Two-Dimensional DNA-Mimetic Molecular Organizations at the Air−Water Interface
Two-Dimensional DNA-Mimetic Molecular Organizations at the Air−Water Interface
复制标题
空气-水界面处的二维 DNA 模拟分子组织
DOI：
10.1021/ja962847u
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发表时间：
1997
影响因子：
15
通讯作者：
Kiyosi Hasebe
中科院分区：
文献类型：
--
作者：
M. Shimomura;F. Nakamura;K. Ijiro;H. Taketsuna;Masaru Tanaka;and Hiroshi Nakamura;Kiyosi Hasebe
剪裁分子结构是超分子化学的最终目标之一，也是设计分子器件的关键。2，3弱的分子间相互作用（如氢键、货车范德华力和疏水相互作用）是组装分子组织不可或缺的结构工具。4，5双螺旋DNA是基于分子间特异性相互作用的分子结构的天然产物之一，由腺嘌呤-胸腺嘧啶和鸟嘌呤-胞嘧啶一维堆叠的碱基对通过互补的多重氢键形成。除了作为遗传信号传递分子信息外，最近还发现DNA可以通过堆叠的碱基对传递电子。6，7对于堆叠碱基对作为分子器件的功能应用，我们在这里报道了在空气-水界面处具有特定分子间相互作用的二维DNA模拟分子组织的剪裁。据报道，即使化学物质被大量水分子包围，在水面上形成的单层组装体的疏水界面也足以形成氢键。8，9已经制备了形成单层的两亲性核碱基，以证明在空气-水界面处与水溶性碱基的互补氢键。10-12空气-水界面上的碱基配对可能是分子组织的驱动力，称为“分子组装定向自组装”。1我们对碱基两亲分子如何通过碱基对界面的互补碱基配对组装成二维分子组装体感兴趣。在本文中，我们已经使用显微荧光成像的碱基对界面的形态观察的2-D分子组装。在氢化钠存在下，胞嘧啶与碘代十八烷发生亲核取代反应，合成了单烷基化核碱基衍生物1-十八烷基胞嘧啶（C18 Cyt）。13如图1所示，当少量（5× 10-4 M）鸟嘌呤核苷（鸟苷和脱氧鸟苷）溶解在中性水亚相中时，C18 Cyt从氯仿溶液扩散到水面上的压力-面积（π-A）等温线发生急剧变化，而其他核苷对等温线的影响很小（图1）。由于酸性亚相（pH 3.0）上的等温线（胞嘧啶部分在该酸性亚相上被完全质子化）不受鸟嘌呤核苷的添加的影响，因此假定C18 Cyt和鸟嘌呤碱基的沃森-克里克碱基对在中性水亚相上形成。鸟苷亚相上的单分子层可以通过普通的Langmuir-Blodgett技术在恒定的表面压力条件下（20 mN m-1）转移到新鲜沉积的金表面上。从鸟苷亚相沉积的C18 Cyt单分子膜的FT-IR反射吸收光谱中的CdO伸缩带（1715和1666 cm-1）强烈表明互补氢
Tailoring of molecular organization is one of final goals of supramolecular chemistry1 and essential for designing molecular devices. 2, 3 Weak intermolecular interactions (eg, hydrogen bonds, van der Waals forces, and hydrophobic interactions) are indispensable architectural tools for assembling molecular organizations. 4, 5 Double-helical DNA, one of natural products of molecular organization based on the specific intermolecular interaction, comprises one-dimensionally-stacked base pairs, adenine-thymine and guanine-cytosine, formed by complementary multiple hydrogen bonds. In addition to transferring molecular information as genetic signals, DNA has recently been discovered to transfer an electron through the stacked base pairs. 6, 7 Toward the functional application of the stacked base pairs as molecular devices, we report here the tailoring of twodimensional DNA-mimetic molecular organizations with the specific intermolecular interaction at the air-water interface. A hydrophobic interface of a monolayer assembly formed on a water surface has been reported to be a sufficient environment for hydrogen bonding even though the chemical substances are surrounded by a large number of water molecules. 8, 9 Monolayer-forming amphiphilic nucleobases have already been prepared to demonstrate complementary hydrogen bonding with water-soluble bases at the air-water interface. 10-12 Base pairing at the air-water interface might be a driving force of molecular organization termed “molecular-recognitiondirected self-assembly”. 1 We are interested in how nucleobase amphiphiles are organized to two-dimensional (2-D) molecular assemblies by the complementary base-pairing at the base pair interface. In this paper, we have used microscopic fluorescence imaging of the base pair interface for the morphological observation of 2-D molecular assemblies. The singly-alkylated nucleobase derivative 1-octadecylcytosine (C18Cyt) was prepared by a nucleophilic substitution reaction of cytosine with octadecyl iodide in the presence of sodium hydride. 13 As shown in Figure 1, the pressure-area (π-A) isotherm of C18Cyt spread from chloroform solution onto a water surface is drastically changed when a small amount (5× 10-4 M) of guanine nucleosides (guanosine and deoxyguanosine) is dissolved in the neutral water subphase, whereas other nucleosides show little effect on the isotherm (Figure 1). 14 Since the isotherm on the acidic subphase (pH 3.0), on which the cytosine moiety was fully protonated, was not affected by addition of guanine nucleosides, the Watson-Crick base pair of C18Cyt and guanine base is assumed to be formed on the neutral water subphase. The monolayer on the guanosine subphase can be transferred on the freshly deposited gold surface by the ordinary Langmuir-Blodgett technique under the constant surface-pressure condition (20 mN m-1). The CdO stretching bands (1715 and 1666 cm-1) in the FT-IR reflection absorption spectrum of C18Cyt monolayer deposited from the guanosine subphase strongly suggest complementary hydrogen