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R. Cheng, Q. Feng, B.J. Ortwerth; A novel chromophore in human lens . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1691.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The aging of human lens is characterized by an increase in water–insoluble proteins associated with high levels of yellow chromophores and non–Trp fluorescence. These chromophores absorb UVA light and may function as photo–sensitizers. In the work presented here, we isolated and characterized a new chromophore from enzymatic digest of normal human lens proteins and cataract lens proteins. Methods: Human lens protein was fractionated into water–soluble and water–insoluble proteins, and then digested with a battery of proteolytic enzymes to release modified amino acids. Bio–Gel P–2 size exclusion chromatography was used to separate the yellow chromophores and the peaks were pooled based on the 330 nm absorbance. RP–HPLC, LC–MS, LC–ms/ms and NMR were employed for the purification and characterization of new yellow chromophores. Results: A novel chromophore, which has a maximum absorbance at 342 nm and fluorescence at Ex/Em of 335/415 nm, was isolated from the peak 1 which was pooled by Bio–Gel P–2 chromatography. LC–MS determined the molecular mass for this chromophore was 370 Da. The absorption spectrum and fluorescence spectrum did not change with the pH from 2 to 11, but it was not survival during the acid hydrolysis. Quantitative analysis of this chromophore in individual normal or cataract human lenses revealed an age related increase of this chromophore in water–insoluble fraction of normal human lenses, and higher level of it in cataract lenses. Conclusions: This is a new chromophore being identified in human lens. It might be a useful biomarker for the aging of lens. Also because of its maximum absorbance at 342 nm, it may function as UVA filter compound to protect lens or photo–sensitizer to cause cataract.
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