Giant sculptures made of DNA
Cavities in the shape of teddy bears were made from "DNA-lego"
Alexander Dubov, N+1
Chemists have improved the technique of assembling DNA origami from individual small parts and obtained complex three-dimensional objects containing up to 30 thousand parts. In such structures, it is possible to make cavities of a given shape, which varies from a helicoid to a teddy bear, scientists write in Nature (Ong et al., Programmable self-assembly of three-dimensional nanostructures from 10,000 unique components).
Assembling complex structures of a given geometry from DNA and RNA molecules using the DNA origami technique allows you to create functional objects that are already being used in structural biology, biophysics and photonics. With the help of complementary bonds, sections of nucleic acids can be cross-linked or functional polymer molecules or inorganic particles can be attached to them. Thanks to this, with the help of DNA, it is possible to obtain both complex two-dimensional systems, for example, images of paintings, and three-dimensional objects that are formed as a result of self-assembly.
Using the traditional DNA origami technique, systems of hundreds of nucleotides can be obtained, and their molecular weight is several megadaltons. It is quite difficult to assemble such systems, therefore, to obtain large three-dimensional systems, a modified DNA origami technique is used, in which an object is made up of separate identical elements. Due to the presence of protruding sections of these elements, they can be connected to each other like designer parts. Unlike traditional DNA origami elements, such DNA bricks do not have a large number of folds, and they consist of short straight sections of nucleotides. However, until now, using this approach, it has not been possible to combine more than several hundred parts into single structures.
Chemists from the USA, Germany, France and China, led by Peng Yin from Harvard University, have proposed an improved version of such DNA bricks, from which, with the help of self-assembly, quite complex three-dimensional structures can be obtained. One element consists of two relatively short DNA strands (52 and 72 nucleotides long), which are complementarily interconnected at a site of 13 nucleotides.
The scheme of connecting DNA into individual parts and assembling them
large three-dimensional objects (drawings from an article in Nature).
By holding such elements for a certain time in a salt solution at an elevated temperature, complex three-dimensional structures of a given geometry consisting of several tens of thousands of elements can be assembled from them. In particular, it is possible to obtain cubes of the correct shape. The maximum mass of the cube that was assembled in this way was almost half a gigadaltone (which is about 100 times more than the mass of the most complex systems assembled by more traditional DNA origami methods). Such a cube contains up to 30 thousand elements.
In addition, scientists have shown that by changing the composition of nucleotides, it is possible to obtain cubic structures with three-dimensional cavities of a given shape: a helicoid, inscriptions, rabbit and teddy bear figures. To confirm the method's operation, the scientists compared the images of objects obtained using transmission electron microscopy with their three-dimensional models.
The shape of three-dimensional cavities of various shapes, in cubes assembled using the proposed method. The figures show a comparison of microphotographs with a computer model.
According to scientists, their proposed technique is cheaper than the traditional DNA origami approach, and in the future it can be used to obtain more complex three-dimensional objects of larger size, for example, using hierarchical assembly methods.
Special bonding elements are used to improve the ability of DNA elements to self-assemble. These can be as simple as short chains of several nucleotides, or, for example, special protein clips that increase the stability of the resulting structures.
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