Light activation of fructose bisphosphatase in isolated spinach chloroplasts and deactivation by hydrogen peroxide

Planta ◽  
1981 ◽  
Vol 151 (3) ◽  
pp. 242-246 ◽  
Author(s):  
Stephen A. Charles ◽  
Barry Halliwell
Keyword(s):  
Hydrogen Peroxide ◽  
Fructose Bisphosphatase ◽  
Light Activation ◽  
Spinach Chloroplasts

scholarly journals Glutathione and ascorbic acid in spinach (Spinacia oleracea) chloroplasts. The effect of hydrogen peroxide and of Paraquat

1983 ◽  
Vol 210 (3) ◽  
pp. 899-903 ◽  
Author(s):  
M Y Law ◽  
S A Charles ◽  
B Halliwell
Keyword(s):  
Hydrogen Peroxide ◽  
Ascorbic Acid ◽  
Spinacia Oleracea ◽  
Reduced Glutathione ◽  
Oxidized Glutathione ◽  
Fructose Bisphosphatase ◽  
Physiological Conditions ◽  
Spinach Chloroplasts ◽  
Apparent Loss

The stroma of spinach chloroplasts contains ascorbic acid and glutathione at millimolar concentrations. [Reduced glutathione]/[oxidized glutathione] and [ascorbate]/[dehydroascorbate] ratios are high under both light and dark conditions and no evidence for a role of oxidized glutathione or dehydroascorbate in the dark-deactivation of fructose bisphosphatase could be obtained. Addition of H2O2 to chloroplasts in the dark decreases the above ratios, an effect that is reversed on illumination. Addition of Paraquat to illuminated chloroplasts caused a rapid oxidation of reduced glutathione and ascorbate, and apparent loss of dehydroascorbate. Paraquat rapidly inactivated fructose bisphosphatase activity, as assayed under physiological conditions.

scholarly journals Action of calcium ions on spinach (Spinacia oleracea) chloroplast fructose bisphosphatase and other enzymes of the Calvin cycle

1980 ◽  
Vol 188 (3) ◽  
pp. 775-779 ◽  
Author(s):  
S A Charles ◽  
B Halliwell
Keyword(s):  
Calcium Ions ◽  
Spinacia Oleracea ◽  
Calvin Cycle ◽  
Complete Inhibition ◽  
Fructose Bisphosphatase ◽  
Spinach Chloroplasts ◽  
Fructose 1,6 Bisphosphate ◽  
Sedoheptulose Bisphosphatase

Thiol-treated spinach (Spinacia oleracea) chloroplast fructose bisphosphatase is powerfully inhibited by Ca2+ non-competitively with respect to its substrate, fructose 1,6-bisphosphate. 500 microM-Ca2+ causes virtually complete inhibition and the Ki is 40 microM. Severe inhibition of sedoheptulose bisphosphatase is also caused by Ca2+. A role for Ca2+ in regulation of the Calvin cycle in spinach chloroplasts is proposed.

Clinical Evaluation of In-office Dental Bleaching Treatments With and Without the Use of Light-activation Sources

10.2341/07-57 ◽  
2008 ◽  
Vol 33 (1) ◽  
pp. 15-22 ◽  
Author(s):  
F. C. Marson ◽  
L. G. Sensi ◽  
L. C. C. Vieira ◽  
E. Araújo
Keyword(s):  
Hydrogen Peroxide ◽  
Clinical Evaluation ◽  
Clinical Relevance ◽  
Light Activation ◽  
Dental Bleaching

Clinical Relevance The use of light-activation sources did not affect the outcome of in-office bleaching with 35% hydrogen peroxide.

scholarly journals Influence of Concentration and Activation on Hydrogen Peroxide Diffusion through Dental TissuesIn Vitro

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Carlos R. G. Torres ◽  
Cristiane S. Souza ◽  
Alessandra B. Borges ◽  
Maria Filomena R. L. Huhtala ◽  
Taciana M. F. Caneppele
Keyword(s):  
Hydrogen Peroxide ◽  
Chemical Activation ◽  
Video Camera ◽  
Diffusion Time ◽  
Light Activation ◽  
Anova Analysis ◽  
Dental Tissues ◽  
Internal Cavities ◽  
Physical And Chemical ◽  
Bleaching Gels

This study evaluated the effect of physical and chemical activation on the diffusion time of different concentrations of hydrogen peroxide (HP) bleaching agents through enamel and dentin. One hundred and twenty bovine cylindrical specimens were divided into six groups (n=20): 20% HP ; 20% HP with light activation; 20% HP with manganese gluconate; 35% HP; 35% HP with light activation; and 35% HP with manganese gluconate. The specimens were fixed over transparent epoxy wells with internal cavities to simulate a pulpal chamber. This chamber was filled with an enzymatic reagent to simulate pulpal fluid. The bleaching gels were applied on enamel surface and the image of the pulpal fluid was captured by a video camera to monitor the time of peroxide penetration in each specimen. ANOVA analysis showed that concentration and type of activation of bleaching gel significantly influenced the diffusion time of HP (P<0.05). 35% HP showed the lowest diffusion times compared to the groups with 20% HP gel. The light activation of HP decreased significantly the diffusion time compared to chemical activation. The highest diffusion time was obtained with 20% HP chemically activated. The diffusion time of HP was dependent on activation and concentration of HP. The higher concentration of HP diffused through dental tissues more quickly.

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