biostudies-literatureAi YDivision of ChemistryNational Institute of General Medical SciencesNIGMS NIH HHS1771-1779https://www.ebi.ac.uk/biostudies/studies/S-EPMC8925997biostudies-literatureUnknown32(7)Isotope-labeled internal standards are routinely used for mass spectrometry (MS)-based absolute quantitation. However, syntheses of isotope-labeled peptides are time-consuming and costly. To tackle this issue, we recently developed a coulometric mass spectrometric (CMS) approach for absolute quantitation without the use of standards, based on the electrochemical oxidation of cysteine or tyrosine-containing peptides followed by mass spectrometric measurement of the oxidation yield. To further expand the utility of this method, herein we present the CMS method for absolute quantitation of peptides based on tryptophan electrochemical oxidation. Several tryptophan-containing peptides, such as WGG, WQPPRARI, WAGGDASGE, RTRPLWVRME, and KVPRNQDWL, were successfully quantified with a quantificatioJournal of the American Society for Mass SpectrometryAbsolute Quantitation of Tryptophan-Containing Peptides and Amyloid β-Peptide Fragments by Coulometric Mass Spectrometry.PMC89259971R15GM137311-01R15 GM137311CHE-1915878Zhao PFnu PIJChen HAi YfalseAbsolute Quantitation of Tryptophan-Containing Peptides and Amyloid β-Peptide Fragments by Coulometric Mass Spectrometry.Isotope-labeled internal standards are routinely used for mass spectrometry (MS)-based absolute quantitation. However, syntheses of isotope-labeled peptides are time-consuming and costly. To tackle this issue, we recently developed a coulometric mass spectrometric (CMS) approach for absolute quantitation without the use of standards, based on the electrochemical oxidation of cysteine or tyrosine-containing peptides followed by mass spectrometric measurement of the oxidation yield. To further expand the utility of this method, herein we present the CMS method for absolute quantitation of peptides based on tryptophan electrochemical oxidation. Several tryptophan-containing peptides, such as WGG, WQPPRARI, WAGGDASGE, RTRPLWVRME, and KVPRNQDWL, were successfully quantified with a quantificatio2021-01-01T00:00:00Z2021 Jul2025-04-05T11:07:12.087Z2025-04-05T11:07:12.087ZS-EPMC89259973410143910.1021/jasms.1c00121