scholarly journals 1-Anilinonaphthalene-8-sulphonate, a fluorescent conformational probe for glutamate dehydrogenase

1969 ◽  
Vol 114 (2) ◽  
pp. 407-417 ◽  
Author(s):  
G. H. Dodd ◽  
G. K. Radda
Keyword(s):  
Ionic Strength ◽  
Glutamate Dehydrogenase ◽  
Structural Transition ◽  
Enzyme Concentration ◽  
Regulatory Mechanisms ◽  
Conformational Equilibria ◽  
Allosteric Transitions

1. The interaction of 1-anilinonaphthalene-8-sulphonate with ox liver glutamate dehydrogenase was examined. 2. The fluorescence of the dye is enhanced 100-fold on binding. 3. A further enhancement is observed when NADH and GTP are added to the enzyme. 4. By using this property of the dye to measure conformational equilibria in the enzyme the effects of coenzyme, inhibitors, enzyme concentration, ionic strength and pH on the allosteric transitions were studied. 5. GTP and NADH interact with the enzyme in a heterotropic manner. 6. The rate of the structural transition brought about by GTP and NADH is biphasic with half-lives of 34 and 200msec. 7. The relation of these observations to regulatory mechanisms is discussed.

THE HETEROGENEITY OF PANCREATIC DEOXYRIBONUCLEASE

1962 ◽  
Vol 40 (2) ◽  
pp. 165-175 ◽  
Author(s):  
G. C. Becking ◽  
R. O. Hurst
Keyword(s):  
Enzyme Activity ◽  
Ionic Strength ◽  
Enzyme Preparation ◽  
Deoxyribonucleic Acid ◽  
Paper Electrophoresis ◽  
Relative Activity ◽  
Enzyme Concentration ◽  
Uranyl Acetate ◽  
Ph Optimum

The action of crystalline pancreatic deoxyribonuclease on sodium oligonucleotides in the presence of manganous ions has been studied and a pH optimum of 6.6 observed. Inhibition of the enzyme activity by increased ionic strength of the digest occurred. The liberation of products soluble in uranyl acetate – trichloroacetate was found to vary with enzyme concentration and the relative activity of the enzyme on oligonucleotides was best determined by a logarithm-plot method. The activity of the enzyme towards deoxyribonucleic acid or sodium oligonucleotides as substrate was not affected by treatment with acetone. Evidence of heterogeneity in the crystalline enzyme preparation was obtained using paper electrophoresis and chromatography on carboxymethylcellulose. Two fractions were separated that showed different ratios of activity towards the two substrates employed.

Cooperative structural transition of PM2 DNA at high ionic strength and its dependence on DNA damages

Nature ◽  
1980 ◽  
Vol 287 (5780) ◽  
pp. 363-364 ◽  
Author(s):  
Urs Kuhnlein ◽  
Siu Sing Tsang ◽  
Jane Edwards
Keyword(s):  
Ionic Strength ◽  
Structural Transition ◽  
High Ionic Strength ◽  
Dna Damages

scholarly journals 373 MITOCHONDRIAL RESPIRATlON OF `HASS' AVOCADOS IN RESPONSE TO ELEVATED CO, CONCENTRATIONS

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 484e-484 ◽  
Author(s):  
Diana Dostal Lange ◽  
Adel A. Kader
Keyword(s):  
Carbon Dioxide ◽  
Cytochrome Oxidase ◽  
Immunoblot Analysis ◽  
Enzyme Concentration ◽  
Regulatory Mechanisms ◽  
Respiratory Enzymes ◽  
Tolerance Level ◽  
Avocado Fruit ◽  
Co Concentrations

Carbon dioxide-enriched atmospheres can be effective in the retardation of ripening and in the reduction of decay of horticultural commodities. However, concentrations in excess of the tolerance level may cause physiological damage. The goal of our research is to elucidate the specific regulatory mechanisms of CO2 actions. Cytochrome oxidase (CytOx) in vitro activity in preclimacteric avocado fruit stored in air or 40% CO2 + 12.6% O2 was evaluated at 20C. Activities were determined during treatment and also after a transfer to air. Fruit treated with 40% CO2 + 12.6% O2 had elevated CytOx in vitro activity when compared to air-stored fruit. Immunoblot analysis was performed to determine if the increase in CytOx activity could be due to an increase in enzyme concentration. The decline in respiration rate of CO,-treated fruit was most likely due to the decrease in intracellular pH and its effect on the activities of important respiratory enzymes, including CytOx. The regulatory mechanisms of other mitochondrial respiratory enzymes in `Hass' avocados exposed to elevated CO2 atmospheres are also under investigation.

Optimal Conditions for the Kinetic Assay of Serum Glutamate Dehydrogenase Activity at 37°C

1972 ◽  
Vol 18 (6) ◽  
pp. 523-527 ◽  
Author(s):  
Graham Ellis ◽  
David M Goldberg
Keyword(s):  
Glutamate Dehydrogenase ◽  
Substrate Inhibition ◽  
Enzyme Concentration ◽  
Ammonium Ions ◽  
Normal Range ◽  
Kinetic Assay ◽  
Ph Optimum ◽  
Absorbance Change ◽  
Glutamate Dehydrogenase Activity ◽  
Serum Glutamate

