Winners round-up
Strange states of matter, the cell’s recycling machinery and molecular machines all inspired the 2016 recipients of science’s most prestigious accolade. CATHAL O’CONNELL reports.
This year’s Nobel Prize in Physics went to three scientists who used the mathematics of topology – a study of shape – to explain the properties of exotic states of matter.
Superfluids, such as liquid helium, form a Bose-einstein condensate – a kind of atomic groupthink where the atoms behave like one giant atom. This generates zero resistance to flow, or superfluidity.
Give liquid helium a stir, for example, and the whirlpool would spin forever. Coupled with its sensational ability to transfer heat, this flow property makes liquid helium the world’s ultimate coolant – used to deep-freeze the 27-kilometre ring of the Large Hadron Collider.
In the 1970s, physicists thought they had the theory of superfluidity wrapped up, but then David Thouless at the University of Washington and Michael Kosterlitz at Brown University realised that miniature whirlpools spinning in opposite directions could link together, like two meshing gears. Tiny temperature rises cause decoupling. That sudden shift in the superfluid’s topology brings unexpected changes in its density and coolant properties.
Thouless also used topology to explain the quantum Hall effect, a baffling phenomenon in flat materials where electrical resistance suddenly takes on multiple values of the number 25,812.807557. He realised electrons can gang together and run along the edge of the flat material, a bit like streams of droplets running down a windowpane. Each additional “stream” decreases the resistance by exactly 25,812.807557 ohms.
Meanwhile, Duncan Haldane at Princeton University used topology to predict strange properties in chains of magnets. A chain can have different magnetic properties depending on whether it has an odd or even number of magnets.
The work has led to the creation of strange materials such as topological insulators. Insulators on the inside but conductors on the outside, they could help make more reliable quantum computers. Yoshinori Ohsumi at the Tokyo Institute of Technology won the prize for medicine for revealing how cells recycle their contents.
Autophagy, literally “self-eating”, refers to the observation that starving cells start breaking down internal organelles for protein – much as a starving person will break down their own muscle tissue.
Aided by an electron microscope, biologists had observed this process in mammalian cells in the 1960s. But Ohsumi wanted to find the genetic controls, so in the 1960s he switched to a cell where gene hunting was easier: baker’s yeast.
Starving yeast cells underwent a similar recycling process, packaging up organelles in compartments called vacuoles. Some strains of yeast, especially those treated with mutagenic chemicals, didn’t form vacuoles in the normal way. Ohsumi guessed that their autophagy
genes had been disrupted. His analysis identified 15 “atg” genes crucial to the mechanism. The same genes were shown to be important for autophagy in human cells.
It turns out recycling is not just important for salvaging nutrients; it’s also crucial for a cell’s hygiene.
When it fails, it can lead to chronic inflammation explaining the link between autophagy and inflammatory diseases such as Crohn’s disease. Autophagy has also been linked to cancer and neurological diseases and plays a big clean-up role during the sometimes messy process of embryonic development. What’s the tiniest machine ever made? How about a 1,000th the width of a human hair? This year’s Nobel Prize in Chemistry went to three chemists for creating the world’s first machines made from individual molecules.
Nature is great at making molecular machines like the motor protein, myosin, which ratchets itself along a fibre to make muscles contract. But to copy nature’s feat, chemists had to learn to make molecules with moving parts.
That happened in 1983 when JeanPierre Sauvage of Strasbourg University linked two ring-shaped molecules to form a chain, called a catenane. His trick was to use a copper ion to pinch the two rings together as they formed. Then in 1991, Fraser Stoddart of Northwestern University created the first rotaxane molecule, which looks like a ring encircling a dumbbell. He also showed the ring could move along the axle. And in 1999, Bernard Feringa of the University of Gronigen developed the first molecular motor, using light and heat to make it spin. Hooking up four motors along a molecular chassis, he created the first nano-car and, when he applied light and heat, it drove itself along a surface. Molecular robots now promise to transform everything from medicine to cleaning up the environment.