Gabriel D A, Carr M E
Center for Thrombosis and Hemostasis, Lineberger Cancer Research Center, U.N.C. School of Medicine, Chapel Hill.
Am J Med Sci. 1989 Jul;298(1):8-14. doi: 10.1097/00000441-198907000-00002.
The physical properties of proteoglycans found in the extracellular matrix influence the behavior of resident macromolecules, micro-ions, and cells. The forces stabilizing structured regions of hyaluronic acid (HA), a major component of extracellular matrix, were measured. The free energy of stability associated with structured regions within human HA was determined by potentiometric titration. A plot of free energy versus temperature demonstrated that the secondary structure was most stable at 25 degrees C and was destabilized at temperatures near 50 degrees C. In the presence of 5 mM CaCl2, the free energy of stability of the structured regions was reduced by 30 cal/mole. Classical light scattering and viscosity measurements confirmed the impact of calcium on HA. CaCl2 (5 mM) reduced the radius of gyration of HA. Above concentrations of 3 mM calcium, the viscosity of 0.1% HA solutions was reduced sharply. The ability of cells to secrete calcium, combined with the exquisite sensitivity of HA to calcium, may permit cell-mediated modification of the extracellular matrix and thus may facilitate cell motility.
细胞外基质中蛋白聚糖的物理性质会影响驻留大分子、微离子和细胞的行为。对细胞外基质的主要成分透明质酸（HA）的结构化区域的稳定力进行了测量。通过电位滴定法测定了与人类HA中结构化区域相关的稳定性自由能。自由能与温度的关系图表明，二级结构在25摄氏度时最稳定，在接近50摄氏度时不稳定。在存在5 mM氯化钙的情况下，结构化区域的稳定性自由能降低了30卡/摩尔。经典光散射和粘度测量证实了钙对HA的影响。氯化钙（5 mM）减小了HA的回转半径。钙浓度高于3 mM时，0.1% HA溶液的粘度急剧降低。细胞分泌钙的能力，加上HA对钙的高度敏感性，可能允许细胞介导的细胞外基质修饰，从而可能促进细胞运动。
