The central step in photosynthesis, the transfer of energy to chemically active electrons, happens in a bulky protein complex called the reaction center. Feeding each reaction center with energy are hundreds of chlorophyll molecules that either convert sunlight into excitation energy or direct the energy, from molecule to molecule, toward the reaction center.
The chlorophylls, and the proteins that hold them, form light-harvesting systems that vary in shape and size across the span of photosynthetic life. But all the systems—in plants, algae, or photosynthesizing bacteria—share a remarkable ability: 99.5% of the solar energy they collect reaches their reaction centers.
Such efficiency is puzzling because the chlorophylls are crowded and coupled to each other. The chance of energy leaking out as phonons is conceivably high. But ironically, as Graham Fleming and his coworkers have now discovered, those couplings, rather than hinder efficient transfer, actually mediate it. 1
Fleming is the deputy...
