Section on Quantitative Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 49 Convent Drive, Bethesda, Maryland 20892-5772, USA.
Laboratoire Interdisciplinaire de Physique CNRS, Université Grenoble Alpes, F-38402 Saint Martin d'Hères Cedex, France.
J Chem Phys. 2018 Oct 28;149(16):163312. doi: 10.1063/1.5028351.
Systematic investigations using neutron and X-ray small angle scattering in near-physiological salt solutions were made to reveal the effect of polymer concentration, pH, and calcium ion concentration on the structure of semi-dilute solutions of four model biopolymers [polyaspartic acid, DNA, chondroitin sulfate, and hyaluronic acid (HA)] representing typical backbone structures. In the low range (<0.01 Å), the scattering response () is dominated by scattering from large clusters. In the intermediate range, () varies approximately as , exposing the linear nature of the scatterers. In these polyelectrolyte solutions, the correlation length displays a power law dependence on the polymer concentration that resembles that of neutral polymer solutions. increases with increasing calcium chloride concentration and with decreasing pH. The effect of the different divalent cations, Ba, Mg, Ca, Sr, and Mn, on the structure of DNA solutions is practically identical. However, in mixed salt conditions at the same ionic strength, the combined effect of mono- and divalent counter-ions on the structure of the polymer solutions deviates significantly from additivity. Anomalous small angle X-ray scattering observations on both DNA and HA solutions reveal that the divalent strontium counter-ions form a tight sheath around the polymer chain. The shape of the divalent ion cloud is similar in these two systems.
采用中子和 X 射线小角散射技术，在近生理盐溶液中对四种模型生物聚合物[聚天冬氨酸、DNA、硫酸软骨素和透明质酸（HA）]的半浓溶液进行了系统研究，以揭示聚合物浓度、pH 值和钙离子浓度对其结构的影响。在低 （<0.01 Å）范围内，散射响应（）主要由大聚集体的散射决定。在中间 范围内，（）大致按 变化，揭示了散射体的线性性质。在这些聚电解质溶液中，相关长度 显示出与聚合物浓度 的幂律关系，类似于中性聚合物溶液。随着氯化钙浓度的增加和 pH 值的降低而增加。不同二价阳离子 Ba、Mg、Ca、Sr 和 Mn 对 DNA 溶液结构的影响实际上是相同的。然而，在相同离子强度的混合盐条件下，单价和二价抗衡离子对聚合物溶液结构的综合影响明显偏离加和性。对 DNA 和 HA 溶液的异常小角 X 射线散射观察表明，二价锶抗衡离子在聚合物链周围形成紧密的鞘。在这两个系统中二价离子云的形状相似。
