Abstract：
Bone is a highly hierarchical complex structure that consists of organic and mineral components represented by collagen molecules (CM) and hydroxyapatite crystals (HAC), respectively. The nanostructure of bone can significantly affect its mechanical properties. There is a lack of understanding how collagen fibrils (CF) in different orientations may affect the mechanical properties of the bone. The objective of this study is to investigate the effect of interaction, orientation, and hydration on atomic models of the bone composed of collagen helix (CH) and HAC, using molecular dynamics simulations and therefrom bone-related disease origins. The results demonstrate that the mechanical properties of the bone are affected significantly by the orientation of the CF attributed to contact areas at 0° and 90° models. The molecular dynamics simulation illustrated that there is significant difference (p < 0.005) in the ultimate tensile strength and toughness with respect to the orientation of the hydrated and un-hydrated CF. Additionally, the results indicated that having the force in a longitudinal direction (0°) provides more strength compared with the CF in the perpendicular direction (90°). Furthermore, the results show that substituting glycine (GLY) with any other amino acid affects the mechanical properties and strength of the CH, collagen−hydroxyapatite interface, and eventually affects the HAC. Generally, hydration dramatically influences bone tissue elastic properties, and any change in the orientation or any abnormality in the atomic structure of either the CM or the HAC would be the main reason of the fragility in the bone, affecting bone pathology.
摘要：
骨是一种高度分层的复杂结构，由胶原蛋白分子（CM）和羟基磷灰石晶体（HAC）代表的有机和矿物质成分组成，分别。骨骼的纳米结构可以显着影响其机械性能。缺乏了解不同取向的胶原纤维（CF）如何影响骨骼的机械性能。这项研究的目的是调查相互作用的影响，定位,以及在由胶原蛋白螺旋（CH）和HAC组成的骨骼原子模型上的水合作用，使用分子动力学模拟和骨相关疾病的起源。结果表明，在0°和90°模型下，归因于接触面积的CF取向会显着影响骨骼的机械性能。分子动力学模拟表明，相对于水合和未水合CF的取向，极限拉伸强度和韧性存在显着差异（p＆lt;0.005）。此外,结果表明，与垂直方向（90°）的CF相比，纵向（0°）的力提供了更大的强度。此外，结果表明，用任何其他氨基酸取代甘氨酸（GLY）会影响CH的机械性能和强度，胶原-羟基磷灰石界面，并最终影响HAC。一般来说,水合作用会极大地影响骨组织的弹性特性，CM或HAC的方向变化或原子结构异常是骨骼脆性的主要原因，影响骨病理学。
