The Blue Crab Exoskeleton-A Model System for Studying the Control of Biomineralization

矿化结构在大多数动物群体中都能找到。生物矿物与骨骼、牙齿、海绵针状物以及软体动物、甲壳类和棘皮动物的贝壳有关，仅举几例。生物矿化还与动脉粥样硬化、肾结石和肿瘤等病理条件有关。在大多数族中，矿物质是钙的盐类，在所有情况下，矿物质都与有机分子伴生。在所有这些体系中，有机分子都参与启动、引导和调节矿物晶体的生长。这些有机分子通常是蛋白质。最近，罗尔博士和其他人发现，这些与生物矿化相关的蛋白质中，有一些带有糖类，被称为糖蛋白。与糖蛋白相关的糖的变化可能在控制生物矿化中发挥作用，这一点也变得越来越明显。他选择蓝蟹的外骨骼作为研究糖蛋白在控制生物矿化中作用的模型系统。螃蟹在很大程度上是此类研究的理想选择，因为螃蟹必须蜕皮才能生长。在为蜕皮做准备的过程中，螃蟹在旧外骨骼下面形成了新外骨骼的外层。新壳必须保持柔软，直到螃蟹从旧壳中出来并膨胀。只有到那时，新的外壳才开始变硬。因此，他的组织在某个时间点无法矿化，然后在蜕皮后一到三个小时内启动矿化。这一现象使他能够分析处于这两种状态的组织，并了解导致矿化的糖蛋白的变化。这些结果将对其他成矿组织具有普遍的应用价值。

Mineralized structures are found in most groups of animals. Biominerals are associated with bones, teeth, sponge spicules, and shells of molluscs, crustaceans and echinoderms to name but a few. Biomineralization is also associated with such pathological conditions as atherosclerosis, kidney stones and tumors. In most groups the minerals are salts of calcium and in all cases the minerals are associated with organic molecules. The organic molecules are involved in initiating, guiding and regulating the growth of the mineral crystals in all of these systems. These organic molecules are often proteins. Recently, Dr. Roer and others have found that some of these proteins associated with biomineralization have sugars attached to them and are referred to as glycoproteins. It is also becoming apparent that changes in the sugars associated with the glycoproteins may play a role in controlling biomineralization.He has chosen the exoskeleton of the blue crab, Callinectes sapidus, as a model system for studying the role of glycoproteins in controlling biomineralization. The crab is ideal for such studies, in large part, because crabs must molt in order to grow. In preparation for the molt, crabs form the outer layers of their new exoskeleton beneath the old one. The new shell must stay soft until the crab emerges from the old shell and expands. Only then does the new shell begin to harden. He thus has a tissue that is incapable of mineralizing at one point in time which then turns on mineralization within one to three hours after it molts. This phenomenon allows him to analyze the tissue in both states and understand the changes in the glycoproteins that are responsible for turning on mineralization. These results will have general application to other mineralizing tissues.