Gert Schansker - Academia.edu (original) (raw)

Papers by Gert Schansker

Significant progress has been made recently in probing the lower S-states by EPR spectroscopy. Th... more Significant progress has been made recently in probing the lower S-states by EPR spectroscopy. The S1 state previously characterised by a broad integer spin EPR signal at g= 4.8 [1, 2] has been shown more recently to exhibit an alternative multiline signal at g=12. The latter signal is detected in Synechocystis preparations but also, after removal of the 23 and 17 kDa extrinsic proteins, in spinach preparations [3]. A half integer spin signal has been recently detected in the S0 state produced either by chemical reduction [4] or after the 3rd flash in a flash sequence [5, 6]. The presence of 0.5–3% methanol is required for the observation of the weak hyperfine structure of the signal, but the signal is also observed as a broad derivative in the absence of methanol [6].

Molecular mechanisms of photoinhibition are clarified on the basis of experiments with leaves and... more Molecular mechanisms of photoinhibition are clarified on the basis of experiments with leaves and isolated chloroplasts of peas and triazine-resistant and susceptible Chenopodium plants.

Biochimica Et Biophysica Acta - Bioenergetics, Sep 1, 1996

The photosynthetic apparatus can be damaged by light energy in the process of photoinhibition. Th... more The photosynthetic apparatus can be damaged by light energy in the process of photoinhibition. The target of this photoinhibition is mainly photosystem II (PSII). The mechanism leading to photoinhibitory damage is not yet known. We have characterized photoinhibition by measuring the photoinactivation of electron transport rates using the electron acceptors silicomolybdate and ferricyanide at different irradiance levels and different pH values. The effects of light on the donor side of PSII were measured with silicomolybdate, the effects on the acceptor side were measured with ferricyanide. We observed that photoinactivation of both donor and acceptor side of PSII are light dose-dependent, donor and acceptor side inactivation being independent processes. The donor side of PSII is less sensitive to photoinhibition than the acceptor side. The difference in pH dependence of donor and acceptor side photoinactivation leads us to propose that light-induced release of bicarbonate from PSII is a primary event leading to photoinhibition. In addition, we report that a photoinhibitory treatment increases the proton permeability of thylakoid membranes. This increase seems to be related to the presence of inactivated PSII reaction centers. It is suggested that radicals formed by inactivated PSII reaction centers causing lipid peroxidation are responsible.

The life of the Groningen (Grootegast) judge and freehold farmer Tonnis Gerrits during the first ... more The life of the Groningen (Grootegast) judge and freehold farmer Tonnis Gerrits during the first half of the 80-year war is depicted in this article, Next to his personal life (including two marriages and a possible bigamous relation), information is given about his family background (with a prioress as a niece) and his ten children. Most ofl his off-spring moved downward socially, with one son even accidentally killing another one. As an exception, however, one greatgranddaughter married an important noblemen.

Water splitting by the oxygen-evolving complex of photosystem II (PS II) proceeds via 5 redox-sta... more Water splitting by the oxygen-evolving complex of photosystem II (PS II) proceeds via 5 redox-states S0 - S4. In an early study preliminary evidence was provided by fluorescent measurements that NO can act as an electron donor to the S2 state (1). Goussias et al. (2) observed that NO destabilizes the S2 state in less than 1 min at −30 °C. We have extended these observations and examined the time of interaction of NO with both the S2 and S3 states at 18–20 °C utilizing flash fluorescence spectroscopy.

Frontiers in Plant Science, Feb 17, 2016

To survive under highly variable environmental conditions, higher plants have acquired a large va... more To survive under highly variable environmental conditions, higher plants have acquired a large variety of acclimation responses. Different strategies are used to cope with changes in light intensity with the common goal of modulating the functional antenna size of Photosystem II (PSII). Here we use a combination of biochemical and biophysical methods to study these changes in response to acclimation to high light (HL). After 2 h of exposure, a decrease in the amount of the large PSII supercomplexes is observed indicating that plants are already acclimating to HL at this stage. It is also shown that in HL the relative amount of antenna proteins decreases but this decrease is far less than the observed decrease of the functional antenna size, suggesting that part of the antenna present in the membranes in HL does not transfer energy efficiently to the reaction center. Finally, we observed LHCII monomers in all conditions. As the solubilization conditions used do not lead to monomerization of purified LHCII trimers, we should conclude that a population of LHCII monomers exists in the membrane. The relative amount of LHCII monomers strongly increases in plants acclimated to HL, while no changes in the trimer to monomer ratio are observed upon short exposure to stress.

