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The SAAP force field. A simple approach to a new all‐atom protein force field by using single amino acid potential (SAAP) functions in various solvents *
Author(s) -
Iwaoka Michio,
Tomoda Shuji
Publication year - 2003
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.10259
Subject(s) - force field (fiction) , chemistry , computational chemistry , ab initio , van der waals force , monte carlo method , ab initio quantum chemistry methods , field (mathematics) , physics , statistical physics , molecule , quantum mechanics , mathematics , organic chemistry , statistics , pure mathematics
Abstract A simple strategy to compose a new all‐atom protein force field (named as the SAAP force field), which utilizes the single amino acid potential (SAAP) functions obtained in various solvents by ab initio molecular orbital calculation applying the isodensity polarizable continuum model (IPCM), is presented. We considered that the total energy function of a protein force field ( E TOTAL ) is divided into three components; a single amino acid potential term ( E SAAP ), an interamino acid nonbonded interaction term ( E INTER ), and a miscellaneous term ( E OTHERS ), which is ignored (or considered to be constant) at the current version of the force field. The E INTER term consists of electrostatic interactions ( E ES' ) and van der Waals interactions ( E LJ' ). Despite simplicity, the SAAP force field implicitly involves the correlation among individual terms of the Lifson's potential function within a single amino acid unit and can treat solvent effects unambiguously by choosing the SAAP function in an appropriate solvent and the dielectric constant (D) of medium. Application of the SAAP force field to the Monte Carlo simulation of ForAla 2 NH 2 in vacuo reasonably reproduced the results of the extensive conformational search by ab initio molecular orbital calculation. In addition, the preliminary Monte Carlo simulations for ForGly 10 NH 2 and ForAla 10 NH 2 showed reversible transitions from the extended to the pseudosecondary structures in water (D = 78.39) as well as in ether (D = 4.335). The result suggested that the new approach is efficient for fast modeling of protein structures in various environments. Decomposition analysis of the total energy function ( E TOTAL ) by using the SAAP force field suggested that conformational propensities of single amino acids (i.e., the E SAAP term) may play definitive roles on the topologies of protein secondary structures. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1192–1200, 2003