Schwarz K
Proc Natl Acad Sci U S A. 1973 May;70(5):1608-12. doi: 10.1073/pnas.70.5.1608.
Silicon was found to be a constituent of certain glycosaminoglycans and polyuronides, where it occurs firmly bound to the polysaccharide matrix. 330-554 ppm of bound Si were detected in purified hyaluronic acid from umbilical cord, chondroitin 4-sulfate, dermatan sulfate, and heparan sulfate. These amounts correspond to 1 atom of Si per 50,000-85,000 molecular weight or 130-280 repeating units. 57-191 ppm occur in chondroitin 6-sulfate, heparin, and keratan sulfate-2 from cartilage, while hyaluronic acids from vitreous humor and keratan sulfate-1 from cornea were Si-free. Large amounts of bound Si are also present in pectin (2580 ppm) and alginic acid (451 ppm). The bound Si is not dialyzable, does not react with ammonium molybdate, is not liberated by autoclaving or 8 M urea, and is stable against weak alkali and acid. Strong alkali and acid hydrolyze the Si-polysaccharide bond. Free, direct-reacting, dialyzable silicate is obtained. Enzymatic hydrolysis of hyaluronic acid or pectin does not liberate silicic acid, but leads to products of low molecular weight still containing Si in bound form. It is concluded that Si is present as a silanolate, i.e., an ether (or esterlike) derivative of silicic acid, and that R(1)-O-Si-O-R(2) or R(1)-O-Si-O-Si-O-R(2) bridges play a role in the structural organization of glycosaminoglycans and polyuronides. Thus, Si may function as a biological crosslinking agent and contribute to architecture and resilience of connective tissue.
硅被发现是某些糖胺聚糖和聚糖醛酸的组成成分，它紧密结合在多糖基质中。在从脐带中提取的纯化透明质酸、硫酸软骨素4、硫酸皮肤素和硫酸乙酰肝素中检测到330 - 554 ppm的结合硅。这些含量相当于每50,000 - 85,000分子量中有1个硅原子或130 - 280个重复单元。硫酸软骨素6、肝素和软骨中的硫酸角质素 - 2中含有57 - 191 ppm的硅，而玻璃体液中的透明质酸和角膜中的硫酸角质素 - 1不含硅。果胶（2580 ppm）和海藻酸（451 ppm）中也存在大量的结合硅。结合硅不能透析，不与钼酸铵反应，高压灭菌或用8 M尿素处理也不会释放出来，并且对弱酸和弱碱稳定。强碱和强酸会水解硅 - 多糖键，从而得到游离的、可直接反应的、可透析的硅酸盐。透明质酸或果胶的酶促水解不会释放硅酸，而是产生仍以结合形式含有硅的低分子量产物。得出的结论是，硅以硅醇盐的形式存在，即硅酸的醚（或酯样）衍生物，并且R(1)-O-Si-O-R(2)或R(1)-O-Si-O-Si-O-R(2)桥在糖胺聚糖和聚糖醛酸的结构组织中起作用。因此，硅可能作为一种生物交联剂发挥作用，并有助于结缔组织的结构和弹性。
