Niwa Masazo, Morikawa Masa aki, Yagi Kenji, Higashi Nobuyuki
Department of Molecular Science and Technology, Faculty of Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.
Int J Biol Macromol. 2002 Mar 8;30(1):47-54. doi: 10.1016/s0141-8130(02)00004-1.
The interaction of a polylysine amphiphile, which consists of a poly-L- or -D-lysine (1L or 1D) segment and two long alkyl chains at the C-terminus, with polynucleotides was studied with respect to the highly organized structure of polylysine assemblies on water. The results of surface pressure-area isotherm measurement showed that both of 1L and 1D formed stable monolayers on water in a neutral pH region. The secondary structure of polylysine segment for the surface monolayer was examined by means of circular dichroism and Fourier transform infrared spectroscopies. The helical structure was retained even at neutral pH, at which polylysine has been known to form a complete random coiled conformation in bulk solution. Protonated, positively charged and coiled 1L monolayer could interact electrostatically with guest polyanions including DNA in the subphase, and at the same time the conformation of the polylysine segment was converted from a random coil to an alpha-helix. Deprotonated, helical monolayers did not interact with single stranded polyadenylic acid, but with double stranded DNA. Double stranded DNA was found to interact more strongly with right-handed 1L monolayer than left-handed 1D monolayer. An obvious difference in the melting temperatures for these complexes was observed and discussed on the basis of difference in the interaction mode.
研究了一种聚赖氨酸两亲分子（由聚-L-或-D-赖氨酸（1L或1D）片段以及C端的两条长烷基链组成）与多核苷酸的相互作用，该相互作用与聚赖氨酸在水面上高度有序的组装结构有关。表面压力-面积等温线测量结果表明，1L和1D在中性pH区域都能在水面上形成稳定的单分子层。通过圆二色性和傅里叶变换红外光谱法研究了表面单分子层中聚赖氨酸片段的二级结构。即使在中性pH值下，螺旋结构依然得以保留，而在这种pH值下，聚赖氨酸在本体溶液中已知会形成完全无规卷曲构象。质子化、带正电荷且呈卷曲状的1L单分子层能够与包括亚相中DNA在内的客体聚阴离子发生静电相互作用，与此同时，聚赖氨酸片段的构象从无规卷曲转变为α-螺旋。去质子化的螺旋状单分子层不与单链聚腺苷酸相互作用，但能与双链DNA相互作用。发现双链DNA与右手性的1L单分子层的相互作用比左手性的1D单分子层更强。基于相互作用模式的差异，观察并讨论了这些复合物在解链温度上的明显差异。
