Orberg Marie-Louise, Schillén Karin, Nylander Tommy
Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Biomacromolecules. 2007 May;8(5):1557-63. doi: 10.1021/bm061194z. Epub 2007 Apr 26.
The interaction between a cationic poly(amido amine) (PAMAM) dendrimer of generation 4 and double-stranded salmon sperm DNA in 10 mM NaBr solution has been investigated using dynamic light scattering (DLS) and steady-state fluorescence spectroscopy. The structural parameters of the formed aggregates as well as the complex formation process were studied in dilute solutions. When DNA is mixed with PAMAM dendrimers, it undergoes a transition from a semiflexible coil to a more compact conformation due to the electrostatic interaction present between the cationic dendrimer and the anionic polyelectrolyte. The DLS results reveal that one salmon sperm DNA molecule forms a discrete aggregate in dilute solution with several PAMAM dendrimers with a mean apparent hydrodynamic radius of 50 nm. These discrete complexes coexist with free DNA at low molar ratios of dendrimer to DNA, which shows that cooperativity is present in the complex formation. The formation of the complexes was confirmed by agarose gel electrophoresis measurements. DNA in the complexes was also found to be significantly more protected against DNase catalyzed digestion compared to free DNA. The number of dendrimers per DNA chain in the complexes was found to be approximately 35 as determined by steady-state fluorescence spectroscopy.
利用动态光散射（DLS）和稳态荧光光谱研究了第4代阳离子聚（酰胺胺）（PAMAM）树枝状大分子与10 mM NaBr溶液中双链鲑鱼精DNA之间的相互作用。在稀溶液中研究了形成的聚集体的结构参数以及复合物的形成过程。当DNA与PAMAM树枝状大分子混合时，由于阳离子树枝状大分子与阴离子聚电解质之间存在静电相互作用，它会从半柔性线圈转变为更紧凑的构象。DLS结果表明，一个鲑鱼精DNA分子在稀溶液中与几个PAMAM树枝状大分子形成离散聚集体，平均表观流体动力学半径为50 nm。在树枝状大分子与DNA的低摩尔比下，这些离散复合物与游离DNA共存，这表明复合物形成过程中存在协同作用。琼脂糖凝胶电泳测量证实了复合物的形成。与游离DNA相比，复合物中的DNA也被发现对DNase催化的消化具有显著更高的抗性。通过稳态荧光光谱测定，复合物中每条DNA链上的树枝状大分子数量约为35。
