These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Phosphorescence of intermediates of the terminal stage of chlorophyll biosynthesis in plants.
    Author: Krasnovsky AA, Belyaeva OB, Kovalev YV, Ignatov NV, Litvin FF.
    Journal: Biochemistry (Mosc); 1999 May; 64(5):587-91. PubMed ID: 10381622.
    Abstract:
    Phosphorescence (radiative triplet state deactivation) of the intermediates involved in chlorophyll a photobiosynthesis from protochlorophyllide (Pchld) was found in greening leaves at 77K. Photoactive Pchld forms showed phosphorescence with the major spectral bands at 920 and 970 nm and 2.5-3 msec lifetime. Photochemical formation of the primary non-fluorescent intermediates (NFI) was accompanied by quenching of Pchld fluorescence and phosphorescence, phosphorescence quenching being less efficient by a factor of two. The primary chlorophyllide form Chld 684/676 that appeared as a result of NFI dark transformation showed phosphorescence with a maximum at 980 nm and 2 msec lifetime. Secondary chlorophyllide forms Chld 690/680 and Chld 695/685, the products of photochemical Chld 684/676 transformation and intermediates in biosynthesis of chlorophyll of the light harvesting complex, emitted phosphorescence with maxima at 990-995 and 1005-1010 nm and 1-2 msec lifetimes. Chlorophyll Chl 675/668, the major product of the non-photochemical "side" reaction of Chld 684/676 that probably underlies the biogenesis of photosystem II, exhibited phosphorescence with a maximum at 954-960 nm and 2 msec lifetime. Analysis of the difference spectra of the side reaction products revealed a minor 930 nm phosphorescence band that might correspond to pheophytin a formed via the "side" reaction. Triplet states of the intermediates were not quenched by carotenoids, and the quantum yields of their population at 77K were not less than 10%. Under physiological conditions the triplet intermediates might be involved in photochemical reactions, in particular, in singlet oxygen photogeneration and photodestruction of the photosynthetic apparatus.
    [Abstract] [Full Text] [Related] [New Search]