UCLA Chemist, Stanford Physicist Win Nobel Prizes
A UCLA chemist and Stanford University physicist were roused from sleep Wednesday morning with news that all scientists dream of: They had won Nobel prizes.
UCLA’s Paul D. Boyer won a share of the chemistry prize for discovering the molecular machinery of the “three-cylinder engine” that turns sunlight into energy powering virtually all living things.
Stanford’s Steven Chu shared the physics prize for his use of lasers to freeze atoms in their tracks, allowing them to be trapped, measured and studied.
Both Boyer and Chu said their initial reaction to the news was disbelief. “At first, I had to be reassured it was real,” said Boyer, on vacation at his nephew’s home in Sea Ranch, Calif. “Then I was overwhelmed.”
Chu, speaking from Stanford, said he had been told for years by well-wishers that he might get the prize, but tried not to get his hopes up. “It can be depressing,” he said. “You can’t think about it. If it happens, it happens.”
Boyer shared his half of the $1-million chemistry prize with John E. Walker of the Medical Research Council Laboratory of Molecular Biology of Cambridge, England, whose X-ray pictures of the energy-producing molecule known as ATP helped unravel its structure. The other half of the prize went to Jens C. Skou of Denmark for work on a different enzyme that uses ATP to activate nerve cells.
The physics prize was equally shared by Chu, William D. Phillips of the U.S. National Institute of Standards and Technology, and Claude Cohen-Tannoudji of France.
Both Boyer and Chu regretted that only three people in each category can win the Nobel Prize each year, and Boyer said he will spend at least some of his winnings recognizing the work of “those unsung fellows” of science--postdoctoral fellows who do research at universities for low pay. “I don’t think they receive enough recognition,” he said.
UCLA’s dean of sciences, Roberto Peccei, said he wasn’t surprised that Boyer would want to use his prize money to help postdoctoral students. “You couldn’t ask for a better person,” he said. He noted that Boyer’s ideas about the machinery behind the cell’s power source were considered heretical at first. “He went out on a limb,” he said.
The chemical ATP, or adenosine triphosphate, energizes every human activity, including the thinking that goes into winning a Nobel Prize. In fact, the amount of ATP produced and used up as energy by a typical student in a single day, said Boyer, would weigh as much as the student’s body.
But exactly how ATP manages to grab energy out of sunlight and send it on to the cell so efficiently was not understood.
Boyer’s revolutionary idea, hatched in the 1980s, was that an enzyme enabling ATP to grab and release energy actually rotated, like a tiny motor. So far, “it’s the only known enzyme that has this rotational mechanism,” he said. “It’s like a three-cylinder motor.”
The enzyme contains three different sites, or chambers, where chemical reactions occur. When Boyer’s experiments showed that all three sites were doing the same reaction in exactly the same way, but at different times, he immediately thought of rotation.
“All the sites were doing it identically,” he said, “and one after another. . . . The only way I could see [to explain that] was internal rotation.”
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One chamber grabs onto the molecular ingredients that go into ATP; the second pushes them close together so they can react; the third sends the completed ATP molecule on its way into the cell. At each step, the chamber changes shape.
Boyer’s idea was not immediately accepted even by his co-workers, who “thought it was a little off base,” the new laureate said. But he was undeterred. “I’m persistent,” he said. “I kept working at the problem for a long time.”
He was also extremely lucky, he said, regretting that the many “post-docs” who worked with him over the years couldn’t share the prize. “They deserve the credit,” he said.
In a larger context, the prize for the work on ATP was in keeping with the growing recognition of advances in the chemistry of life, said Stanford chemist Richard Zare. “We’re going to learn more and more as we understand that the body is some really marvelous chemical factory,” he said. “And in many ways, this factory is controlled by the mind, and that too is controlled by chemistry. It’s amazing.”
The physics prize for the second year in a row went to experimental work at extremely cold temperatures, near the unreachable absolute-zero point (about minus 459 degrees Fahrenheit) where all motion stops. However, rather than the more conventional kinds of “refrigerators” used in last year’s prizewinning work, Stanford’s Chu won the prize for cooling his atoms with precisely tuned laser beams.
Since the invention of laser cooling in the mid-1980s, thousands of papers have been written on its properties and applications, said University of Colorado physicist Eric Cornell, who created a new form of matter using the technique in 1995.
“Laser cooling has been so important, someone had to win a Nobel Prize for it,” he said. The applications range from atomic clocks precise to one second in 3 billion years (more than half the age of the solar system) to methods for reaching inside a cell’s nucleus to pin down a molecule of DNA.
