Predatory protocells

Artificial protocells have learned to hunt each other

Alexander Ershov, N+1

Chemists from the University of Bristol have developed a system of microscopic water-soluble particles, so-called protocells, which can hunt and attack each other. It is assumed that the research of protocells can lead to the creation of fundamentally new technologies for the chemical industry and pharmaceuticals, can also be used to eliminate the consequences of oil spills or create computational chemical systems. A description of the work of the Bristol scientists is published in Nature Chemistry (Qiao et al., Predatory behavior in synthetic protocell communities).

Protocell research is at the intersection of colloidal chemistry and bioengineering. This term refers to microparticles of very different compositions, but they all share the ability to exhibit properties resembling living cells. For example, protocells have already been used for protein synthesis (they pack a natural synthesis system isolated from living cells), for fixing natural enzymes and selective protein channels on membranes, for organizing chemical "communication" between colloidal particles and bacteria. It is assumed that in the future protocells will be able to fill a functional niche between classical chemical catalysts and live bacteria that are used in biotechnology. Compared to the latter, the work of protocells should be much more predictable and they may be able to function in such harsh conditions where bacteria die.

However, until now, research on protocells has focused primarily on individual particles, on endowing each of them with more and more complex functions. In the new work, the authors decided to use a different approach – to explore the possibilities of collective behavior of particles. To do this, chemists developed a system of two types of protocells, one of which was supposed to "hunt" the other.

Protocells are "prey" in a fluorescent microscope

The two types of particles are arranged as follows. The Hunters were coacervate droplets of PDDA polymer with an energy molecule of ATP attached to it, on which proteinase K (an enzyme that is often used for non-specific protein hydrolysis) was fixed. Microparticles with a shell of bovine serum albumin molecules (a simple and cheap "standard protein" of biochemistry), chemically crosslinked with each other, acted as "prey". Inside these microparticles were packed filler molecules: dextran polymer or DNA fragments.

Since the two types of particles had an opposite electric charge on the surface ("hunters" positive and "prey" negative), they were attracted to each other in solution. As soon as the two types of particles came into contact, proteinase K began to "eat" the protein shell of the other particle and its contents went into solution – the process was observed by the authors using an optical microscope and a cell sorter. On average, it took no more than 60 minutes for the "hunter particle" to completely destroy the "prey". At the same time, not all the contents of the first particle went into solution, it partially dissolved in a coacervate drop with proteinase. After absorbing the first "prey", the particles could continue to "hunt" further. Interestingly, based on the subsequent analysis of the contents of each individual particle of the "hunter", it was possible to restore the entire history of its "nutrition".

The structure of the hunter particle and the prey particle, as well as the process of their fusion
and the resulting particle is a hunter with fragments of "prey".
Figure from an article in Nature Chemistry.

The main conclusion of their article is the possibility of creating protocell systems that could not perform complex functions independently, but engage in "division of labor" and specialize in individual reactions. It can be expected that the creation of such systems will be a process technologically simpler than attempts to bring colloidal particles closer to real cells at the individual level.

Unusual applications of colloidal particles are not limited to the creation of biomimetic protocells. For example, recently Russian chemists presented a system of logic gates based on micro- and nanoparticles. Potentially, these valves can be used for calculations in solution or to create a "smart" control system for chemical reactions. Another group of chemists, this time from the USA, used clusters of colloidal particles as a "liquid" information carrier. The data in it is recorded in the form of clusters that form particles connecting with each other.

Portal "Eternal youth" http://vechnayamolodost.ru  07.10.2016