Kok D J, Blomen L J, Westbroek P, Bijvoet O L
Eur J Biochem. 1986 Jul 1;158(1):167-72. doi: 10.1111/j.1432-1033.1986.tb09734.x.
A polysaccharide associated with coccoliths of the marine alga Emiliania huxleyi (coccoliths are elaborately shaped calcite biominerals) was isolated and its influence on the crystallization of calcium oxalate monohydrate crystals was studied. Crystallization was monitored in a carefully controlled system by measuring the incorporation of 45Ca tracer from a supersaturated solution into seed crystals of calcium oxalate monohydrate in the absence and in the presence of polysaccharide. The method allowed differentiation between effects on solubility, growth and agglomeration of crystals. At the very low concentrations used in this study, the polysaccharide had no significant effect on the solubility product; it strongly inhibited the growth and strongly stimulated the agglomeration of the crystals. Thus, the two processes of growth and agglomeration, being both crystal-surface-related processes, may react in opposite directions upon surface adhesion of the additive. This finding opens new insights on how a mineralization process may be controlled. The inhibitory effect on growth is shown to proceed through a monolayer type of adsorption of the polysaccharide onto the crystal surface. The portion of the polysaccharide used for the stimulatory effect on agglomeration shows a different type of adsorption, whereby less crystal surface is covered per molecule of polysaccharide. This strongly suggests, that the mechanism whereby agglomeration is stimulated operates through 'viscous binding', with the polysaccharide bridging the gap between two crystal surfaces. In the discussion these findings are related to some possible biological functions of the polysaccharide.
一种与海洋藻类赫氏颗石藻的颗石相关的多糖（颗石是形状精巧的方解石生物矿物）被分离出来，并研究了其对一水合草酸钙晶体结晶的影响。在一个精心控制的系统中，通过测量在不存在和存在多糖的情况下，来自过饱和溶液的45Ca示踪剂掺入一水合草酸钙籽晶中的情况来监测结晶过程。该方法能够区分对晶体溶解度、生长和团聚的影响。在本研究使用的极低浓度下，多糖对溶度积没有显著影响；它强烈抑制晶体生长并强烈促进晶体团聚。因此，生长和团聚这两个过程，都是与晶体表面相关的过程，在添加剂的表面粘附时可能会有相反的反应。这一发现为矿化过程如何被控制开启了新的见解。对生长的抑制作用被证明是通过多糖在晶体表面的单层吸附来进行的。用于促进团聚的多糖部分表现出不同类型的吸附，即每分子多糖覆盖的晶体表面较少。这有力地表明，促进团聚的机制是通过“粘性结合”起作用的，多糖桥接了两个晶体表面之间的间隙。在讨论中，这些发现与多糖的一些可能的生物学功能相关。
