The Green Party( Biologists conducting Space Shuttle e...)

Biologists conducting Space Shuttle experiments may be one step closer to shedding light on the biggest power booster on the planet: a protein in green plants called Photosystem I.

A German research team recently presented the results of their Space Shuttle experiment designed to crystallize Photosystem I molecules. According to the researchers, "This experiment has yielded the best data set thus far obtained from Photosystem I crystals."

During photosynthesis, the cells in green plants undergo two simultaneous reactions, both of which rely on a separate kind of protein. Photosystem I protein molecules use the trapped energy in sunlight to convert carbon dioxide into carbon and oxygen. This provides the plant food in the form of carbohydrates, lipids, proteins and nucleic acids - the building blocks of life. Photosystem II protein molecules use light energy to split water into hydrogen and oxygen for plant respiration.

Scientists crystallize protein molecules in order to study their complex internal structures. Because the molecules are too small to study directly under a microscope, scientists use X-ray diffraction to get a picture of the molecule.

Shining X-rays through a crystal produces a scattering pattern, which is a type of blueprint. Think of a shadow cast through a picket fence - the shape of the shadow would tell you that the fundamental building block of the fence is a rectangular board. Shining X-rays through a protein crystal indicates the protein's shape, where it's located, and ultimately how it may work.

High quality crystals - composed of ordered and repeating units of a particular protein - are required for X-ray diffraction. Some of the crystals grown in the microgravity conditions of space are more perfectly ordered than crystals grown on Earth. Microgravity can also affect the rate at which the proteins initiate new growth. Space crystals have shown a 10 to 20-fold larger volume compared to the Earth-grown counterparts.
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Contact: John Horack
john.horack@msfc.nasa.gov
256-544-1872
NASA/Marshall Space Flight Center--Space Sciences Laboratory
10-May-1999