Abstract
This paper analyzes, in terms of a triangular kinetic scheme, the possible effects of an intermediate in the photochemical behavior of simple heme proteins. Both steady-state and transient phenomena are analyzed. The magnitude of the quantum yield for a given system is determined by a competition between quenching and ligand detachment, measured by the two rate constants, κ-1 and κ2, respectively; as a first approximation, it can be described by a single parameter, namely the ratio κ-1/κ2. The individual values of κ-1 and κ2 can only be determined at light intensities so high that the measured quantum yield becomes itself a function of light intensity. Under these conditions the relaxation time for transient approach to the steady-state can be complex, corresponding to heavily damped chemical oscillations. It is pointed out that when the model is extended to include more than one intermediate, multiple oscillations are possible. In this more general case the system in the steady-state may also show pseudocooperativity or anticooperativity.
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- Brunori M., Bonaventura J., Bonaventura C., Antonini E., Wyman J. Carbon monoxide binding by hemoglobin and myoglobin under photodissociating conditions. Proc Natl Acad Sci U S A. 1972 Apr;69(4):868–871. doi: 10.1073/pnas.69.4.868. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GIBSON Q. H., AINSWORTH S. Photosensitivity of haem compounds. Nature. 1957 Dec 21;180(4599):1416–1417. doi: 10.1038/1801416b0. [DOI] [PubMed] [Google Scholar]
- Haldane J., Smith J. L. The Oxygen Tension of Arterial Blood. J Physiol. 1896 Dec 3;20(6):497–520. doi: 10.1113/jphysiol.1896.sp000634. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Noble R. W., Brunori M., Wyman J., Antonini E. Studies on the quantum yields of the photodissociation of carbon monoxide from hemoglobin and myoglobin. Biochemistry. 1967 Apr;6(4):1216–1222. doi: 10.1021/bi00856a035. [DOI] [PubMed] [Google Scholar]