Molecular machines with light drive

Professor Rainer Herges, spokesman of the Collaborative Research Center 677 “Function by switching”

Kiel research team builds first nanorobots for the production of molecules

The idea of ​​molecular machines has long been discussed in nanoscience: artificially produced chemical compounds capable of performing mechanical work. Such “nanorobots” could, for example, transport medical agents, repair defective cells or measure temperatures in the body that indicate inflammation. A research team from the Institute of Organic Chemistry of the Christian-Albrechts-Universität zu Kiel (CAU) has now succeeded in producing a molecule that itself can produce molecules. It is driven by UV light. In the principle used, the chemists based their research on synthetic methods of nature such as the production of ATP molecules, the universal energy source of cells. Their results were presented in the renowned trade magazineCommunications Chemistry .


The problem of sticky fingers


Already in the 1980s, engineer Kim Eric Drexler hovered the idea of ​​molecular machines as so-called “assembler” (by assemble, engl. for assembling): They should be able to grab single atoms and place them precisely to build complex molecular structures. Ultimately, they would be able to reproduce themselves, Drexler said. This vision was the beginning of an intense scientific controversy: Opponents who did not consider the construction of such nanorobots made of molecules in principle, argued essentially two arguments that are referred to in research as the problems of “thick and sticky fingers”. Thus, an assembler would have countless “fingers” on the nanoscale in order to grab the different atoms and place each – but simply lack the space. The main obstacle for such “molecular builders”, however, is the difficulty referred to as “sticky fingers” (“sticky fingers”).

Research results of recent years, however, suggest that the development of such assembler is in principle possible. Of these, Rainer Herges, Professor of Organic Chemistry and spokesman for the Collaborative Research Center 677 “Function by switching” at the CAU, is convinced. “After all, such molecular assemblers already exist in nature, for example in the form of ribosomes that produce proteins in cells or for the synthesis of ATP, adenosine triphosphate. The principle of these biochemical syntheses should therefore be reproduced artificially in the laboratory, “Herges describes his approach. In this way, he and his research team produced the first artificial assembler to run on UV light.


UV light controls processes
 

To achieve this, the scientists systematically reduced the complexity of biological processes to such an extent that they could be implemented using methods from synthetic chemistry. They brought the reactants, four vanadate ions, in close proximity to each other and linked them into a ring. Via an Assembler molecule that can be controlled by UV light, they triggered a reaction process in which a new molecule forms. The scientists were also able to solve the “sticky-finger problem” with UV light: irradiated with light with a wavelength of 365 nanometers, the outer shape of the assembler molecule changes. Its ends compress like a pair of pliers, the space inside becomes too small and the new molecule is released. UV light was chosen by the research team as an external source of energy, 
 

Paradigm shift in chemical synthesis


For example, similar functioning molecular machines that could turn amino acids into proteins would be able to trigger a paradigm shift in chemical synthesis methods with fewer by-products and shorter synthesis processes, Herges said. In addition, the Kiel research team emphasizes that the energy of the resulting molecule is higher than that of the starting materials. “Even though their fabrication is challenging, molecular assemblers could be a new way to turn light energy into chemical energy in the long run,” Herges points out.

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