Napier M A, Hadler N M
Proc Natl Acad Sci U S A. 1978 May;75(5):2261-5. doi: 10.1073/pnas.75.5.2261.
Natural-abundance (13)C NMR at 25.16 MHz has been used to study a 2.5% matrix of hyaluronic acid at various degrees of polymerization and at various ionic strengths. Peak assignment is facilitated by comparing proton-decoupled and off-resonance-decoupled spectra of a hyaluronidase-depolymerized matrix with spectra from relevant monosaccharides. In contrast to the spectrum following depolymerization, the spectrum for intact matrix has considerable broadening, particularly for peaks assigned to the N-acetylglucosamine moiety. This is most dramatic for the hydroxymethylene carbon. With the addition of Ca(2+) above 5 mM these broadened peaks narrow and approach the sharpness observed for the hyaluronidase digest. There is no shift in resonance peak positions. These changes are quantitatively less impressive if Na(+) is substituted for Ca(2+). The data suggest the existence of a considerable degree of order in regions of the matrix at physiological concentrations of Ca(2+). Within such a matrix the translational movement of lysine and glucose is enhanced relative to that in a matrix of agarose. Further addition of Ca(2+) abrogates not only matrix order, but the enhanced diffusivity as well.
25.16兆赫兹的天然丰度(13)C核磁共振已被用于研究不同聚合度和不同离子强度下2.5%的透明质酸基质。通过比较透明质酸酶解聚基质的质子去耦和非共振去耦光谱与相关单糖的光谱，有助于进行峰归属。与解聚后的光谱相比，完整基质的光谱有相当大的展宽，特别是对于归属于N-乙酰葡糖胺部分的峰。对于羟亚甲基碳来说，这种情况最为明显。当加入高于5毫摩尔的Ca(2+)时，这些展宽的峰会变窄，并接近透明质酸酶消化物所观察到的尖锐程度。共振峰位置没有移动。如果用Na(+)代替Ca(2+)，这些变化在数量上就不那么明显了。数据表明，在生理浓度的Ca(2+)下，基质区域存在相当程度的有序性。在这样的基质中，赖氨酸和葡萄糖的平移运动相对于琼脂糖基质有所增强。进一步添加Ca(2+)不仅会消除基质的有序性，还会消除增强的扩散性。
