Section on Tissue Biophysics and Biomimetics, Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 13 South Drive, Bethesda, Maryland 20892, USA.
J Chem Phys. 2009 Nov 14;131(18):184902. doi: 10.1063/1.3262308.
Hyaluronic acid (HA) is an anionic biopolymer that is almost ubiquitous in biological tissues. An attempt is made to determine the dominant features that account for both its abundance and its multifunctional role, and which set it apart from other types of biopolymers. A combination of osmotic and scattering techniques is employed to quantify its dynamic and static properties in near-physiological solution conditions, where it is exposed both to mono- and divalent counterions. An equation of state is derived for the osmotic pressure Pi in the semidilute concentration region, in terms of two variables, the polymer concentration c and the ionic strength J of the added salt, according to which Pi=1.4x10(3)c(9/4)/J(3/4) kPa, where c and J are expressed in mole. Over the physiological ion concentration range, the effect of the sodium chloride and calcium chloride on the osmotic properties of HA solutions is fully accounted for by their contributions to the ionic strength. The absence of precipitation, even at high CaCl(2) concentrations, distinguishes this molecule from other biopolymers such as DNA. Dynamic light scattering measurements reveal that the collective diffusion coefficient in HA solutions exceeds that in aqueous solutions of typical neutral polymers by a factor of approximately 5. This property ensures rapid adjustment to, and recovery from, stress applied to HA-containing tissue. Small angle x-ray scattering measurements confirm the absence of appreciable structural reorganization over the observed length scale range 10-1000 A, as a result of calcium-sodium ion exchange. The scattered intensity in the transfer momentum range q>0.03 A(-1) varies as 1/q, indicating that the HA chain segments in semidilute solutions are linear over an extended concentration range. The osmotic compression modulus c partial differential Pi/partial differential c, a high value of which is a prerequisite in structural biopolymers, is several times greater than in typical neutral polymer solutions.
透明质酸（HA）是一种阴离子生物聚合物，几乎存在于所有生物组织中。本文试图确定其丰富度和多功能性的主要特征，以及使其与其他类型生物聚合物区分开来的特征。本文采用渗透压和散射技术相结合的方法，在接近生理条件的溶液中定量研究其动态和静态特性，此时它既暴露于单价离子又暴露于二价离子中。根据状态方程，在半浓区，渗透压 Pi 可以表示为两个变量的函数，聚合物浓度 c 和加入盐的离子强度 J，根据该方程，Pi=1.4x10(3)c(9/4)/J(3/4) kPa，其中 c 和 J 的单位为摩尔。在生理离子浓度范围内，氯化钠和氯化钙对 HA 溶液渗透压的影响可以完全用它们对离子强度的贡献来解释。即使在高浓度 CaCl(2)下也没有沉淀，这使该分子有别于其他生物聚合物，如 DNA。动态光散射测量表明，HA 溶液中的集体扩散系数比典型中性聚合物在水溶液中的扩散系数大 5 倍左右。这种特性确保了 HA 组织能够快速适应和从施加的压力中恢复。小角 X 射线散射测量证实，在观察到的长度范围内 10-1000 A 内，没有明显的结构重排，这是由于钙-钠离子交换的结果。在传递动量范围 q>0.03 A(-1)内的散射强度随 1/q 变化，表明在半浓溶液中 HA 链段在扩展的浓度范围内是线性的。渗透压压缩模量 c 偏微分 Pi/偏微分 c，它是结构生物聚合物的一个重要前提，其值比典型的中性聚合物溶液大几倍。
