research Categories: >> Primary Processes in Photoystem I:
Primary Processes in Photoystem I:
Photosynthetic organisms use a twofold strategy
to capture and store solar energy. An antenna system first collects
light and then transfers the energy to an electron transfer system
that converts electronic excitation into redox energy that can be
used for cell growth. In most photosynthetic systems, the antenna
and electron transfer functions are located on separable complexes
and can be studied independently. However, in Photosystem I of
oxygenic photosynthetic organisms, along with some anoxygenic
bacterial relatives, the antenna and electron transfer functions are
fused into a single large complex that serves both functions.
Experiments are proposed to improve our current fragmentary
understanding of the energy trapping processes, primary
photoschemistry and early secondary electron transfer reactions in
this important class of photosynthetic reaction centers. The
particular system that will be studied is Photosystem I of oxygenic
photosynthetic organisms, for which good structural information is
now available. Overall goals of the work are to understand the
coupling of the antenna system to the electron transfer system and
the pathway of the early electron transfer processes.
Specific proposed experiments include: 1) Dichroism
and transient anisotropy experiments on long wavelength absorbing antenna
pigments in Photosystem I, 2) Studies on Photosystem I mutants in the quinone
and pigment binding regions, 3) Separation of the Photosystem I reaction center
complex into antenna and electron transfer domains using protein engineering and
4) Analysis of Photosystem I energy trapping and electron transfer in a newly-discovered
chlorophyll d-containing organism, Acaryochloris marina. These experiments will give
new insights into the energy trapping and primary electron transfer processes in
reaction centers that contain integral core antenna pigments and will help to
identify and characterize some of the early electron acceptors in these systems.
This project will increase our understanding of how plants and other photosynthetic organisms convert the energy of sunlight into chemical energy. The process of photosynthesis supplies all of our food and most of our energy needs. This project is designed to give detailed knowledge of the chemical mechanism of this essential biological process..