Simulating protein control of Calcite Crystallisation by Ovocleidin-17

鸟类的蛋壳由大约95%的碳酸钙组成，其中含有一种蛋白质基质，它既控制晶体的放置方式，又防止蛋壳变得太脆。这个过程非常快--一只母鸡可以在大约20小时内下一个蛋。壳本身有一个复杂的结构，其特征对于它所包含的胚胎的健康是必不可少的。最近的实验数据已经确定了几种与蛋壳形成有关的蛋白质。有一类蛋白质(C型凝集素样蛋白)似乎在控制各种鸟类的方解石沉积方面特别重要，尽管这些蛋白质如何做到这一点还不是很清楚。对卵磷脂-17(鸡肉)和安斯卡林(鹅)的研究表明，这两种蛋白质都能促进晶体的形成，并对晶体的生长和形状有很强的影响。要理解这是如何发生的，模拟是必不可少的。我们将模拟在水存在的情况下，卵叶绿素-17与各种CaCO3表面之间的相互作用。这将使我们能够了解分子的哪些部分决定晶体的形状，以及它们为什么重要。一个特别的亮点将是在Hector上使用超动力学来确定ovocleidin-17如何影响无定形碳酸钙颗粒的自由能以及它们向晶相的转变。这些模拟将为寻求设计新分子以产生特定晶体类型和形状的实验小组提供极其有价值的信息。这是仿生学的一部分，仿生学是一种用生物学思想来指导寻找新材料和新工艺的策略。

Eggshells in birds are made of about 95% calcium carbonate, with a matrix of proteins which both controls how the crystals are laid down and prevents the shell from becoming too brittle. The process is very fast - a hen can make an egg in about 20 hours. The shell itself has a complicated structure whose features are essential for the health of the embryo it contains. Recent experimental data have identified several proteins associated with the formation of egg shells. One class of proteins (C-type lectin-like proteins) appears to be particularly important in controlling calcite deposition for various bird species, although how the proteins do this is not well understood. Studies with ovocleidin-17 (chicken) and ansocalcin (goose) have showed that these proteins both encourage crystals to form and have a strong effect on their growth and shape. Simulations are essential to understand how this happens. We will model the interaction between ovocleidin-17 and various CaCO3 surfaces in the presence of water. This will enable us to understanding what parts of the molecule determine the shape of the crystal and why they are important. A particular highlight will be the use of metadynamics on HECToR to determine how ovocleidin-17 affects the free energy of amorphous calcium carbonate particles and their transformation to a crystalline phase. These simulations will provide extremely valuable information for experimental groups seeking to design new molecules to produce particular crystal types and shapes. This is part of biomimetics, the strategy of using biological ideas to guide the search for new materials and processes.