AMBER forcefield

Force field

$E_{\rm total} = \sum_{\rm bonds} K_r (r - r_{eq})^2 + \sum_{\rm angles} K_\theta (\theta - \theta_{eq})^2 + \sum_{\rm dihedrals} {V_n \over 2} [1 + {\rm cos}(n\phi - \gamma)] + \sum_{i<j} \left [ {A_{ij} \over R_{ij}^{12}} - {B_{ij} \over R_{ij}^6} + {q_iq_j \over \epsilon R_{ij}} \right ] + \sum_{\rm H-bonds} \left [ {C_{ij} \over R_{ij}^{12}} - {D_{ij} \over R_{ij}^{10}} \right ]$

Parameters

ff94

• Wendy D. Cornell, Piotr Cieplak, Christopher I. Bayly, Ian R. Gould, Kenneth M. Merz, David M. Ferguson, David C. Spellmeyer, Thomas Fox, James W. Caldwell, and Peter A. Kollman "A Second Generation Force Field for the Simulation of Proteins, Nucleic Acids, and Organic Molecules", Journal of the American Chemical Society 117 pp 5179 - 5197 (1995)

ff99

Param99 was developed for organic and biological molecules using the restrained electrostatic potential (RESP) approach to derive the partial charges:

• Junmei Wang, Piotr Cieplak, Peter A. Kollman "How well does a restrained electrostatic potential (RESP) model perform in calculating conformational energies of organic and biological molecules?", Journal of Computational Chemistry 21 pp. 1049-1074 (2000)

ff02

The ff02 force field is a polarisable variant of ff99. The charges were determined at the B3LYP/cc- pVTZ//HF/6-31g* level, and hence are more like "gas-phase" charges.

• Piotr Cieplak, James Caldwell and Peter Kollman "Molecular mechanical models for organic and biological systems going beyond the atom centered two body additive approximation: aqueous solution free energies of methanol and N-methyl acetamide, nucleic acid base, and amide hydrogen bonding and chloroform/water partition coefficients of the nucleic acid bases", Journal of Computational Chemistry 22 pp. 1048-1057 (2001)

External links

• AMBER parameters

References

1. David A. Pearlman, David A. Case, James W. Caldwell, Wilson S. Ross, Thomas E. Cheatham, Steve DeBolt, David Ferguson, George Seibel and Peter Kollman "AMBER, a package of computer programs for applying molecular mechanics, normal mode analysis, molecular dynamics and free energy calculations to simulate the structural and energetic properties of molecules", Computer Physics Communications 91 pp. 1-41 (1995)