TCB Publications - Abstract

Ioan Kosztin and Klaus Schulten. Structure, function, and quantum dynamics of pigment-protein complexes. In Masoud Mohseni, Yasser Omar, Greg Engel, and Martin B. Plenio, editors, Quantum Effects in Biology, pp. 123-143. Cambridge University Press, 2014.

KOSZ2014 Pigment - protein complexes serve as sensors, light-driven ion pumps, as well as light harvesting elements in many living cells. Their function, based on the interaction of pigment electrons with the sun light, is grounded in quantum physics. The function is greatly affected by geometrical constraints of the proteins that typically arrange pigments in closely interacting groups exhibiting strong inter-pigment quantum coherence in the form of excitonic coupling. The quantum mechanical properties of the pigment-protein complexes arise despite the relatively high, namely physiological, temperatures found in living cells. The pigment-protein complexes found in cells do not only avoid degradation through thermal effects, but rather exploit thermal quantum behavior to improve their functional characteristics. This is demonstrated in this chapter for the optical transitions found in pigment-protein complexes as well as for electron transfer reactions initiated by electronically excited pigments. After an introduction of pigment-protein complexes of photosynthetic light harvesting complexes, the theory of thermally assisted optical transitions and electron transfer is described and applied. The readers are introduced to a fascinating chapter of physical biology, namely quantum behavior at elevated temperatures. The resulting effects are often avoided in other fields of physics, where quantum phenomena are studied preferably under conditions of low temperature, but these effects are essential in quantum biology given the temperature preference of living cells.

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