How to model this type of radiation damage?

From: Mischa Machius
Date: 4 October 2011 20:16
Y'all,

I have several instances of this feature afflicting some glutamates. The red blob is negative difference density. I assume it's a form of radiation damage, but it doesn't seem to be the typical decarboxylation type. I'd appreciate any suggestions as to what the damaged product could be and/or how to best model this feature.

Thanks so much in advance.

Cheers!
MM



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From: Roger Rowlett

At first glance, it looks like it could be modeled by a partially reduced carboxylate (to aldehyde or carbonyl radical). Is there any precedent for such a radiation-induced photoelectron reduction? Like you, I only remember seeing decarboxylations of Asp and Glu. To get an aldehyde or  carbonyl radical, it would seem you need an oxygen acceptor in the crystal matrix: thiols, which can make thiyl radicals could possibly act as oxygen or OH radical acceptors.  J. Phys. Chem. Lett. 2010, 19, 2898 suggests a mechanism by which thiols can be oxidized to S-hydroxythiols under ionizing radiation conditions. This is of course all speculation. :)

_______________________________________
Roger S. Rowlett
Gordon & Dorothy Kline Professor
Department of Chemistry
Colgate University
13 Oak Drive
Hamilton, NY 13346