It’s Nobels season — that time of the year when we find out which groundbreaking, paradigm-shifting, world-changing achievements beat out the rest to win what is arguably the most prestigious award on Earth.
From a light switch for the brain to the discovery of an ultra-elusive subatomic particle hailing from beyond our solar system to a solution to one of the most enduring puzzles in all of organic chemistry, the researchers behind this year’s scientific prizes each revolutionized the ways that scientists understand the world around them.
Take a look at the science behind each of this year’s awards.
Shining a light
A galaxy of nearly 90 billion neurons exists within a single human brain. But unlike stars in the void, neurons communicate with one another via some 100 trillion connections, allowing the human mind to learn, adapt and interact with its surroundings.
For scientists to understand how individual actions arise from such complexity, they needed a tool to directly link neural circuits to specific behaviors, said Abdel El Manira, a neuroscientist at the Karolinska Institute in Stockholm. “Neuroscientists dreamed of a neuronal switch, a tool to turn specific neurons on or off with great precision,” El Manira said during the Oct. 5 announcement of this year’s prize in physiology or medicine by the Nobel Assembly at Karolinska Institute.
Enter the bright idea that won. It’s a technology called optogenetics, which involves using light to precisely activate specific cells, like neurons, and watch how behavior changes. For their foundational contributions to optogenetics, biophysicists Peter Hegemann of Humboldt University in Berlin and Georg Nagel, of the Julius-Maximilians-Universität Würzburg in Germany, and neuroscientist Karl Deisseroth of Stanford University shared this year’s prize.
The prize winners’ story starts in an unlikely place: the eye spot of a single celled green alga called Chlamydomonas. In the early 2000s, Hegemann, then at the Max Planck Institute for Biochemistry in Martinsreid, Germany, and Nagel, at the Max Planck Institute for Biophysics in Frankfurt, discovered a unique protein in the alga’s eye spot. When illuminated, the protein generated an electrical impulse, enabling the organism to move. Further research revealed that when the protein, called channelrhodopsin, was exposed to light, it opened like a pore, allowing positively charged ions to flow into a cell, generating the electrical impulse. “They had just discovered the switch neuroscientists had long dreamed of,” El Manira said.
Building on the Hegemann and Nagel’s work, Deisseroth began testing whether channelrhodopsin could be used to activate brain cells. He and his colleagues first inserted the gene for channelrhodopsin into cultures of rat nerve cells and found that the cells reacted to light instantaneously. They then introduced the gene into nerve cells in the brains of living mice, along with optical fibers fed through the rodents’ skulls. By beaming blue light through the fibers, the researchers were able to control the movements of the rodents’ whiskers. This technology gave researchers the ability to test the links between certain brain circuits and behaviors.
“The technology, which soon became known as optogenetics, transformed neuroscience,” El Manira said. In addition to exposing the inner workings of healthy brains, he noted, “it has also helped reveal how brain circuits are disrupted, with implications for conditions such as blindness, depression and dementia.”
For example, the technology has been used improve vision in some patients with retinitis pigmentosa, a disease that degrades light-sensing cells in the retina. It’s also helping researchers investigate the role that a person’s heart plays in how they experience and interact with their surroundings.
Capturing a ghost
At the South Pole, there exists a block of ice unlike any other on Earth. Buried deep beneath the surface of the Antarctic ice sheet, a cubic kilometer of ice is threaded with thousands of beadlike sensors. Known as the IceCube Neutrino Observatory, this immense instrument enables researchers to detect the most elusive particle in the universe — the neutrino.
Detecting neutrinos from beyond our solar system had been a goal of scientists for decades, as that could help understand where and how the universe accelerates particles to extraordinary energies.
The researcher who led the creation of the Antarctic observatory, physicist Francis Halzen of the University of Wisconsin–Madison, received this year’s Nobel Prize in physics. Halzen was awarded “for his decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin,” Mark Pearce, a physicist and chair of the Nobel committee for physics, during the Oct. 6 announcement by the Royal Swedish Academy of Sciences.
