Figure 1.

Tandem mass spectra of (A) esterified tryptic peptide 143–149 of βB1-crystallin containing a deamidated Gln146 and (B) esterified tryptic peptide 150–159 of βB1-crystallin containing a deamidated Asn157 from the soluble protein of a 55-year-old human lens. The parent ion of peptide 143–149 was singly charged with m/z = 927.6 (expected = 927.5), and the parent ion of peptide 150–159 was doubly charged with m/z = 589.6 (expected 589.4). The observed y and b fragment ions are indicated in the spectra. The asterisk indicates the position of the deamidated residue.