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Biochemistry (Moscow)

, Volume 84, Issue 6, pp 644–651 | Cite as

Algorithm for Extracting Weak Bands Kinetics from the Transient Absorption Spectra of the Rhodobacter sphaeroides Reaction Center

  • R. A. KhatypovEmail author
  • A. M. Khristin
  • L. G. Vasilyeva
  • V. A. Shuvalov
Article

Abstract

An algorithm to extract kinetics of the ion radical bands from the strong absorption background in the transient absorption spectra of the Rhodobacter sphaeroides reaction centers upon femtosecond excitation of the primary electron donor is suggested. The rising kinetics of the transient absorption band at 1020 nm and the bleaching kinetics of the 545-nm band constructed using the proposed method are adequately fitted by the kinetic equations for sequential electron transfer from the excited primary donor to the BA (monomeric bacteriochlorophyll) molecule, and then to the HA (bacteriopheophytin serving as an electron acceptor) molecule with the rate constants of 3.5 ± 0.2 and 0.8 ± 0.1 ps, respectively. The kinetics of the bacteriochlorophyll absorption band at 600 nm shows both the ultrafast bleaching of the P870 dimer and slower bleaching of the BA monomer due to its transition to the anion radical. The plotted kinetics of the ion radical bands is in agreement with the concentration profiles of the charge-separated states produced by the global target analysis of experimental data using the model of sequential electron transfer in the reaction centers.

Keywords

femtosecond spectroscopy bacterial reaction centers electron transfer 

Abbreviations

ΔA

absorbance changes

ΔGauss

the fraction of Gauss absorption band changes

BA

monomeric BChl in the active chain of cofactors

BChl

bacteriochlorophyll

HA

bacteriopheophytin serving as an electron acceptor

P

primary electron donor

QA

primary quinone acceptor

QB

secondary quinone acceptor

RC

reaction center

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Notes

Acknowledgements

The authors are grateful to A. Ya. Shkuropatov and A. A. Zabelin for their help during the study and discussion of the results.

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Copyright information

© Pleiades Publishing, Ltd. 2019

Authors and Affiliations

  • R. A. Khatypov
    • 1
    Email author
  • A. M. Khristin
    • 1
  • L. G. Vasilyeva
    • 1
  • V. A. Shuvalov
    • 1
    • 2
  1. 1.Institute of Basic Biological Problems, Pushchino Scientific Center for Biological ResearchRussian Academy of SciencesPushchino, Moscow RegionRussia
  2. 2.Semenov Institute of Chemical PhysicsRussian Academy of SciencesMoscowRussia

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