Studies on the Photoreduction of Quinone Analogues in Bacterial Photosynthetic Reaction Centers
McComb, James Craig
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/70375
Description
Title
Studies on the Photoreduction of Quinone Analogues in Bacterial Photosynthetic Reaction Centers
Author(s)
McComb, James Craig
Issue Date
1986
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Abstract
The kinetics and thermodynamics of photo-induced electron transfer were studied in photosynthetic reaction centers from Rhodopseudomonas sphaeroides, R-26 mutant, which were chemically depleted of ubiquinone (Q-10) and reconstituted with various quinone analogues. Ubiquinone prenylogues were found to reconstitute both the primary and secondary quinone acceptor function of the protein, with shorter-chained prenylouges giving rise to smaller electron transfer equilibrium constant (= Q$\sb{\rm A}$Q$\sb{\rm B}\sp{-}$/Q$\sb{\rm A}\sp{-}$Q$\sb{\rm B}$), faster post-flash association kinetics (P$\sp{+}$Q$\sb{\rm A}\sp-$ + Q $\rightarrow$ P$\sp{+}$Q$\sb{\rm A}\sp{-}$Q$\sb{\rm B},$ and thermodynamically less stable semiquinones (P$\sp{+}$Q$\sb{\rm A}$Q$\sb{\rm B}\sp{-} \rightarrow$ P$\sp{+}$Q$\sb{\rm A}$ + Q$\sp{-}$). Plastoquinone A, menaquinone-8, and other prenylquinone analogues were found to not restore secondary electron acceptor function. 2,3 dimethyl, 5,6 dimethoxy benzoquinone, however, did restore functional Q$\sb{\rm B}$ activity. Synthetic analogues such as duroquinone or anthraquinone did not restore secondary electron transfer, and high redox potential analogues such as benzoquinone were found to transfer charge out of the protein binding sites and reacted through a mechanism involving the quinone pool. The role of the isoprenoid side chain was analysed in terms of the enthalpy-entropy compensation effect, in which the side chain structure gave rise to cooperative interactions of the protein with the quinone ring structure.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
