Institute of Chemistry, University of Bialystok, Ciolkowskiego 1K, 15-425 Bialystok, Poland.
Institute of Mathematics and Physics, University of Technology and Life Sciences, Kaliskiego 7, 85-796 Bydgoszcz, Poland.
Molecules. 2019 Jun 16;24(12):2248. doi: 10.3390/molecules24122248.
In this paper, we explain the amphoteric character of the cartilage surface by studying a lipid bilayer model built from phospholipids. We examined the interfacial tension values and molecular dynamics simulation in solutions of varying pH. The effects of negative and positive charge density (or fixed charges) on the (cartilage/cartilage) friction coefficient were investigated. In physiological (or synovial) fluid, after the isoelectric point (pI), the curve of interfacial tension decreases rapidly as it reaches pH 7.4 and then approaches a constant value at higher pH. It was shown that the curve of the interfacial tension curve exhibits a maximum value at the isoelectric point with a Gaussian shape feature. The phospholipid bilayers facilitate an almost frictionless contact in the joint. Moreover, the slippage of the bilayer and the short-range repulsion between the surfaces of the negatively charged cartilage surfaces are the main determinants of the low frictional properties of the joint.
本文通过研究由磷脂构建的双层膜模型解释了软骨表面的两性特征。我们研究了不同 pH 值溶液中的界面张力值和分子动力学模拟。考察了（软骨/软骨）摩擦系数随负电荷和正电荷密度（或固定电荷）的变化。在生理（或滑液）流体中，在等电点（pI）之后，界面张力曲线在 pH 值为 7.4 时迅速下降，然后在较高 pH 值时接近恒定值。结果表明，界面张力曲线在等电点处呈现出最大值，具有高斯形状特征。磷脂双层膜有助于在关节中实现几乎无摩擦的接触。此外，双层膜的滑移和带负电荷的软骨表面之间的短程排斥是关节低摩擦特性的主要决定因素。
