scholarly journals 8-vinyl reduction and chlorophyll a biosynthesis in higher plants

1993 ◽  
Vol 291 (3) ◽  
pp. 939-944 ◽  
Author(s):  
B J Whyte ◽  
W T Griffiths
Keyword(s):  
Triticum Aestivum ◽  
Chlorophyll A ◽  
Redox State ◽  
Higher Plants ◽  
Solid Phase ◽  
Compositional Analysis ◽  
The Individual ◽  
Vinyl Reductase ◽  
Kinetics Of ◽  
Chlorophyll A Biosynthesis

A technique involving solid-phase extractions and polyethylene h.p.l.c. suitable for the routine compositional analysis of the total protochlorophyllide pool of plants is described. The resynthesis kinetics of the individual components of the pool have been studied in briefly illuminated etiolated tissue of wheat (Triticum aestivum) and cucumber (Cucumis sativus) during subsequent redarkening. The data are interpreted in terms of a precursor-product relationship between the di- and mono-vinyl analogues of protochlorophyllide during their reaccumulation in darkness. The interconversion is assumed to be catalysed by an 8-vinyl reductase, which shows greater activity in wheat than in cucumber. Analyses of the redox state of the nicotinamide nucleotide of the pool during the process are compatible with NADPH as the cofactor of the putative reductase.

Developmental control of N-CAM sialylation state by Golgi sialyltransferase isoforms

Development ◽  
1988 ◽  
Vol 104 (1) ◽  
pp. 147-154 ◽  
Author(s):  
K.C. Breen ◽  
C.M. Regan
Keyword(s):  
Enzyme Assay ◽  
Specific Activity ◽  
Solid Phase ◽  
Competitive Inhibitor ◽  
Temporal Expression ◽  
Ferric Ions ◽  
Developmentally Regulated ◽  
Sialyltransferase Activity ◽  
The Individual ◽  
Kinetics Of

A rat brain Golgi sialyltransferase activity capable of the differentiation-dependent control of N-CAM sialylation state is described. The specific activity of Golgi sialyltransferase was found to be developmentally regulated with respect to both endogenous and exogenous protein acceptors, with a particular elevation on postnatal days 10–12 when the heavily sialylated or ‘embryonic’ form of N-CAM is re-expressed. The subsequent developmental decrease in activity was associated with a significant decrease in apparent Km for the CMP-NeuNAc substrate, but not for the asialofetuin exogenous acceptor, which could not be attributed to the temporal expression of an endogenous competitive inhibitor. The apparent Vmax remained constant for CMP-NeuNAc but was significantly reduced for asialofetuin. Sialyltransferase activity, which was optimal at pH 7.0-7.5, was also modulated by various cations. Zinc abolished enzyme function, in contrast to ferric ions which stimulated activity fourfold-sevenfold. The marked activation of the adult form of the enzyme by potassium and magnesium ions, together with the alterations in kinetic constants, suggested this activity to be distinct from that derived from postnatal day-12 tissue. The kinetics of [14C]sialic acid incorporation into immuno-precipitated N-CAM demonstrated the individual polypeptides to be sialylated, possibly by addition of polysialosyl units, in a developmental sequence. The presence of four distinct sialyltransferase activities was demonstrated by non-denaturing gel electrophoresis followed by solid-phase enzyme assay. These isoforms were temporally expressed during development, two being correlated with the postnatal reexpression of the ‘embryonic’ form of N-CAM.

Utilization of induction and quenching kinetics of chlorophyll a fluorescence for in vivo salinity screening studies in wheat (Triticum aestivum vars. Kharchia-65 and Fielder)

1993 ◽  
Vol 71 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Sankaran KrishnaRaj ◽  
Bruce T. Mawson ◽  
Edward C. Yeung ◽  
Trevor A. Thorpe
Keyword(s):  
Triticum Aestivum ◽  
Salt Stress ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Triticum Aestivum L ◽  
Fluorescence Signal ◽  
Salt Tolerant ◽  
In Vivo Screening ◽  
Kinetics Of

The potential of utilizing induction and quenching kinetics of chlorophyll a fluorescence as consistent and reliable markers for in vivo salt (sodium sulphate) tolerance screening studies was investigated by comparing two wheat (Triticum aestivum L.) varieties with varying responses to salinity, viz. Kharchia-65 (salt-tolerant) and Fielder (salt-susceptible). Three-week-old seedlings were treated with a range of salt concentrations (0 to 2%) over a 1- to 2-week period. Both the maximum rates of fluorescence induction and quenching measured from leaf sections decreased significantly in Fielder compared with Kharchia-65 as the salt concentration increased. Alterations in other fluorescence parameters, such as the maximum yield of fluorescence signal in the absence and presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea by the variety Fielder indicated a minimal reduction in the size of the primary electron acceptor pool associated with photosystem II following salt stress. In contrast, these parameters were altered to a lesser extent by salt treatments in Kharchia-65. The effect of salinity stress on leaf morphology of both varieties indicated no major anatomical alterations apart from a negligible increase in leaf thickness. Total chlorophyll content of Kharchia-65 increased significantly as a result of salt stress, owing to an increase in both chlorophyll a and chlorophyll b, whereas Fielder showed no significant variations. The results indicate that total fluorescence quenching and maximum rates of both induction and quenching appear to be reliable indicators for in vivo screening of salt-tolerant wheat genotypes. Key words: Triticum aestivum L., wheat, chlorophyll a fluorescence, salt stress, in vivo screening.

