Abstract
The quenching of the triplet state of Zn-cytochrome c in electrostatic complexes with cytochrome oxidase and its soluble Cu A domain has been studied by laser flash photolysis. The triplet state of free Zn-cytochrome c decayed with a rate of about 200 s −1. With the oxidase, biphasic decay with rate constants of 2 × 10 5 and 2 × 10 3 s −1, respectively, was observed. At high ionic strength ( I = 0.2) the decay was the same as with free Zn-cytochrome c. The quenching was also eliminated by reduction of the oxidase. The decay rate in the complex with the Cu A domain was 4 × 10 4 s −1. The results are interpreted in terms of rapid electron transfer to Cu A and a slower one to cytochrome a. No electron transfer products were detected, because the backward reaction is faster than the forward one. This can be explained by the high driving force (1.1 eV) for the forward electron transfer, taking the system into the inverted Marcus region. The distance in the electrostatic complex between cytochrome c and the electron acceptor, presumed to be Cu A, is calculated to be 16 Å.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
