Authors: Blake E Ziegler Rick A Marta Michael B Burt Sabrina M Martens Jonathan K Martens Terry B McMahon
Publish Date: 2013/12/04
Volume: 25, Issue: 2, Pages: 176-185
Abstract
Infrared multiple photon dissociation IRMPD spectroscopy experiments and quantum chemical calculations have been used to explore the possible structures of protonated azidothymidine and the corresponding protonated dimer Many interesting differences between the protonated and neutral forms of azidothymidine were found particularly associated with ketoenol tautomerization Comparison of computational vibrational and the experimental IMRPD spectra show good agreement and give confidence that the dominant protonated species has been identified The protonated dimer of azidothymidine exhibits three intramolecular hydrogen bonds The IRMPD spectrum of the protonated dimer is consistent with the spectrum of the most stable computational structure This work brings to light interesting ketoenol tautomerization and exocyclic hydrogen bonding involving azidothymidine and its protonated dimer The fact that one dominant protonated species is observed in the gas phase despite both the keto and enol structures being similar in energy is proposed to be the direct result of the electrospray ionization process in which the dominant protonated dimer structure dissociates in the most energetically favorable wayThe generous financial support of the Natural Sciences and Engineering Research Council is gratefully acknowledged as is the financial support of the European Commission through the NEST/ADENTURE program EPITOPES Project 15637 The authors are very grateful for the valuable assistance of the CLIO team Maitre J Lemaire V Steinmetz D Scuderi and J M Ortega along with the CLIO technical support staff for their assistance during our stay in Orsay France The computational work was made possible by the facilities of the Shared Hierarchical Academic Research Computing Network SHARCNETwwwsharcnetca and Compute/Calcul Canada
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