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Are proteins ideal mixtures of amino acids? Analysis of energy parameter sets
Author(s) -
Godzik Adam,
Skolnick Jeffrey,
Koliński Andrzej
Publication year - 1995
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560041016
Subject(s) - consistency (knowledge bases) , ideal (ethics) , basis (linear algebra) , state (computer science) , resolution (logic) , protein structure , amino acid , mathematics , chemistry , statistical physics , thermodynamics , computational chemistry , physics , computer science , algorithm , geometry , philosophy , biochemistry , epistemology , artificial intelligence
Various existing derivations of the effective potentials of mean force for the two‐body interactions between amino acid side chains in proteins are reviewed and compared to each other. The differences between different parameter sets can be traced to the reference state used to define the zero of energy. Depending on the reference state, the transfer free energy or other pseudo‐one‐body contributions can be present to various extents in two‐body parameter sets. It is, however, possible to compare various derivations directly by concentrating on the “excess” energy— a term that describes the difference between a real protein and an ideal solution of amino acids. Furthermore, the number of protein structures available for analysis allows one to check the consistency of the derivation and the errors by comparing parameters derived from various subsets of the whole database. It is shown that pair interaction preferences are very consistent throughout the database. Independently derived parameter sets have correlation coefficients on the order of 0.8, with the mean difference between equivalent entries of 0.1 kT . Also, the low‐quality (low resolution, little or no refinement) structures show similar regularities. There are, however, large differences between interaction parameters derived on the basis of crystallographic structures and structures obtained by the NMR refinement. The origin of the latter difference is not yet understood.