ISSN:
1573-6881
Keywords:
Bacterial photosynthesis
;
cytochrome
;
hydrogen bond
;
infrared spectroscopy, membrane protein
;
purple bacteria
;
site-directed mutagenesis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract The primary electron donor in the photosynthetic reaction center from purple bacteria is a bacteriochlorophyll dimer containing four conjugated carbonyl groups that may form hydrogen bonds with amino acid residues. Spectroscopic analyses of a set of mutant reaction centers confirm that hydrogen bonds can be formed between each of these carbonyl groups and histidine residues in the reaction center subunits. The addition of each hydrogen bond is correlated with an increase in the oxidation potential of the dimer, resulting in a 355-mV range in the midpoint potential. The resulting changes in the free-energy differences for several reactions involving the dimer are related to the electron transfer rates using the Marcus theory. These reactions include electron transfer from cytochrome c2 to the oxidized dimer, charge recombination from the primary electron acceptor quinone, and the initial forward electron transfer.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02110097
Permalink
