Abstract
Recent studies of the lifetime of fluorescence after picosecond pulse excitation of photosynthetic organisms revealed relatively complex decay kinetics that indicated a sum of three exponential components with lifetimes spanning the range from about 0.1-2.5 ns. These fluorescence lifetime data were examined in the context of a simple photochemical model for photosystem II that was used previously to account for fluorescence yield data obtained during continuous illumination. The model, which consists of a single fluorescing species of antenna chlorophyll and a reaction center, shows that, in general, the decay kinetics after pulse excitation should consist of the sum of two exponential decays. The model also shows that in going from open to closed reaction centers the lifetime of fluorescence may increase much more than the yield of fluorescence and surprisingly long fluorescence lifetimes can be obtained. However, conditions can be stated where fluorescence will decay essentially as a single component and with lifetime changes that are proportional to the yield changes. A heterogeneity was also introduced to distinguish photosystem IIα units, which can transfer excitation energy among themselves but not the photosystem I, and photosystem IIβ units, which can transfer energy to photosystem I but not to other photosystem II units. It is proposed that the rather complex fluorescence lifetime data can be accounted for in large part by the simple photochemical model with the α, β heterogeneity in photosystem II.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Butler W. L., Kitajima M. Fluorescence quenching in photosystem II of chloroplasts. Biochim Biophys Acta. 1975 Jan 31;376(1):116–125. doi: 10.1016/0005-2728(75)90210-8. [DOI] [PubMed] [Google Scholar]
- Butler W. L., Strasser R. J. Tripartite model for the photochemical apparatus of green plant photosynthesis. Proc Natl Acad Sci U S A. 1977 Aug;74(8):3382–3385. doi: 10.1073/pnas.74.8.3382. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Klimov V. V., Klevanik A. V., Shuvalov V. A., Kransnovsky A. A. Reduction of pheophytin in the primary light reaction of photosystem II. FEBS Lett. 1977 Oct 15;82(2):183–186. doi: 10.1016/0014-5793(77)80580-2. [DOI] [PubMed] [Google Scholar]
- Melis A., Homann P. H. A selective effect of Mg2+ on the photochemistry at one type of reaction center in photosystem II of chloroplasts. Arch Biochem Biophys. 1978 Oct;190(2):523–530. doi: 10.1016/0003-9861(78)90306-5. [DOI] [PubMed] [Google Scholar]