Isolierung von PS II-Partikeln mit in vivo Eigenschaften aus Euglena gracilis, Stamm Z / Isolation of PS II-Particels with in vivo Characteristics from Euglena gracilis, Stamm Z

1982 ◽  
Vol 37 (3-4) ◽  
pp. 256-259 ◽  
Author(s):  
F. Schuler ◽  
P. Brandt ◽  
W. Wießner
Keyword(s):  
Euglena Gracilis ◽  
Fluorescence Emission ◽  
Improved Method ◽  
Ps Ii ◽  
Ps I ◽  
Emission And Absorption Spectra ◽  
Chlorophyll Protein ◽  
Ps Ii Activity ◽  
Photosystem Ii Particles

Abstract An improved method for isolation of (photosystem II)-particles from Euglena gracilis, strain Z was established. PS II-particles isolated by ultrasonic treatment and following differential centrifugation show fluorescence emission and absorption spectra identical with in vivo properties of Euglena gracilis. These PS II-particles have only PS II-activity and contain CP a, the typical chlorophyll-protein-complex of PS II. No contamination of PS I-components are detectable.

Is the in vivo Photosystem I Function Resistant to Photoinhibition? An Answer from Photoacoustic and Far-Red Absorbance Measurements in Intact Leaves

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1038-1044 ◽  
Author(s):  
Michel Havaux ◽  
Murielle Eyletters
Keyword(s):  
Light Stress ◽  
Red Light ◽  
Light Treatment ◽  
High Light ◽  
Saturation Curve ◽  
Strong Light ◽  
Ps Ii ◽  
Fluorescence Measurements ◽  
Ps I

Abstract Preillumination of intact pea leaves with a strong blue-green light of 400 W m-2 markedly inhibited both photoacoustically monitored O2-evolution activity and PS II photochemistry as estimated from chlorophyll fluorescence measurements. The aim of the present work was to examine, with the help of the photoacoustic technique, whether this high-light treatment deteriorated the in vivo PS I function too. High-frequency photoacoustic measurements indicated that photochemical conversion of far-red light energy in PS I was preserved (and even transiently stimulated) whereas photochemical energy storage monitored in light exciting both PS I and PS II was markedly diminished. Low-frequency photoacoustic measurements of the Emerson enhancement showed a spectacular change in the PS II/PS I activity balance in favor of PS I. It was also observed that the linear portion of the saturation curve of the far-red light effect in the Emerson enhancement was not changed by the light treatment. Those results lead to the conclusion that, in contrast to PS II, the in vivo PS I photofunctioning was resistant to strong light stress, thus confirming previous suggestions derived from in vitro studies. Estimation of the redox state of the PS I reaction center by leaf absorbance measurements at ca. 820 nm suggested that, under steady illumination, a considerably larger fraction of PS I centers were in the closed state in high-light pretreated leaves as compared to control leaves, presumably allowing passive adjustment of the macroscopic quantum yield of PS I photochemis­ try to the strongly reduced photochemical efficiency of photoinhibited PS II.

scholarly journals Biochemical Characterization on Photosynthetic Activities during Dark Incubated Senescence of Wheat Primary Leaves by Gibberellic Acid

2019 ◽  
pp. 1-5
Author(s):  
G. Fareeda ◽  
S. D. S. Murthy
Keyword(s):  
Water Oxidation ◽  
Biochemical Characterization ◽  
Crop Yields ◽  
Moderate Increase ◽  
Ps Ii ◽  
Annual Crops ◽  
Ps I ◽  
Treated Leaf ◽  
Photosynthetic Activities ◽  
Ps Ii Activity

In annual crop plants like maize, rice and wheat etc. Senescence limits crop yields of annual crops like maize rice and wheat. Delayed leaf senescence is a desirable agronomic trait to improve crop yield. In this study 10 µM GA reduced the loss of wheat primary leaves under incubated dark conditions. GA reduced the loss of pigments, proteins, electron transport activities, spectral properties. The restoration of WCE activity by GA was closely associated with the restoration of PS II activity compared to that of PS I. GA treated leaf thylakoid membranes showed an increase in absorption at 680 nm moderate increase at 480 nm and 440 nm at 72 h during dark incubation. GA protected the degradation of water oxidation complex polypeptides (33, 23, 17 KDa) of PS II and slightly protected the PS I polypeptides.

scholarly journals Balancing the two photosystems: photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts

2000 ◽  
Vol 355 (1402) ◽  
pp. 1351-1359 ◽  
Author(s):  
John F. Allen ◽  
Thomas Pfannschmidt
Keyword(s):  
Electron Transport ◽  
Genetic System ◽  
Regulatory Function ◽  
State Transitions ◽  
Transcriptional Level ◽  
Reaction Centre ◽  
Ps Ii ◽  
Ps I

Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi–autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation–reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo , using light favouring one or other photosystem, and in vitro , when site–specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post–translational ‘state transitions’ in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra–nuclear genetic system.

Photoinhibition in vivo and in vitro Involves Weakly Coupled Chlorophyll–Protein Complexes‡¶

2002 ◽  
Vol 75 (6) ◽  
pp. 613 ◽  
Author(s):  
Stefano Santabarbara ◽  
Ilaria Cazzalini ◽  
Andrea Rivadossi ◽  
Flavio M. Garlaschi ◽  
Giuseppe Zucchelli ◽  
...  
Keyword(s):  
Protein Complexes ◽  
Weakly Coupled ◽  
Chlorophyll Protein Complexes ◽  
Chlorophyll Protein

scholarly journals Silica-Coated Fe3O4 Nanoparticles as a Bifunctional Agent for Magnetic Resonance Imaging and ZnII Fluorescent Sensing

2021 ◽  
Vol 20 ◽  
pp. 153303382110365
Author(s):  
Lin Qiu ◽  
Shuwen Zhou ◽  
Ying Li ◽  
Wen Rui ◽  
Pengfei Cui ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Contrast Agent ◽  
Quantum Interference ◽  
Inductively Coupled Plasma ◽  
Fluorescence Emission ◽  
Mri Contrast Agent ◽  
Core Shell ◽  
Resonance Imaging

Bifunctional magnetic/fluorescent core-shell silica nanospheres (MNPs) encapsulated with the magnetic Fe3O4 core and a derivate of 8-amimoquinoline (N-(quinolin-8-yl)-2-(3-(triethoxysilyl) propylamino) acetamide) (QTEPA) into the shell were synthesized. These functional MNPs were prepared with a modified stöber method and the formed Fe3O4@SiO2-QTEPA core-shell nanocomposites are biocompatible, water-dispersible, and stable. These prepared nanoparticles were characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), thermoelectric plasma Quad II inductively coupled plasma mass spectrometry (ICP-MS), superconducting quantum interference device (SQUID), TG/DTA thermal analyzer (TGA) and Fourier transform infrared spectroscopy (FTIR). Further application of the nanoparticles in detecting Zn2+ was confirmed by the fluorescence experiment: the nanosensor shows high selectivity and sensitivity to Zn2+ with a 22-fold fluorescence emission enhancement in the presence of 10 μM Zn2+. Moreover, the transverse relaxivity measurements show that the core-shell MNPs have T2 relaxivity (r2) of 155.05 mM−1 S−1 based on Fe concentration on the 3.0 T scanner, suggesting that the compound can be used as a negative contrast agent for MRI. Further in vivo experiments showed that these MNPs could be used as MRI contrast agent. Therefore, the new nanosensor provides the dual modality of magnetic resonance imaging and optical imaging.

Sign in / Sign up

Export Citation Format

Share Document