Cooling atoms is the only way to slow them down enough to study how they behave and make use of their sometimes peculiar properties. At room temperature, atoms speed around at thousands of miles per second, making them impossible to pin down.
While people think of lasers as hot, their value comes from their extreme precision--the result of lining up light waves exactly, crest for crest and trough for trough. In 1985, Chu came up with a way of slowing atoms by bombarding them with precisely tuned laser beams.
In effect, the atoms became stuck, so sluggish that they seemed to be immersed in a very thick fluid. The laser cooling system was thus dubbed “optical molasses,” the term used to describe it today.
Atoms hit with laser beams coming from opposite directions could be trapped between the two streams. Chu’s atom trap trained three pairs of opposing laser beams on a small clump of atoms, effectively pinning them down so that they floated in place.
Laser cooling has allowed researchers to study the behavior of atoms in great detail, said Cornell. When atoms get that cold, collisions between them take place “at a leisurely pace,” he said.
Atoms colliding and sticking together is the basis of most chemical reactions. Laser cooling “has started a new kind of collision physics,” he said. “You can actually watch and manipulate the atoms as they collide.”
Cornell and his colleagues used laser cooling in 1995 to freeze a bunch of atoms to such an extreme degree that they clumped into a single super atom--a result predicted by Einstein 70 years ago but never seen. Stanford’s Zare, along with several other researchers, predicted that Cornell’s feat would win its own Nobel Prize in physics. This year’s prize “foreshadows what will soon be another award,” he said.
Chu stressed the enormous technical implications of the technique. “It’s a springboard,” he said, for a wide variety of experiments “that were never possible before.”
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For example, one of his former students, now at Yale, had used laser cooling to develop a gyroscope so precise it could measure the change in the force of gravity produced by moving 0.3 of a millimeter farther from the center of the Earth. Such sensitive tools can be used to prospect for oil, among other things.
“And it’s gone way beyond physics,” he said, noting that many biologists were using the same kinds of laser traps to trap bacteria. “You could hold onto single molecules of DNA this way,” he said.
Chu, who couldn’t take time to be interviewed until he had finished teaching his regularly scheduled 11 a.m. class, was the third physicist in a row from Stanford to win a Nobel Prize. “I don’t think any of us recall that kind of repeat,” said Blas Cabrera, chairman of the Stanford physics department. “We’re extremely excited and pleased.”
All in all, it was a very good year for California. Of the five Americans winning Nobel Prizes in medicine and science this year, four were from California.
Each of the physics laureates contributed different approaches to cooling atoms, Chu said.
Phillips was in Long Beach attending a conference when he heard the news, according the Reuters. “I was flabbergasted,” he said. “One can always hope, but this came out of the blue.”
Cohen-Tannoudji, who talked to The Times from his apartment on the Left Bank in Paris on Wednesday, said he was “simply overjoyed.” A member of the French Academy of Sciences and holder of the chair of atomic and molecular physics at the College of France since 1973, Cohen-Tannoudji last year received the highest French scientific distinction, the gold medal of the National Center of Scientific Research, for his work on the chilling of atoms.
“I’ve been getting so many telephone calls I haven’t had the chance to talk to my children,” he said.
Times staff writer John-Thor Dahlburg contributed to this story from Paris.
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The Energy Machine
The Nobel Prize for chemistry was awarded for studies of adenosine triphosphate (ATP), which is used by the body’s cells to store energy. It is produced by an enzyme, called ATP synthase, that is located in the membranes of cells. Although one part of the enzyme remains anchored to the membrane, the other part rotates like a turbine as it produces ATP by joining a phosphate group to adenosine diphosphate (ADP).
1) HYDROGEN IONS: Flow through membrane
2) MEMBRANE PROTEIN: Spins as hydrogen flows through membrane
3) GAMMA SUBUNIT: Fixed to membrane protein so it also spins
4) ENZYME
The enzyme contains three alpha (white) and three beta (shaded) subunits surrounding a rotating gamma subunit. The rotation changes the three-dimensional structure of the beta subunits.
POSITION 1
An ADP molecule and a phosphate enter a beta.
POSITION 2
As the enzyme rotates, the beta contracts, bringing ADP and phosphate closer together so that they can bond.
POSITION 3
Completed ATP is released from the beta, allowing it to expand and bind ADP and phosphate, beginning the cycle once again.