Kinetics and Mechanism of Decomposition of 1,3-Bis(4-methylphenyl)triazene Catalyzed with Substituted Benzoic Acids in 25% Aqueous Methanol-General or Specific Catalysis?

1994 ◽  
Vol 59 (9) ◽  
pp. 2029-2041
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná
Keyword(s):  
Benzoic Acids ◽  
Hammett Equation ◽  
Aqueous Methanol ◽  
Mechanism Of Decomposition ◽  
Kinetics Of Decomposition ◽  
Independent Variable ◽  
Amino Derivatives ◽  
Substituted Benzoic Acids ◽  
The Individual ◽  
Kinetics Of

The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catalyzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 °C. The rate constants observed (297 data) have be used as values of independent variable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjugated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed rate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the product of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to substrate, which has been proved. The behaviour of 4-dimethylamino, 4-amino, and 3-amino derivatives is anomalous (lower catalytic activity as compared with benzoic acid). This supports the presumed participation of conjugated base in the title process.

Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride

1989 ◽  
Vol 54 (5) ◽  
pp. 1311-1317
Author(s):  
Miroslav Magura ◽  
Ján Vojtko ◽  
Ján Ilavský
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Reaction Rates ◽  
Activation Energies ◽  
The Individual ◽  
Kinetics Of

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.

Fully Automated Parallel Oligonucleotide Synthesizer

2001 ◽  
Vol 66 (8) ◽  
pp. 1299-1314 ◽  
Author(s):  
Michal Lebl ◽  
Christine Burger ◽  
Brett Ellman ◽  
David Heiner ◽  
Georges Ibrahim ◽  
...  
Keyword(s):  
Solid Phase ◽  
Building Blocks ◽  
Solid Support ◽  
Continuous Operation ◽  
Gear Pump ◽  
Oligonucleotide Synthesis ◽  
Center Of Rotation ◽  
Microtiter Plates ◽  
The Individual ◽  
Design And Construction

Design and construction of automated synthesizers using the tilted plate centrifugation technology is described. Wash solutions and reagents common to all synthesized species are delivered automatically through a 96-channel distributor connected to a gear pump through two four-port selector valves. Building blocks and other specific reagents are delivered automatically through banks of solenoid valves, positioned over the individual wells of the microtiterplate. These instruments have the following capabilities: Parallel solid-phase oligonucleotide synthesis in the wells of polypropylene microtiter plates, which are slightly tilted down towards the center of rotation, thus generating a pocket in each well, in which the solid support is collected during centrifugation, while the liquid is expelled from the wells. Eight microtiterplates are processed simultaneously, providing thus a synthesizer with a capacity of 768 parallel syntheses. The instruments are capable of unattended continuous operation, providing thus a capacity of over two millions 20-mer oligonucleotides in a year.

Triticum aestivum Assay - A Useful Tool for Environmental Monitoring and Toxicity Assessment

2019 ◽  
Vol 47 (4) ◽  
pp. 1005-1018
Author(s):  
Alexandra JITĂREANU ◽  
Ioana-Cezara CABA ◽  
Adriana TRIFAN ◽  
Silvica PĂDUREANU ◽  
Luminița AGOROAEI
Keyword(s):  
Triticum Aestivum ◽  
Higher Plants ◽  
Low Cost ◽  
Environmental Pollutants ◽  
Rapid Test ◽  
Toxicity Assessment ◽  
Pollution Monitoring ◽  
Present Review ◽  
Digital Object Identifier ◽  
Biological Assays

The present review summarizes the literature data regarding the application of Triticum aestivum assay as an alternative method for toxicity assessment of environmental pollutants or potential therapeutic agents. Plant bioassays present several advantages among other biological assays (simplicity, low cost, rapid test activation, a wide array of assessment endpoints). They present a good correlation with animal and human cells models, and are a reliable tool for genotoxicity assessment. Furthermore, in the context of toxicology guidelines that promote the substitution of assays using animal models with other bioassays, genotoxicity assays using higher plants models have gained in popularity. The present review focuses on three major aspects regarding Triticum aestivum assay - its utility in environmental pollution monitoring, its application in genotoxicity assessment studies, and its application in phytotoxicity evaluation of nanomaterials.   ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********

Compositional Analysis of Organosolv Poplar Lignin by Using High-Performance Liquid Chromatography/High-resolution Multi-stage Tandem Mass Spectrometry

2021 ◽  
Author(s):  
Jifa Zhang ◽  
Yuan Jiang ◽  
Leah F Easterling ◽  
Anton Anster ◽  
Wanru Li ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
High Performance ◽  
Compositional Analysis ◽  
Complex Mixtures ◽  
Tandem Mass ◽  
Multi Stage ◽  
The Individual ◽  
Environmentally Friendly Process

Organosolv treatment is an efficient and environmentally friendly process to degrade lignin into small compounds. The capability of characterizing the individual compounds in the complex mixtures formed upon organosolv treatment...

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

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