scholarly journals Initial-rate studies of a thermophilic glucokinase from Bacillus stearothermophilus

1987 ◽  
Vol 248 (1) ◽  
pp. 13-20 ◽  
Author(s):  
H Ishikawa ◽  
T Maeda ◽  
H Hikita
Keyword(s):  
Thermal Stability ◽  
Ternary Complex ◽  
Bacillus Stearothermophilus ◽  
Initial Rate ◽  
Rate Equations ◽  
Rate Data ◽  
Michaelis Constant ◽  
Wide Range ◽  
State Assumption ◽  
Reaction Schemes

The initial rates of phosphorylation of glucose catalysed by glucokinase from Bacillus stearothermophilus were measured over a wide range of glucose, MgATP2-, MgADP- and glucose 6-phosphate concentrations. The results of the effects of the inhibitors on the initial rates suggest that the reaction mechanism is essentially the ordered Bi Bi, in which glucose adds to the enzyme before MgATP2- and glucose 6-phosphate is released from the enzyme after the dissociation of MgADP-, and also suggest that the final step in which glucose 6-phosphate is released is irreversible. For many reaction schemes, the rate equations were derived on the basis of the pseudo-steady-state assumption and were used to correlate the experimental rate data. From this result, we concluded that the reaction obeys the ordered mechanism accompanied by the formation of a non-productive ternary complex, glucose-MgADP--enzyme. By using the experimental Dalziel coefficients phi i, some kinetic parameters were evaluated. The enzyme was characterized by the thermal stability and the low Michaelis constant, the values of which were 54 microM for glucose and 32 microM for MgATP2-.

scholarly journals The interpretation of kinetic data for enzyme-catalysed reactions involving three substrates

1969 ◽  
Vol 114 (3) ◽  
pp. 547-556 ◽  
Author(s):  
K. Dalziel
Keyword(s):  
Kinetic Data ◽  
Initial Rate ◽  
Rate Equations ◽  
Rate Data ◽  
Designed Experiments

The analysis and interpretation of initial-rate data for reactions involving three substrates, obtained in suitably designed experiments, are discussed. Possible mechanisms for such reactions are classified, the rate equations are compared and the extent to which they can be distinguished experimentally is considered.

scholarly journals Kinetic studies of bovine liver carbamoyl phosphate synthetase

1974 ◽  
Vol 141 (3) ◽  
pp. 807-816 ◽  
Author(s):  
Keith R. F. Elliott ◽  
Keith F. Tipton
Keyword(s):  
Initial Rate ◽  
Kinetic Studies ◽  
Bovine Liver ◽  
Kinetic Mechanism ◽  
Rate Equations ◽  
British Library ◽  
Rate Data ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Lending Library

A through study of initial-rate data has been made on carbamoyl phosphate synthetase from bovine liver. On the basis of the results the order of substrate binding to the enzyme is ATPMg followed by HCO3−, ATPMg and NH4+. A model for the enzymic mechanism is proposed, and the rate equations describing it are presented. Details of the derivation of the initial-rate equation for the kinetic mechanism proposed have been deposited as Supplementary Publication SUP 50032 (6 pages) at the British Library, Lending Division (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7QB, U.K., from whom copies may be obtained on the terms indicated in Biochem. J. (1973), 131, 5.

scholarly journals Intracellular Ionic Strength Sensing Using NanoLuc

2021 ◽  
Vol 22 (2) ◽  
pp. 677
Author(s):  
Tausif Altamash ◽  
Wesam Ahmed ◽  
Saad Rasool ◽  
Kabir H. Biswas
Keyword(s):  
Thermal Stability ◽  
Phase Separation ◽  
Drug Discovery ◽  
Ionic Strength ◽  
Cellular Signaling ◽  
Live Cells ◽  
Protein Activity ◽  
Cellular Survival ◽  
Cellular Processes ◽  
Wide Range

