Analysis of Acidic Peptides by Mass Spectrometry

Friday, November 1, 2019

Dr. Carolyn J. Cassady

Department of Chemistry & Biochemistry

The University of Alabama


Mass spectrometry has become a common method for peptide analysis and sequencing, particularly in the positive ion mode with sequence-informative fragmentation generated by collision-induced dissociation (CID).  Highly acidic peptides can be difficult to analyze by these common mass spectrometry techniques due to their tendency to deprotonate rather than protonate.  Three strategies for ionizing and sequencing acidic peptides will be discussed: (1) use of negative (deprotonated) ions with alternative dissociation techniques, (2) metallation of the peptide coupled with electron-based dissociation, and (3) enhancement of peptide protonation using chromium(III). In particular, Cr(III) has been found to cause even highly acidic peptides to form positive ions (enhanced protonation) by a process involving the binding of a superacid aqua-Cr(III) complex to the peptide during the desolvation process in electrospray ionization (ESI).


A.B. Chemistry, Pfeiffer College, Misenheimer, NC
PhD. Chemistry, Purdue University, West Lafayette, IN
Post-Doc. Naval Research Laboratory, Washington, DC
Industrial Experience: ARCO Chemical Co., Newtown Square, PA; Midwest Research
Institute, Kansas City, MO
Professor of Chemistry and Biochemistry and College Leadership Board Faculty Fellow,
The University of Alabama, Tuscaloosa, AL
Research Emphasis:  Analytical and bioanalytical chemistry, mass spectrometry, gas-
phase ion chemistry

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