PMID: 37908Aug 14, 1979

Redox titration of electron acceptor Q and the plastoquinone pool in photosystem II

Biochimica Et Biophysica Acta
John H Golbeck, B Kok


The primary photochemical quencher Q and the secondary electron acceptor pool in Photosystem II have been titrated. We used particles of Scenedesmus mutant No. 8 that lack System I and allowed the system to equilibrate with external redox mediators in darkness prior to measurement of the fluorescence rise curve. The titration of Q, as indicated by the dark level of Fi, occurs in two discrete steps. The high-potential component (Qh) has a midpoint potential of +68 mV (pH 7.2) and accounts for approximately 67% of Q. The pH sensitivity of the midpoint potential is -60 mV, indicating the involvement of 1 H+/e. The low-potential component (Q1) accounts for the remaining 33% of Q and shows a midpoint potential near--300 mV (pH 7.2). The plastoquinone pool, assayed as the half-time of the fluorescence rise curve, titrates as a single component with a midpoint potential 30--40 mV more oxidizing than that of Qh, i.e., at 106 mV (pH 7.2). The Em shows a pH sensitivity of -60 mV/pH unit, indicating the involvement of 1 H+/e. The observation that all 12--14 electron equivalents in the pool titrate as a single component indicates that the heterogeneity otherwise observed in the secondary acceptor system is a kinetic rather than a thermodyn...Continue Reading


Jun 1, 1993·Photosynthesis Research·Q J GroomDonald O Ort
Sep 1, 1992·Proceedings of the National Academy of Sciences of the United States of America·L NedbalJ Whitmarsh
Mar 9, 1992·FEBS Letters·Y ShahakG Hauska
Jan 23, 1985·Biochimica Et Biophysica Acta·John H Golbeck, J T Warden
Jan 1, 1983·Journal of Cellular Biochemistry·K K Karukstis, K Sauer
Jan 14, 2003·Annual Review of Biophysics and Biomolecular Structure·John H Golbeck
Jun 22, 2016·Biochimica Et Biophysica Acta·Lucie BergdollFrauke Baymann
Jan 1, 1986·Photosynthesis Research·M T BlackP Horton
Sep 7, 2019·Proceedings of the National Academy of Sciences of the United States of America·Sven De CausmaeckerA William Rutherford
Jan 26, 2020·Nature Communications·Jan M SchullerVille R I Kaila


Aug 31, 1973·Biochimica Et Biophysica Acta·B Bouges-Bocquet
Apr 8, 1969·Biochimica Et Biophysica Acta·W A Cramer, W L Butler
Nov 1, 1965·Plant Physiology·B Kok, E A Datko
Jul 5, 1967·Biochimica Et Biophysica Acta·J Amesz, D C Fork
Jul 1, 1976·Proceedings of the National Academy of Sciences of the United States of America·B KeS Sahu
Jan 18, 1974·Biochimica Et Biophysica Acta·B R Velthuys, J Amesz

Related Concepts

Fluorescence Spectroscopy

Trending Feeds


Coronaviruses encompass a large family of viruses that cause the common cold as well as more serious diseases, such as the ongoing outbreak of coronavirus disease 2019 (COVID-19; formally known as 2019-nCoV). Coronaviruses can spread from animals to humans; symptoms include fever, cough, shortness of breath, and breathing difficulties; in more severe cases, infection can lead to death. This feed covers recent research on COVID-19.

Sexual Dimorphism in Neurodegeneration

There exist sex differences in neurodevelopmental and neurodegenerative disorders. For instance, multiple sclerosis is more common in women, whereas Parkinson’s disease is more common in men. Here is the latest research on sexual dimorphism in neurodegeneration

HLA Genetic Variation

HLA genetic variation has been found to confer risk for a wide variety of diseases. Identifying these associations and understanding their molecular mechanisms is ongoing and holds promise for the development of therapeutics. Find the latest research on HLA genetic variation here.

Super-resolution Microscopy

Super-resolution microscopy is the term commonly given to fluorescence microscopy techniques with resolutions that are not limited by the diffraction of light. Here are the latest discoveries pertaining to super-resolution microscopy.

Genetic Screens in iPSC-derived Brain Cells

Genetic screening is a critical tool that can be employed to define and understand gene function and interaction. This feed focuses on genetic screens conducted using induced pluripotent stem cell (iPSC)-derived brain cells.

Brain Lower Grade Glioma

Low grade gliomas in the brain form from oligodendrocytes and astrocytes and are the slowest-growing glioma in adults. Discover the latest research on these brain tumors here.

CD4/CD8 Signaling

Cluster of differentiation 4 and 8 (CD8 and CD8) are glycoproteins founds on the surface of immune cells. Here is the latest research on their role in cell signaling pathways.

Alignment-free Sequence Analysis Tools

Alignment-free sequence analyses have been applied to problems ranging from whole-genome phylogeny to the classification of protein families, identification of horizontally transferred genes, and detection of recombined sequences. Here is the latest research.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is a disease characterized by unexplained disabling fatigue; the pathology of which is incompletely understood. Discover the latest research on chronic fatigue syndrome here.