The Mona Lisa of DNA
The smallest copy of "Gioconda" was collected by DNA origami
Alexander Dubov, N+1
American biochemists have developed a method for obtaining nanometer resolution images with an area of up to 0.5 square microns based on DNA origami technology. With this approach, in particular, it was possible to obtain the world's smallest image of the Gioconda, scientists write in an article published in Nature (Tikhomirov et al., Fractal assembly of micrometre-scale DNA origami arrays with arbitrary patterns).
Due to the formation of complementary bonds between individual sections of small DNA molecules, using the DNA origami method, systems of a given shape and with the desired location of functional sections can be obtained from them. Now they are trying to use such technology for various purposes, for example, for the delivery of drugs or the creation of complex molecular structures. If labels of a certain composition are attached to DNA molecules, then with the help of DNA origami, images with nanorecision can also be obtained. However, the area of such images by now did not exceed 0.05 square microns, and their resolution was also very small.
To increase the area of images based on DNA origami, a group of American biochemists from the California Institute of Technology, led by Lulu Qian, has developed a technique of "fractal assembly" (fractal assembly), which allows you to combine small elements of such DNA images into large two-dimensional arrays. In their work, the authors proposed an algorithm that allows you to determine the sequence of the main DNA molecule and the "paper clips" that fold it into the desired shape in order to obtain a predetermined image.
Connection diagram of the image elements. Blue, green and orange indicate different types of "paper clips" inside and between cells, black – "end clips" (from an article in Nature).
To obtain a single image element, the authors of the work used a technique proposed back in 2006. With the help of it, scientists were able to obtain a square element with a side less than 100 nanometers, consisting of 22 small sections of DNA connected to each other due to a given sequence of nucleotides and the presence of special bonding elements. Labels were attached to them in the right places, which can then be seen as a pixel using an atomic force microscope. As a result, one element of the image consisted of more than 100 pixels, although slightly unevenly distributed over the area (there was a small empty area in the middle of such an element).
Macroscopic visualization of the process of fractal assembly of DNA origami elements using a wooden puzzle (from the press release of The World's Smallest Mona Lisa - VM).
To get a complete image, biochemists collected arrays of 8 by 8 from such elements, consisting of a total of 8704 pixels. To stitch the cells together, the authors of the work proposed two more types of "paper clips", similar to those that fasten DNA chains inside one cell. Long connecting elements were located between the cells, and on those edges that should not be connected to other cells, there were "end clips" that could not form connections. Scientists obtained images of such DNA paintings using atomic force microscopy.
Images that were obtained using the proposed technique (from an article in Nature).
Using the proposed algorithm, scientists were able to obtain an image of a Gioconda on a square with a side of several hundred nanometers, as well as images of a rooster, bacteria, an electrical circuit and a chessboard with figures.
The authors of the work suggest that the technique developed by them can also be used to attach proteins, other polymer molecules or nanoparticles, thus creating molecular machines of a given structure or electric nanocains.
DNA origami is not the first technology with which scientists have obtained a microscopic image of the Gioconda. Recently, scientists have obtained a similar picture using an array of quantum dots. However, the resolution of such a picture was about one micron.
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