PMID: 36908Jun 5, 1979

Quantitative estimation of the photosynthetic proton binding inside the thylakoids by correlating internal acidification to external alkalinisation and to oxygen evolution in chloroplasts

Biochimica Et Biophysica Acta
F Haraux, Y de Kouchkovsky

Abstract

The external alkalinisation delta pHe, or the rate of oxygen evolution vO2, of a suspension of envelope-free chlorplasts was correlated with their internal acidification, estimated from the transmembrane delta pHei. Knowing the external buffer value, the concentration of the total protons moved Hi was calculated from the delta pHe, measured with a glass electrode ([Hi] was also obtained from vO2), and the free proton concentration [Hi+] was determined from delta pHei, measured with 9-aminoacridine. This gives a ratio gamma i = theta [Hi]/theta [Hi+], which is independent of the thylakoids internal volume. Within a large pHi range, scanned by varying the light intensity, gamma i was kept reasonably constant; it was hardly sensitive to pHi. This apparent invariability implies a continuous change of the internal buffer value beta i with pHi, since beta i/gamma i = -2.3.....10pHi, a relationship which inlcudes neither the total concentration of protonizable groups [Ai] nor pKi. As gamma i approximately Ki[Ai]/(Ki + [Hi+i]2, to keep gamma i constant when pHi drops, pKi and [Ai] must increase. This may be achieved by a progressive unmasking of anionic functions, initially inaccessible in the membrane. The relative slowness of this pr...Continue Reading

References

Jul 7, 1977·Biochimica Et Biophysica Acta·J E TillbergU Heber
Apr 1, 1974·Proceedings of the National Academy of Sciences of the United States of America·G HindS Izawa
Aug 9, 1972·Biochimica Et Biophysica Acta·D W DeamerA R Crofts
Jun 1, 1977·Journal of Bioenergetics and Biomembranes·E De Benedetti, F M Garlaschi

Citations

Aug 1, 1992·The International Journal of Biochemistry·W Nel, S E Terblanche
May 1, 1983·Quarterly Reviews of Biophysics·S W Thorne, J T Duniec
Mar 16, 1981·Biochemical and Biophysical Research Communications·Y de Kouchkovsky, F Haraux
Nov 13, 1990·European Journal of Biochemistry·H StrotmannW Baum

Related Concepts

Etioplasts
Darkness
Respiratory Chain
Hydrogen-Ion Concentration
Light
Mathematics
Dioxygen
Dark Reactions of Photosynthesis
Fluorescence Spectroscopy

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