Solution studies of chitosan 6‐O‐sulfate
Solution studies of chitosan 6‐O‐sulfate
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DOI：
10.1002/macp.1989.021901116
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发表时间：
1989-11
影响因子：
2.5
通讯作者：
M. Terbojevich;C. Carraro;A. Cosani;B. Focher;A. Naggi;G. Torri
中科院分区：
文献类型：
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作者：
M. Terbojevich;C. Carraro;A. Cosani;B. Focher;A. Naggi;G. Torri
商业壳聚糖及其高度脱乙酰化的同源物可以在 O-6 水平上选择性且广泛地硫酸化。可以使用硫酸和氯磺酸的 2:1 混合物（方法 I）或吡啶-SO3 络合物，然后用铜离子保护 2-NH2 和 3-OH 基团（方法 II）。研究了在促进聚两性电解质结构的 pH 条件下具有不同乙酰化程度的硫酸化壳聚糖的性质。通过方法 II 制备的乙酰化程度为 20% 的壳聚糖 6-O-硫酸盐的光散射和特性粘度 ([η]) 测量表明存在分子和结构异质性，这可能是由于母体壳聚糖高度乙酰化区域中的有序结构所致。对用亚硝酸解聚得到的片段进行核磁共振分析证实了这一假设。在通过方法I获得的化合物和高度脱乙酰化的壳聚糖6-O-硫酸盐中未观察到异质性。离子强度降低时聚两性电解质的 [η] 增加可以用通过硫酸基团和相邻残基上的质子化氨基之间的静电相互作用稳定的更刚性的构象来解释。
Commercial chitosan, and highly deacetylated congeners thereof, can be selectively and extensively sulfated at the O-6 level. Either a 2:1 mixture of sulfuric and chlorosulfonic acid (Method I) or a pyridine-SO3 complex, following protection of the 2-NH2 and 3-OH groups with copper ions (Method II), can be used. The properties of sulfated chitosan with different degrees of acetylation are studied at pH conditions which promote a polyampholyte structure. Light scattering and intrinsic viscosity ([η]) measurements of chitosan 6-O-sulfate with a degree of acetylation of 20%, prepared by Method II, indicate the presence of molecular and structural heterogeneity, probably due to ordered structures in highly acetylated regions of the parent chitosan. This hypothesis is confirmed by the NMR analysis of the fragments obtained by depolymerization with nitrous acid. The heterogeneity is not observable in compounds obtained by Method I and in highly deacetylated chitosan 6-O-sulfate. The [η] increase of the polyampholyte on decreasing ionic strength can be explained in terms of a more rigid conformation stabilized by electrostatic interactions between the sulfate groups and the protonated amino groups on neighbouring residues.