Hyaluronan forms specific stable tertiary structures in aqueous solution:: A 13C NMR study
Hyaluronan forms specific stable tertiary structures in aqueous solution:: A 13C NMR study
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DOI：
10.1073/pnas.96.9.4850
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发表时间：
1999-04-27
影响因子：
11.1
通讯作者：
Heatley, F
中科院分区：
文献类型：
--
作者：
Scott, JE;Heatley, F
在125.8 MHz处获得了睾丸透明质酸酶消化前后的高分子量透明质酸(HA)水溶液以及透明质酸甲酯的(13)C NMR谱，通过使用选择性去偶技术分配了羰基峰，消化和未消化的HA的谱图显示出尖锐的信号，除了归属于高聚物中的乙酰氨基羰基碳的谱线，该谱线变宽了很多。由此证明，该 C=O 的迁移率降低是由旋转受限引起的。作为刚性 CO-NH 单元的一部分，NH 的旋转同样受到限制，这可能是因为 NH 与相邻 HA 分子上的羧酸根之间存在分子间氢键。通过比较酯化的 HA 和未修饰的 HA 证实了这种键。羧酸酯的甲酯化伴随着乙酰胺基 C=O 共振的变化，这与 CO-NH 基团迁移率的增加一致。酯 C=O 共振很尖锐，证明它们不参与空间限制结构，例如涉及未酯化羧酸酯基团的拟议 H 键。 C=O 共振报告了环境以及酰胺和羧酸根基团的相互关系。水溶液中高分子质量 HA 的详细结构考虑了 NMR 和 X 射线纤维衍射数据，反向平行 HA 链在由特定 H 键和疏水键稳定的网络中重叠。这种高度协作的结构，形式上相当于蛋白质中的β-折叠结构，但在低分子量HA溶液中并不稳定。结果与涉及软骨素和硫酸角质素的细胞外基质形状模块的结构有关，它们的立体化学类似于 HA。
(13)C NMR spectra of aqueous solutions of hyaluronan (HA) of high molecular mass, before and after digestion with testicular hyaluronidase, and of hyaluronan methyl ester were obtained at 125.8 MHz, Carbonyl peaks were assigned by using selective decoupling techniques, Spectra of digested and undigested HA showed sharp signals, except for that assigned to the acetamido carbonyl carbon in the high polymer, which was much broadened. The decreased mobility of this C=O, thus demonstrated, was caused by restricted rotation. As part of the rigid CO-NH unit, rotation of NH was therefore similarly restricted, probably because of an intermolecular H bond from NH to carboxylate groups on neighbouring HA molecules. This bond was confirmed by comparing esterified HA with unmodified HA. Methyl esterification of carboxylates was accompanied by changes in acetamido C=O resonances consistent with increased mobility of CO-NH groups. Ester C=O resonances were sharp, proving that they did not participate in sterically restricted structures such as the proposed H bonds involving unesterified carboxylate groups. C=O resonances report on the environments and on the interrelationships of amide and carboxylate groups. A detailed structure suggested for high-molecular-mass HA in aqueous solution takes account of NMR and x-ray fiber diffraction data, Antiparallel HA chains overlap in meshworks stabilized by specific H bonds and hydrophobic bonds. This highly cooperative structure, formally equivalent to beta-sheets seen in proteins, is not stable in low-molecular-mass HA solution. The results relate to structures proposed for shape modules in extracellular matrix involving chondroitin and keratan sulfates, which resemble HA in their stereochemistry.