¹³C NMR Reveals No Evidence of n–π* Interactions in Proteins

Authors

Bradley Worley, University of Nebraska-LincolnFollow
Georgia Richard, University of Nebraska-Lincoln
Gerard S. Harbison, University of Nebraska - LincolnFollow
Robert Powers, University of Nebraska - LincolnFollow

Date of this Version

8-2012

Citation

Worley B, Richard G, Harbison GS, Powers R (2012) 13C NMR Reveals No Evidence of n2p* Interactions in Proteins. PLoS ONE 7(8): e42075. doi:10.1371/ journal.pone.0042075

Comments

Copyright 2012 Worley et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Abstract

An n ‒ Π* interaction between neighboring carbonyl groups has been postulated to stabilize protein structures. Such an interaction would affect the ¹³C chemical shielding of the carbonyl groups, whose paramagnetic component is dominated by n ‒ Π* and Π ‒ Π* excitations. Model compound calculations indicate that both the interaction energetics and the chemical shielding of the carbonyl group are instead dominated by a classical dipole-dipole interaction. A set of high resolution protein structures with associated carbonyl ¹³C chemical shift assignments verifies this correlation and provides no evidence for an inter-carbonyl n ‒ Π* interaction.