Recently discovered regularity in alternation of the chirality sense in the hierarchies of structural organisation levels of proteins and nucleic acids is based on a deep interconnection of macromolecule symmetry with its physical-chemical properties. Chirality of molecular structures is usually described in terms of binary logic, i.e. the structures are either chiral, or achiral. To reveal physical mechanisms determining the role of homochirality of primary structures of proteins and nucleic acids in processes of folding and conformational rearrangements it is necessary to use a suitable continuous measure of chirality and find the relationship between its changes and changes of the physical characteristics of macromolecules in such processes. In this work the chirality index suggested by A.V. Luzanov is used as a continuous measure of chirality, its changes during foldings of a number of mini-proteins of the Trp-cage class are calculated and compared with the corresponding changes in entropy. The distinctive quality of the chirality index consists in its changing sign with the change of the chirality sense. Due to this property the degree of molecular symmetry is related to the modulus of the chirality index: the lower the modulus, the more symmetric is the molecule. The calculated values of entropies of mini-proteins correlate with their chirality index moduli.
chirality, chirality index, entropy, conformational transformations, mini-proteins
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