| Summary: | 碩士 === 國立成功大學 === 化學系 === 89 === Ultraviolet (UV) light has been shown an important factor leading to the formation of cataract. For UV light, UVA (320 - 400 nm) and UVB (280 — 320 nm) can be absorbed by lens; however, UV light with wavelength less than 340 nm can be shielded through the absorption by the ozone in the stratosphere. It is then interesting to investigate the in vivo and in vitro effects of UVA on lens crystallins. In the in vitro study, it was found that the ANS fluorescence intensity of α-crystallin decreased with the increase of irradiation time and found it was up to 30% decrease after 30-hour irradiation, suggesting tertiary structural changes leading to a less hydrophobicity surface exposed. The decrease of the emission intensity of tryptophan fluorescence with the concomitant increase of non-tryptophan fluorescence of α-crystallin indicates a conversion of tryptophan to its photoproduct(s). Chaperone-like activity of α-crystallin against dithiothreitol (DTT) induced insulin B chain precipitation show a gradual increase with the increase of irradiation time for up to 30 hours. In the in vivo study, no cataract formation was observed for up to 12-week irradiation. Gel filtration chromatogram showed the amount of high molecular weight aggregate increased, whereas that of αL-, β- and γ-crystallins decreased. ANS fluorescence, tryptophan fluorescence, and non-tryptophan fluorescence intensities of α-crystallin showed the same results as that from in vitro study; however, the Chaperone-like activity ofα-crystallin against dithiothreitol (DTT) induced insulin B chain precipitation showed a gradual decrease with the irradiation up to 12 weeks. Two-dimension gel electrophoretic analysis of lens total proteins compared to normal lenses showed three additional protein spots were observed for in vivo irradiation lenses. This in vivo study indicates the occurrences of the in vivo chaperone-like function ofα-crystallin and of the modification and truncation of lens crystallins during UVA irradiation.
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