Acta botanica neerlandica, 1994

Frontiers in Plant Science, Jun 2, 2022

The photosynthetic electron transport chain is mineral rich. Specific mineral deficiencies can mo... more The photosynthetic electron transport chain is mineral rich. Specific mineral deficiencies can modify the electron transport chain specifically. Here, it is shown that on the basis of 2 short Chl fluorescence and P700 + measurements (approx. 1 s each), it is possible to discriminate between 10 out of 12 different mineral deficiencies:

Biochemistry, Feb 6, 2002

The manganese cluster of the oxygen-evolving enzyme of photosystem II is chemically reduced upon ... more The manganese cluster of the oxygen-evolving enzyme of photosystem II is chemically reduced upon interaction with nitric oxide at -30 degrees C. The state formed gives rise to an S = 1/2 multiline EPR signal [Goussias, Ch., Ioannidis, N., and Petrouleas, V. (1997) Biochemistry 36, 9261] that is attributed to a Mn(II)- Mn(III) dimer [Sarrou, J., Ioannidis, N., Deligiannakis, Y., and Petrouleas, V. (1998) Biochemistry 37, 3581]. In this work, we sought to establish whether the state could be assigned to a specific, reduced S state by using flash oxymetry, chlorophyll a fluorescence, and electron paramagnetic resonance spectroscopy. With the Joliot-type O(2) electrode, the first maximum of oxygen evolution was observed on the sixth or seventh flash. Three saturating pre-flashes were required to convert the flash pattern characteristic of NO-reduced samples to that of the untreated control (i.e., O(2) evolution maximum on the third flash). Measurements of the S state-dependent level of chlorophyll fluorescence in NO-treated PSII showed a three-flash downshift compared to untreated controls. In the EPR study, the maximum S(2) multi-line EPR signal was observed after the fourth flash. The results from all three methods are consistent with the Mn cluster being in a redox state corresponding to an S(-2) state in a majority of centers after treatment with NO. We were unable to generate the Mn(II)-Mn(III) multi-line signal using hydrazine as a reductant; it appears that the valence distribution and possibly the structure of the Mn cluster in the S(-2) state are dependent on the nature of the reductant that is used.

Plant Cell and Environment, Feb 5, 2020

In several systems, from plant's canopy to algal bioreactors, the decrease of the antenna size ha... more In several systems, from plant's canopy to algal bioreactors, the decrease of the antenna size has been proposed as a strategy to increase the photosynthetic efficiency. However, still little is known about possible secondary effects of such modifications. This is particularly relevant because the modulation of the antenna size is one of the most important light acclimation responses in photosynthetic organisms. In our study, we used an Arabidopsis thaliana mutant (dLhcb2), which has a 60% decrease of Lhcb1 and Lhcb2, the two main components of the major Photosystem II antenna complex. We show that the mutant maintains the photosynthetic and photoprotective capacity of the Wild Type (WT) and adapts to different light conditions by remodelling its photosynthetic apparatus, but the regulatory mechanism differs from that of the WT. Surprisingly, it does not compensate for the decreased light-harvesting capacity by increasing other pigment-protein complexes. Instead, it lowers the ratio of the cytochrome b 6 f and ATP synthase to the photosystems, regulating linear electron flow and maintaining the photosynthetic control at the level of these complexes as in the WT. We show that targeting the reduction of two specific antenna proteins, Lhcb1 and Lhcb2, represents a viable solution to obtain plants with a truncated antenna size, which still maintain the capacity to acclimate to different light conditions.

