Probing the Mesh Formed by the Semirigid Polyelectrolytes
Probing the Mesh Formed by the Semirigid Polyelectrolytes
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DOI：
10.1021/ma3021486
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发表时间：
2013-01
期刊：
影响因子：
5.5
通讯作者：
K. Salamon;D. Aumiler;G. Pabst;T. Vuletić
中科院分区：
文献类型：
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作者：
K. Salamon;D. Aumiler;G. Pabst;T. Vuletić
我们将半固态聚电解质脱氧核糖核酸（DNA）和透明质酸（HA）在半稀状态下的构象和动力学联系起来，在宽浓度范围内（10−3−10 2 g/L）。无盐聚电解质不同于不带电的聚合物，因为它们可能形成相当刚性的各向同性网状结构。聚电解质的特征网格尺寸称为德热涅相关长度ξ。我们直接探测DNA与HA形成的网状结构，采用荧光相关光谱法（FCS）测量微量加入荧光标记DNA片段的扩散系数。对于无盐溶液，我们发现DNA或HA网尺寸必须比碎片大2 - 3倍，才能开始自由扩散（就像在稀释溶液中一样）。对于较紧的网格（浓度为0.1 ~ 1 g/L），碎片扩散系数仅为自由扩散值的一半。相反，片段显示自由扩散系数，就好像在10mm缓冲液中DNA或HA中没有网格一样。这很好地符合添加盐的聚电解质的ξ值消失的事实。当筛孔尺寸小于碎片尺寸（大于1 g/L）时，扩散系数进一步下降，在缓冲液和纯水中，在最高测量浓度（10 g/L）下，扩散系数分别达到相似的值。我们还对HA和DNA（范围3 - 130 g/L）进行了小角度x射线散射（SAXS），以补充我们之前的介电光谱（范围0.01 - 5 g/L）研究。这些方法结合起来，在FCS研究的范围内提供了de Gennes长度ξ的参考值。
We correlate conformation and dynamics of the semirigid polyelectrolytes deoxyribonucleic acid (DNA) and hyaluronic acid (HA) in the semidilute regime, across a broad concentration range (10 −3 − 10 2 g/L). Salt-free polyelec- trolytes are distinct from uncharged polymers as they presumably form a rather rigid, isotropic mesh. The polyelectrolyte characteristic mesh size is known as de Gennes correlation length ξ. We directly probed the mesh formed by DNA and HA, by employing fluorescence correlation spectroscopy (FCS) to measure the diffusion coefficient of fluorescently labeled DNA fragments added in trace amounts. For the salt-free solutions we found that the DNA or HA mesh size has to be 2−3 times larger than the fragments for them to start to diffuse freely (as if in the dilute solution). For a tighter mesh (concentrations 0.1−1 g/L), the fragment diffusion coefficient is only half the free diffusion value. Conversely, fragments show the free diffusion coefficientas if there is no meshin DNA or HA in 10 mM buffer. This complies well with the fact that the ξ fades for polyelectrolytes with added salt. The diffusion coefficient falls off further when the mesh size gets smaller than the fragment size (above 1 g/L) and a similar value is reached in buffer as well as in pure water, respectively, at the highest measured concentrations (10 g/L). We also performed small-angle X-ray scattering (SAXS) on HA and DNA (range 3−130 g/L) to complement our previous dielectric spectroscopy (DS) studies (range 0.01−5 g/L). Combined, these methods provide reference values of the de Gennes length ξ across the range studied by FCS.