Open AccessThe quantum topological electrostatic potential as a probe for functional group transferability
Author(s) -
Popelier P. L. A.,
Devereux M.,
Rafat M.
Publication year - 2004
Publication title -
acta crystallographica section a
Language(s) - English
Resource type - Journals
eISSN - 1600-5724
pISSN - 0108-7673
DOI - 10.1107/s0108767304016228
Subject(s) - molecule , chemistry , ab initio , conjugated system , aldehyde , density functional theory , group (periodic table) , biomolecule , topology (electrical circuits) , computational chemistry , crystallography , organic chemistry , biochemistry , polymer , mathematics , combinatorics , catalysis
The electrostatic potential can be used as an appropriate and convenient indicator of how transferable an atom or functional group is between two molecules. Quantum‐chemical topology (QCT) is used to define the electron density of a molecular fragment and the electrostatic potential it generates. The potential generated on a grid by the terminal aldehyde group of the biomolecule retinal is compared with the corresponding aldehyde group in smaller molecules derived from retinal. The terminal amino group in the free amino acid lysine was treated in a similar fashion. Each molecule is geometry‐optimized by an ab initio calculation at B3LYP/6‐311G+(2d,p)//HF/6‐31G(d) level. The amino group in lysine is very little influenced by any part of the molecule further than two C atoms away. However, the aldehyde group in retinal is influenced by molecular fragments six C atoms away. This dramatic disparity is ascribed to the difference in saturation in the carbon chains; retinal contains a conjugated hydrocarbon chain but lysine an aliphatic one.