From: Phosphorylation and Glycosylation of Bovine Lens MP20 Invest. Ophthalmol. Vis. Sci.. 2005;46(2):627-635. doi:10.1167/iovs.04-0894 Figure Legend: ESI-MS/MS analysis of the mono- and diphosphorylated MP20 tryptic peptide 168-173. Phosphorylation of this peptide results in a missed cleavage by trypsin. (A) Sequence analysis of the doubly charged ion at m/z 405.3 corresponding to the monophosphorylated peptide. Inset: predicted m/z for the y and b ion series, including phosphorylation at Ser-170. *Observed losses of 98 Da due to losses of phosphoric acid. [M+2H*]2+: loss of phosphoric acid from the doubly charged unfragmented peptide. Losses of 17 and 18 Da are due to losses of NH3 and H2O, respectively. (B) Sequence analysis of the doubly charged ion at m/z 445.3 corresponding to the diphosphorylated peptide. Inset: predicted m/z for the y and b ion series, including phosphorylation at Ser-170 and Thr-171. Observed losses of 98 (*) and 196 (**) Da due to losses of one and two phosphoric acid groups. [M+2H*]2+: loss of phosphoric acid from the doubly charged unfragmented peptide. Date of download: 10/16/2017 The Association for Research in Vision and Ophthalmology Copyright © 2017. All rights reserved.