27 October 2014

Complex structures from standard DNA blocks

Scientists have developed a technology for the construction of large volume nanostructures
made of DNA bricks like Lego blocks

DailyTechInfo based on Gizmag materials: Large 3D nanostructures built from Lego-like DNA bricks

Scientists from the Wyss Institute for Biologically Inspired Engineering at Harvard University have developed a technology for manufacturing tiny crystalline nanostructures that act as a kind of building "bricks" similar to Lego blocks used to create larger volumetric nanostructures. These "bricks", in turn, are used as a building material for the process of self-assembly of larger structures, a process that follows a predetermined program and uses principles similar to the principles of the formation of DNA molecules from a certain set of base molecules.

Using specially prepared sets of "building material", which included "bricks" of 32 different types, scientists managed to collect about 100 types of complex three-dimensional structures, the size of which is comparable to the size of not the smallest viruses. And this size of the created nanostructures is approximately 1000 times larger than the sizes of nanostructures created earlier with the help of other DNA methods.

The technology of self-assembly of nanostructures from "bricks" is quite accurately copied from the principles of coupling of Lego blocks. The basis of this technology is the rules by which DNA molecules are constructed, the chains of which consist of base pairs, A (adenine) binds only to T (thymine), while C (cytosine) binds only to G (guanine). Each DNA brick is created by combining a set of bases located perpendicular to each other, and the location and sequence of the coupling of the bases determines the role of this brick in the process of self-assembly of the future large structure.

Each DNA brick has the shape of a cube, the length of the face of which is equal to the length of six linked bases. The entire cubic volume of the brick is filled with a "spiral" of interlocked 24 bases, the sequence of which determines with which other brick this brick can interlock. However, as additional structural elements, scientists use other types of DNA bricks, "one-dimensional" Z-crystals and X-crystals that are elongated along the Z and X axes, and "two-dimensional" ZX-crystals and XY-crystals.

A specialized computer program developed by scientists allows you to draw a model of a nanostructure having a shape of almost any complexity, which will then need to be built by self-assembly. Further simple calculations using this program allow you to break this model into elementary blocks and calculate the sequence of DNA chains for each brick, which will allow you to determine the correct sequence of the self-assembly process. The maximum sizes of the nanostructures created in the program are now about 80 nanometers, but in the future these sizes can be increased almost indefinitely, if necessary.

The researchers believe that the technology of self-assembly from DNA bricks developed by them will be useful for the development of technologies for the manufacture of universal inorganic circuits for various purposes and other nanoscale technologies. In addition, the technology can be used in the so-called protein crystallography, an area where the structures and properties of various proteins used in biotechnology, in the manufacture of pharmaceuticals and in the academic field of structural biology are studied with atomic resolution.

"The DNA technology we have developed allows us to program the creation of complex three-dimensional structures, nodes of complex molecular machines and such machines as a whole," says William Shih, one of the participants in these studies, "And the complexity of the objects created in this way is not inferior, and often exceeds the complexity of such objects of natural origin."

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