DNA nanotechnology provides a versatile foundation for the chemical assembly of nanostructures. Plasmonic nanoparticle assemblies are of particular interest because they can be tailored to exhibit a broad range of electromagnetic phenomena. In this Letter, we report the assembly of DNA-functionalized nanoparticles into heteropentamer clusters, which consist of a smaller gold sphere surrounded by a ring of four larger spheres. Magnetic and Fano-like resonances are observed in individual clusters. The DNA plays a dual role: it selectively assembles the clusters in solution and functions as an insulating spacer between the conductive nanoparticles. These particle assemblies can be generalized to a new class of DNA-enabled plasmonic heterostructures that comprise various active and passive materials and other forms of DNA scaffolding.

We developed a sequential strand-displacement strategy for multistep DNA-templated synthesis (DTS) and used it to mediate an efficient six-step DTS that proceeded in 35% overall yield (83% average yield per step). The efficiency of this approach and the fact that the final product remains linked to a DNA sequence that fully encodes its reaction history suggests its utility for the translation of DNA sequences into high-complexity synthetic libraries suitable for in vitro selection.

A biotemplating strategy for fabrication of metallic nanoparticle arrays has been developed. The templates are self-assembled DNA nanostructures, which dictate nanoparticle synthesis in the gas-solid phase (during thermal evaporation).

This paper reports an introduction of extra structural features into self-assembled DNA polyhedra.

Multistep synthesis in the laboratory typically requires numerous reaction vessels, each containing a different set of reactants. In contrast, cells are capable of performing highly efficient and selective multistep biosynthesis under mild conditions with all reactants simultaneously present in solution1,2,3,4. If the latter approach could be applied in the laboratory, it could improve the ease, speed and efficiency of multistep reaction sequences. Here, we show that a DNA mechanical device—a DNA walker moving along a DNA track—can be used to perform a series of amine acylation reactions in a single solution without any external intervention. The products of these reactions are programmed by the sequence of the DNA track, but they are not related to the structure of DNA. Moreover, they are formed with speeds and overall yields that are significantly greater than those previously achieved by multistep DNA-templated small-molecule synthesis. A DNA walker moving along a DNA track can perform the multistep synthesis of an oligoamide in a single solution without any external intervention.

This chapter discusses our efforts in using DNAzymes in DNA nano-machines and DNA analysis systems. 10–23 DNAzymes can cleave specific phos-phodiester bonds in RNA. We use them to construct an autonomous DNA-RNA chimera nanomotor, which constantly extracts chemical energy from RNA substrates and transduces the energy into a mechanical motion: cycles of contraction and extension. The motor's motion can be reversibly turned on and off by a DNA analogue (brake) of the RNA substrate. Addition and removal of the brake stops and restarts, respectively, the motor's motion. Furthermore, when the RNA substrates are preorganized into a one-dimensional track, a DNAzyme can continuously move along the track so long as there are substrates available ahead. Based on a similar mechanism, a novel DNA detection system has been developed. A target DNA activates a DNAzyme to cleave RNA-containing molecular beacons (MB), which generates an enhanced fluorescence signal. A following work integrates two steps of signal amplifications: a rolling-circle amplification (RCA) to synthesize multiple copies of DNAzymes, and the DNAzymes catalyze a chemical reaction to generate a colorimetric signal. This method allows detection of DNA analytes whose concentration is as low as 1 pM.

Many G-quadruplex-forming, biological DNAs, such as telomeres and a c-Myc (an oncogene) promoter region, have been shown by an in vitro study to be peroxidase apoenzymes.

Was spricht gegen windschief? Ein rationaler Ansatz ermöglichte es, die Selbstorganisation eines DNA-Oktaeders zu programmieren (siehe Struktur; der Farbgradient deutet den Abstand vom Oktaederzentrum an). Eine genaue Strukturuntersuchung ergab, dass die Assoziation der Nanoobjekte stereoselektiv war (die Ansicht einer Ecke zeigt den schiefen Hohlraum, der die Bestimmung der Chiralität der Oktaeder ermöglichte).