The reactivity of the S 3 and S 2 states towards NO and NH 2 OH was studied and compared using th... more The reactivity of the S 3 and S 2 states towards NO and NH 2 OH was studied and compared using the period-4 oscillations in the F 0-value induced by a train of single turnover Xenon flashes spaced 100 ms apart to monitor the reaction kinetics. The flash frequency also determined the time resolution of the assay, i.e. 100 ms. The S 2 and S 3-states were created by one and two single turnover pre-flashes, respectively. The NO-concentration-dependence of the S 3-decay indicated that at low NO-concentrations an S 2-state was formed as an intermediate, whereas at higher concentrations a seemingly monophasic decay to the S 1-state was observed. The sigmoidal concentration dependence indicated that a fast interaction of the S 3-state with (at least) two NO-molecules is necessary for the fast S 3 to S 1 decay (τ ~0.4 s at 1.2 mM NO). The pH-dependence of the S 3-decay suggests that a protonation-reaction (pK ~6.9) is involved in the S 3 to S 1 decay. At intermediate NO-concentrations the protonation is only partially rate limiting, since the pH effect is more pronounced at high compared to intermediate NO-concentrations. A comparison of the reactivity of NO and hydroxylamine suggests that hydroxylamine reacts more efficiently with the S 1 and S 2 states, whereas NO reacts more efficiently with the S 3-state. Based on our present knowledge of the oxygen evolving complex a possible reaction mechanism is proposed for the interaction between NO and the S 3 state.

Photosynthesis Research, Aug 1, 1993

Silicomolybdate (SiMo) and its effects on thylakoids have been characterized to evaluate its use ... more Silicomolybdate (SiMo) and its effects on thylakoids have been characterized to evaluate its use as a probe for Photosystem II (PS II). It can accept electrons at two places in the electron transport chain: one at PS II and the other at PS I. In the presence of 1 μM 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) only the site at PS II is available. It is suggested that SiMo must disp;ace bicarbonate from its binding site to be able to function as an electron acceptor. This displacement is non-competitive. The binding of SiMo is inhibited differentially by PS II inhibitors: dinoseb>ioxynil> diuron. This difference is determined by the different positions of the inhibitors within the QB binding niche and their interaction with bicarbonate. The experimental results show that the SiMo-binding niche is located between the parallel helices of the D1 and D2 proteins of PS II, close to the non-heme iron. We conclude that SiMo is an electron acceptor with unique characteristics useful as a probe of the acceptor side of PS II.

Journal of Photochemistry and Photobiology B-biology, 1997

The two-electron gate of Photosystem II (PSII) is known to function by transferring electrons fro... more The two-electron gate of Photosystem II (PSII) is known to function by transferring electrons from the reduced one electron acceptor QA− (a bound plastosemiquinone) to the oxidized two-electron acceptor QB (a bound plastoquinone), and then again from QA− to the singly reduced QB−, producing plastoquinol QBH2. In this article, we have three chloroacetates (monochloroacetate, MCA; dichloroacetate, DCA; and trichloroacetate, TCA),

Journal of Biological Inorganic Chemistry, Jun 1, 2000

We compare the interaction of nitric oxide with the S states of the oxygen evolving complex (OEC)... more We compare the interaction of nitric oxide with the S states of the oxygen evolving complex (OEC) of photosystem II and the dinuclear Mn cluster of Thermus thermophilus catalase. Flash fluorescence studies indicate that the S3 state of the OEC in the presence of ca. 0.6 mM NO is reduced to the S1 with an apparent halftime of ca. 0.4 s at about 18 degrees C, compared with a biphasic decay, with approximate halftimes of 28 s for S3 to S2 and 140 s for S2 to S1 in the absence of NO. Under similar conditions the S2 state is reduced by NO to the S1 state with an approximate halftime of 2 s. These results extend a recent study indicating a slow reduction of the S1 state at -30 degrees C, via the S0 and S(-1) states, to a Mn(II)-Mn(III) state resembling the corresponding state in catalase. The reductive mode of action of NO is repeated with the di-Mn cluster of catalase: the Mn(III)-Mn(III) redox state is reduced to the Mn(II)-Mn(II) state via the intermediate Mn(II)-Mn(III) state. The kinetics of this reduction suggest a decreasing reduction potential with decreasing oxidation state, similar to what is observed with the active states of the OEC. What is unique about the OEC is the rapid interaction of NO with the S3 state of the OEC, which is compatible with a metalloradical character of this state.

