isoAsp analysis of bovine lens alpha-crystallin

Isomerization of Asp residues has been long thought to occur only in a few tissues. Recent reports suggested that such post-translational protein modifications may occur in all tissues and proteins in vivo, including serum. For proof of concept using comprehensive analysis, the MS-based proteomic approach is straightforward; however, the isomerization of Asp has not been involved in proteomics studies because of no change in molecular weight. Here, we show a novel strategy, isoAsp-Quest, a database search-oriented large-scale isoAsp identification method.