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Finding the Light

James Lee helped show that hydrogen can be produced photosynthetically by algae in illuminated water.
James Lee helped show that hydrogen can be produced photosynthetically by algae in illuminated water.

Several ORNL biologists interested in studying green plant cells and radiation focused on photosynthesis. In this process, plants synthesize carbohydrates (tissues) from airborne carbon dioxide and water, using light as an energy source.

William Arnold and Robert Emerson identified the photosynthetic unit in pio-neering studies that led to Arnold's 1966 discovery of delayed light, an internationally recognized fundamental discovery in photosynthesis. (Arnold also is known for coining the term "nuclear fission," used universally to describe the process of splitting atomic nuclei.) Roderick Clayton provided evidence for the electronic nature of the first step of photosynthesis.

In the 1970s and 1980s Robert Pearlstein developed theoretical models that described the migration of light energy in the chlorophyll antenna lattice of green plants and bacteria. Later in the 1980s Elias Greenbaum and his ORNL colleagues Perry Eubanks, Jim Thompson, Mark Reeves, and Ginger Tevault used photosynthesis in spinach and later algae to split water molecules to produce oxygen and the energy-rich gas, hydrogen. In 1985 Greenbaum demonstrated direct electrical contact of photosynthetic electrons with platinum metal nanoparticles; this work was featured on the cover of Science magazine. In 1995, Greenbaum, working in collaboration with Ida Lee and James Lee, discovered the diode properties of isolated Photosystem I reaction centers. In 2000, the continuation of this work led to the first measurement of photovoltages of isolated photosynthetic reaction centers.

In 2002 Greenbaum and his associates at ORNL and the University of Southern California investigated the use of photosynthetic reaction centers for restoring sight to the legally blind. ORNL has had only a handful of photosynthesis researchers, but they all have made noteworthy contributions to this field.

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