Role of single-point mutations and deletions on transition temperatures in ideal proteinogenic heteropolymer chains in the gas phase

摘要

A coarse-grained statistical mechanics-based model for ideal heteropolymer proteinogenic chains of non-interacting residues is presented in terms of the size K of the chain and the set of helical propensities associated with each residue j along the chain. For this model, we provide an algorithm to compute the degeneracy tensor associated with energy level where is the number of residues with a native contact in a given conformation. From these results, we calculate the equilibrium partition function and characteristic temperature at which a transition from a low to a high entropy states is observed. The formalism is applied to analyze the effect on characteristic temperatures of single-point mutations and deletions of specific amino acids along the chain. Two probe systems are considered. First, we address the case of a random heteropolymer of size K and given helical propensities on a conformational phase space. Second, we focus our attention to a particular set of neuropentapeptides, [Met-5] and [Leu-5] enkephalins whose thermodynamic stability is a key feature on their coupling to and receptors and the triggering of biochemical responses.