When the cytochrome b 6 / f complex from chloroplasts is incorporated into liposomes, reduction of external plastocyanin by plastoquinol is stimulated under uncoupling conditions. An extra H + /e − is ejected from the...
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When the cytochrome b 6 / f complex from chloroplasts is incorporated into liposomes, reduction of external plastocyanin by plastoquinol is stimulated under uncoupling conditions. An extra H + /e − is ejected from the vesicles during the reaction, in addition to the scalar proton liberated from plastoquinol. This is stimulated by valinomycin/K + and abolished under uncoupling conditions. furthermore, the formation of a membrane potential during the reaction, negative inside the vesicles, is observed with the help of carbocyanine dyes. We conclude that the cytochrome b 6 / f complex, like the cytochrome bc 1 from mitochondria, functions as an electrogenic proton translocator.
f 1 -ATPases from bovine mitochondria and Escherichia coli both contain 5 subunits named α, β, γ, δ and ε. Sequence analysis shows that the δ subunits are not related, nor are the ε subunits. The counterpart of...
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f 1 -ATPases from bovine mitochondria and Escherichia coli both contain 5 subunits named α, β, γ, δ and ε. Sequence analysis shows that the δ subunits are not related, nor are the ε subunits. The counterpart of mitochondrial δ is bacterial ε. The subunit equivalent to bacterial δ is mitochondrial oligomycin sensitivity conferral protein.
Oxidant-induced reduction of cytochrome [Cyt] b6 is completely dependent on a reduced component within the isolated Cyt B6-f complex. This component can be reduced by dithionite or by NADH/N-methylphenazonium methosul...
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Oxidant-induced reduction of cytochrome [Cyt] b6 is completely dependent on a reduced component within the isolated Cyt B6-f complex. This component can be reduced by dithionite or by NADH/N-methylphenazonium methosulfate. It is a 2H+/2e- carrier with a midpoint potential of 100 mV at pH 7.0, which is very similar to the midpoint potential of the plastoquinone pool in chloroplasts. Oxidant-induced reduction of Cyt b6 is stimulated by plastoquinol-1 as well as by plastoquinol -90. The midpoint potential of the transient reduction of Cyt b/6 was not shifted by added plastoquinol. Quinone analysis of the purified Cyt b6-f complex revealed .apprx. 1 plastoquinone/Cyt f. The endogenous quinone is heterogeneous, a form more polar than plastoquinone A, probably plastoquinone-C, dominating. This is different from the thylakoid membrane where plastoquinone-A is the main quinone. The endogenous quinone can be extracted from the lyophilized Cyt b6-f complex by acetone, but not by hydrocarbon solvents. Oxidant-induced reduction of Cyt b6 was observed in the lyophilized and hexane-extracted complex, but was lost in the acetone-extracted complex. Reconstitution was achieved either with plastoquinol-1 or plastoquinol-9, suggesting that a plastoquinol molecule is involved in oxidant-induced reduction of Cyto b6.
The kinetics of redox changes of P-700, plastocyanin and cytochrome [Cyt] f in chloroplasts suspended in a fluid medium at sub-zero temperatures were studied following excitation of the chloroplasts with either a sing...
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The kinetics of redox changes of P-700, plastocyanin and cytochrome [Cyt] f in chloroplasts suspended in a fluid medium at sub-zero temperatures were studied following excitation of the chloroplasts with either a single-turnover flash, a series offlashes or continuous light. The kinetics of reduction of P-700+ and those of oxidation of plastocyanin are consistent with a bimolecular reaction between these 2 components as previously suggested (Olsen et al. 1980). Cyt f shows heterogeneity with respect to its kinetics of oxidation by photosystem [PS] I. In contrast to the situation when plastoquinol is the electron donor, reduction of Cyt f by electrons derived from diaminodurene occurs with sigmoidal kinetics that shows a good fit to an apparent equilibrium constant of 12 between the Cyt and P-700. The rate of electron transfer from plastoquinol to PS I depends on the redox state of the plastoquinone pool. In relation to current ideas about the lateral heterogeneity of PS I and PS II in the thylakoid membrane, the results are consistent with the function of plastocyanin as a mobile carrier of electrons in the intrathylakoid space.
The leaf alkanes of P. argentatum (guayule), P. tomentosum var. stramonium, P. fruticosum var. trilobatum, and the 1st filial (f1) generations obtained from crosses with guayule were investigated by GC [gas chromatogr...
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The leaf alkanes of P. argentatum (guayule), P. tomentosum var. stramonium, P. fruticosum var. trilobatum, and the 1st filial (f1) generations obtained from crosses with guayule were investigated by GC [gas chromatography] and mass spectrometry[ms] and are useful in chemotaxonomic studies. The identified n-alkanes ranged from C19 to C40 with either n-C29 or n-C31 as the main component. The alkane chemistry of guayule with n-C31 being the main component predominated in most of the f1 hybrids. The presence of iso-branched alkanes (C27, C29, C31) in P. tomentosum and its hybrids could be detected by GC/MS. These preliminary investigations indicate that epiculticular wax alkanes can be useful in inheritance studies of guayule and its hybrids.
Denote C0（I, I） as the set of all continuous mappings of the interval. Let f∈C0（I, I）, for any positive integer n, we define fn inductively byf1= f, fn=f·fn-1 and f0=the identity *** 1. Let p∈I. If. there e...
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Denote C0（I, I） as the set of all continuous mappings of the interval. Let f∈C0（I, I）, for any positive integer n, we define fn inductively byf1= f, fn=f·fn-1 and f0=the identity *** 1. Let p∈I. If. there exists a positive integer n, such that fn（p）=p, then p is called a periodic point off.
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