Imagine a microscopic world, no, smaller than that, a “nanoscopic” world where vehicles and machines, built from a few dozen atoms, move stuff around and do things with it. Sound like fiction? Well, it’s on its way to reality and it has won a Frenchman, a Scot and a Dutchman the Nobel Prize for Chemistry.
Building Molecules
Chemistry is the study of materials and their properties but finding ways of making new substances is an important area of the science. In 1828 Friedrich Wöhler made urea starting from ammonia and cyanide; the first time that a natural substance had been made from non-living matter. In the almost two hundred years since then, chemists have put together a toolkit of reactions including acid-base and RedOx reactions, that they can use to build almost any molecule that they can imagine.
Most of these interesting molecules are based on the hydrocarbons found in petroleum because carbon has the property of forming strong chemical bonds with itself and with atoms of other elements. We can start with methane and build up long chains of atoms such as polymers like polythene or make the carbon atoms form rings such as in benzene.
More recently chemists have learned how to build larger, more complex molecules, which act as drugs, or dyes or enzymes and have begun to understand how biological molecules such as DNA and proteins are put together in cells.
Slopping your reactants into a beaker, giving them a stir and hoping for the best will only give you a small yield of the substance you want at best. Making particular molecules involves knowing exactly which simpler molecules will react together, probably with a catalyst, and whether energy in the form of heat or light is needed.
Chemical Meccano
Chemical reactions usually involve making and breaking the chemical bonds between atoms, with the products formed as gases, solids or solutions. Making molecules that behave like the components of a machine – chains, rods, wheels, motors – seems very different. Nevertheless, the same toolkit of reactions is used. Jean-Pierre Sauvage made the first of these strange molecules in 1983 at the Louis Pasteur University in Strasbourg, France. He used copper atoms as a catalyst to make two ring shaped molecules loop together like two links in a chain. There was no chemical bond between the two rings, and each ring could move and spin independently of the other. The molecules are too small to see, of course, but instruments confirmed that 42% of the reactants had formed the pairs of linked molecules. Soon Sauvage was able to add more links to make a chain of rings. Sauvage called his molecules, catenanes from the Latin word for chain.
[http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/fig_ke_en_16_molecularchain.pdf]
Meanwhile Fraser Stoddart and his team at the University of Sheffield were building interesting new structures. He had started by trying to make an antidote to the toxic weedkiller Paraquat. His investigations showed that large square paraquat-like molecules could be made to fit over straight rigid molecules, just like fitting a wheel on an axle. Stoddart called the molecules, rotaxanes. Next he was able to make the “wheel” jump to and fro between two sites on the rod, like the shuttle in a weaving loom, controlled by the temperature.
[http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/fig_ke_en_16_molecularshuttle.pdf]
Stoddart’s and Sauvage’s teams worked together to develop their control of the movements of catenanes and rotaxanes. Stoddart said they had developed pieces of molecular Meccano that could be put together to make controllable machines. In 2004 in Los Angeles, Stoddart joined three rotaxanes together to make a “lift” that could raise or lower objects 0.7 nm. He fixed these molecules to a gold foil with a tiny gold lever attached to it. Changing the conditions made the lever move with a measurable force.
At the University of Groningen, Bernard Feringa was also working on molecular machines. In 1999 he announced that he had made a molecule made up of rings of carbon atoms that would rotate like a wheel in one direction, one million times a second, but only when uv light was shone on it. By attaching four of these molecules to a fixed “chassis” molecule he built a molecular four-wheel-drive car powered by uv light.
[http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/fig_ke_en_16_nanocar.pdf]
It was for the ingenuity of these inventions that have opened up a new field of chemistry that Sauvage, Stoddart and Feringa have been awarded the Nobel prize.
A Nano-Industrial Revolution
The development of these molecular machines are doing for the nano-world what the steam engine and electric motor did for ours. Other chemists are building more and more complicated molecular machines. It will soon become possible to build tiny machines that can, for example, deliver drugs to specific cells in the body and carry out repairs to cells or replace damaged muscles. Or they can be used to make new types of energy storage batteries or remote controlled nano-bots to carry out whatever tasks we can dream of. We already have nano-scale computers and soon we will have the nano-scale machines to do their bidding.
The Winners
The Nobel Prize Medal
Bernard “Ben” Feringa was born in Holland in 1951. He studied at the University of Groningen, Holland and returned there in 1984 after working for Shell, the petrochemical company. He became a professor in 1988.
Jean-Pierre Sauvage was born in Paris in 1944, during World War 2. He has spent almost all his academic life in Strasbourg where he is now Emeritus Professor and he is also a visiting scholar at Northwestern University.
Fraser Stoddart was born in Edinburgh in 1942. His parents were farmers and had no electricity or modern conveniences. As an only child, Fraser entertained himself with jigsaw puzzles which gave him his interest in topology, the study of shape. He took his degree and doctorate at Edinburgh University and then spent three years researching in Canada. In 1970 he took up a post at the University of Sheffield but took three years off to work for the chemical company ICI, where he began his work on Paraquat. His experiences converted a shy young man to one who was assertive and authoritative. In 1990 he was offered a professorship at Birmingham University. He accepted on condition that his research was funded as he wished. Success followed and he was offered a position at the University of California at Los Angeles in 1997. Here he devoted more of his time to molecular machines. Hundreds of academic papers were produced and his fame resulted in the award of a knighthood in 2006. He is currently a professor at Northwestern University, USA.
By The Way
The Physics and Physiology & Medicine prizes also had a chemical theme. The physics Prize was awarded for work on the properties of unusual states of matter at very low temperature. The Physiology and Medicine Prize was awarded for study of the breakdown of dead cells and the re-use of the materials released, a process called autophagy. This involved identifying the proteins produced by genes that took part in the process.
Tasks
- You can read more about the work done by Sauvage, Stoddart and Feringa athttp://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/popular-chemistryprize2016.pdf
- What is the difference between the way two rings of atoms are linked in Sauvage’s catenane, and the bonds between atoms in a simple molecule, such as methane?
- Why do you think Fraser Stoddart had to become more assertive as he progressed in his research?
- Molecular machines like rotaxanes can be used to move other groups of atoms such as a sheet of gold. Can you think of any applications for this?
- Many molecules will spin around in solution. What was special about Ben Feringa’s rotating molecule?
- What applications do you think will be important for nano-machines using Sauvage’s, Stoddart’s and Feringa’s discoveries?
Bibliography
- http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2016/press.html
The Nobel prize site gives you access to a lot more information about the 2016 Nobel Prize for Chemistry. - https://www.newscientist.com/article/mg13318122-800-science-the-wonderful-world-of-molecular-meccano/
A report from 1992 on some of the first steps in the story of molecular machines. - https://www.newscientist.com/article/dn8885-first-molecular-machine-combination-revealed/
A report from 2006 on a molecular machine that swims.
Peter Ellis