Neutrinos are subatomic particles that are chargeless, incredibly small and so ethereal that they often pass through objects without interacting. In fact, billions of neutrinos pass through each of us every second, most of which are formed by nuclear fusion reactions in the sun. But some of these ghostly particles were thought to have originated much farther away, in high-energy particle collisions so distant as to lie beyond the limits of observations. Because neutrinos are not deflected by magnetic fields and rarely interact with matter, the detection of a high-energy neutrino’s trajectory could enable the identification of its distant source. An instrument capable of that task could therefore open a new window into the cosmos.
In the 1980s, Halzen realized that the South Pole was an ideal location for detecting the rare flashes of light that are generated when neutrinos collide with atomic nuclei. Ice deep inside the Antarctic ice sheet presented a large, transparent medium plunged in darkness, in a spot free from earthquakes and biological interference. It was the perfect stage for a neutrino lightshow.
Halzen’s vision was realized in 2011, when IceCube completed construction. “The biggest risk we took is that nobody knew whether a kilometer-field detector was actually large enough to discover neutrinos beyond our atmosphere from the universe,” Halzen said in a phone call during the announcement ceremony. “It only took us two years to detect them.”
And the discoveries didn’t end there. In 2018, researchers using IceCube data reported that they had traced a neutrino back to the brilliant core of a distant galaxy, called a blazar, thereby identifying a source for the energetic particles for the first time. And in 2023, researchers used a decade of IceCube data to produce the first map of the Milky Way using anything besides light, simultaneously reporting the first evidence of high-energy neutrinos hailing from within the galaxy.
Plans for a global network of neutrino detectors are now in motion. So scientists will soon be even better equipped to pinpoint and demystify the distant cosmic accelerators that launch the mysterious particles across the vast reaches of space.
Giving chemistry a hand
In nature, the building blocks of life exhibit a striking pattern. Many can exist in two versions that are mirrored images of one another, much like your right and left hand. Such molecules are said to be chiral. However, they overwhelmingly occur as just one of these chiral forms — for instance, amino acids are nearly always left-handed.
This uniformity, known as homochirality, had long puzzled scientists. When chemists first attempted to produce chiral molecules in the lab, they ended up with even proportions of right- and left-handed molecules, or enantiomers.
“It is this puzzle that this year’s laureates have solved,” Heiner Linke, chair of the Nobel Committee for Chemistry said during the Oct. 7 Nobel Prize in chemistry announcement by the Royal Swedish Academy of Sciences.
Henri Kagan, of the Université Paris-Saclay, and Kenso Soai, of the Tokyo University of Science, split the prize for discoveries leading “to a chemical reaction that spontaneously, without the involvement of other chiral molecules, creates only one mirror image,” said Linke, a physicist at Lund University in Sweden. “This is the first time this had happened since the processes that led to the chirality of life billions of years ago.”
Putting aside the laureates’ impact on one of organic chemistry’s greatest mysteries, their research has immensely benefitted the development of pharmaceuticals. So many active drug molecules are chiral, and one enantiomer of a drug might have the desired therapeutic effect while its other might have no effect or even be harmful, Linke said.
A notorious example of such harm occurred in the 1950s, when thousands of babies with severe birth defects were born to women who had taken a sedative called thalidomide. It was later revealed that one of thalidomide’s enantiomers was the source of the birth defects. Even making the drug with only the “safe” orientation didn’t solve the problem: It could switch handedness in the body.
In 1986, Kagan and his colleagues became the first to report chemical reactions that produced specific enantiomers in proportions far exceeding what chemists previously assumed was possible using catalysts.
Nine years later, Soai and his colleagues reported that they had figured out how to make a chiral catalyst that could, in turn, be used to form itself. That allowed them to perform reactions that resulted in products made almost entirely of one enantiomer. “This is not the final answer,” Soai said of his groundbreaking work on chirality, while calling into the ceremony from Japan. Speaking to future generations, he said “the study of chirality should be more and more developed.”
Even so, as Nobel committee member Peter Somfai, a chemist at Lund University in Sweden, said during the ceremony: “This is probably the coolest experiment in organic chemistry.”
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