Tryptophan and Non-Tryptophan Fluorescence of the Eye Lens Proteins Provides Diagnostics of Cataract at the Molecular Level.
Tryptophan and Non-Tryptophan Fluorescence of the Eye Lens Proteins Provides Diagnostics of Cataract at the Molecular Level.
复制标题
眼镜蛋白的色氨酸和非色氨酸荧光在分子水平上提供白内障的诊断。
DOI：
10.1038/srep40375
复制
发表时间：
2017-01-10
影响因子：
4.6
通讯作者：
Gakamsky D
中科院分区：
文献类型：
--
作者：
Gakamsky A;Duncan RR;Howarth NM;Dhillon B;Buttenschön KK;Daly DJ;Gakamsky D
猪和人眼透镜蛋白的非色氨酸（non-Trp）荧光的化学性质通过质谱（MS）和荧光稳态和寿命光谱鉴定为Trp和Arg氨基酸残基的翻译后修饰（PTM）。荧光强度分布测量沿着与年龄相关的核性白内障的人眼晶状体的光轴显示增加的浓度的荧光PTM朝向透镜中心符合增加的光密度在透镜核仁。观察到“游离”色氨酸衍生物羟基色氨酸（OH-Trp）、N-甲酰犬尿氨酸（NFK）、犬尿氨酸（Kyn）、羟基犬尿氨酸（OH-Kyn）及其残基的荧光寿命之间的显著差异。值得注意的是，这些残基在模型肽中的寿命常数大大大于它们的“游离”对应物。可以在Trp吸收带的红边激发Trp、其衍生物和精氨酸嘧啶（ArgP）的荧光，这允许将这些PTM的发射光谱归一化为Trp的荧光强度，以半定量地确定它们的浓度。我们表明，在乳化的手术后人类白内障蛋白质样本以及整个晶状体中，OH-Trp、NFK和ArgP发射的累积分数在总荧光光谱中占主导地位，并且这与白内障等级和年龄密切相关。
The chemical nature of the non-tryptophan (non-Trp) fluorescence of porcine and human eye lens proteins was identified by Mass Spectrometry (MS) and Fluorescence Steady-State and Lifetime spectroscopy as post-translational modifications (PTM) of Trp and Arg amino acid residues. Fluorescence intensity profiles measured along the optical axis of human eye lenses with age-related nuclear cataract showed increasing concentration of fluorescent PTM towards the lens centre in accord with the increased optical density in the lens nucleolus. Significant differences between fluorescence lifetimes of “free” Trp derivatives hydroxytryptophan (OH-Trp), N-formylkynurenine (NFK), kynurenine (Kyn), hydroxykynurenine (OH-Kyn) and their residues were observed. Notably, the lifetime constants of these residues in a model peptide were considerably greater than those of their “free” counterparts. Fluorescence of Trp, its derivatives and argpyrimidine (ArgP) can be excited at the red edge of the Trp absorption band which allows normalisation of the emission spectra of these PTMs to the fluorescence intensity of Trp, to determine semi-quantitatively their concentration. We show that the cumulative fraction of OH-Trp, NFK and ArgP emission dominates the total fluorescence spectrum in both emulsified post-surgical human cataract protein samples, as well as in whole lenses and that this correlates strongly with cataract grade and age.