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Abstract：
Hyaluronan (HA) is a linear, regular polysaccharide that plays as a chief structural and functional component in peri- and extracellular matrices, thus contributing significantly to many basic cellular processes. To understand more comprehensively the response of the supramolecular organization of HA polymers to changes in their aqueous environment, we study the effects of Ca2+ concentration and pH on the morphology and rigidity of films of end-grafted HA polymers on planar supports (HA brushes), as a well-defined in vitro model system of HA-rich matrices, by reflection interference contrast microscopy and quartz crystal microbalance. The thickness and softness of HA brushes decrease significantly with Ca2+ concentration but do not change with pH, within the physiological ranges of these parameters. The effect of Ca2+ on HA brush thickness is virtually identical to the effect of Na+ at 10-fold higher concentrations. Moreover, the thickness and softness of HA brushes decrease appreciably upon HA protonation at pH less than 6. Effects of pH and calcium ions are fully reversible over large parameter ranges. These findings are relevant for understanding the supramolecular organization and dynamics of HA-rich matrices in biological systems and will also benefit the rational design of synthetic HA-rich materials with tailored properties.
摘要：
透明质酸（HA）是一种线性，在周围和细胞外基质中起主要结构和功能成分的常规多糖，从而对许多基本的细胞过程做出了重大贡献。为了更全面地了解HA聚合物的超分子组织对其水环境变化的响应，我们研究了Ca2浓度和pH值对平面载体（HA刷）上末端接枝HA聚合物膜的形态和刚度的影响，作为一个定义明确的富含HA的基质体外模型系统，通过反射干涉对比显微镜和石英晶体微天平。HA刷的厚度和柔软度随着Ca2+浓度的增加而显著降低，但不随pH值的增加而改变。在这些参数的生理范围内。Ca2对HA刷厚度的影响实际上与Na在10倍以上浓度下的影响相同。此外，在小于6的pH下HA质子化后，HA刷的厚度和柔软度会明显下降。pH和钙离子的影响在大的参数范围内是完全可逆的。这些发现对于理解生物系统中富含HA的基质的超分子组织和动力学是相关的,并且还将有利于具有定制性质的合成的富含HA的材料的合理设计。
