With only a few exceptions, life on earth depends on photosynthesis, the process by which plants, algae and certain bacteria use the energy of sunlight to live.  Light energy is converted into chemical potential energy in photosynthetic organisms in membrane-bound pigment-protein complexes called reaction centers (bacteria) or photosystem I and photosystem II (plants).  In the purple photosynthetic bacterial reaction center, the membrane-spanning multi-step charge separation process utilizes only one of two electron-transport chains, referred to as the A-side cofactors.  The cofactors on the B-side, which are arranged in pseudo-mirror image of those on the A-side, normally do not participate in charge separation.  B-side electron transfer has been elicited in mutant reaction centers, however.  A history of studies on mutant RCs that give B-side charge separation, starting with just a few percent yield and working up to yields as high as ~70%, will be described.  These studies probe the origins of directionality of electron transfer in the bacterial RC, including the relative contributions of electronic and energetic factors.

Switching sides: Re-engineering electron transfer in photosynthetic bacterial reaction centers

248th National Meeting (2014)

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