透明质酸半稀溶液结构和动力学的介电谱研究
Structure and dynamics of hyaluronic acid semidilute solutions: a dielectric spectroscopy study
摘要：
利用介电谱研究了透明质酸钠半稀溶液的基本长度尺度。在无盐制度下，在MHz范围内检测到的弛豫模式的长度尺度与HA浓度为$c_\mathrm{HA}^{-0.5}$，并对应于de Gennes-Pfeuty-Dobrynin相关长度的聚电解质在半稀溶液。对于长的基因组DNA的情况，观察到相同的缩放。相反，在kHz范围内检测到的模式的长度尺度也随着HA浓度而变化，如$c_\mathrm{HA}^{-0.5}$，其不同于DNA的情况（$c_\mathrm{DNA}^{-0.25}$）。观察到的行为表明，在kHz范围内的弛豫揭示了de Gennes-Dobrynin重整化德拜屏蔽长度，而不是链的平均尺寸，作为相关的长度尺度。类似地，随着添加的盐的增加，观察到静电对HA持久长度的贡献与德拜长度成比例，与在DNA的情况下观察到的Odijk-Skolnick-Fixman静电持久长度相关的比例相反。我们认为，所观察到的kHz范围松弛的功能是由于弱得多的静电相互作用，导致没有曼宁缩合以及相当高的灵活性的HA相比，DNA。
英文摘要：
Dielectric spectroscopy is used to investigate fundamental length scales describing the structure of hyaluronic acid sodium salt (Na-HA) semidilute aqueous solutions. In salt-free regime, the length scale of the relaxation mode detected in MHz range scales with HA concentration as $c_\mathrm{HA}^{-0.5}$ and corresponds to the de Gennes-Pfeuty-Dobrynin correlation length of polyelectrolytes in semidilute solution. The same scaling was observed for the case of long, genomic DNA. Conversely, the length scale of the mode detected in kHz range also varies with HA concentration as $c_\mathrm{HA}^{-0.5}$ which differs from the case of DNA ($c_\mathrm{DNA}^{-0.25}$). The observed behavior suggests that the relaxation in the kHz range reveals the de Gennes-Dobrynin renormalized Debye screening length, and not the average size of the chain, as the pertinent length scale. Similarly, with increasing added salt the electrostatic contribution to the HA persistence length is observed to scale as the Debye length, contrary to scaling pertinent to the Odijk-Skolnick-Fixman electrostatic persistence length observed in the case of DNA. We argue that the observed features of the kHz range relaxation are due to much weaker electrostatic interactions that lead to the absence of Manning condensation as well as a rather high flexibility of HA as compared to DNA.
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