Network model of a protein globule.

Phase transition of a protein globule is considered in the frameworks of (i) the generalized mean-field theory for the order parameter, characterizing the extent of the deviation of a protein three-dimensional structure from its native state and (ii) the network model that treats a protein globule as a small-world network with a significant percent of long-range links between amino acid residues. Temperature dependencies of the introduced order parameter are defined and phase-transition temperatures are found on the basis of the function defining the distribution of links' numbers for protein residues. An important role of long-range links, promoting considerable rise of thermal protein stability, is demonstrated by the example of a correlation between protein melting temperature and a fraction of disulfide bonds.