Electron–Phonon Coupling in Cyanobacterial Photosystem I

• Published in: The journal of physical chemistry. B Vol. 122; no. 33; pp. 7943 - 7955
• Main Authors: Cherepanov, Dmitry A, Milanovsky, Georgy E, Gopta, Oksana A, Balasubramanian, Ramakrishnan, Bryant, Donald A, Semenov, Alexey Yu, Golbeck, John H
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 23.08.2018
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/acs.jpcb.8b03906

One of the fundamental problems in biophysics is whether the protein medium at room temperature can be properly treated as a fluid dielectric or whether its dynamics is determined by a highly ordered molecular structure resembling the properties of crystalline and amorphous solids. Here, we measured the recombination between reduced A1 and the oxidized chlorophyll special pair P700 over a wide temperature range using preparations of photosystem I from the cyanobacterium Synechococcus sp. PCC 7002 depleted of the iron–sulfur clusters. We found that the dielectric properties of the protein matrix in early electron transfer reactions of photosystem I resemble the behavior of solids that require an implicit treatment of electron–phonon coupling even at ambient temperatures. The quantum effects of electron–phonon coupling in proteins could account for a variety of phenomena, such as the weak sensitivity of electron transfer in pigment–protein complexes to changing environmental conditions including temperature, driving force, polarity, and chemical composition.