A Japanese-UK research team has now demonstrated that cryoEM image analysis may be exploited to obtain structural information of sufficient resolution to reveal the absolute three-dimensional (3D) configuration of a designed DNA nanostructure. With their technique they have obtained structural information at sufficient resolution to visualize the DNA helix and reveal the absolute stereochemistry of a self-assembled DNA tetrahedron. Each edge is a 7 nm, 20 base pair duplex, and the edges are connected covalently through single unpaired adenosine nucleotides, making it a rigid, triangulated structure that could serve as a building block for larger 3D structures or as a molecular cage. This DNA tetrahedron is the smallest 3D nanostructure made by DNA self-assembly.
DNA origami, tiny shapes and patterns self-assembled from DNA, have been heralded as a potential breakthrough for the creation of nanoscale circuits and devices. One roadblock to their use has been that they are made in solution, and they stick randomly to surfaces - like a deck of playing cards thrown onto a floor. Random arrangements of DNA origami are not very useful; if they carry electronic circuits for example, they are difficult to find and 'wire-up' into larger circuits. A collaboration between Caltech and IBM research Almaden has found a way to position and orient DNA origami on surfaces by creating sticky patches in the shape of origami - as a demonstration they positioned and aligned triangular DNA origami on triangular sticky patches. This success knocks down one of the major roadblocks for the use of DNA origami in computer nanotechnology.
Various forms of hyperthermia - a form of cancer treatment with elevated temperature in the range of 41-45C - have been intensively developed for the past few decades to provide cancer clinics with more effective and advanced cancer therapy techniques. The recent use of nanomaterials has shown promising for developing more effective hyperthermia agents. While most nanomedical hyperthermia research is conducted with various nanoparticles, carbon nanotubes are also of interest in these thermal ablation applications. So far, however, the utility of carbon nanotubes for in vivo use has been limited by self-association - i.e. they stick to each other. A new study has now demonstrated that DNA-encasement of multi-walled carbon nanotubes (MWCNTs) results in well-dispersed, single MWCNTs that are soluble in water and that display enhanced heat production efficiency relative to non-DNA-encased MWCNTs.
It its more than 25 years of existence, Scanning Tunneling Microscopy has predominantly brought us extremely detailed images of matter at the molecular and atomic level. The Scanning Tunneling Microscope (STM) is a non-optical microscope that scans an electrical probe over a surface to be imaged to detect a weak electric current flowing between the tip and the surface. It allows scientists to visualize regions of high electron density and hence infer the position of individual atoms and molecules on the surface of a lattice. Now, researchers in Japan have managed to partially sequence a single DNA molecule with a STM - a significant step towards the realization of electronic-based single-molecule DNA sequencing.
Reciprocating devices are a common part of the macroscopic world. Examples of reciprocating machines are petrol and diesel engines or a hydraulic pump. At the core of these machines is a piston and cylinder assembly where the piston executes a reciprocating motion inside the cylinder. Reciprocating motion like that in a piston has not been available in a nanoscale machine until now. Ned Seeman and his team at New York University have designed a DNA device that exhibits reciprocal motion. They have used the PX-JX2 device, a robust sequence-dependent nanomechanical DNA machine, as the basis for constructing a pair of reciprocal devices, wherein one device assumes one state, while the other device assumes the opposite state.
Molecular-size motors have evolved in nature, where they are used in virtually every important biological process. In contrast, the development of synthetic nanomotors that mimic the function of these amazing natural systems and that could be used in man-made nanodevices is in its infancy. Building nanoscale motors is not just an exercise in scaling down the design of a macroworld engine to nanoscale dimensions. In addition to organic molecules, scientists increasingly are looking to DNA as a very promising way to fabricate nanomotors. The concept of a single DNA molecule nanomotor was already introduced in early 2002. However, this and subsequent designs require addition and removal of fuel and waste strands for motor function, although some artificial nanomotors can utilize alternative energy sources, including hydrolysis of the DNA backbone and ATP. Researchers at the University of Florida have now designed a photoswitchable single-molecule DNA nanomotor. It is the first fully reversible single-molecule DNA nanomachine driven by photons without any additional DNA strands as fuel.
Proteins that bind to specific sites of DNA are essential to all biological functions of DNA. These DNA-binding proteins include transcription factors which modulate the process of transcription, various polymerases, nucleases which cleave DNA molecules, and histones which are involved in chromosome packaging in the cell nucleus. Developing methods to precisely determine the locations and occupancy of DNA-binding proteins is instrumental to scientists' understanding of cellular processes like gene expression and regulation. Motivated by the desire to overcome some of the inherent limitations of existing biochemical techniques for mapping protein binding sites on DNA, scientists at UCLA have now demonstrated the viability of a single molecule approach to directly visualize and map protein binding sites on DNA using fluorescent quantum dots, allowing multicolor, nanometer-resolution localization.
Studies have already shown the complexity of architecture that is achievable using DNA as building blocks. For instance, nanofabrication via molecular self-assembly has already resulted in simple DNA polyhedra with connectivities of a cube, octahedron, and a tetrahedron. Platonic solids - any one of five solids whose faces are congruent regular polygons and whose polyhedral angles are all congruent - are the most efficient at enclosing large volumes. The more complex the polyhedron, the greater its ability to encapsulate cargo, because the capsule size can be maximized while keeping the pore-size of the capsule minimal. The most complex platonic solid is the icosahedron and therefore this would be most suitable for achieving cargo encapsulation. The DNA shell of such a capsule could protect vulnerable drugs from degradation by proteins until they reach their target site. It could also prevent dangerous drugs from leaking out until the capsule reaches its intended target. The DNA shell could also allow attachment to a protein that could ferry the drug-loaded capsule to a target.