A DNA aptamer structure is the basis of a molecular machine that can be instructed to grab or release the human blood‐clotting factor α‐thrombin, depending on the operator DNA sequence addressing it. In the picture the aptamer structure, which assumes a conformation characterized by two stacked guanine quadruplex structures, is linked to thrombin (gray ellipse).

DNA-templated polyaniline nanowires and networks are synthesized using three different methods. The resulting DNA/polyaniline hybrids are fully characterized using atomic force microscopy, UV–vis spectroscopy and current–voltage measurements. Oxidative polymerization of polyaniline at moderate pH values is accomplished using ammonium persulfate as an oxidant, or alternatively in an enzymatic oxidation by hydrogen peroxide using horseradish peroxidase, or by photo-oxidation using a ruthenium complex as photo-oxidant. Atomic force microscopy shows that all three methods lead to the preferential growth of polyaniline along DNA templates. With ammonium persulfate, polyaniline can be grown on DNA templates already immobilized on a surface. Current–voltage measurements are successfully conducted on DNA/polyaniline networks synthesized by the enzymatic method and the photo-oxidation method. The conductance is found to be consistent with values measured for undoped polyaniline films.

Towards the construction of DNA templated nanowires for self-assembled nanodevices, nanocrystals of the p-type semiconductor CuS were grown selectively and densely on DNA both in solution and stretched on a surface. Atomic force microscopy and transmission electron microscopy measurements display chains of CuS nanoparticles up to 10nm diameter separated by less than 40nm. By increasing the number of nucleation sites through the use of bundles of DNA, highly dense coverage of the DNA with nanocrystals is observed.

The construction of autonomous DNA-based nanomachines is an important challenge. To this end we have combined DNA tweezers with the transcription machinery of prokaryotic organisms and created a gene that codes for the production of an mRNA strand to bring about a conformational change in the tweezers. Gel electrophoresis and FRET experiments demonstrate that the transcription process successfully reads out the gene and automatically brings the machine to the desired state.Precise nanoscale movements can be achieved reversibly and reproducibly with molecular machines based on DNA. A variety of motion, including stretching 1-4 and twisting, 5,6 can be performed by these devices in well-defined steps. Recently, a DNA machine that binds, carries, and releases a single protein molecule upon instruction has been developed. 7 Generally, these machines operate through the manual addition of a "fuel" strand, consisting of single stranded DNA (ssDNA) that affects a conformational change in the device. 3 The machine is returned to its original configuration by the introduction of a "removal" strand fully complementary to the fuel strand. To a large extent, DNA in these studies is regarded as a structural material with controllable selfassembly properties rather than as a biological molecule. The sequence and highly specific base pairing rules in DNA are used for designing the type of motion the nanomachine performs rather than as a genetic code. The fact that DNA is part of a highly evolved system for protein synthesis in organisms has been largely irrelevant. In this letter we take advantage of the properties of nucleic acids as a genetic material, which can be synthesized and controlled by the gene expression machinery, to genetically program the automatic "closing" of DNA-based tweezers.Gene expression consists of two processes: transcription and translation. The product of transcription is a messenger RNA (mRNA) molecule, which then can serve as a template for protein synthesis during translation. It is during transcription that gene regulation occurs through a complex series of switches based on responses to stimuli or the cell's environment. So far, nanomachines have been controlled with DNA rather than RNA, although this nucleic acid has similar self-*

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