PMID: 36138Apr 11, 1979

The buffering capacity of the internal phase of thylakoids and the magnitude of the pH changes inside under flashing light

Biochimica Et Biophysica Acta
W JungeT Runge

Abstract

The buffering capacity inside thylakoids is determined and the magnitude of flash-induced pH changes inside is calibrated in the pH range from 6.4 to 8.1. The work is based on flash-induced absorption changes of neutral red in a chloroplast suspension in which the outer phase is strongly buffered by bovine serum albumin. It is shown that neutral red is bound inside thylakoids. The binding can be described by a simple isotherm with an apparent Km = 4 microM and satruation at 1 neutral red per 17 chlorophylls. The apparent pK of neutral red is shifted from 6.6 in solution to 7.25 when bound inside. It is demonstrated that neutral red is a clean indicator of pH changes inside, i.e. when properly used it shows no response to other events. Although bound it reports pH changes which occur in the internal osmolar (aqueous) volume of thylakoids. This is obvious from the influence of chemically very different buffers on the magnitude of the absorption changes of neutral red. These act in a manner proportional to their calculated buffering capacity in aqueous solution. The intrinsic buffering capacity of the internal phase is determined with the aid of these buffers, at pH 7.2 it is between 0.8 and 1 mM (at 60 mosM). The absence of large...Continue Reading

References

Jan 1, 1993·Photosynthesis Research·J Lavergne, W Junge
Jun 25, 2013·Photosynthesis Research·Julia ZaksGraham R Fleming
Aug 23, 2003·Trends in Biochemical Sciences·Nathan N Alder, Steven M Theg
Nov 10, 2000·Journal of Photochemistry and Photobiology. B, Biology·A WardakW I Gruszecki
May 1, 1983·Quarterly Reviews of Biophysics·S W Thorne, J T Duniec
Dec 20, 2000·Proceedings of the National Academy of Sciences of the United States of America·C A SackstederDavid M Kramer
Nov 20, 2002·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·W JungeJürgen Clausen
Apr 9, 2014·Proceedings of the National Academy of Sciences of the United States of America·Sergey KoroidovJohannes Messinger
Oct 1, 1987·Proceedings of the National Academy of Sciences of the United States of America·W Junge
Apr 21, 2006·Biochimica Et Biophysica Acta·A Y MulkidjanianDmitry A Cherepanov
Jan 23, 1995·FEBS Letters·G Groth, W Junge
Nov 20, 2012·Biochemistry. Biokhimii︠a︡·A N Tikhonov
Aug 16, 2017·Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences·Geoffry A DavisDavid M Kramer

Related Concepts

Buffers
Photopsia
Darkness
ALB
Neutral Red
Chloroplasts
Xenon
Spectrophotometry
Chemicals
Etioplasts

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