Forster resonance energy transfer molecule, design

Here the chromophores can be farther apart (10-100 A long-range interactions) since this mechanism does not require any overlapping of orbitals. The Forster radius designates the distance between donor and acceptor at which the efficiency of energy transfer amounts to exactly 50%. Half of the excited donor molecules are then deactivated by fluorescence resonance energy transfer, and the other 50% by fluorescence or phosphorescence. 

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