Fred W. McLafferty

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTElectron Capture Dissociation of Multiply Charged Protein Cations. A Nonergodic ProcessRoman A. Zubarev, Neil L. Kelleher, and Fred W. McLaffertyView Author Information Department of Chemistry, Baker Laboratory Cornell University, Ithaca, New York 14853-1301 Cite this: J. Am. Chem. Soc. 1998, 120, 13, 3265–3266Publication Date (Web):March 24, 1998Publication History Received6 October 1997Published online24 March 1998Published inissue 1 April 1998https://doi.org/10.1021/ja973478kCopyright © 1998 American Chemical SocietyRequest reuse permissionsArticle Views5758Altmetric-Citations1640LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (80 KB) Get e-AlertscloseSUBJECTS:Circular dichroism spectroscopy,Crystal cleavage,Dissociation,Ions,Peptides and proteins Get e-Alerts

Mass spectrometry is used extensively to identify unkown chemicals in almost all areas of chemistry, biochemistry, medical chemistry, and the environmental sciences. This massive work has been compiled and written by two acknowledged leaders in their field. McLafferty and Stauffer are the authors of two previous books on mass spectral data, and of various database versions of the data--but the present 7-volume work, Registry of Mass Spectral Data, 2nd Edition is, by far, the most complete and up-to-date collection of mass spectra available in book form. In it are presented the registry spectra for 108,173 compounds.

For proteins of < 20 kDa, this new radical site dissociation method cleaves different and many more backbone bonds than the conventional MS/MS methods (e.g., collisionally activated dissociation, CAD) that add energy directly to the even-electron ions. A minimum kinetic energy difference between the electron and ion maximizes capture; a 1 eV difference reduces capture by 10(3). Thus, in an FTMS ion cell with added electron trapping electrodes, capture appears to be achieved best at the boundary between the potential wells that trap the electrons and ions, now providing 80 +/- 15% precursor ion conversion efficiency. Capture cross section is dependent on the ionic charge squared (z2), minimizing the secondary dissociation of lower charge fragment ions. Electron capture is postulated to occur initially at a protonated site to release an energetic (approximately 6 eV) H. atom that is captured at a high-affinity site such as -S-S- or backbone amide to cause nonergodic (before energy randomization) dissociation. Cleavages between every pair of amino acids in mellitin (2.8 kDa) and ubiquitin (8.6 kDa) are represented in their ECD and CAD spectra, providing complete data for their de novo sequencing. Because posttranslational modifications such as carboxylation, glycosylation, and sulfation are less easily lost in ECD than in CAD, ECD assignments of their sequence positions are far more specific.

Characterization and verification of the structures of large biomolecules with high-resolution tandem Fourier transform mass spectrometry with electrospray ionization is critically dependent on the technique used to fragment the multiply charged ions produced. Infrared multiphoton dissociation (IRMPD) of ionized proteins as large as carbonic anhydrase (29 kDa) yields fragment information similar to, but with valuable additions to, that of other dissociation techniques. IRMPD yields product ions on-axis, providing efficient dissociation in further stages; MS3 of ubiquitin (8.6 kDa) yields 11 new sequence ions. Optimum irradiation times for protein ion dissociation vary by more than a factor of 6, with times for oligonucleotides far lower, possibly due to photon resonance with a P-O stretching frequency. IRMPD provides far greater selectivity than collisionally activated dissociation and also appears to yield much less mass discrimination and to dissociate much more stable ions. A technique to remove product ions on formation from the laser beam should improve the present efficiencies of 30-80%.