Distonic Ions Editorial

Authors: Richard A J O’Hair Michael L Gross

Publish Date: 2013/03/21

Volume: 24, Issue: 4, Pages: 467-468

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Abstract

Welcome to this JASMS focus issue on Distonic Ions The idea to run this focus arose from the enthusiastic reception for the “Distonic Radical Ions Fundamentals and Applications” session of the 60th ASMS Conference held in Vancouver May 20–24 2012 This session cochaired by Professors Michael Siu and Richard O’Hair was comprised of six presentations spanning a range of topics Interest in the subject of distonic ions which was one of the “hot” subjects in mass spectrometry and ion chemistry 25 or more years ago has seen a renaissance owing in part to the use of electron capture dissociation ECD and electrontransfer dissociation ETD two processes that convert closedshell cations into radical cationsGiven the editorinchief’s early contributions to this area some reminiscences of those early days of ion chemistry may be of interest to you One of the first papers 4 by Jaffe Billets and Kaplan described that dialkylNnitrosamines radical cations acted as gasphase acids presumably because an intramolecular proton transfer had occurred to produce a –N = OH+ along with a free radical site located remotely from the charge site The EIinduced fragmentation to lose OH is consistent with the hypothesis This is one of the first examples where evidence was presented that an unusual species with localized charge and spin did existIn our own work 6 reported 1 year later we produced a species •CH2NH3 + in an ionmolecule reaction between the cyclopropane radical cation and neutral ammonia in a driftcell ion cyclotron resonance mass spectrometer the predecessor of today’s FTICR instrument We knew the product was unusual because it was more acidic than the conventional isomer CH3NH2 +• Details of this process were revealed in a 1972 sequel paper that represented one of my first independent efforts as an assistant professor 7 Unfortunately we were not sufficiently clever to name these species to be “distonic” and to realize their general importance in ion chemistry That awaited the work of Leo Radom Nevertheless we hope the reader will understand our enthusiasm for this subjectAlthough interest in distonic ions decreased over the years as the subject of mass spectrometry moved into biochemistry biology and the various “omics” the subject has been the topic of 81 papers and two reviews since 1980 Scopus search Furthermore there have been many presentations at ASMS conferences over the years on the subject of distonic ionsThe articles presented in this Focus issue nicely highlight the current range of interest in distonic ions and can be classified into two main categories 1 the chemistry of “small molecule” distonic ions and 2 distonic ions derived from biomoleculesProfessor Hilka Kenttamaa and her group have been actively pursuing the reactivity of distonic ions and related biradical and triradical ions for the past 2 decades so it is fitting to start with an article that describes both gasphase and condensedphase work on isomeric distonic ions of the pyridine radical cation Widjaja Jin Nash and Kenttämaa Other papers dealing with “small” distonic ions include the use of UV–vis spectroscopy to determine the structure of the product from the reaction of NO2 to carboncentered radicals Kirk Trevitt Blanksby the use of distonic ions to model a key combustion intermediate Li Lam Khairallah White O’Hair da Silva some novel distonic ions derived from oxidized transition metal–thiolate complexes Lu Campbell Chauhan Grapperhaus ChenThe papers on biological distonic ions include A Consideration of the Isomers of the Radical Cations of Tryptophan Piatkivskyi Osburn Jaderberg Grzetic Steill Oomens Zhao Lau Verkerk Hopkinson Siu and Ryzhov Radical Migrations in Peptides Zhang and Julian The Chemistry of SulfurBased Radicals Derived from the Amino Acid Side Chains of Cysteine Tan and Xia and Methionine Lau Lo Zhao Siu and Hopkinson and The Mechanisms of Phosphate Cleavage in Radical Cations of a Phosphopeptide Model System Quan Hao Song Siu and ChuAs these Focus articles hopefully show distonic ions remain important species in mass spectrometry and we predict that interest in them will grow again Thus we hope you will enjoy this focus section and find some application of the concept in your own researchRichard A J O’Hair Associate Editor School of Chemistry Bio21 Institute of Molecular Science and Biotechnology ARC Centre of Excellence for Free Radical Chemistry and Biotechnology The University of Melbourne Victoria 3010 Australia email rohairunimelbeduau

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