Mao C, Sun W, Shen Z, Seeman N C
Department of Chemistry, New York University, New York 10003, USA.
Nature. 1999 Jan 14;397(6715):144-6. doi: 10.1038/16437.
The assembly of synthetic, controllable molecular mechanical systems is one of the goals of nanotechnology. Protein-based molecular machines, often driven by an energy source such as ATP, are abundant in biology. It has been shown previously that branched motifs of DNA can provide components for the assembly of nanoscale objects, links and arrays. Here we show that such structures can also provide the basis for dynamic assemblies: switchable molecular machines. We have constructed a supramolecular device consisting of two rigid DNA 'double-crossover' (DX) molecules connected by 4.5 double-helical turns. One domain of each DX molecule is attached to the connecting helix. To effect switchable motion in this assembly, we use the transition between the B and Z forms of DNA. In conditions that favour B-DNA, the two unconnected domains of the DX molecules lie on the same side of the central helix. In Z-DNA-promoting conditions, however, these domains switch to opposite sides of the helix. This relative repositioning is detected by means of fluorescence resonance energy transfer spectroscopy, which measures the relative proximity of two dye molecules attached to the free ends of the DX molecules. The switching event induces atomic displacements of 20-60 A.
合成可控分子机械系统的组装是纳米技术的目标之一。基于蛋白质的分子机器在生物学中很常见，通常由ATP等能源驱动。此前已有研究表明，DNA的分支基序可为纳米级物体、连接物和阵列的组装提供组件。在此，我们展示了此类结构还可为动态组装提供基础：可切换分子机器。我们构建了一种超分子装置，它由两个通过4.5个双螺旋圈连接的刚性DNA“双交叉”（DX）分子组成。每个DX分子的一个结构域连接到连接螺旋上。为了在该组装中实现可切换运动，我们利用了DNA的B型和Z型之间的转变。在有利于B-DNA的条件下，DX分子的两个未连接结构域位于中心螺旋的同一侧。然而，在促进Z-DNA形成的条件下，这些结构域会切换到螺旋的相反侧。这种相对重新定位通过荧光共振能量转移光谱法进行检测，该方法测量附着在DX分子自由端的两个染料分子的相对接近程度。切换事件会引起20 - 60埃的原子位移。