This paper describes our recent efforts on the self-assembly of three-dimensional (3D) DNA nanostructures from DNA star motifs (tiles). DNA star motifs are a family of DNA nanostructures with 3, 4, 5, or 6 branches; they are named as 3-, 4-, 5-, 6-point-star motifs, respectively. Such motifs are programmed to further assemble into nanocages (regular polyhedra or irregular nanocapsules) with diameters ranging from 20 nm to 2 microm. Among them, DNA nanocages derived from 3-point-star motif consists of a group of regular polyhedra: tetrahedra, hexahedra (or cubes), dodecahedra and buckyballs (containing 4, 8, 20, and 60 units of the 3-point-star motif, respectively). An icosahedron consists of twelve 5-point-star motifs and is similar to the shapes of spherical viruses. 6-point-star motifs can not assemble into regular polyhedra; instead, some sphere-like or irregular cages with diameters about 1-2 microm will form. Similar large cages can also assemble from the 5-point-star motif when the DNA concentrations are higher than those for assembling regular icosahedra. In our study, we have identified several important factors for assembly of well-defined 3D nanostructures, including the concentration, the flexibility, and the arm length of the DNA tiles and the association strength between the DNA tiles.

The overlapping of self-assembled, two-dimensional DNA crystal lattices generates complex Moiré nanopatterns (see image). This work suggests a novel hierarchical self-assembly approach for nanopatterning, which could potentially greatly increase the pattern complexities.

Supramolecular structures A variety of patterned materials and nanostructures have been made from DNA, by exploiting its programmability to control molecular interactions. But making larger, more complex three-dimensional structures with current fabrication methods would require hundreds of unique DNA strands, an impractical proposition. Help is at hand. A team from Purdue University has developed a modular approach that can be likened to a DNA equivalent of Lego bricks. A few DNA molecules are programmed to fold into a basic structural unit, with four, twenty or sixty copies of that unit then assembling according to reaction conditions into tetrahedra, dodecahedra or buckyballs, respectively. Other complex structures should also be accessible using this strategy.

Molecular self-assembly is a promising approach to the preparation of nanostructures. DNA, in particular, shows great potential to be a superb molecular system. Synthetic DNA molecules have been programmed to assemble into a wide range of nanostructures. It is generally believed that rigidities of DNA nanomotifs (tiles) are essential for programmable self-assembly of well defined nanostructures. Recently, we have shown that adequate conformational flexibility could be exploited for assembling 3D objects, including tetrahedra, dodecahedra, and buckyballs, out of DNA three-point star motifs. In the current study, we have integrated tensegrity principle into this concept to assemble well defined, complex nanostructures in both 2D and 3D. A symmetric five-point-star motif (tile) has been designed to assemble into icosahedra or large nanocages depending on the concentration and flexibility of the DNA tiles. In both cases, the DNA tiles exhibit significant flexibilities and undergo substantial conformational changes, either symmetrically bending out of the plane or asymmetrically bending in the plane. In contrast to the complicated natures of the assembled structures, the approach presented here is simple and only requires three different component DNA strands. These results demonstrate that conformational flexibility could be explored to generate complex DNA nanostructures. The basic concept might be further extended to other biomacromolecular systems, such as RNA and proteins.

DNA is a versatile building material for nanoconstruction because of its remarkable molecular-recognition capability and well-predicted duplex conformation. A number of DNA motifs have been engineered, which can assemble into well-defined nanostructures in Mg(2+)-containing buffer solution. XRD studies reveal that the DNA conformation is slightly influenced by divalent cations (such as Mg(2+) or Ca(2+)). This phenomenon can be utilized in DNA self-assembly for regulating self-assembled DNA nanostructures. As an initial step, a symmetric cross motif forms flat, periodic, 2D lattices in Mg(2+)-containing solutions, but long nanofibers in Ca(2+)-containing solutions. The obtained DNA fibers can serve as templates to fabricate CaCO(3) nanotubes and nanowires.

This paper develops a novel strategy for DNA self-assembly. Multiple copies of one single component DNA strand can self-assemble into continuous DNA duplexes with single-stranded side chains along the duplexes. Association among the side chains aligns the duplexes into DNA 2D crystals.

Two types of DNA star motifs (tiles) can recognize and associate with like tiles to form 2D arrays but exclude unlike tiles even though the local interactions between any two tiles are exactly the same.

Beyond its biological importance, short DNA sequences are of increasing interest as excellent and versatile building blocks, in material science and nanotechnology. DNA nanotechnology has been rapidly developed and has branched into several significantly different directions. Controlling DNA nanostructures is one of the most important branches, in which well‐defined static nanostructures are constructed from rationally designed DNA motifs. The diversity and complexity of such DNA nanostructures also endow them with promising applications in nanofabrications, nanoelectronics, biodiagnostics, and DNA computations. In this review, we will summarize our recent efforts in this direction. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.

A subtle balance of flexibility and stress is found to be critical for a DNA nanostructure to be a good self-assembly block.

We have developed a strategy for preparing antibody nanoarrays by DNA templating. In the resulting tetragonal antibody arrays, each spot is a similarly orientated, individual antibody molecule (IgG). The separation between two adjacent IgG molecules is only approximately 20 nm.