Structure of plant photosystem I determined at 3.4 Å
Plant photosystem I is a nanophotochemical structure that plays an important part in photosynthesis. It consists of a reaction center and light-harvesting complexes. The photosystem generates the most negative redox potential known in nature (–1 V), uses almost every photon it traps to drive electron transport and produces a quantum yield of almost one.
This structure of plant photosystem I is shown viewed from the stroma. Structural elements not in the previous model are shown in red. Chlorophylls in the reaction center are shown as yellow or cyan. Psa and LHC subunits also are indicated. Reprinted with permission of Nature.
Researchers from Tel Aviv University in Israel previously determined the photosystem’s structure at 4.4 Å resolution but have found even more details in a new structure at 3.4-Å resolution.
As reported in the May 3 issue of Nature, the scientists used x-ray crystallography to determine the structure of the photosystem from pea (Pisum sativum), which revealed 17 protein subunits, including details of 11 of the 12 subunits making up the reaction center.
- A quantum of electromagnetic energy of a single mode; i.e., a single wavelength, direction and polarization. As a unit of energy, each photon equals hn, h being Planck's constant and n, the frequency of the propagating electromagnetic wave. The momentum of the photon in the direction of propagation is hn/c, c being the speed of light.
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