Significant progress has been made recently in probing the lower S-states by EPR spectroscopy. Th... more Significant progress has been made recently in probing the lower S-states by EPR spectroscopy. The S1 state previously characterised by a broad integer spin EPR signal at g= 4.8 [1, 2] has been shown more recently to exhibit an alternative multiline signal at g=12. The latter signal is detected in Synechocystis preparations but also, after removal of the 23 and 17 kDa extrinsic proteins, in spinach preparations [3]. A half integer spin signal has been recently detected in the S0 state produced either by chemical reduction [4] or after the 3rd flash in a flash sequence [5, 6]. The presence of 0.5–3% methanol is required for the observation of the weak hyperfine structure of the signal, but the signal is also observed as a broad derivative in the absence of methanol [6].

Molecular mechanisms of photoinhibition are clarified on the basis of experiments with leaves and... more Molecular mechanisms of photoinhibition are clarified on the basis of experiments with leaves and isolated chloroplasts of peas and triazine-resistant and susceptible Chenopodium plants.

Biochimica Et Biophysica Acta - Bioenergetics, Sep 1, 1996

The photosynthetic apparatus can be damaged by light energy in the process of photoinhibition. Th... more The photosynthetic apparatus can be damaged by light energy in the process of photoinhibition. The target of this photoinhibition is mainly photosystem II (PSII). The mechanism leading to photoinhibitory damage is not yet known. We have characterized photoinhibition by measuring the photoinactivation of electron transport rates using the electron acceptors silicomolybdate and ferricyanide at different irradiance levels and different pH values. The effects of light on the donor side of PSII were measured with silicomolybdate, the effects on the acceptor side were measured with ferricyanide. We observed that photoinactivation of both donor and acceptor side of PSII are light dose-dependent, donor and acceptor side inactivation being independent processes. The donor side of PSII is less sensitive to photoinhibition than the acceptor side. The difference in pH dependence of donor and acceptor side photoinactivation leads us to propose that light-induced release of bicarbonate from PSII is a primary event leading to photoinhibition. In addition, we report that a photoinhibitory treatment increases the proton permeability of thylakoid membranes. This increase seems to be related to the presence of inactivated PSII reaction centers. It is suggested that radicals formed by inactivated PSII reaction centers causing lipid peroxidation are responsible.

The life of the Groningen (Grootegast) judge and freehold farmer Tonnis Gerrits during the first ... more The life of the Groningen (Grootegast) judge and freehold farmer Tonnis Gerrits during the first half of the 80-year war is depicted in this article, Next to his personal life (including two marriages and a possible bigamous relation), information is given about his family background (with a prioress as a niece) and his ten children. Most ofl his off-spring moved downward socially, with one son even accidentally killing another one. As an exception, however, one greatgranddaughter married an important noblemen.

Water splitting by the oxygen-evolving complex of photosystem II (PS II) proceeds via 5 redox-sta... more Water splitting by the oxygen-evolving complex of photosystem II (PS II) proceeds via 5 redox-states S0 - S4. In an early study preliminary evidence was provided by fluorescent measurements that NO can act as an electron donor to the S2 state (1). Goussias et al. (2) observed that NO destabilizes the S2 state in less than 1 min at −30 °C. We have extended these observations and examined the time of interaction of NO with both the S2 and S3 states at 18–20 °C utilizing flash fluorescence spectroscopy.

Frontiers in Plant Science, Feb 17, 2016

To survive under highly variable environmental conditions, higher plants have acquired a large va... more To survive under highly variable environmental conditions, higher plants have acquired a large variety of acclimation responses. Different strategies are used to cope with changes in light intensity with the common goal of modulating the functional antenna size of Photosystem II (PSII). Here we use a combination of biochemical and biophysical methods to study these changes in response to acclimation to high light (HL). After 2 h of exposure, a decrease in the amount of the large PSII supercomplexes is observed indicating that plants are already acclimating to HL at this stage. It is also shown that in HL the relative amount of antenna proteins decreases but this decrease is far less than the observed decrease of the functional antenna size, suggesting that part of the antenna present in the membranes in HL does not transfer energy efficiently to the reaction center. Finally, we observed LHCII monomers in all conditions. As the solubilization conditions used do not lead to monomerization of purified LHCII trimers, we should conclude that a population of LHCII monomers exists in the membrane. The relative amount of LHCII monomers strongly increases in plants acclimated to HL, while no changes in the trimer to monomer ratio are observed upon short exposure to stress.

