TY - JOUR
T1 - Comparing the temperature dependence of photosynthetic electron transfer in chloroflexus aurantiacus and rhodobactor sphaeroides reaction centers
AU - Guo, Zhi
AU - Lin, Su
AU - Xin, Yueyong
AU - Wang, Haiyu
AU - Blankenship, Robert E.
AU - Woodbury, Neal
PY - 2011/9/29
Y1 - 2011/9/29
N2 - The process of electron transfer from the special pair, P, to the primary electron donor, HA, in quinone-depleted reaction centers (RCs) of Chloroflexus (Cf.) aurantiacus has been investigated over the temperature range from 10 to 295 K using time-resolved pump-probe spectroscopic techniques. The kinetics of the electron transfer reaction, P* → P+H A-, was found to be nonexponential, and the degree of nonexponentiality increased strongly as temperature decreased. The temperature-dependent behavior of electron transfer in Cf. aurantiacus RCs was compared with that of the purple bacterium Rhodobacter (Rb.) sphaeroides. Distinct transitions were found in the temperature-dependent kinetics of both Cf. aurantiacus and Rb. sphaeroides RCs, at around 220 and 160 K, respectively. Structural differences between these two RCs, which may be associated with those differences, are discussed. It is suggested that weaker protein-cofactor hydrogen bonding, stronger electrostatic interactions at the protein surface, and larger solvent interactions likely contribute to the higher transition temperature in Cf. aurantiacus RCs temperature-dependent kinetics compared with that of Rb. sphaeroides RCs. The reaction-diffusion model provides an accurate description for the room-temperature electron transfer kinetics in Cf. aurantiacus RCs with no free parameters, using coupling and reorganization energy values previously determined for Rb. sphaeroides, along with an experimental measure of protein conformational diffusion dynamics and an experimental literature value of the free energy gap between P* and P +HA-.
AB - The process of electron transfer from the special pair, P, to the primary electron donor, HA, in quinone-depleted reaction centers (RCs) of Chloroflexus (Cf.) aurantiacus has been investigated over the temperature range from 10 to 295 K using time-resolved pump-probe spectroscopic techniques. The kinetics of the electron transfer reaction, P* → P+H A-, was found to be nonexponential, and the degree of nonexponentiality increased strongly as temperature decreased. The temperature-dependent behavior of electron transfer in Cf. aurantiacus RCs was compared with that of the purple bacterium Rhodobacter (Rb.) sphaeroides. Distinct transitions were found in the temperature-dependent kinetics of both Cf. aurantiacus and Rb. sphaeroides RCs, at around 220 and 160 K, respectively. Structural differences between these two RCs, which may be associated with those differences, are discussed. It is suggested that weaker protein-cofactor hydrogen bonding, stronger electrostatic interactions at the protein surface, and larger solvent interactions likely contribute to the higher transition temperature in Cf. aurantiacus RCs temperature-dependent kinetics compared with that of Rb. sphaeroides RCs. The reaction-diffusion model provides an accurate description for the room-temperature electron transfer kinetics in Cf. aurantiacus RCs with no free parameters, using coupling and reorganization energy values previously determined for Rb. sphaeroides, along with an experimental measure of protein conformational diffusion dynamics and an experimental literature value of the free energy gap between P* and P +HA-.
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U2 - 10.1021/jp204239v
DO - 10.1021/jp204239v
M3 - Article
C2 - 21827152
AN - SCOPUS:80053107244
SN - 1520-6106
VL - 115
SP - 11230
EP - 11238
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 38
ER -