A flock of bionanorobots
DNA helped drive a swarm of molecular motors from microtubules
Alexander Dubov, N+1
Chemists have learned to control a swarm of molecular motors using DNA molecules. It turned out that using DNA linkers of several types, it is possible to force microtubules to form into groups, separate back or cause their joint translational and rotational movement, scientists report in Nature Communications (Keya et al., DNA-assisted swarm control in a biomolecular motor system).
A swarm of robots usually consists of a set of identical relatively simple mechanisms in design, the collective behavior of which is determined by swarm intelligence and is based only on interaction with each other and with the environment without a control center giving commands to each individually. Usually, a swarm of robots is tasked with taking one form or another or performing specified movements.
Similar tasks arise during the transition to the molecular level. It is known that swarming behavior may be characteristic of some biological systems, in particular biomolecular motors or cytoskeleton elements. The smallest molecular robots capable of collective work today are microtubules – hollow cylinders assembled from tubulin with a diameter of about 25 nanometers and a length of 2 to 20 micrometers. Their collective behavior is based on the work of kinesin and connecting elements, which provide mutual organization at sufficiently large distances, many times larger than the size of individual microtubules. Such systems can be used, for example, to create an active fluid that can flow without the application of an external force.
A group of Japanese and American chemists led by Akira Kakugo from Hokkaido University has found a way to control the movement of individual elements and their collective behavior in a similar artificial system consisting of a large number of molecular motors, the role of which was performed by microtubules. In order to control their behavior, scientists sewed small sections of DNA to them. For visualization, several different fluorescent dyes were also sewn to the DNA, by which different microtubules could be distinguished from each other.
The modified microtubules were placed on a glass substrate coated with small kinesin molecules that cause molecular motors to move, moving along them at the expense of ATP energy. To group the authors of the work used two types of microtubules: long and flexible (15 to 20 micrometers long) or short and rigid (about 5 micrometers long). The formation of such swarms occurred with the help of connecting elements, also representing small sections of single-stranded DNA molecules. By adding one type of DNA (complementary to those sections that are sewn to microtubules), microtubules can be connected to each other, and with the help of another type of DNA (binding linkers of the first type), on the contrary, they can be separated. Both processes take from several tens of minutes to an hour.
In the presence of ATP molecules, individual microtubules simply make random movements independently of each other, but if they are combined into a group, joint movements become more orderly. So, if you collect short microtubules in a swarm, they form linear structures that make a joint translational movement. Long microtubules, in turn, form cyclic structures that begin to rotate. At the same time, the speed of movement after joining into a swarm is close to the speed of individual microtubules (approximately 0.6 micrometers per second for individual microtubules and 0.5 microns per second for a swarm).
In addition, using photosensitive azobenzene groups on DNA molecules, it is possible to switch the system from collective swarm behavior to single behavior using light, and then each molecular motor begins to act independently of the others.
According to the authors of the work, the results of the work will be useful both for a fundamental understanding of the principles of operation and possible management of the collective work of molecular motor systems, and for the development of DNA nanotechnology and the creation of information coding systems at the molecular level.
It is possible to use light irradiation to control the swarm behavior of robots not only at the molecular level, but also for small traditional robots controlled by vibration motors. So, a swarm of Kilobots robots with the help of a single light source can be forced to scatter in different directions, forming shapes of a given shape on the plane.
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