Acta botanica neerlandica, 1994

Frontiers in Plant Science, Jun 2, 2022

The photosynthetic electron transport chain is mineral rich. Specific mineral deficiencies can mo... more The photosynthetic electron transport chain is mineral rich. Specific mineral deficiencies can modify the electron transport chain specifically. Here, it is shown that on the basis of 2 short Chl fluorescence and P700 + measurements (approx. 1 s each), it is possible to discriminate between 10 out of 12 different mineral deficiencies:

Biochemistry, Feb 6, 2002

The manganese cluster of the oxygen-evolving enzyme of photosystem II is chemically reduced upon ... more The manganese cluster of the oxygen-evolving enzyme of photosystem II is chemically reduced upon interaction with nitric oxide at -30 degrees C. The state formed gives rise to an S = 1/2 multiline EPR signal [Goussias, Ch., Ioannidis, N., and Petrouleas, V. (1997) Biochemistry 36, 9261] that is attributed to a Mn(II)- Mn(III) dimer [Sarrou, J., Ioannidis, N., Deligiannakis, Y., and Petrouleas, V. (1998) Biochemistry 37, 3581]. In this work, we sought to establish whether the state could be assigned to a specific, reduced S state by using flash oxymetry, chlorophyll a fluorescence, and electron paramagnetic resonance spectroscopy. With the Joliot-type O(2) electrode, the first maximum of oxygen evolution was observed on the sixth or seventh flash. Three saturating pre-flashes were required to convert the flash pattern characteristic of NO-reduced samples to that of the untreated control (i.e., O(2) evolution maximum on the third flash). Measurements of the S state-dependent level of chlorophyll fluorescence in NO-treated PSII showed a three-flash downshift compared to untreated controls. In the EPR study, the maximum S(2) multi-line EPR signal was observed after the fourth flash. The results from all three methods are consistent with the Mn cluster being in a redox state corresponding to an S(-2) state in a majority of centers after treatment with NO. We were unable to generate the Mn(II)-Mn(III) multi-line signal using hydrazine as a reductant; it appears that the valence distribution and possibly the structure of the Mn cluster in the S(-2) state are dependent on the nature of the reductant that is used.

Plant Cell and Environment, Feb 5, 2020

In several systems, from plant's canopy to algal bioreactors, the decrease of the antenna size ha... more In several systems, from plant's canopy to algal bioreactors, the decrease of the antenna size has been proposed as a strategy to increase the photosynthetic efficiency. However, still little is known about possible secondary effects of such modifications. This is particularly relevant because the modulation of the antenna size is one of the most important light acclimation responses in photosynthetic organisms. In our study, we used an Arabidopsis thaliana mutant (dLhcb2), which has a 60% decrease of Lhcb1 and Lhcb2, the two main components of the major Photosystem II antenna complex. We show that the mutant maintains the photosynthetic and photoprotective capacity of the Wild Type (WT) and adapts to different light conditions by remodelling its photosynthetic apparatus, but the regulatory mechanism differs from that of the WT. Surprisingly, it does not compensate for the decreased light-harvesting capacity by increasing other pigment-protein complexes. Instead, it lowers the ratio of the cytochrome b 6 f and ATP synthase to the photosystems, regulating linear electron flow and maintaining the photosynthetic control at the level of these complexes as in the WT. We show that targeting the reduction of two specific antenna proteins, Lhcb1 and Lhcb2, represents a viable solution to obtain plants with a truncated antenna size, which still maintain the capacity to acclimate to different light conditions.

