The Fenna-Matthews-Olson (FMO) complex is a trimeric pigment-protein complex found in green sulfur bacteria. It mediates the transfer of excitation energy from light-harvesting antenna complexes to the bacterial reaction center. Each monomer contains eight bacteriochlorophyll a molecules bound to the protein scaffold, mostly via histidine amino acids. The FMO complex serves as a molecular wire, transporting excitons generated during light harvesting to the reaction center for photochemical reactions. Excitation energy transfer via the FMO complex is fast and highly efficient, occurring with quantum coherence such that little energy is lost as heat or radiation.

1. BY SHARIQA AISHA
DEPARTMENT OF BIORESOURCES
UNIVERSITY OF KASHMIR

2.  The Fenna-Matthews-Olson (FMO) complex is a
water-soluble complex and was the first pigment-
protein complex (PPC) to be structure analyzed by x-
ray spectroscopy.
 It appears in green sulfur bacteria and mediates the
excitation energy transfer from light-harvesting
chlorosomes to the membrane-embedded bacterial
reaction center (bRC).
 Its structure is trimeric (C3-symmetry). Each of the
three monomers contains eight bacteriochlorophyll a
(BChl a) molecules. They are bound to the protein
scaffold via chelation of their central magnesium
atom either to amino acids of the protein (mostly
histidine) or water-bridged oxygen atoms (only one
BChl a of each monomer).
The FMO protein trimer

3.  Fenna–Matthews–Olson (FMO) complex, a
trimeric pigment–protein complex which lies
between the antennae complexes and the
reaction center of the photosystem II of sulfur
green bacteria, and whose primary function is to
serve as a molecular wire transporting the
excitons generated during light harvesting by the
pigments toward the reaction center where the
cascade of redox chemical reactions take place.
 The excitation energy transfer dynamics are
required to be fast or otherwise it is lost.
 It is now known that this transport occurs with
quantum coherence; that is, very little energy is
dissipated as heat or radiation, making it an
almost 100% efficient process.