Journal article
Role of 2-oxo and 2-thioxo modifications on the proton affinity of histidine and fragmentation reactions of protonated histidine
AKY Lam, CA Hutton, RAJ O'Hair
Rapid Communications in Mass Spectrometry | WILEY | Published : 2010
DOI: 10.1002/rcm.4671
Abstract
A combination of electrospray ionisation (ESI), multistage and high-resolution mass spectrometry experiments was used to compare the gas-phase chemistry of the amino acids histidine (1), 2-oxohistidine (2), and 2-thioxo-histidine (3). Collision-induced dissociation (CID) of all three different proton-bound heterodimers of these amino acids led to the relative gas-phase proton affinity order of: histidine >2-thioxo-histidine >2-oxo-histidine. Density functional theory (DFT) calculations confirm this order, with the lower proton affinities of the oxidised histidine derivatives arising from their ability to adopt the more stable keto/thioketo tautomeric forms. All protonated amino acids predomi..
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Funding Acknowledgements
We thank the ARC for financial support via the ARC Centre of Excellence in Free Radical Chemistry and Biotechnology. The authors gratefully acknowledge the generous allocation of computing time from both the Victorian Partnership for Advanced Computing and the NCI National Facility. The authors would also like to thank the ARC and VICS for funding of the LTQ FT hybrid mass spectrometer instrument. AKYL acknowledges the award of a Melbourne Research Scholarship from The University of Melbourne. The authors would also like to acknowledge discussions with Christopher K. Barlow and Brett Paterson, and Barbara Li for advice on the synthesis of 2-oxo-histidine.