A COMPARISON OF CONFORMATIONAL ENERGIES CALCULATED BY SEVERAL MOLECULAR MECHANICS METHODS

Several commonly used molecular mechanics force fields have been teste d for accuracy in conformational energy calculations. Differences in p erformance between the force fields are discussed for different classe s of structures. MMFF93 and force fields based on the MM2 or MM3 funct ional form are found to perform significantly better than other force fields in the test, with average conformational energy errors around 0 .5 kcal/mol. CFF91 also reaches this accuracy for the subset in which fully determined parameters are used, but it doubles the overall error due to use of estimated parameters. Harmonic force fields generally h ave average errors exceeding 1 kcal/mol. Factors influencing accuracy are identified and discussed. (C) 1996 by John Wiley & Sons, Inc.