Simulating protein control of Calcite Crystallisation by Ovocleidin-17

鸟类的蛋壳是由大约95%的碳酸钙组成的，还有一种蛋白质基质，它既控制着晶体的排列方式，又防止蛋壳变得太脆。这个过程非常快，一只母鸡大约20小时就能下一个蛋。蛋壳本身具有复杂的结构，其特征对它所包含的胚胎的健康至关重要。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。一类蛋白质（c型凝集素样蛋白质）在控制各种鸟类方解石沉积方面似乎特别重要，尽管人们还不太清楚这些蛋白质是如何做到这一点的。对卵黄素-17（鸡）和鹅钙素（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。模拟对于理解这是如何发生的至关重要。我们将模拟ovocleidin-17和各种CaCO3表面在水存在下的相互作用。这将使我们了解分子的哪些部分决定了晶体的形状，以及它们为什么重要。一个特别的亮点将是在HECToR上使用元动力学来确定ovocleidin-17如何影响无定形碳酸钙颗粒的自由能及其向结晶相的转变。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组提供极有价值的信息。这是仿生学的一部分，这是一种利用生物学思想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.