Methyl guanine isomer distinction by hydrogen / deuterium exchange using a fourier transform mass spectrometer

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Abstract

Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA Differentiation of the seven isomers of methyl guanine has been accomplished by monitoring gas-phase hydrogen/deuterium (H/D) exchange reactions of the protonated molecular ions with deuterium oxide (D2O) in a Fourier transform mass spectrometer. In each case a distinctive reaction rate for the first H/D exchange was observed, and exchanges of up to three deuterium atoms occurred with characteristic ion abundances that could be used to differentiate the isomers. O6-Methyl guanine, for example, showed only one slow H/D exchange with D2O, whereas l-methyl guanine exchanged two hydrogen atoms at a significantly faster rate. On comparison of the possible resonance structures of each protonated isomer with the experimental information about the number and rate of H/D exchanges observed, a reaction mechanism involving a concerted proton abstraction-deuterium cation donation was proposed.

Original languageEnglish
Pages (from-to)296-305
Number of pages10
JournalJournal of the American Society for Mass Spectrometry
Volume4
Issue number4
DOIs
StatePublished - Apr 1993

Funding

Acknowledgment is given to the Office of Health and Environmental Research, U.S. Deparhnent of Energy under contract DE-AC05-840R21400 with Martin Marietta Systems, Inc., and the Postgraduate Research Training Program under contract DE-AC05-760ROU033 between the U.S. Department of Energy and Oak Ridge Associated Universities.

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