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International Journal of Medicinal Chemistry
Volume 2012, Article ID 682495, 16 pages
http://dx.doi.org/10.1155/2012/682495
Research Article

A DFT and Semiempirical Model-Based Study of Opioid Receptor Affinity and Selectivity in a Group of Molecules with a Morphine Structural Core

Department of Chemistry, Faculty of Sciences, University of Chile, P.O. Box 653, Santiago, Chile

Received 31 May 2012; Accepted 20 September 2012

Academic Editor: O. Bruno

Copyright © 2012 Tamara Bruna-Larenas and Juan S. Gómez-Jeria. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We report the results of a search for model-based relationships between mu, delta, and kappa opioid receptor binding affinity and molecular structure for a group of molecules having in common a morphine structural core. The wave functions and local reactivity indices were obtained at the ZINDO/1 and B3LYP/6-31 levels of theory for comparison. New developments in the expression for the drug-receptor interaction energy expression allowed several local atomic reactivity indices to be included, such as local electronic chemical potential, local hardness, and local electrophilicity. These indices, together with a new proposal for the ordering of the independent variables, were incorporated in the statistical study. We found and discussed several statistically significant relationships for mu, delta, and kappa opioid receptor binding affinity at both levels of theory. Some of the new local reactivity indices incorporated in the theory appear in several equations for the first time in the history of model-based equations. Interaction pharmacophores were generated for mu, delta, and kappa receptors. We discuss possible differences regulating binding and selectivity in opioid receptor subtypes. This study, contrarily to the statistically backed ones, is able to provide a microscopic insight of the mechanisms involved in the binding process.