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Nobels awarded for physics, chemistry.

Nobels awarded for physics, chemistry

Electrons, photons, neutrinos and mesons--these subatomic particles form the background for the Nobel prizes this year in physics and chemistry.

In contrast to last year's Nobel prize in physics, awarded for very recent work on superconductivity, the Royal Swedish Academy of Sciences reached back to work done nearly three decades ago to select the 1988 physics prize winners. Three Americans -- Leon Lederman, director of the Fermi National Accelerator Laboratory in Batavia, Ill., Melvin Schwartz of Digital Pathways Inc. in Mountain View, Calif., and Jack Steinberger, now at the European physics research center CERN in Geneva, Switzerland -- won the prize for work they did in 1960 to 1962 while at Columbia University in New York City.

During that time, they became the first researchers to devise a way to produce a stream of neutrinos in the laboratory. When they did so, the trio found a new type of neutrino, a discovery that helped lead to the creation of the current family tree showing the relationships among all subatomic particles.

The neutrino is a neutral particle with little or no mass and very little interaction with other particles. It is so noninteractive that billions of neutrinos pass unimpeded through each square centimeter of the Earth every second. Until Schwartz suggested a method, no one knew how to create a stream of neutrinos to study in the laboratory.

To produce neutrinos the group used high-energy protons from a particle accelerator to bombard a beryllium target, producing a shower of protons, neutrons and the smaller pi-mesons (pions). As the pions traveled away from the target they disintegrated into mu-mesons (muons) and neutrinos. The researchers filtered out all particles but the neutrinos by passing the beam through a 44-foot-thick barrier of steel. The neutrinos then entered a 10-ton aluminum detection chamber, where a few neutrinos out of the hundreds of billions passing through interacted enough with the aluminum atoms to be detected.

From previous research the scientists knew neutrinos could create either electrons or muons as they interacted with matter. But in the detector the neutrinos from pion disintegration created only muons, indicating there must be two types of neutrinos -- one for muons and one for electrons. The academy awarded the 1988 Nobel prize to the three not only for the discovery of the muon neutrino, but also for the method for producing high-energy neutrino streams.

The Nobel prize in chemistry went to three West Germans -- Johann Deisenhofer, now working at the Howard Hughes Medical Institute in Dallas, Robert Huber of the Max-Planck Institute for Biochemistry in Martinsried, West Germany, and Hartmut Michel of the Max-Planck Institute for Biophysics in Frankfurt am Main, West Germany -- for determining the structure of a bacterial protein that performs simple photosynthesis. The cytochrome protein, which sits astride the bacterial membrane with one part inside the cell and one part outside, uses a specialized molecular architecture to absorb photons of light and uses that light energy to transfer electrons and hydrogen ions across the membrane.

Bacteria use the resulting difference in the concentrations of hydrogen ions (pH) and electrons (voltage) inside and outside the cell to make one of life's most basic chemical energy sources, adenosine triphosphate. This type of photosynthesis is simpler than that in plants, but the German trio's discovery contributes to the understanding of the mechanisms of photosynthesis in general.

Michel solved the biggest technical difficulty of the project in 1982 when the discovered how to purify and crystallize the membrane-bound protein. Deisenhofer and Huber then joined Michel to perform X-ray crystallographic measurements on the purified protein, which allowed the team to elucidate its structure in 1985.
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Author:Vaughan, Christopher
Publication:Science News
Date:Oct 29, 1988
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