Labtimes 2017-06

page 32 Lab Times 6-2017 Journal Club Robots are designed to ease our work load. They can do so in factories but also in miniature. In a world’s first, David Leigh and colleagues have created teeny tiny molecular machines, capable of building other molecules. Functional molecule synthesis in Manchester, UK Science Fiction Becomes Fact Pixabay/TheDigitalArtist I f you can imagine down to a millionth of a millimetre – that’s how much each molecular robot measures. Even if it was possible to stack a billion billion (that’s 18 zeros in case you’re wondering), it would only be about the same height as a grain of salt. “Molecular machines represent the ul- timate in miniaturisation. The shrinking of the concept of machines down to the mo- lecular level. You can’t get any smaller than that,” says team leader David Leigh from the University of Manchester, UK. Crucially, when it comes to molecular machines, we know for sure this is possi- ble. How do we know that? Simple. There’s already a working nanotechnology system out there and we call it biology. From har- vesting energy from the sun to DNA repli- cation, every single biological process de- pends fundamentally on molecular ma- chines. Machines vs chemists “In biology, molecular machines are important for the construction of natural products, important processes within all our bodies. They control the order and lo- cation, in which chemical reactions happen. Building molecular machines is our attempt to answer the question ‘can chemists do the same?’,” says chemist Leoni Palmer, one of the scientists also involved in this study. “Biology has evolved to use molecular machines for a good reason,” adds Leigh. “When we learn how to do the same, how to use molecular machines to control motion and use that motion to perform tasks, it will change our whole approach to all kinds of functional molecules and material design,” says Leigh. Chasing this idea, Leigh and his team have spent the last few years perfecting their molecular machines. Their first at- tempt, published in 2016, was ‘only’ able to pick up a molecule, move it to a differ- ent place and put it down ( Nature Chem , 8:138-43). Coincidentally, this was also the year when Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard Feringa won the No- bel Prize in Chemistry for their design and synthesis of simple molecular machines. Building on from this success, Leigh’s team now presents a new and improved 2017 version. More agile and sophisticated than the previous model, this updated ver- sion is capable of more than just moving substrates, it can actually build other mol- ecules ( Nature , 549: 374-8). Just like in a car factory The easiest way to explain how the new machine works is to compare them to ro- bots on an assembly line in a car factory. These robots can pick up specific pieces and position them in place, while they’re riveted to the bodywork of the car during manufacture. The same robots can be pro- grammed to build different designs or even different cars. “We’ve taken the same approach with our molecular robots,” says Leigh. “It has a robotic molecular arm where it holds a substrate molecule, then it can move be- tween different positions where chemical reactions can occur. By programming the molecular robots about where to hold the substrate and when to move it to a different place, we can build different molecules us- ing the same molecular robot. You can pro- gramme it to do different things.” Lego-like system Starting with the same set of reagents, Leigh’s robot can build four different mol- ecules just by varying the way the differ- ent reagents are assembled. “If you think of Lego, you can add the same blocks in different ways,” explains the researcher. “The four programmes use the same build- ing blocks to be added in different places and different spatial positions, depending upon the nature of the programme. With four programmes we can build four differ- ent molecules, which contain exactly the same building blocks just arranged in a dif- ferent way,” says Leigh. In this particular case, the team opted for a thiol and an alkene as building blocks, to be added to an α , β -unsaturated aldehyde in a tandem reaction. This is just an exam- ple; the aim for the future is to gradually

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