Sigmoidal reduction kinetics of the photosystem II acceptor side in intact photosynthetic materials during fluorescence induction

Joly, David,Carpentier, Robert Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.2

Illumination of dark-adapted photosynthetic samples leads to fluorescence induction (FI) that can be described by a triphasic O-J-I-P fluorescence rise. Its kinetics follows the accumulation of reduced photosystem II (PSII) acceptors. In isolated thylakoid membranes, FI is often used to study photosynthetic electron transport. A simple quantitative analysis method was recently developed to fit these FI traces and also lead to a better understanding of action sites of artificial electron acceptors. However, a quantitative method was still lacking for FI in intact systems like leaves, where the FI kinetics shows a clear I-peak. Here, we present a new quantitative method to analyze experimental FI traces in leaves and intact chloroplasts. It revealed a sigmoidicity in the reduction kinetics of the PSII acceptor side of intact systems. The results also show that the origin of each phase is independent of the photosynthetic material used. The effects of decyl-plastoquinone on intact chloroplasts retarded predominantly the I-P rise and clearly indicates that this phase is related to the accumulation of a reduce PQ pool, as observed in isolated thylakoid membranes.

Biological water-oxidizing complex: a nano-sized manganese-calcium oxide in a protein environment.

Najafpour, Mohammad Mahdi,Moghaddam, Atefeh Nemati,Yang, Young Nam,Aro, Eva-Mari,Carpentier, Robert,Eaton-Rye, Julian J,Lee, Choon-Hwan,Allakhverdiev, Suleyman I W. Junk ; Kluwer Academic Publishers 2012 Photosynthesis research Vol.114 No.1

<P>The resolution of Photosystem II (PS II) crystals has been improved using isolated PS II from the thermophilic cyanobacterium Thermosynechococcus vulcanus. The new 1.9 resolution data have provided detailed information on the structure of the water-oxidizing complex (Umena et al. Nature 473: 55-61, 2011). The atomic level structure of the manganese-calcium cluster is important for understanding the mechanism of water oxidation and to design an efficient catalyst for water oxidation in artificial photosynthetic systems. Here, we have briefly reviewed our knowledge of the structure and function of the cluster.</P>

Efficacy of a Second Brain Biopsy for Intracranial Lesions after Initial Negativity

Mohamed Chabaane,Aymeric Amelot,Maximilien Riche,Franck Bielle,Karima Mokhtari,Alexandre Carpentier,Mehdi Touat,Bertrand Mathon 대한신경과학회 2020 Journal of Clinical Neurology Vol.16 No.4

Background and Purpose The rationale for performing a second brain biopsy after initial negativity is not well evaluated in the literature. This study was designed to 1) assess the efficacy of a second brain biopsy when the first biopsy was nondiagnostic, 2) identify possible factors associated with an increased diagnostic rate in the second biopsy, and 3) analyze additional morbidity induced by the second biopsy. Methods We performed a retrospective cohort study from 2009 to 2019, during which 1,919 patients underwent a brain biopsy, including 30 who were biopsied twice (1.6%). The specific histological diagnosis rate, diagnosis-associated factors, and complication rate were assessed for the 30 twice-biopsied patients. Results The second biopsy allowed a specific histological diagnosis in 86.7% of the patients who had initially undergone a nondiagnostic brain biopsy [odds ratio (OR)=7.5, 95% confidence interval (CI)=3.0–18.7, p<0.001]. The multivariate analysis showed that only prebiopsy corticosteroid administration (OR=2.6, 95% CI=1.1–6.0, p=0.01) was an important factor in predicting a nondiagnostic biopsy. None of the patients developed a symptomatic complication after the first biopsy, while two (6.0%) patients experienced a transient complication after the second biopsy (p=0.49). Conclusions Performing a second brain biopsy in patients who have an initial nondiagnostic biopsy is effective in most cases. We advocate that a second biopsy be systematically considered in the diagnosis algorithm of these patients after it has been verified that molecular testing cannot help to obtain a diagnosis. Corticosteroid administration can lead to nondiagnostic biopsies and should be avoided when possible during the prebiopsy period.

Erratum to: Dehydroascorbate reductase and glutathione reductase play an important role in scavenging hydrogen peroxide during natural and artificial dehydration of Jatropha curcas seeds

Samar A. Omar,Nabil I. Elsheery,Hazem M. Kalaji,Zeng-Fu Xu,Song Song-Quan,Robert Carpentier,이춘환,Suleyman I. Allakhverdiev 한국식물학회 2013 Journal of Plant Biology Vol.56 No.4

Changes in H2O2 and the main antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR), in endospermic and embryonic tissues were studied in developing and artificially dried Jatropha curcas seeds. Immature seeds were desiccation-tolerant at 80 days after flowering, as they were able to germinate fully after artificial drying on silica gel had reduced their water content to 10–12% of fresh weight. In both endospermic and embryonic tissues, H2O2 level and, consequently, lipid peroxide content, decreased during seed development as well as after artificial dehydration of developing seeds. All examined antioxidant enzymes except DHAR showed a decrease in total activity in mature stages as compared with early stages. Expression analysis of SOD genes revealed that the decrease in total SOD activities was related to the decrease in Cu/Zn-SOD expression, while the continuous activity of SOD during maturation was related to an increase in Mn-SOD expression. Artificial drying resulted in increased SOD and DHAR activity, irrespective of the developmental stage. Our results revealed weak participation of CAT and APX in H2O2 scavenging, as well as no significant alterations in GR activities either during maturation or after artificial drying. Changes in SOD and GR isoenzyme patterns occurred during maturation-related drying, but not after artificial drying. These results highlight the role of ascorbate-glutathione cycle enzymes (DHAR and GR) in H2O2 scavenging during maturation or after artificial drying of developing J. curcas seeds.

Dehydroascorbate Reductase and Glutathione Reductase Play an Important Role in Scavenging Hydrogen Peroxide during Natural and Artificial Dehydration of Jatropha curcas Seeds

Omar, Samar A.,Elsheery, Nabil I.,Kalaji, Hazem M.,Xu, Zeng-Fu,Song-Quan, Song,Carpentier, Robert,Lee, Choon-Hwan,Allakhverdiev, Suleyman I. 한국식물학회 2012 Journal of Plant Biology Vol.55 No.6

Changes in $H_2O_2$ and the main antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR), in endospermic and embryonic tissues were studied in developing and artificially dried Jatropha curcas seeds. Immature seeds were desiccation-tolerant at 80 days after flowering, as they were able to germinate fully after artificial drying on silica gel had reduced their water content to 10-12% of fresh weight. In both endospermic and embryonic tissues, $H_2O_2$ level and, consequently, lipid peroxide content, decreased during seed development as well as after artificial dehydration of developing seeds. All examined antioxidant enzymes except DHAR showed a decrease in total activity in mature stages as compared with early stages. Expression analysis of SOD genes revealed that the decrease in total SOD activities was related to the decrease in Cu/Zn-SOD expression, while the continuous activity of SOD during maturation was related to an increase in Mn-SOD expression. Artificial drying resulted in increased SOD and DHAR activity, irrespective of the developmental stage. Our results revealed weak participation of CAT and APX in $H_2O_2$ scavenging, as well as no significant alterations in GR activities either during maturation or after artificial drying. Changes in SOD and GR isoenzyme patterns occurred during maturation-related drying, but not after artificial drying. These results highlight the role of ascorbate-glutathione cycle enzymes (DHAR and GR) in $H_2O_2$ scavenging during maturation or after artificial drying of developing J. curcas seeds.