The Folded Conformation of Perezone Revisited. Long Range nOe Interaction in Small Molecules: Interpretable Small Signals or Useless Large Artifacts?

Elizabeth Reyes-López, Beatriz Quiroz-García, Pablo Carpio-Martínez, Jesús Jiménez-Barbero, Nuria Esturau-Escofet, Gabriel Cuevas

Abstract


The nuclear Overhauser effect (nOe) is a consequence of the cross-relaxation and it involves the transfer of nuclear spin polarization from one population to another intra or inter-molecularly. It is generally accepted that a proton-proton distance between 4 and 5 Å is the upper limit for the occurrence of measurable nOe´s in small molecules. However, we herein show how detectable nOe´s may, in fact, take place between alkyl groups of quinones with substitutions at 1-4 relative positions, showing distances longer than 6 Å. Although the signals of interest are very small, of the order of 1% of a normal nOe, so a priori are considered artifacts originated by decoupling modulation, they maintain, properties that make them interesting and give them coherence as interpretable signals. If the signals of interest are not artifacts these observations represent an important breakthrough with impact on the standard protocols that are commonly used for determination of molecular structure and conformation.

Keywords


NOE; conformational analysis; π/π interactions; hydrodynamic radii; NMR spectroscopy

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Copyright (c) 2017 Elizabeth Reyes-López, Beatriz Quiroz-García, Pablo Carpio-Martínez, Jesús Jiménez-Barbero, Nuria Esturau-Escofet, Gabriel Cuevas

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Journal of the Mexican Chemical Society (J. Mex. Chem. Soc.) Vol 61, No 3 (2017). Quarterly publication (July-September). Edited and distributed by Sociedad Química de México, A.C. Barranca del Muerto 26, Col. Crédito Constructor, Del. Benito Juárez, C.P. 03940, Mexico City. Phone: +5255 56626837; +5255 56626823 Contact: soquimex@sqm.org.mx http://www.sqm.org.mx Editor-in-Chief: Ignacio González-Martínez. Indexed Journal. Certificate of reserved rights granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): 04-2005-052710530600-102. Certificate of lawful title and content: Under procedure. ISSN-e granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): Under Procedure. ISSN granted by the Instituto Nacional del Derecho de Autor (INDAUTOR): 1870-249X. Postal registration of printed matter deposited by editors or agents granted by SEPOMEX: IM09-0312 Copyright © Sociedad Química de México, A.C. Total or partial reproduction is prohibited without written permission of the right holder. The Figures/schemes quality and the general contents of this publication are full responsibility of the authors. Updated October 26th, 2017 by Adriana Vázquez (editorial assistant, e-mail: editor.jmcs@gmail.com), J. Mex. Chem. Soc., Sociedad Química de México, A.C.