PNNL

Abstract

While a-linked amino acids in the L-form are utilized exclusively in mammalian protein building, ß-linked and D-form amino acid modifications following protein construction also have important biological roles. These amino acid modifications result in peptide and protein isomers such as epimers and diasteroisomers which can influence the structures and biological functions of antibiotics, bacterial envelopes, and long-lived proteins found in cataracts, Alzheimer’s disease, and Parkinson’s disease. However, to date the structural elucidation and separation of these isomers has been analytically challenging and limited the understanding of their potential presence and roles in biological systems. Here we utilized a new ultrahigh resolution ion mobility spectrometry (IMS)-MS platform to separate amyloid ß (Aß) peptides containing L-aspartic acid, D-aspartic acid, L-isoaspartic acid, and D-isoaspartic acid residues. We show the capability for complete separation of peptide isomer variants of the Aß(6-16) tryptic fragment and illustrate its potential in detecting similar species in studies involving age-related diseases and disorders resulting from protein misfolding.