title: Thermal Adaptability of the Light-Harvesting Complex 2 from Thermochromatium tepidum: Temperature-Dependent Excitation Transfer Dynamics.
abstract: The photosynthetic purple bacterium Thermochromatium (Tch.) tepidum is a thermophile that grows at an optimal temperature of ∼50 °C. We have investigated, by means of steady-state and time-resolved optical spectroscopies, the effects of temperature on the near-infrared light absorption and the excitation energy transfer (EET) dynamics of its light-harvesting complex 2 (LH2), for which the mesophilic counterpart of Rhodobacter (Rba.) sphaeroides 2.4.1 (∼30 °C) was examined in comparison. In a limited range around the physiological temperature (10-55 °C), the B800-to-B850 EET process of the Tch. tepidum LH2, but not the Rba. sphaeroides LH2, was found to be characteristically temperature-dependent, mainly because of a temperature-tunable spectral overlap. At 55 °C, the LH2 complex from Tch. tepidum maintained efficient near-infrared light harvesting and B800-to-B850 EET dynamics, whereas this EET process was disrupted in the case of Rba. sphaeroides 2.4.1 owing to the structural distortion of the LH2 complex. Our results reveal a remarkable thermal adaptability of the light-harvesting function of Tch. tepidum, which could enhance our understanding of the survival strategy of this thermophile in response to environmental challenges.
authors.affiliation: Department of Chemistry, Renmin University of China , Beijing 1000872, P. R. China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Chemistry, Renmin University of China , Beijing 1000872, P. R. China.
authors.forename: Ning-Jiu
authors.initials: NJ
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, Renmin University of China , Beijing 1000872, P. R. China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Renmin University of China , Beijing 1000872, P. R. China.
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Fu
authors.affiliation: Faculty of Science, Ibaraki University , Mito 310-8512, Japan.
authors.forename: Long-Jiang
authors.initials: LJ
authors.lastname: Yu
authors.affiliation: Department of Chemistry, Renmin University of China , Beijing 1000872, P. R. China.
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Zhang
authors.affiliation: Faculty of Science, Ibaraki University , Mito 310-8512, Japan.
authors.forename: Zheng-Yu
authors.initials: ZY
authors.lastname: Wang-Otomo