Horstmann H J, Rohen J W, Sames K
Mech Ageing Dev. 1983 Feb;21(2):121-36. doi: 10.1016/0047-6374(83)90069-6.
The composition of the trabecular meshwork proteins of human eyes ranging in age from 36 days to 84 years was examined by polyacrylamide gel electrophoresis and amino acid analysis. Proteins of different molecular weights could be extracted from the tissue with acetic acid. Although their electrophoretic patterns became less distinct with increasing age, proteins of molecular weights ranging from 50 000 to 69 000 always prevailed. The amino acid compositions of the acetic acid-insoluble trabecular meshwork residues revealed the prevalence of collagenous proteins. The peptide maps produced by treatment with cyanogen bromide indicate that most of the fragments solubilized from the trabecular meshwork of younger eyes are derived from type I collagen. Beyond 40 years of age, the trabecular meshwork was resistant to cyanogen bromide and pepsin digestion. A rough estimate of the distribution of collagen types in the trabecular meshwork was based on 3-hydroxyproline/4-hydroxyproline ratios, indicating an age-related increase of type I collagen from about 55 to 70 per cent, and of type IV collagen from about 2 to 5 per cent of the total protein present. During ageing, some of the protein-bound methionine is oxidized to methionine sulfoxide, reaching about 35 per cent of the total methionine content at the age of 20 years and, with a slower rate of oxidation, a mean value of 40 per cent at 80 years of age. Electron-microscopic analysis of specimens remaining undissolved after cyanogen bromide cleavage and pepsin treatment no longer revealed regular collagenous fibrils but rather elastic-like fibers surrounded by wide sheaths consisting of fine fibrils with a regular cross-banding periodicity of 40-50 nm. In addition, clusters of so-called curly (lattice) collagen were found. The amino acid composition of this insoluble material suggests that altered collagen-like molecules prevail among the proteins of the residues.
采用聚丙烯酰胺凝胶电泳和氨基酸分析方法，对年龄从36天到84岁的人眼小梁网蛋白质组成进行了检测。用乙酸可从组织中提取不同分子量的蛋白质。尽管随着年龄增长其电泳图谱变得不那么清晰，但分子量在50000至69000之间的蛋白质始终占主导。乙酸不溶性小梁网残渣的氨基酸组成显示胶原蛋白占优势。用溴化氰处理产生的肽图表明，从较年轻眼睛的小梁网中溶解的大多数片段来自I型胶原。40岁以后，小梁网对溴化氰和胃蛋白酶消化具有抗性。基于3-羟脯氨酸/4-羟脯氨酸的比率对小梁网中胶原类型的分布进行了粗略估计，结果表明I型胶原在总蛋白中的占比随年龄增长从约55%增加到70%，IV型胶原从约2%增加到5%。在衰老过程中，一些与蛋白质结合的甲硫氨酸被氧化为甲硫氨酸亚砜，在20岁时达到总甲硫氨酸含量的约35%，随着氧化速率减慢，80岁时的平均值为40%。对经溴化氰裂解和胃蛋白酶处理后仍未溶解的标本进行电子显微镜分析，不再显示规则的胶原纤维，而是显示出类似弹性的纤维，周围有由细纤维组成的宽鞘，细纤维具有40 - 50纳米的规则交叉带周期。此外，还发现了所谓的卷曲（晶格）胶原簇。这种不溶性物质的氨基酸组成表明，在残渣蛋白质中，改变的类胶原分子占主导。
