From: Erin Johnson <ejohnson29@ucmerced.edu>
Date: Fri, Apr 8, 2011 at 5:09 AM
Subject: Comments on Definition of the Hydrogen Bond
To: arunan@ipc.iisc.ernet.in


Professor E. Arunan
Department of Inorganic and Physical Chemistry
Indian Institute of Science
Bangalore, India, 560012


Dear Prof. Arunan,

I have just learned of your recent work on redefining the hydrogen bond and wanted to draw your attention to a paper we have recently published [J. Am. Chem. Soc., 2010, 132 (18), pp 6498–6506]. This work presents an index to identify non-covalent interactions (NCI) from the electron density and its reduced gradient. It facilitates characterization of hydrogen bonds and identities them in real space.  I have attached pictures for the examples of water dimer and the C-G DNA base pairs. Furthermore, we have recently found (and are about to submit for publication) that integration of NCI regions is able to reproduce hydrogen-bonding potential-energy curves, capturing both attractive and repulsive regimes.

Thus, we believe that the following sentence could be added to the C6 criterion for hydrogen bonding:

“Hydrogen bonds are revealed by analysis of the reduced density gradient in real space as attractive interactions, whose binding is directly related to the net difference between attractive and repulsive contributions to the NCI region.”

Best regards,

Erin R. Johnson

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Dr. Erin R. Johnson
Assistant Professor
School of Natural Sciences
University of California, Merced
Merced, CA, 95343
Office: S&E, Room 332
Phone: 209-228-4179
Fax: 209-228-4060