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  • 11
    Electronic Resource
    Electronic Resource
    Immobilized plant thylakoid membranes as a biosensor for herbicides (1990)
    Springer
    Biotechnology techniques 4 (1990), S. 363-368 
    Details
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Thylakoid membranes isolated from spinach leaves were used as the biological sensing material to elaborate a biosensor for the detection of small amount of the herbicides atrazine and diuron. Free and immobilized thylakoid membranes were compared for their responses to inhibition by herbicides by following the variation of the photocurrent. Immobilized thylakoid membranes were twice as sensitive to inhibition by herbicides than the native thylakoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157437
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  • 12
    Electronic Resource
    Electronic Resource
    The 16 and 23 kDa extrinsic polypeptides and the associated Ca2+ and Cl- modify atrazine interaction with the photosystem II core complex (1990)
    Springer
    Photosynthesis research 24 (1990), S. 221-227 
    Details
    ISSN: 1573-5079
    Keywords: atrazine ; calcium ; chloride ; depleted-photosystem II ; DCIP-photoreduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The oxygen evolving complex of photosystem II (PS II) contains three extrinsic polypeptides of approximate molecular weights 16, 23 and 33 kDa. These polypeptides are associated with the roles of Cl-, Ca2+ and Mn2+ in oxygen evolution. We have shown that selective removal of 16 and 23 kDa polypeptides from the above complex by NaCl washing of PS II enriched membrane fragments renders the PS II core complex more susceptible to the herbicide atrazine. On the other hand, when both native and depleted preparations were resupplied with exogenous Ca2+ and Cl-, we obtained a reduction of atrazine inhibition which was much stronger in the depleted preparations than in the native ones. It is concluded that removal of 16 and 23 kDa polypeptides in general, and disorganization of associated Ca2+ and Cl- in particular, enhances atrazine penetration to its sites of action in the vicinity of the PS II complex. The above could be interpreted if we assume a reduced plastoquinone affinity at the QB (secondary plastoquinone electron acceptor) pocket of D1 polypeptide following transmembranous modifications caused by the depletion of these polypeptides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00032309
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  • 13
    Electronic Resource
    Electronic Resource
    Variable thermal dissipation in a Photosystem I submembrane fraction (1994)
    Springer
    Photosynthesis research 40 (1994), S. 263-268 
    Details
    ISSN: 1573-5079
    Keywords: photoacoustie spectroscopy ; Photosystem I ; electron transport ; thermal dissipation ; plastoquinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoacoustic spectroscopy was used to study the thermal deactivation processes in a Photosystem I submembrane fraction isolated from spinach. A large part of the thermal dissipation was variable. The yield of this variable thermal emission depended on the redox state of the Photosystem. It increased with the measuring modulated light intensity coinciding with the gradual closure of the reaction centers. Thermal deactivation was maximal when the reaction centers were closed by a saturating illumination. Extrapolation of the data at zero light intensity indicated that the yield of non-variable thermal emission represented about 37% of the maximal emission. The presence of methylviologen as artificial electron acceptor decreased the yield of variable thermal emission whereas inhibition following heat stress treatments increased it. The significance of the variable and non-variable components of thermal dissipation is discussed and the measured energy storage is suggested to originate from the reduction of the plastoquinone pool during cyclic electron transport around Photosystem I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034775
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  • 14
    Electronic Resource
    Electronic Resource
    Heat-stress stimulation of oxygen uptake by Photosystem I involves the reduction of superoxide radicals by specific electron donors (1993)
    Springer
    Photosynthesis research 35 (1993), S. 213-218 
    Details
    ISSN: 1573-5079
    Keywords: electron transport ; oxygen uptake ; Photosystem I ; superoxide radicals ; superoxide dismutase ; heat stress ; electron donors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Photosystem I submembrane fraction isolated from spinach was used to study the mechanism of heat-stress stimulation of oxygen uptake by the photosystem. Various artificial electron donors were shown to generate electron transport reactions with various degrees of thermally induced stimulation. A strong stimulation was observed with durohydroquinone as electron donor with a maximal effect at 50 °C. The degree of stimulation obtained was independent from the redox potential of the electron donors and from their oxidation site because the enzyme superoxide dismutase fully inhibited the stimulation. Instead, it is proposed that thermal stress causes the release of membrane bound superoxide dismutase from the thylakoids thus allowing the reduced form of electron donors with specific properties to reduce O2 − radicals to H2O2 besides the usual disproportionation of O2 − into O2 and H2O2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016552
