Molecular Recognition of Amiloride Analogs: A Molecular Electrostatic Potential Analysis. 1. Pyrazine Ring Modifications

Document Type

Article

Publication Date

5-1-1992

Abstract

Ab initio molecular electrostatic potential (MEP) patterns are used to determine the electrostatic requirements for the formation of a stable blocking complex between amiloride analogs and the epithelial sodium channel of Rana ridibunda. MEP maps calculated in the 3-21G(*) and STO-3G basis sets for amiloride and analogs with pyrazine ring modifications are used to interpret differences in the microscopic rate constants for analog-channel binding determined by Li et al. MEP maps of the protonated analogs are correlated to differences in the value of kon, the microscopic association constant Those analogs with kon values similar to amiloride are found to have a MEP maximum that is localized over the side chain, as well as strong, distinguishing minima in the MEP pattern off the carbonyl oxygen and positions 3,4, and 5 of the pyrazine ring. MEP maps of a model-encounter complex (protonated analog and formic acid anion) are correlated to differences in koff, the microscopic dissociation constant. The major conclusions of this work are that (1) a stable blocking complex is formed with analogs which have a deep, localized minimum off the 6 position of the pyrazine ring, (2) the stability of the blocking complex is directly related to the depth of that minimum, (3) substitution at position 6 affects not only the depth but also the location and size of the minimum off position 6, and (4) steric factors may influence the optimal binding of the 6-position ligand to the ion channel. The MEP analysis also suggests that the distance between the proton donors of the chelating guanidinium moiety and the deep, localized minimum off position 6 of the pyrazine ring may define an important spatial requirement for all those analogs which form a stable blocking complex with the channel. © 1992, American Chemical Society. All rights reserved.

Identifier

0026778297 (Scopus)

Publication Title

Journal of Medicinal Chemistry

External Full Text Location

https://doi.org/10.1021/jm00087a022

e-ISSN

15204804

ISSN

00222623

PubMed ID

1315872

First Page

1643

Last Page

1649

Issue

9

Volume

35

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