Thermoluminescence
Mostrando 37-48 de 50 artigos, teses e dissertações.
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37. Connectivity of Photosystem II Is the Physical Basis of Retrapping in Photosynthetic Thermoluminescence
Energy transfer between photosystem II (PSII) centers is known from previous fluorescence studies. We have studied the theoretical consequences of energetic connectivity of PSII centers on photosynthetic thermoluminescence (TL) and predict that connectivity affects the TL Q band. First, connectivity is expected to make the Q band wider and more symmetric tha
The Biophysical Society.
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38. Heterogeneity and Photoinhibition of Photosystem II Studied with Thermoluminescence1
Thermoluminescence (TL) signals were recorded from grana stacks, margins, and stroma lamellae from fractionated, dark-adapted thylakoid membranes of spinach (Spinacia oleracea L.) in the absence and in the presence of 2,6-dichlorphenylindophenol (DCMU). In the absence of DCMU, the TL signal from grana fractions consisted of a homogenous B-band, which o
American Society of Plant Physiologists.
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39. Energetics of photosynthetic glow peaks
By postulating temperature-dependent equilibria between two or more electron carriers acting as traps for electrons or holes, it is possible to modify the Randall-Wilkins theory of thermoluminescence so as to explain the abnormally large apparent activation energies and apparent frequency factors observed in photosynthetic glow curves when fitted by unmodifi
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40. The PsbY Protein Is Not Essential for Oxygenic Photosynthesis in the Cyanobacterium Synechocystis sp. PCC 68031
A tetra-manganese cluster in the photosystem II (PSII) pigment-protein complex plays a critical role in the photosynthetic oxygen evolution process. PsbY, a small membrane-spanning polypeptide, has recently been suggested to provide a ligand for manganese in PSII (A.E. Gau, H.H. Thole, A. Sokolenko, L. Altschmied, R.G. Herrmann, E.K. Pistorius [1998] Mol Gen
American Society of Plant Physiologists.
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41. Potato Plants Lacking the CDSP32 Plastidic Thioredoxin Exhibit Overoxidation of the BAS1 2-Cysteine Peroxiredoxin and Increased Lipid Peroxidation in Thylakoids under Photooxidative Stress
The CDSP32 protein (chloroplastic drought-induced stress protein of 32 kD) is a thioredoxin participating in the defense against oxidative damage. We recently have identified in vitro the BAS1 2-Cys peroxiredoxin, a peroxide-detoxifying enzyme, as a target for CDSP32. Here, we report the characterization under stress conditions of transgenic potato (Sola
The American Society for Plant Biologists.
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42. Photodamage of the Photosynthetic Apparatus and Its Dependence on the Leaf Developmental Stage in the npq1 Arabidopsis Mutant Deficient in the Xanthophyll Cycle Enzyme Violaxanthin De-epoxidase
The npq1 Arabidopsis mutant is deficient in the violaxanthin de-epoxidase enzyme that converts violaxanthin to zeaxanthin in excess light (xanthophyll cycle). We have compared the behavior of mature leaves (ML) and developing leaves of the mutant and the wild type in various light environments. Thermoluminescence measurements indicated that high photon flux
American Society of Plant Physiologists.
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43. Polyphenolic Allelochemicals from the Aquatic Angiosperm Myriophyllum spicatum Inhibit Photosystem II1
Myriophyllum spicatum (Haloragaceae) is a highly competitive freshwater macrophyte that produces and releases algicidal and cyanobactericidal polyphenols. Among them, β-1,2,3-tri-O-galloyl-4,6-(S)-hexahydroxydiphenoyl-d-glucose (tellimagrandin II) is the major active substance and is an effective inhibitor of microalgal exoenzymes. However, this mode of act
American Society of Plant Biologists.
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44. The violaxanthin cycle protects plants from photooxidative damage by more than one mechanism
When light energy absorbed by plants becomes excessive relative to the capacity of photosynthesis, the xanthophyll violaxanthin is reversibly deepoxidized to zeaxanthin (violaxanthin cycle). The protective function of this phenomenon was investigated in a mutant of Arabidopsis thaliana, npq1, that has no functional violaxanthin deepoxidase. Two major consequ
The National Academy of Sciences.
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45. Acridones: a chemically new group of protonophores.
Although the interaction of proton-conducting ionophores (protonophores) with photosynthetic electron transport has been extensively studied during the past decade, the mode of action of protonophores remained uncertain. For a better understanding of the molecular mechanism of the action of protonophores, the introduction of chemically new types of molecules
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46. A Mutation in the D-de Loop of D1 Modifies the Stability of the S2QA- and S2QB- States in Photosystem II.
Photosystem II electron transfer, charge stabilization, and photoinhibition were studied in three site-specific mutants of the D1 polypeptide of Synechocystis PCC 6803: E243K, E229D, and CA1 (deletion of three glutamates 242-244 and a substitution, glutamine-241 to histidine). The phenotypes of the E229D and E243K mutants were similar to that of the control
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47. Mutation of Residue Threonine-2 of the D2 Polypeptide and Its Effect on Photosystem II Function in Chlamydomonas reinhardtii1
The D2 polypeptide of the photosystem II (PSII) complex in the green alga Chlamydomonas reinhardtii is thought to be reversibly phosphorylated. By analogy to higher plants, the phosphorylation site is likely to be at residue threonine-2 (Thr-2). We have investigated the role of D2 phosphorylation by constructing two mutants in which residue Thr-2 has b
American Society of Plant Physiologists.
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48. Exposure to cosmic radiation of British Airways flying crew on ultralonghaul routes.
British Airways has carried out radiation monitoring in Concorde for more than 20 years and has used a heuristic model based on data quoted by the National Aeronautics and Space Administration (NASA) to model radiation exposure in all longhaul fleets. From these data it has been calculated that no flight deck crew would exceed the control level of 6 mSv/y cu