ASCORBIC ACID GLYCATION & SENILE CATARACT FORMATION

蛋白质的非酶糖基化是一种缓慢的 在血清和血清中持续进行的修饰反应 纸巾。这种反应被称为美拉德反应， 受到越来越多的关注，因为它可能对许多 糖尿病期间观察到的后遗症。据了解， 最初的碳水化合物-蛋白质加合物经历了一系列复杂的 化学反应，这最终可能导致产生 1)蛋白质-蛋白质交联物，2)多种蛋白质结合 生色团和3)产生蓝色的复杂分子 紫外光照射时的荧光。这些 二次反应在晶状体组织中可能非常重要， 因为晶状体的蛋白质周转率很低或根本没有，而蛋白质在 晶状体核可能存在于整个生命过程中。因为它 已知老年性白内障晶状体中确实含有交联物 蛋白质以及蛋白质结合的发色团和荧光团 与糖基化产生的那些类似，有人提出 美拉德反应的产物可能是一个主要因素 在白内障的形成中。这种反应被认为仅限于 然而，最近的研究表明，抗坏血酸是 也能够通过美拉德反应修饰晶状体蛋白质。 抗坏血酸存在于浓度较高的环境中， 与晶状体蛋白的反应多于葡萄糖，但人们对此知之甚少 抗坏血酸蛋白质加合物的化学。这项工作 这里描述的将被用于隔离和识别 抗坏血酸和模型α-N之间形成的产物 封闭的氨基酸。这些结果将与 晶状体蛋白的体外修饰产物 抗坏血酸和从人类晶状体中分离出来的产品 蛋白质。α-晶状体蛋白的特定修饰位点 将被确定，此外，这些影响 对α-晶状体蛋白性质的修饰将是 调查过了。将进行初步试验，以 描述孵化引起的蛋白质交联链的性质 生理条件下晶状体中含有抗坏血酸的晶体蛋白。

The non-enzymatic glycosylation of proteins represents a slow modification reaction which proceeds continuously in serum and in tissues. This reaction is termed the Maillard reaction and is receiving increasing attention as it may be responsible for many of the sequelae observed during diabetes. It is known that the initial carbohydrate-protein adducts undergo a complex series of chemical reactions, which can ultimately cause the production of 1) protein-protein crosslinks, 2) a variety of protein-bound chromophores and 3) complex molecules which produce a blue fluorescence when irradiated with ultraviolet light. These secondary reactions are likely to be very important in lens tissue, because lens exhibits little or no protein turnover, and proteins in the lens nucleus may have been present throughout life. Since it is known that senile cataractous lenses do contain crosslinked proteins as well as protein-bound chromophores and fluorophores similar to those produced by glycosylation, it has been suggested that the products of the Maillard reaction may be a major factor in cataractogenesis. This reaction was thought to be limited to glucose, however, it has been recently shown that ascorbic acid is also capable of modifying lens proteins via the Maillard reaction. Ascorbic acid is present in higher concentrations and is more reactive with lens proteins than glucose, yet little is known about the chemistry of ascorbic acid protein adducts. The work described here will be undertaken to isolate and identify the products formed between ascorbic acid and model alpha-N blocked amino acids. These results will be compared to the products produced by the in vitro modification of lens crystallins by ascorbic acid and to products isolated from human lens proteins. The specific sites of modification in alpha-crystallin will be identified, and in addition the effects of these modifications on the properties of alpha-crystallin will be investigated. Preliminary experiments will be carried out to describe the nature of the protein crosslinks induced by incubating lens crystallins with ascorbic acid under physiological conditions.