DNA condensation with spermine dendrimers: interactions in solution, charge inversion, and morphology control
DNA condensation with spermine dendrimers: interactions in solution, charge inversion, and morphology control
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DOI：
10.1039/c1sm05485f
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发表时间：
2011-07
期刊：
影响因子：
3.4
通讯作者：
Dennis Kurzbach;Caroline Velte;Philipp Arnold;Gönül Kızılsavaş;D. Hinderberger
中科院分区：
文献类型：
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作者：
Dennis Kurzbach;Caroline Velte;Philipp Arnold;Gönül Kızılsavaş;D. Hinderberger
在本报告中，我们使用连续波电子顺磁共振波谱 (CW EPR) 和透射电子显微镜 (TEM) 表征了 884 个碱基对、双链 DNA 和自旋标记的第二代树突 (SL-G2) 的结构缩合物的形成，这些树突是基于精胺的阳离子。溶液中 DNA 和 SL-G2 之间的静电相互作用导致 DNA 凝结成致密结构。在特定的电荷比为 2.3（阳离子电荷/阴离子电荷）时，该结构表现为平行有序、拉伸的 DNA 和 SL-G2 的粗棒状缩合物。根据 DNA 浓度、电荷比和用一价盐调节的离子强度，通过 TEM 观察到多种结构。通过添加锰 (II) 盐，可以通过 CW EPR 观察到 DNA 的电荷反转。这是可以实现的，因为顺磁性 Mn2+ 离子通常在添加盐后立即静电结合到强 DNA 聚离子上，并且只有在从 DNA 分子中排出时才会产生 EPR 信号。在电荷比为 2.3 时，Mn(II) 离子从形成的 DNA 树状复合物中排出，这表明 DNA 的电荷反转。由于基于硝基氧的 SL-G2 和 Mn2+-离子的 CW EPR 光谱在光谱上是不同的，因此可以同时观察到缩合剂与 DNA 的相互作用以及 DNA 与 Mn2+ 抗衡离子的相互作用。虽然缩合剂和 DNA 之间的相互作用没有改变，但无论溶液中存在的条件如何，当条件变化时，缩合体/聚集体的形态都会发生巨大变化，这一点可以从 Mn2+ 信号和 TEM 数据中推断出来。
In this report, we characterize the formation of structured condensates of 884 base pair, double stranded DNA and spin-labeled, second generation dendrons (SL-G2) that are spermine-based and cationic using continuous wave electron paramagnetic resonance spectroscopy (CW EPR) and transmission electron microscopy (TEM). The electrostatic interaction between DNA and SL-G2 in solution leads to condensation of DNA into densely packed structures. At a particular charge ratio of 2.3 (cationic charges/anionic charges), the structures appear as thick rod-like condensates of parallelly ordered, stretched DNA and SL-G2. Depending on the concentration of DNA, the charge ratio and the ionic strength, which has been adjusted with monovalent salts, a large variety of structures were observed by TEM. By adding manganese(II) salts charge inversion of DNA could be observed by CW EPR. This could be achieved, because paramagnetic Mn2+ ions are usually electrostatically bound to the strong DNA polyions immediately after adding the salt and only give rise to an EPR signal when expelled from the DNA molecules. At a charge ratio of 2.3 the Mn(II) ions are expelled from the formed DNA dendriplexes, which indicates an inverted charge of the DNA. Since CW EPR spectra of the nitroxide-based SL-G2 and Mn2+-ions are spectroscopically distinct, the interaction of the condensation agent with DNA and the interaction of DNA with Mn2+ counterions could be observed simultaneously. While the interaction between condensation agent and DNA did not change, irrespective of the conditions present in the solution, condensate/aggregate morphology changed drastically when the conditions were varied, as could be inferred from the Mn2+ signal and TEM data.