β Scribed by David Hall; Nicola Pavitt
No coin nor oath required. For personal study only.
A number of force fields of the molecular mechanics type have been tested for their ability to represent as an energy minimum, the observed crystal structure for three cyclic hexapeptides, cyclo-(-Ala-Ala-Gly-Gly-Ala-Gly-), cyclo-(-Ala-Ala-Gly-Ala-Gly-Gly-), and cyclo-(-D-Ala-D-Ala-Gly-Gly-Gly-Gly-). The most effective force field tested was that recently proposed by Kollman and co-workers, notwithstanding its use of "united" atoms for CH, CH,, and CH, groups. Fields proposed by Levitt, and adaptations of that of Scheraga and co-workers, were also effective. Force fields in which hydrogens bonded to electronegative atoms were not specified explicitly were less accurate in representation.
The various force fields were measured by their ability to represent, as an energy minimum, the observed crystal structure of three cyclic hexapeptides, cyclo-(-Ala-Ala-Gly-Gly-Ala-Gly-), I,I7 cyclo-(-Ala-Ala-Gly-Ala-Gly-Gly-), 11,17 and cyclo-(-D-Ala-D-Ala-Gly-Gly-Gly-Gly-), 111.'' Energy was calculated as the total of intra-and
π SIMILAR VOLUMES
Relaxed" force constants ate uniquely defined for systems mvolvmg redundant coordinates, in contradlstmctton to the usual "rlgd" force constants, and thus thcu use allows me3mngful correlallons to be made between force fields calculatcd for rcxtants. tranntion state, and product of a chemical reacti
It is noticed that inclusion of an electrostatic term in the molecular-mechanical treatment of hydrocarbons would compel the nonbonding parameters of different force fields to become more alike than they are at present. Apart from removing the discontinuity in passing from the calculation of an unfu
## Abstract A force field of the triclinic framework of AlPO~4~β34, important in methanolβhydrocarbon conversion reactions, was developed using an empirical potential function. Molecular dynamics simulation of an AlPO~4~β34 triclinic framework segment of 1216 atoms, containing the template molecule
## Abstract The transferability of molecular mechanics parameters derived for small model systems to larger biopolymers such as proteins can be difficult to assess. Even for small peptides, molecular dynamics simulations are typically too short to sample structures significantly different than init