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Keywords:

  • aqueous transfer;
  • BIPSE model;
  • heat capacity change;
  • heat denaturation temperature;
  • hydrogen bonding;
  • limiting mechanisms of thermostability;
  • N-alkyl amides;
  • protein stability;
  • stability curves

Abstract

This article shows that the stability profiles of thermophilic proteins are significantly displaced toward higher temperatures as compared to those of mesophilic proteins. A similar trend characterizes the aqueous transfer of N-alkyl amides. In fact, as a general feature of transfer processes, liquid dissolution profiles are centered at temperatures higher than those of solid ones. This behavior is governed by packing contributions. A partition of the unfolding thermodynamics based on the analysis of phenomenological temperatures common to dissolution and unfolding phenomena provides a clue to understanding the mechanism of thermal stabilization. In fact, the position of stability profiles along the temperature axis does not appear to depend on solvation of internal residues. Instead, it is notably affected by solidlike components, whose progressive decrease appears to drive the heat denaturation temperature increase of most thermostable proteins. As a corollary, it is shown that there are actually two limiting mechanisms of thermal stabilization. Proteins 2004. © 2003 Wiley-Liss, Inc.