‘Pick-up, Transport and Release of a Molecular Cargo using a Small-Molecule Robotic Arm’’ Salma Kassem, Alan T. L. Lee, David A. Leigh, Augustinas Markevicius and Jordi Solà, Nature Chem, 8, 138-143 (2016). Full Article.
The mechanical manipulation of matter at atomic length-scales has fascinated scientists since it was proposed by Feynman in his celebrated lecture ‘There’s Plenty of Room at the Bottom’.1 Indeed, the concept of using molecules to manipulate other molecules in robotic fashion is an intriguing one that has some precedence in biology: for example, in metazoan fatty acid synthase a growing fatty acid chain, tethered to an embedded carrier protein, is passed between enzyme domains in the protein superstructure in a manner reminiscent of the way a robotic arm manipulates objects on a factory assembly line (Figure 1).2 However, up to now there have been no small-molecule machines (as opposed to proteins or DNA) that can transport molecular fragments in a similar manner.3
Figure 1. Cartoon representation of a programmable small-molecule robot able to transport a molecular cargo (shown in red) in either direction from blue-to-green or green-to-blue platform sites.
Now chemists at the University of Manchester have made a molecular machine with a ‘robotic arm’ that is able to pick up a molecular cargo, reposition it, set it down and release it at a second site approximately 2 nm (0.000002 mm) away from the starting position (Figure 2).4 The relocation of molecular fragments with a nanoscale robotic arm—making and breaking chemical bonds in a process during which the cargo is unable to exchange with others in the bulk—is the first step towards the controlled manipulation of molecular-level structures through programmable small-molecule robotics.
Figure 2. Chemical structure of a programmable molecular robotic arm (shown in black) able to reposition a molecular cargo (shown in red) in either direction from blue-to-green or green-to-blue platform sites.
Modern day factory assembly lines often feature robots that pick up, reposition and connect components in a programmed manner. Small-molecule robots should be able to manipulate substrates to control molecular construction, in a manner reminiscent of that observed in biology and factory assembly lines (Figure 3). Such nanotechnology has the potential to ultimately revolutionize how molecules and materials are made.5
Figure 3. Stylised ’nanopunk’ representation of the programmed operation of the molecular robotic arm. [Video credit: Stuart Jantzen, www.biocinematics.com] [Click here to download the HD version of the video]
 Feynman, R. P. There’s plenty of room at the bottom. Eng. Sci. 23, 22–36 (1960).
 Brignole, E. J., Smith, S. & Asturias, F. J. Conformational flexibility of metazoan fatty acid synthase enables catalysis. Nature Struct. Mol. Biol. 16, 190–197 (2009).
 Erbas-Cakmak, S., Leigh, D. A., McTernan, C. T. & Nussbaumer, A. L. Artificial molecular machines. Chem. Rev. 115, 10081–10206 (2015).
 Kassem, S., Lee, A. T. L., Leigh, D. A., Markevicius, A., Solà, J. Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm. Nature Chem. 8, 138-143 (2016).
 Kay, E. R & Leigh, D. A. Rise of the molecular machines. Angew. Chem. Int. Ed. 54, 10080–10088 (2015).