Maruyama A, Watanabe H, Ferdous A, Katoh M, Ishihara T, Akaike T
Department of Biomolecular Engineering, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori, Yokohama, Japan.
Bioconjug Chem. 1998 Mar-Apr;9(2):292-9. doi: 10.1021/bc9701510.
The polyionic interaction between DNA and polycations grafted with hydrophilic dextran side chains was evaluated. The comb-type copolymers, poly(L-lysine)-graft-dextran, were successfully prepared by employing a reductive amination reaction between epsilon-amino groups of poly(L-lysine) (PLL) and the reductive ends of dextran (Dex). A coupling efficacy on the order of 70% was obtained regardless of intrinsic philicities of the solvents used, either aqueous buffer or DMSO. The resulting graft copolymers, which varied in the degree of grafting and the length of hydrophilic side chains, formed a soluble complex with DNA. They also affected the melting behavior of double-stranded DNA (dsDNA) in different ways. Copolymers having a high degree of grafting thermally stabilized dsDNA without affecting its reversible transition between single-stranded and double-stranded forms. However, copolymers with a low degree of grafting or with a high degree of grafting of short dextran chains impeded the reversibility of this transition. Furthermore, highly grafted copolymers also accelerated the hybridization of DNA strands in a low-ionic strength medium. It is of particular note that these copolymers scarcely altered circular dichroismic signals of dsDNA even when the copolymers were added in excess. This suggested that the copolymer interacted with dsDNA without affecting its native structure or physicochemical properties. Finally, the copolymer even formed a stable complex with a short oligonucleotide (20 bases). We, therefore, concluded that, by regulating the degree of grafting and the molecular weight of grafted side chains, it would be possible to design novel different graft copolymers capable of acting as carriers of functional genes to target cells or tissue.
评估了DNA与接枝有亲水性葡聚糖侧链的聚阳离子之间的聚离子相互作用。通过聚（L-赖氨酸）（PLL）的ε-氨基与葡聚糖（Dex）的还原端之间的还原胺化反应，成功制备了梳型共聚物聚（L-赖氨酸）-接枝-葡聚糖。无论使用的溶剂是水性缓冲液还是二甲基亚砜，其固有亲水性如何，均获得了约70%的偶联效率。所得的接枝共聚物，其接枝度和亲水性侧链长度各不相同，与DNA形成了可溶性复合物。它们还以不同方式影响双链DNA（dsDNA）的解链行为。接枝度高的共聚物使dsDNA热稳定，而不影响其在单链和双链形式之间的可逆转变。然而，接枝度低或短葡聚糖链接枝度高的共聚物阻碍了这种转变的可逆性。此外，高度接枝的共聚物还加速了低离子强度介质中DNA链的杂交。特别值得注意的是，即使过量添加共聚物，这些共聚物也几乎不会改变dsDNA的圆二色性信号。这表明共聚物与dsDNA相互作用而不影响其天然结构或物理化学性质。最后，该共聚物甚至与短寡核苷酸（20个碱基）形成了稳定的复合物。因此，我们得出结论，通过调节接枝度和接枝侧链的分子量，有可能设计出新型的不同接枝共聚物，它们能够作为功能性基因的载体靶向细胞或组织。
