Nanoclader
DNA robot taught to sort nanoparticles
Scientists from the California University of Technology have assembled a robot with two "legs" and a "hand" from single-stranded DNA. It can walk on a DNA substrate and deliver molecular loads to the right place.
All the actions that a DNA robot is capable of are realized thanks to the principle of DNA complementarity - the ability of its chains to reversibly stick together. On the substrate on which the robot moved, short single-stranded DNA molecules were "sewn", a pair of which were sequences in the "legs" of the robot. Their length was calculated in such a way that at any given time the robot could hold on to the substrate with only one "foot". Alternately connecting with one or the other "leg", the robot could move in a random direction without expending energy on it.
As a cargo, the scientists used a DNA sequence partially complementary to the robot's "arm". Having stumbled upon a suitable cargo, the robot contacted him, and then continued random movements. At the destination of the cargo, the robot was "waiting" for a DNA sequence that is completely complementary to the cargo and, accordingly, binds to it even more tightly. After leaving the cargo to her, the robot proceeded to transfer the next molecule.
Experiments have shown that the delivery efficiency was about 80%: in other words, every fifth cargo for some reason did not reach the final destination. The authors attribute this to possible errors in the synthesis of DNA sequences.
The researchers also tested the robot's ability to sort by offering it two types of cargo at the same time, which had to be carried to different endpoints. In 24 hours, one robot successfully sorted six DNA molecules on a 58×58 nm substrate with fluorescent labels of two colors "sewn" to them.
Figure Demin Liu / Caltech, Sorting Molecules with DNA Robots – VM
At the same time, he needed about five minutes for one step, and the length of each of them was about six nanometers. By launching several robots to work at the same time, scientists were able to speed up the sorting process.
So far, the efficiency of the DNA robot has been shown only for DNA with fluorescent molecules "sewn" to it, but in the future it can be adapted for the transfer of particles of any type. In addition, since random movements are energetically "free", each robot can be used as many times as desired.
An article describing the technology and principles of the DNA robot is published in the journal Science.
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15.09.2017