Bone: ultrastructure, mineralogy and chemistry

骨骼是构成我们骨骼的材料，是一种精细的工程材料，由矿物质和胶原蛋白两种成分等量组成。这种矿物质由钙和磷酸盐的微小晶体组成，这是我们身体中必不可少的两种化学物质。胶原蛋白是一种蛋白质，是我们体内含量最多的一种蛋白质，也存在于皮肤和肌腱中。骨骼的胶原蛋白形成了一缕一缕的“原纤维”，它们捆绑在一起，沿着我们长骨的轴线排列，但是矿物质在哪里呢？以前的研究人员认为它主要存在于胶原蛋白内部，填补了端到端胶原蛋白分子之间的小空隙。然而，我们的研究表明，这种观点是错误的，骨骼中几乎所有的矿物质都以细长支柱的形式存在，这些支柱与胶原原纤维平行，并像木棒围绕木桶一样堆积在它们周围。这些支柱本身是由更小的晶体片组成的，它们显然是粘在一起形成支柱的。

Bone, the material out of which our bones are constructed, is a finely engineered material made of equal amounts of two components: mineral and collagen. The mineral consists of tiny crystals of a salt of calcium and phosphate, two of the essential chemicals in our body. Collagen is a protein, the most abundant one in our body, also found in skin and tendons. The collagen of bone forms wispy “fibrils” that are bundled together and lined up along the axes of our long bones, but where is the mineral? Previous researchers thought that it was mainly inside the collagen, filling little gaps between end-to-end molecules of collagen. Our research has shown, however, that this view is mistaken, and that almost all the mineral in bone is in the form of slender struts that run parallel to the collagen fibrils and are stacked around them like staves around a barrel. These struts are themselves composed of even smaller crystal flakes that are apparently glued together to make the struts.