Model rearrangements of peptide backbone-radicals via intramolecular hydrogen-atom transfer

PHYS 650

Damian Moran, dmoran@cbms.mq.edu.au, Department of Chemistry and Biolmolecular Sciences, Macquarie University, Sydney, 2109, Australia and Leo Radom, School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
Peptide radicals are ubiquitous in biological systems and have been shown to be key participants in a wide range of important reactions. Therefore, we are conducting a computational exploration of peptide backbone-radicals and their rearrangements via intramolecular hydrogen-atom shifts using the methods G3(MP2)-RAD, MPWB1K and BMK to predict rearrangement enthalpies and barriers. Model systems have been considered, and we have found that transformation of a nitrogen-centered radical to a carbon-centered radical is always exothermic. Furthermore, hydrogen-migration barriers generally decrease as the ring size in the transition structure (TS) increases, with a marked barrier lowering being found when moving to TS rearrangements proceeding via larger cyclic TSs. Finally, we have explored the convergence of substituent effects on rearrangement barriers and shown that the influence of end-group effects decays significantly with the length of the polypeptide chain adjacent to the migrating hydrogen atom.
 

Cyber Science, Chemistry
1:20 PM-5:20 PM, Thursday, 14 September 2006 Grand Hyatt San Francisco -- San Miguel, Oral

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006