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Two pigment molecules (BChls) vibrating

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Photosynthetic life forms bottle the energy of sun light. How do they do it? Fast! Indeed, the first nanosecond after absorption of sun light is crucial in photosynthetic light harvesting. During this time absorbed solar energy is in its least stable form, that of electronically excited molecules which decay by re-emitting a photon (fluorescence) at a rate of 1 every nanosecond (1 every 0.000000001 seconds). Fluorescence would be wasteful to the organism and to avoid it the molecular excitation energy is transported over tens to hundreds of nanometers through an energy transfer network to so-called photosynthetic reaction centers where it is converted into a more stable form of energy (see our recent review on light harvesting). The fast transport is achieved by transferring excitation energy between clusters of strongly interacting pigment molecules that act as stepping stones and as a result the excitation energy is used in about 0.1 nanoseconds, i.e., within 10% of the fluorescence decay time, thus bottling sun light with an efficiency of 90%. The thermal motion of the pigment molecules and their protein scaffold greatly influences the excitation transport. A recent study showed that correlated thermal fluctuations that arise in pigment clusters affect the excitation transfer particularly strongly, typically slowing transfer it down. Pigment clusters that avoid correlated thermal motion increase the efficiency of light harvesting. More information can be found here.