Abstract Optimal concentrations of ammonium ions, 2-oxoglutarate, and NADH were defined for serum glutamate dehydrogenase (EC 1.4.1.2) activity at 37°C. Substrate inhibition was not observed with the last two compounds. The pH optimum in triethanolamine buffer is 7.4, and activity is inhibited by increasing the buffer concentration beyond 50 mmol/liter. Activation by ADP exceeds that promoted by L-leucine, and there is little advantage in having both present. Activity is linear with time and with enzyme concentration to a limiting absorbance change of 0.300 at 340 nm, and precision was satisfactory. Data indicate the normal range to lie between 0 and 4 U/liter.

scholarly journals Conformational variation in superhelical deoxyribonucleic acid

1978 ◽  
Vol 171 (1) ◽  
pp. 281-283 ◽  
Author(s):  
A M Campbell
Keyword(s):  
Light Scattering ◽  
Ionic Strength ◽  
Structural Transition ◽  
Deoxyribonucleic Acid ◽  
Dna Molecules ◽  
Experimental Conditions ◽  
Low Ionic Strength

Sedimentation experiments have shown that superhelical DNA undergoes a sharp structural transition at low ionic strength. Light-scattering experiments show that this is due to a change in conformation of the DNA rather than to a change in interactions among DNA molecules. The results show that two possible conformations can occur for superhelical DNA under routine experimental conditions and may explain the discrepancies in the number of early unwinding sites exposed by different techniques.

scholarly journals Bioactivity of toothpaste containing bioactive glass in remineralizing media: effect of fluoride release from the enzymatic cleavage of monofluorophosphate.

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Anthony L. B. Maçon ◽  
Esther M. Valliant ◽  
Jonathan S. Earl ◽  
Julian R. Jones
Keyword(s):  
Alkaline Phosphatase ◽  
Ionic Strength ◽  
Bioactive Glass ◽  
Human Saliva ◽  
Enzyme Concentration ◽  
Fluoride Release ◽  
Enzymatic Cleavage ◽  
Media Effect ◽  
Fluoride Ions

AbstractObjectives. The aim was to introduce a new methodology to characterize toothpaste containing bioactive glass and to evaluate the effect of release of fluoride ions, by cleaving monofluorophosphate (MFP), on the mineral forming ability of Sensodyne Repair & Protect (SRP). which contains NovaMinTM (bioactive glass, 45S5 composition).Methods. SRP, NovaMin particles, and placebo paste (PLA) which did not contain NovaMin, were immersed into a remineralization media (RS), which mimics the ionic strength of human saliva, for 3 days with different concentrations of alkaline phosphatase (ALP): 0, 25 and 75 U.LResults. Hydroxyapatite (HA) formed on the surface of BG alone (after 1 h) and in toothpaste (after 2 h), whereas PLA did not induce any precipitation. ALP cleaved MFP at different rates depending on the enzyme concentration. Increasing the concentration of ALP from 0 and 75 U.L

scholarly journals The equilibrium constants of the glutamate dehydrogenase systems

1967 ◽  
Vol 105 (2) ◽  
pp. 691-695 ◽  
Author(s):  
P. C. Engel ◽  
K. Dalziel
Keyword(s):  
Free Energy ◽  
Ionic Strength ◽  
Glutamate Dehydrogenase ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Standard Free Energy ◽  
Free Energy Change ◽  
Energy Change ◽  
Heat Of Reaction ◽  
Standard Free Energy Change

1. Equilibrium constants for the oxidation of glutamate by NAD+ and NADP+, catalysed by glutamate dehydrogenase, have been measured in phosphate buffers of different ionic strengths and at several temperatures. 2. The equilibrium constants for both systems vary markedly with ionic strength. Thermodynamic values for the two systems obtained by extrapolation to zero ionic strength differ significantly from one another. The standard free-energy change for NADP+ reduction has been calculated from that for NAD+ reduction. 3. The heat of reaction has been estimated and is the same with both coenzymes. 4. The thermodynamic data are discussed in relation to earlier data.

scholarly journals RNase reverses segment sequence in the anterior of a beetle egg (Callosobruchus maculatus, Coleoptera)

2016 ◽  
Author(s):  
Jitse M. van der Meer
Keyword(s):  
Callosobruchus Maculatus ◽  
Genetic Regulation ◽  
Enzyme Concentration ◽  
Mirror Image ◽  
Regulatory Mechanisms ◽  
Segment Sequence ◽  
Cytoplasmic Rna ◽  
Regulation Mechanisms ◽  
Anterior Segments ◽  
Segment Pattern

AbstractThe genetic regulation of anterior-posterior segment pattern development has been elucidated in detail for Drosophila, but it is not canonical for insects. A surprising diversity of regulatory mechanisms is being uncovered not only between insect Orders, but also within the Order of the Diptera. This raises the question whether the same diversity of regulatory mechanisms exists within other insect Orders. This paper draws attention to the promise of the pea beetle Callosobruchus maculatus for elucidating the evolution of pattern regulation mechanisms in Coleoptera and other insect Orders. Introduction of RNase in eggs of Callosobruchus replaces anterior segments with posterior segments oriented in mirror image symmetry to the original posterior segments (double abdomens). Reversal is specific for RNase activity, for treatment of the anterior egg pole and for cytoplasmic RNA. Yield depends on developmental stage, enzyme concentration and temperature. A maximum of 30% of treated eggs reversed segment sequence after puncture in 10.0 μg/ml RNase S reconstituted from S-protein and S-peptide at 30 °C. This result sets the stage for an analysis of the genetic regulation of segment pattern formation in the long germ embryo of the Coleopteran Callosobruchus and for comparison with the short germ embryo of the Coleopteran Tribolium.

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