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  • 15
    Electronic Resource
    Electronic Resource
    The efficiency of electron transfer from QA − to the donor side of Photosystem II decreases during induction of photosynthesis: Evidences from chlorophyll fluorescence and photoacoustic techniques (1996)
    Springer
    Photosynthesis research 47 (1996), S. 13-20 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; photoacoustics ; Photosystems I and II ; photosynthetic induction ; reaction centers (active, inactive) ; quinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amplitudes ratio of the fast and slow phases (Afast/Aslow) in the kinetics of the dark relaxation of variable chlorophyll fluorescence (FV) was studied after various periods of illumination of dark-adapted primary barley leaves. Simultaneously, photosynthetic activity was monitored using the photoacoustic technique and the photochemical and non-photochemical fluorescence quenching parameters. The ratio Afast/Aslow changed with the preceding illumination time in a two-step manner. During the first stage of photosynthetic induction (0–20 s of illumination), characterized by a drop in O2-dependent photoacoustic signal following an initial spike and by a relatively stable small value of photochemical FV quenching, the ratio Afast/Aslow remained practically unaltered. During the second stage (20–60 s of illumination), when both the rate of O2 evolution and the photochemical FV quenching were found to be sharply developed, a marked increase in the above ratio was also observed. A linear correlation was found between the value of the photochemical quenching and the ratio Afast/Aslow during the second phase of photosynthetic induction. It is concluded that the slow phase appearing in the kinetics of FV dark relaxation is not due to the existence of Photosystem II reaction centres lacking the ability to reduce P700+ with high rates, but is instead related to the limitation of electron release from Photosystem I during the initial stage of the induction period of photosynthesis. This limitation keeps the intersystem electron carriers in the reduced state and thus increases the probability of back electron transfer from QA − to the donor side of Photosystem II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017749
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  • 16
    Electronic Resource
    Electronic Resource
    Hg2+, Cu2+, and Pb2+ -induced changes in Photosystem II photochemical yield and energy storage in isolated thylakoid membranes: A study using simultaneous fluorescence and photoacoustic measurements (1999)
    Springer
    Photosynthesis research 59 (1999), S. 167-174 
    Details
    ISSN: 1573-5079
    Keywords: cyclic electron transport ; fluorescence ; metal ions ; Photosystem II ; thermal dissipation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Simultaneous fluorescence and photoacoustic measurements have been used to study the effects of metal ions (copper, lead, and mercury) during dark incubation of thylakoid membranes. The values of the chlorophyll fluorescence parameters Fo (initial fluorescence yield with the reaction centers in the open state), Fm (maximal fluorescence yield), Ft (steady state fluorescence yield) and the calculated parameters, Φo (maximal quantum yield of Photosystem II photochemistry) and Φt (actual quantum yield of Photosystem II photochemistry), strongly decreased in the presence of the metal ions coinciding with an increase in the non-photochemical deexcitation rate constant k(N). It was observed that photosynthetic energy storage measured by photoacoustic spectroscopy also decreased but a large portion of energy storage remained unaffected even at the highest metal ion concentrations used. A maximal inhibition of photosyntheti c energy storage of 80% and 50% was obtained with Hg2+ and Cu2+-treated thylakoids, respectively, while energy storage was insensitive to Pb2+. The results are consistent with the known predominant inhibition of the donor side of Photosystem II by the metal ions. The insensitive portion of energy storage is attributed to the possible recurrence of cyclic electron transport around Photosystem II that would depend on the extent of inhibition produced on the acceptor side by the metal ion used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006194621553
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  • 17
    Electronic Resource
    Electronic Resource
