The key elements in this type of experiment are selectivity in the excitation and probe mechanisms and polarization information. All of these ingredients are being developed along with ultrafast time resolution to follow the pathways of energy transfer in a number of examples where cofactors are relatively nearby and the transfer is not necessarily predictable from Fvrster theory. One example is the reaction center. Excitation of the bacteriopheophytin or the accessory bacteriochlorophyll results in rapid energy transfer to the special pair followed by electron transfer. A detailed study of these processes is underway, aimed at characterizing the states of the supermolecule. In order to do a complete job of measuring anisotropies at all possible excitation wavelengths we are constructing an OPA device that can be scanned over the 500-950 nm region. This construction is now underway.
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