Determination of Intact Protein Molecular Mass from Multiple-Charge Electrospray Mass Spectra

The use of multiple-charge ions in protein and peptide analysis, such as determination of intact protein molecular mass is discussed.

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byO. David Sparkman

In this technical article the use of multiple-charge ions in protein and peptide analysis, such as the determination of intact protein molecular mass is discussed.

In order to form a multiple-charge ion, an analyte molecule must have more than one site which can be ionized. In electrospray analyses, these charge locii may be any of the functional groups that we normally associate with protonation (positive charge) or deprotonation (negative charge). Amines are excellent proton acceptors and a very common site for positive charges. Carboxylic acids can donate the acidic proton from the –OH group and form a negative ion. While negative ion formation at acidic sites can occur for proteins, we most typically evaluate protein molecules in electrospray as positive ions.

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Meet the Author(s):

O. David Sparkman
O. David Sparkman is currently an Adjunct Professor of Chemistry at the University of the Pacific in Stockton, California; Contractor to the National Institute of Standards and Technology Mass Spectrometry Data Center; President of ChemUserWorld.com; and a former American Chemical Society Instructor (1978–2006) and American Society for Mass Spectrometry Member-at-large for Education (2004–2006). At the University of the Pacific, Prof. Sparkman teaches courses in mass spectrometry and analytical chemistry and manages the mass spectrometry facility. Over the past 28 years, he has developed and taught five different ACS courses in mass spectrometry; he holds positions on the Editorial Advisory Boards of the European Journal of Mass Spectrometry and the HD Science GC/MS Update – Part B; and is the Book Review Editor for the European Journal of Mass Spectrometry. He is the author of Mass Spectrometry Desk Reference (Global View Publishing: Pittsburgh, PA, 1st ed. 2000; 2nd ed. 2006). Prof. Sparkman is a member of the Editorial Boards of the John Wiley Encyclopedia of Environmental Analysis and Remediation and Encyclopedia of Analytical Chemistry, Editor of and a contributor to the Mass Spectrometry Section of the Encyclopedia of Analytical Chemistry, and a contributor to the Encyclopedia of Environmental Analysis and Remediation. Along with J. Throck Watson, he developed the Mass Spectral Interpretation Quick Reference Guide. He also provides general consulting service in mass spectrometry for a number of instrument manufacturers, manufacturing companies, and government agencies.

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