Sato Yuichi, Moriyama Rui, Choi Sung Won, Kano Arihiro, Maruyama Atsushi
Precursory Research for Embryonic Science and Technology (PRESTO) and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
Langmuir. 2007 Jan 2;23(1):65-9. doi: 10.1021/la0615847.
We have demonstrated that cationic comb-type copolymers consisting of a polycation backbone and abundant grafts of water-soluble polymers stabilize DNA hybrids. Furthermore, the copolymers were found to accelerate strand exchange reaction between a double-stranded DNA and its complementary single-stranded DNA. In this article, we investigated the effects of PLL-g-Dex on base pairs of a self-complementary DNA octamer, d(GGAATTCC). The soluble interpolyelectrolyte complex (IPEC) between the DNA and copolymer allowed us to characterize the complex by using spectroscopic methods under physiological ionic condition. Chemical shifts of nucleobase proton signals were not changed by PLL-g-Dex. Furthermore, the copolymer slightly changed the von't Hoff DeltaH accompanying the helix-coil transition of the octamer. These results indicated that the base pairs of the duplex DNA in the IPEC were not perturbed by the polycationic copolymer. It was obviously shown by temperature dependencies of proton and phosphorus NMR spectra that DNA/copolymer interaction was considerably enhanced in response to ds DNA formation. An increase in the density and total number of DNA negative charges upon hybrid formation likely caused the higher affinity of the copolymer with the ds form over that of the copolymer with the ss form. The IPEC formation of CCCs with DNA, however, seems highly sensitive to the coil-helix transition of the DNA.
我们已经证明，由聚阳离子主链和大量水溶性聚合物接枝组成的阳离子梳型共聚物可稳定DNA杂交体。此外，还发现该共聚物能加速双链DNA与其互补单链DNA之间的链交换反应。在本文中，我们研究了聚赖氨酸-接枝-右旋糖酐（PLL-g-Dex）对自互补DNA八聚体d(GGAATTCC)碱基对的影响。DNA与共聚物之间形成的可溶性聚电解质络合物（IPEC）使我们能够在生理离子条件下使用光谱方法对该络合物进行表征。PLL-g-Dex不会改变核碱基质子信号的化学位移。此外，该共聚物略微改变了八聚体螺旋-线圈转变时的范特霍夫焓变（DeltaH）。这些结果表明，IPEC中双链DNA的碱基对不受聚阳离子共聚物的干扰。质子和磷核磁共振谱的温度依赖性清楚地表明，响应于双链DNA的形成，DNA/共聚物相互作用显著增强。杂交形成时DNA负电荷密度和总数的增加可能导致共聚物对双链形式的亲和力高于对单链形式的亲和力。然而，CCC与DNA形成IPEC似乎对DNA的线圈-螺旋转变高度敏感。
