During photosynthesis, the cells in green plants undergo two simultaneous reactions, both of which rely on a separate kind of protein. 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. I molecule, from Brookhaven National Laboratory Protein Databank , and Image Library of Biological Macromolecules, Jena, Germany.
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. In the microgravity environment of the Space Shuttle, scientists have shown some improved capability to grow macromolecular crystals with a higher degree of order.