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Several sets of OPLS parameters have been published. There is OPLS-ua (united atom), which includes hydrogen atoms next to carbon implicitly in the carbon parameters, and can be used to save simulation time. OPLS-aa (all atom) includes every atom explicitly.
IFF uses employs the same potential energy function as other common force fields (CHARMM, [15] AMBER, [16] OPLS-AA, [17] CVFF, [18] DREIDING, [19] GROMOS, [20] PCFF, [21] COMPASS), including options for 12-6 and 9-6 Lennard-Jones potentials, and can be used standalone or as a plugin to these force fields to utilize existing parameters.
OPLS-AA, MMFF, GBSA solvent model, conformational sampling, minimizing, MD. Includes the Maestro GUI which provides visualizing, molecule building, calculation setup, job launch and monitoring, project-level organizing of results, access to a suite of other modelling programs.
Part of force field of ethane for the C-C stretching bond. In the context of chemistry, molecular physics, physical chemistry, and molecular modelling, a force field is a computational model that is used to describe the forces between atoms (or collections of atoms) within molecules or between molecules as well as in crystals.
OPLS AMBER CHARMM GAFF MMFF QVBMM UFF Comments Abalone: UA 94, 96, 99SB, 03, GS, ii, Automatic FF generator [1] No No No No UFF-Dreiding-like field For proteins, DNA, ligands AMBER: Yes Yes Via chamber tool since v11 Yes No No No Ascalaph Designer: UA 94, 99SB, 03 No No No No No Avogadro: No No No Yes 94, 94s No Yes Balloon: No No No No 94 No ...
A hydroxyl group, for example, can be both a hydrogen bond donor, and a hydrogen bond acceptor, and it would be impossible to treat this with one OH pseudo-atom. About half the atoms in a protein or nucleic acid are non-polar hydrogens, so the use of united atoms can provide a substantial savings in computer time.
Most commonly, by writing the constituent B, C, N, O, P and S atoms in lower-case forms b, c, n, o, p and s, respectively. In the latter case, bonds between two aromatic atoms are assumed (if not explicitly shown) to be aromatic bonds. Thus, benzene, pyridine and furan can be represented respectively by the SMILES c1ccccc1, n1ccccc1 and o1cccc1.
The Lennard-Jones Potential is a mathematically simple model for the interaction between a pair of atoms or molecules. [3] [4] One of the most common forms is = [() ()] where ε is the depth of the potential well, σ is the finite distance at which the inter-particle potential is zero, r is the distance between the particles.