Class II force fields

Inadequate availability of experimental data can considerably inhibit the development of improved energy functions for more accurate simulations of energetic, structural, and spectroscopic properties. This has led to the development of class II force fields such as CFF and the Merck Molecular Force Field (MMFF), which are both based primarily on quantum mechanical calculations of the energy surface. The purpose of MMFF, which has been developed by Thomas Halgren at Merck and Co., is to be able to handle all functional groups of interest in pharmaceutical design. 

T. Hagler, Derivation of class II force fields. 1. Methodology and quantum force field for the alkyl functional group and alkane molecules, J. Comput. Chem. 15 162 (1994). 

Hagler, ]. Comput. Chem., 15, 162 (1994). Derivation of Class II Force Fields. I. Methodology and Quantum Force Field for the Alkyl Functional Group and Alkane Molecules. 

Ewig CS, Thacher TS, Hagler AT (1999) Derivation of class II force fields. VII. Nonbonded force field parameters for organic compounds, J Phys Chem B, 103 6998-7014... 

Peng, Z.W., et al. 1997. Derivation of class II force fields, 4. van der Waals parameters of alkali metal cations and halide anions. / Phys Chem A 101 7243. 

COMPASS. COMPASS is an example of a Class II force field parameterized by using an analytic representatiOTi of the ab initio (e.g., HF/6-31G ) potential energy surface. The functional form of the COMPASS force field is the same as CFF93 and includes an out-of-plane potential term (angle X), a U 6-9 potential as well as nonharmonic terms for bond stretching and angle bending, a Fourier cosine series for torsion, and a number of cross-coupled terms for the bonded interactions. The form of the COMPASS force field described in detail by Sun [12] is... 

Maple JR, Hwang M-J, Stockfisch TP, Dinur U, Waldman M, Ewig CS, Hagler AT (1994) Derivation of class II force fields. J Comput Chem 15 161-182... 

Basically two ways of parametrization can be followed. Class I force fields like AMBER (Case et al. 2005) or GROMOS (2011), work with a simpler energy expression and their parameterization is based on experimental data. They find a wide application to proteins, nucleic acids, and carbohydrates, as well as their complexes. Class II force fields, e.g., the Merck Molecular Force Field (Halgren 1996) include higher order and cross terms, too they are calibrated to... 

CARBOHYDRATE PARAMETER SETS IN CLASS II FORCE FIELDS... 

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