PMID: 45396Feb 1, 1979

The quantum yield of flash-induced proton release by bacteriorhodopsin-containing membrane fragments

Biophysical Journal
D R Ort, W W Parson


The quantum yield of proton release by bacteriorhodopsin was measured from volume changes after excitation of purple membrane fragments by short flashes. At low ionic strengths, about 0.25 mol of protons is released per einstein absorbed. This agrees well with quantum yields reported recently for the conversion of bacteriorhodopsin into a metastable state (M) that absorbs near 412 nm. However, the quantum yield of proton release increases gradually with increasing ionic strength; it plateaus with a value of 0.43 +/- 0.03 at ionic strengths above 200 mM. Changing the ionic strength has no detectable effect on the quantum yield of formation of the M spectral state. It thus appears that as many as two protons can be released and rebound in each photochemical cycle at high ionic strengths. The quantum yield of proton release is essentially independent of pH over the range 6.0-8.75. The quantum yield decreases with increasing flash strength, apparently due to photoreversal of the initial photochemical reaction.


Apr 1, 1992·Journal of Bioenergetics and Biomembranes·J K Lanyi
Jan 1, 1985·The Journal of Membrane Biology·M E DumontF M Richards
Mar 10, 2001·Journal of Photochemistry and Photobiology. B, Biology·K HuY Zhang
Aug 1, 1980·Proceedings of the National Academy of Sciences of the United States of America·C CarmeliL Packer
Jan 1, 1983·Proceedings of the National Academy of Sciences of the United States of America·T Marinetti, D Mauzerall
Nov 1, 1984·Proceedings of the National Academy of Sciences of the United States of America·Q LiT G Ebrey
Mar 1, 1984·Proceedings of the National Academy of Sciences of the United States of America·G S HarbisonR G Griffin
Nov 1, 1983·Archives of Biochemistry and Biophysics·E LamL Packer
Aug 1, 1988·Photochemistry and Photobiology·R Renthal, A Hollub

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