The reactivity of the S 3 and S 2 states towards NO and NH 2 OH was studied and compared using th... more The reactivity of the S 3 and S 2 states towards NO and NH 2 OH was studied and compared using the period-4 oscillations in the F 0-value induced by a train of single turnover Xenon flashes spaced 100 ms apart to monitor the reaction kinetics. The flash frequency also determined the time resolution of the assay, i.e. 100 ms. The S 2 and S 3-states were created by one and two single turnover pre-flashes, respectively. The NO-concentration-dependence of the S 3-decay indicated that at low NO-concentrations an S 2-state was formed as an intermediate, whereas at higher concentrations a seemingly monophasic decay to the S 1-state was observed. The sigmoidal concentration dependence indicated that a fast interaction of the S 3-state with (at least) two NO-molecules is necessary for the fast S 3 to S 1 decay (τ ~0.4 s at 1.2 mM NO). The pH-dependence of the S 3-decay suggests that a protonation-reaction (pK ~6.9) is involved in the S 3 to S 1 decay. At intermediate NO-concentrations the protonation is only partially rate limiting, since the pH effect is more pronounced at high compared to intermediate NO-concentrations. A comparison of the reactivity of NO and hydroxylamine suggests that hydroxylamine reacts more efficiently with the S 1 and S 2 states, whereas NO reacts more efficiently with the S 3-state. Based on our present knowledge of the oxygen evolving complex a possible reaction mechanism is proposed for the interaction between NO and the S 3 state.

Photosynthesis Research, Aug 1, 1993

Silicomolybdate (SiMo) and its effects on thylakoids have been characterized to evaluate its use ... more Silicomolybdate (SiMo) and its effects on thylakoids have been characterized to evaluate its use as a probe for Photosystem II (PS II). It can accept electrons at two places in the electron transport chain: one at PS II and the other at PS I. In the presence of 1 μM 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) only the site at PS II is available. It is suggested that SiMo must disp;ace bicarbonate from its binding site to be able to function as an electron acceptor. This displacement is non-competitive. The binding of SiMo is inhibited differentially by PS II inhibitors: dinoseb>ioxynil> diuron. This difference is determined by the different positions of the inhibitors within the QB binding niche and their interaction with bicarbonate. The experimental results show that the SiMo-binding niche is located between the parallel helices of the D1 and D2 proteins of PS II, close to the non-heme iron. We conclude that SiMo is an electron acceptor with unique characteristics useful as a probe of the acceptor side of PS II.

Journal of Photochemistry and Photobiology B-biology, 1997

The two-electron gate of Photosystem II (PSII) is known to function by transferring electrons fro... more The two-electron gate of Photosystem II (PSII) is known to function by transferring electrons from the reduced one electron acceptor QA− (a bound plastosemiquinone) to the oxidized two-electron acceptor QB (a bound plastoquinone), and then again from QA− to the singly reduced QB−, producing plastoquinol QBH2. In this article, we have three chloroacetates (monochloroacetate, MCA; dichloroacetate, DCA; and trichloroacetate, TCA),

Journal of Biological Inorganic Chemistry, Jun 1, 2000

We compare the interaction of nitric oxide with the S states of the oxygen evolving complex (OEC)... more We compare the interaction of nitric oxide with the S states of the oxygen evolving complex (OEC) of photosystem II and the dinuclear Mn cluster of Thermus thermophilus catalase. Flash fluorescence studies indicate that the S3 state of the OEC in the presence of ca. 0.6 mM NO is reduced to the S1 with an apparent halftime of ca. 0.4 s at about 18 degrees C, compared with a biphasic decay, with approximate halftimes of 28 s for S3 to S2 and 140 s for S2 to S1 in the absence of NO. Under similar conditions the S2 state is reduced by NO to the S1 state with an approximate halftime of 2 s. These results extend a recent study indicating a slow reduction of the S1 state at -30 degrees C, via the S0 and S(-1) states, to a Mn(II)-Mn(III) state resembling the corresponding state in catalase. The reductive mode of action of NO is repeated with the di-Mn cluster of catalase: the Mn(III)-Mn(III) redox state is reduced to the Mn(II)-Mn(II) state via the intermediate Mn(II)-Mn(III) state. The kinetics of this reduction suggest a decreasing reduction potential with decreasing oxidation state, similar to what is observed with the active states of the OEC. What is unique about the OEC is the rapid interaction of NO with the S3 state of the OEC, which is compatible with a metalloradical character of this state.