    Potential for use of a cyanobacterium Synechocystis sp. immobilized in poly(vinylalcohol): Application to the detection of pollutants (1999)
    Springer
    Biotechnology techniques 13 (1999), S. 559-562 
    Details
    ISSN: 1573-6784
    Keywords: cyanobacterium ; immobilization ; photoelectrochemical cell ; poly(vinylalcohol) ; pollutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A cyanobacterium, Synechocystis sp. PCC 6803, was immobilized by entrapment in poly(vinylalcohol) bearing styrylpyridinium groups. Its properties in a single-compartment micro-photoelectrochemical cell using platinum electrodes in potentiosatic mode were compared with the native material. The operational activity was measured in the presence of an electrolytic solution containing 20 mM sodium phosphate, 0.15 mM NaCl and 1 mM MgCl2. The best conditions of use are pH 7.0, 38 °C and a 2,5-dichlorobenzoquinone concentration equal to 350 μM with native cyanobacteria or pH 6.5, 25 °C and 500 μM 2,5-dichlorobenzoquinone after entrapment. Using this procedure, the photocurrent could be inhibited by pollutants such as Diuron or HgCl2. After entrapment, the detection limits (corresponding to a 10% inhibition) were respectively 0.5 μM and 50 μM for Diuron and HgCl2 after five minutes of incubation. A permeabilization technique was used to increase sensitivity of the procedure to the detection of HgCl2 (25% inhibition with 50 μM after five minutes of incubation).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008991531206
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  • 18
    Electronic Resource
    Electronic Resource
    Photocurrent genration by thylakoid membranes immobilized in an albumin-glutaraldehyde cross-linked matrix (1988)
    Springer
    Biotechnology letters 10 (1988), S. 133-136 
    Details
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Thylakoid membranes immobilized in an albumin-glutaraldehyde cross-linked matrix were used for photocurrent generation by a photoelectrochemical cell in potentiostatic mode. This type of preparation was quite suited for such application because it retains a substantial volume of electrolyte within the porous network formed. This property allowed for introducing electron transfer inhibitors and artificial electron acceptors and further it permitted proper migration of electroactive species from the thylakoid membranes to the working electrode as required for efficient photocurrent generation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01024640
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  • 19
    Electronic Resource
    Electronic Resource
    The photosynthetic partial reactions involved in photoelectrochemical current generation by thylakoid membranes (1987)
    Springer
    Biotechnology letters 9 (1987), S. 111-116 
    Details
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A thylakoids containing photoelectrochemical cell was used to monitor the photocurrent under photentiostatic mode using specific electron donnors and acceptors, and inhibitors of electron transfer. It is shown that both photosystem I and II can generate a photocurrent under the appropriate conditions. The photocurrent was also monitored in the absence of oxygen evolution thus suggesting a possible application for hydrogenase catalysed hydrogen production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032748
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  • 20
    Electronic Resource
    Electronic Resource
    A fast bioassay for phytotoxicity measurements using immobilized photosynthetic membranes (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 178-183 
    Details
    ISSN: 0006-3592
    Keywords: bioassay ; phytotoxicity ; photosynthesis ; immobilized membranes ; oxygen evolution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The potential of thylakoid membranes immobilized in an albumin-glutaraldehyde crosslinked matrix in a fast bioassay for phytotoxicity measurements in aqueous samples is studied. Free and immobilized preparations are compared for their electron transport activity measured as the initial rate of oxygen evolution with 2,5-cichlorobenzoquinone as the artificial electron acceptor. Immobilized thylakoids were much stable under storage conditions; in the dark, at 4°C, they were fully stable in terms of photosynthetic activity for a period of 200 h. The immobilized membranes were as sensitive as the free thylakoids for the detection of most of the compounds tested (metal cations, sulfite, nitrite, and herbicides), all known as inhibitors of photosynthetic electron transport. In some instances, the immobilized preparations were even more sensitive than the free counterparts. The sensitivity could be further increased by lowering chlorophyll concentration in the assay. The short incubation period required (∼10 to 15 min) and the small volume of the assay (3 mL) suggest that this type of material should be useful in the detection of locations or effluents with phytotoxic character. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440206
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