspects of protein folding is discussed.
Shakhnovich
E I
EI
Institute of Protein Research, Academy of Sciences of the U.S.S.R., Moscow Region.
Gutin
A M
AM
D008433:Mathematics; D008962:Models, Theoretical; D010455:Peptides; D011487:Protein Conformation; D011506:Proteins; D013816:Thermodynamics
D010455:Peptides; D011506:Proteins