Figure 1.

(a) Analytical HPLC trace showing the separation of the four isoforms of the αA-crystallin tryptic peptide (55–65) TVLDSGISEVR. Peptide standards were synthesized which contained all possible Ser combinations, that is L-Ser (59)/ D-Ser (62); L-Ser (59)/ L-Ser (62); D-Ser (59)/D-Ser (62); D-Ser (59)/L-Ser (62) (b). (i) MS/MS spectrum of one of the four peaks (the peak eluting at 52.2 min in (a) obtained by LC/MS of the tryptic digest of a 40-year-old human cataract lens. This peptide corresponds to D-Ser (59)/D-Ser (62). (ii) MS/MS spectrum of the synthetic L-Ser (59)/ L-Ser (62) peptide. Analytical HPLC was performed prior to LC/MS/MS. MS/MS spectra of the other three Ser isoforms from the lens protein digest were almost identical. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]