ASCORBIC ACID GLYCATION AND SENILE CATARACT FORMATION

在过去的二十年里，对晶状体蛋白结构和晶状体晶体蛋白基因表达的研究取得了重大进展。我们正在获得关于小鼠和大鼠白内障的越来越详细的知识，但导致人类老年性白内障的机制仍然不清楚。许多体外实验模仿了这些白内障的特征，但几乎没有人证实这些反应是显著的，或者是过程中的因果关系。我们的实验室一直在研究晚期糖基化终产物在这一过程中的作用。具体地说，我们正在调查抗坏血酸的氧化产物是否与这些晶状体中出现的蛋白质-蛋白质交联物、发色团和荧光团有关。在这里描述的工作中，我们希望找到体外抗坏血酸的小牛晶状体蛋白和从印度获得的老年人晶状体和白内障中的蛋白质修饰之间的共同结构。提出了一种从蛋白质中分离这些修饰的方案。此外，常见的化合物将通过质谱学、光谱性质和质子核磁共振进行鉴定。此外，我们打算研究培养的人晶状体中抗坏血酸的降解，并测量外部因素对这些晶状体中抗坏血酸的氧化和掺入蛋白质的影响。

In the last two decades, major advances have been made in understanding lens protein structure and lens crystallin gene expression. We are obtaining increasingly detailed knowledge about cataracts in mice and rats, but the mechanisms that result in age-onset cataract in humans, still remains elusive. Many in vitro experiments mimic features seen in these cataracts, but there is little in the way of confirmation that these reactions are significant, or causal in the process. Our laboratory has been investigating the role of advanced glycation endproducts in this process. Specifically, we are investigating whether the oxidation products of ascorbic acid are responsible for the protein-protein crosslinks, chromophores and fluorophores seen in these lenses. In the work described here we hope to find common structures between calf lens proteins ascorbylated in vitro and the protein modifications seen in aged human lenses and cataracts obtained from India. A scheme for the isolation of these modifications from proteins is presented. Also, the common compounds will be identified by mass spectrometry, their spectral properties and proton NMR. In addition, we intend to study the degradation of ascorbic acid in cultured human lenses, and to measure the effect of external agents to bring about the oxidation and incorporation of ascorbic acid into the proteins in these lenses.