N Sukumar - Reciprocal carbonyl–carbonyl interactions in small molecules and proteins

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Abdur Rahim, Pinaki Saha, Kunal Kumar, N. Sukumar, Bani Kanta Sarma,


Nature  Comm.8, 78 (2017). DOI:  10.1038/s41467-017-00081-x



  Carbonyl-carbonyl n→π* interactions where a lone pair (n) of the  oxygen atom of a carbonyl group is delocalized over the π*  orbital of a nearby carbonyl group have attracted a lot of  attention in recent years due to their ability to affect the 3D  structure of small molecules, polyesters, peptides, and proteins.  In this paper, we report the discovery of a “reciprocal”  carbonyl-carbonyl interaction with substantial back and forth  n→π* and π→π* electron delocalization between neighboring  carbonyl groups. We have carried out experimental studies,  analyses of crystallographic databases and theoretical  calculations to show the presence of this interaction in both  small molecules and proteins. In proteins, these interactions are  primarily found in polyproline II (PPII) helices. As PPII are the  most abundant secondary structures in unfolded proteins, we  propose that these local interactions may have implications in  protein folding.
  DOI: 10.1038/s41467-017-00081-x

  Address (URL): doi.org/10.1038/s41467-017-00081-x