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Consistent force field calculations on 2,5‐diketopiperazine and its 3.6‐dimethyl derivatives
Author(s) -
Karplus Susan,
Lifson Shneior
Publication year - 1971
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360101014
Subject(s) - dihedral angle , planarity testing , chemistry , planar , force field (fiction) , potential energy , computational chemistry , crystallography , molecular physics , atomic physics , molecule , hydrogen bond , physics , organic chemistry , quantum mechanics , computer graphics (images) , computer science
The minimum energy conformations are calculated for 2, 5‐diketopiperazine (DKP) and its 3,6‐dimethyl derivatives (DL‐DMDKP and LL‐DMDKP), using a consistent force field approach developed previously. The energy function parameters that were not required in earlier calculations on alkanes, amides, mid lactams are fitted to spectral and conformational data on the diketopiperazines. Vibrational assignments are suggested for DKP. Conformational energies are also determined over a range of selected values for ring dihedral angles, and the shape of the potential energy functions is examined over deviations from planarity. DKP and LL‐DMDKP are found to have non‐planar minimum energy conformations, separated from planar by less than a kcal/mole. DL‐DMKP exhibits a nearly flat trough about the planar conformation. Calculations of minimum energies with one dihedral angle coordinate constrainted show a coupling between bond angles and dihedral angles in agreement with recent suggestions of Benedetti.