Figure 8. Determination of deamidation of Asn to Asp in tryptic fragments of αB-crystallin

Isotopic distribution of a tryptic fragment (residues 124-149; sequence: IPADVDPLTITSSDGVLTVNGF; mass of 2,624) of αB-crystallin during MALDI-TOF mass spectrometric analysis showing deamidation of αB-crystallin Asn₁₄₆ to Asp. The major isotopic species had mass of 2,625, which was due to the gain of one mass unit following the conversion of Asn to Asp. Using a similar approach, the modifications observed in the spots 1-8 of WS-HMW proteins (Figure 5B) and in spots 2-34 of WI proteins (Figure 7) of cataractous lenses were determined and are summarized in Table 8.