Q. How the DNA nanoarchitecturing works?
DNA Nano architectures constructs that can be self-assembled from branched DNA molecules. Their components can be simple branched species or more complex structural motifs. Simple branched DNA junctions have been produced that comprise 3-12 double helices flanking a branch point. Species can be assembled or/and ligated into DNA stick polyhedra, where edges are DNA double helices and vertices correspond to branch points of junctions. The first such molecule was a DNA molecule with the connectivity of a cube. Otherpolyhedra produced to date contain a tetrahedron, an octahedron as well as a truncated octahedron. Branched junctions are somewhat floppy, so only branching and linking topologies of polyhedral are well defined unless all faces are triangles. Other individual objects which have been built are topological targets, like knots and Borromean rings. DNA is an ideal species to use as a topological building block since a half-turn of DNA is equivalent to a node, which is fundamental topological feature of a catenane or aknot. DNA doublecrossover (DX) molecule is another key element in DNA nanoarchitectures. This motif comprise two helices joined twice by strands that connect them, leading to parallel helix axes; connection points are separated typically by Two-dimensional DNA lattice. One and two double helical turns. Each of connection points is a four-arm junction, so motif can be explained as two four-arm junctions joined twice to eachother at adjacent arms. These are robust motifs, generally three to six double helical turns in length and their structures can be reliably predicted. This system can be extended, leading to molecules containing three or more helices joined laterally. Even though most often built to be roughly planar motifs, angles canbe varied between pairs of helices, using helicity of DNA, for example a six-helix cyclic motif has been reported that approximates a hexagonal tube (→DNA nanotubes). DX molecules and their relatives can be used as tiles to produce two-dimensional crystalline arrangements by self-assembly (→DNA self-assembly). An extra motif can be included in these tiles, visible when crystal is viewed in an atomic force microscope. Accompanying picture demonstrates how arrangements of two 16 × 4 nm tiles produce 32-nm stripes (top) or four tiles produce 64-nm stripes (bottom). Along with periodic arrangements, aperiodic patterns can also be generated algorithmically. Single-stranded bacteriophages have been used to produce greatly extended versions of parallel DNA motif, capable of yielding highly elaborate patterns, in a method known as DNA origami. This is done by using bacteriophage genome (several thousand nucleotides)as a template to which a large number of "staple strands" are added to fold genome into a specific shape, including holes in the middle; addition of strands containing extra domains enable the generation of further features. Smiley faces and a map of western hemisphere are instances of patterns generated by this method.