biostudies-literatureRiggs DLNational Institute of General Medical SciencesNIGMS NIH HHS2875-2882https://www.ebi.ac.uk/biostudies/studies/S-EPMC5696650biostudies-literatureUnknown12(11)Deamidation of asparagine is a spontaneous and irreversible post-translational modification associated with a growing list of human diseases. While pervasive, deamidation is often overlooked because it represents a relatively minor chemical change. Structural and functional characterization of this modification is complicated because deamidation of asparagine yields four isomeric forms of Asp. Herein, radical directed dissociation (RDD), in conjunction with mass spectrometry, is used to identify and quantify all four isomers in a series of model peptides that were subjected to various deamidation conditions. Although primary sequence significantly influences the rate of deamidation, it has little impact on the relative proportions of the product isomers. Furthermore, the addition of ammoniACS chemical biologySequence and Solution Effects on the Prevalence of d-Isomers Produced by Deamidation.PMC5696650R01 GM107099R01GM107099Julian RRGomez SVRiggs DLfalseSequence and Solution Effects on the Prevalence of d-Isomers Produced by Deamidation.Deamidation of asparagine is a spontaneous and irreversible post-translational modification associated with a growing list of human diseases. While pervasive, deamidation is often overlooked because it represents a relatively minor chemical change. Structural and functional characterization of this modification is complicated because deamidation of asparagine yields four isomeric forms of Asp. Herein, radical directed dissociation (RDD), in conjunction with mass spectrometry, is used to identify and quantify all four isomers in a series of model peptides that were subjected to various deamidation conditions. Although primary sequence significantly influences the rate of deamidation, it has little impact on the relative proportions of the product isomers. Furthermore, the addition of ammoni2017-01-01T00:00:00Z2017 Nov2025-05-31T22:28:49.985Z2025-05-31T22:28:49.985ZS-EPMC56966502898444410.1021/acschembio.7b00686