Intracellular ionic strength regulates myriad cellular processes that are fundamental to cellular survival and proliferation, including protein activity, aggregation, phase separation, and cell volume. It could be altered by changes in the activity of cellular signaling pathways, such as those that impact the activity of membrane-localized ion channels or by alterations in the microenvironmental osmolarity. Therefore, there is a demand for the development of sensitive tools for real-time monitoring of intracellular ionic strength. Here, we developed a bioluminescence-based intracellular ionic strength sensing strategy using the Nano Luciferase (NanoLuc) protein that has gained tremendous utility due to its high, long-lived bioluminescence output and thermal stability. Biochemical experiments using a recombinantly purified protein showed that NanoLuc bioluminescence is dependent on the ionic strength of the reaction buffer for a wide range of ionic strength conditions. Importantly, the decrease in the NanoLuc activity observed at higher ionic strengths could be reversed by decreasing the ionic strength of the reaction, thus making it suitable for sensing intracellular ionic strength alterations. Finally, we used an mNeonGreen–NanoLuc fusion protein to successfully monitor ionic strength alterations in a ratiometric manner through independent fluorescence and bioluminescence measurements in cell lysates and live cells. We envisage that the biosensing strategy developed here for detecting alterations in intracellular ionic strength will be applicable in a wide range of experiments, including high throughput cellular signaling, ion channel functional genomics, and drug discovery.

scholarly journals Rate Equation Modelling of Nonlinear Dynamics in Directly Modulated Multiple Quantum Well Laser Diodes

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 355-360 ◽  
Author(s):  
Stephen Bennett ◽  
Christopher M. Snowden ◽  
Stavros Iezekiel
Keyword(s):  
Nonlinear Dynamics ◽  
Quantum Well ◽  
Multiple Quantum Well ◽  
Period Doubling ◽  
Rate Equations ◽  
Multiple Quantum ◽  
Quantum Well Laser ◽  
Wide Range ◽  
Multiple Quantum Well Laser ◽  
Good Agreement

A theoretical (using rate equations) and experimental study of the nonlinear dynamics of a distributed feedback multiple quantum well laser diode is presented. The analysis is performed under direct modulation. Period doubling and period tripling are identified in both the measurements and simulations. Period doubling is found over a wide range of modulation frequencies in the laser. Computational results using rate equations show good agreement with the experimental results.

scholarly journals Thermal Stability and Luminescent Properties of Tri-cellulose Acetate Composites Containing Dy(SSA)3Phen Complex

2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Xiangwei Sun ◽  
Feiyue Wu ◽  
Yan Luo ◽  
Mengjun Huang ◽  
Yuntao Li ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Cellulose Acetate ◽  
Ternary Complex ◽  
Fluorescence Spectra ◽  
Luminescent Properties ◽  
Rare Earth Complex ◽  
Luminescent Materials ◽  
Sulfosalicylic Acid ◽  
Composition And Structure ◽  
Fluorescent Materials

Dysprosium (Dy) ternary complex was prepared using 5-sulfosalicylic acid (SSA) as the first ligand and 1,10-phenanthroline (Phen) as the second ligand, denoted as Dy(SSA)3Phen. The complex was blended with tri-cellulose acetate (TCA) via a cosolvent method to obtain polymer luminescent materials. The composition and structure of the rare-earth complex were characterized by means of elemental analysis, infrared (IR) spectra, and thermogravimetric analysis (TGA). The fluorescence spectra displayed this pure Dy(SSA)3Phen complex, and the TCA/Dy(SSA)3Phen composites all emit blue light. The (90/10) composite possesses fine luminescent properties with quantum yield of 33.5% and thermal stability for potential usage as blue fluorescent materials.

scholarly journals Rates of reactions catalysed by a dimeric enzyme. Effects of the reaction scheme and the kinetic parameters on co-operativity

1991 ◽  
Vol 280 (1) ◽  
pp. 131-137 ◽  
Author(s):  
H Ishikawa ◽  
H Ogino ◽  
H Oshida
Keyword(s):  
Substrate Inhibition ◽  
Reaction Scheme ◽  
Rate Equations ◽  
Kinetic Behaviour ◽  
Hill Coefficients ◽  
S Curve ◽  
Almost All ◽  
The Hill ◽  
Rate Behaviour ◽  
Reaction Schemes

For the reaction S in equilibrium P catalysed by a dimeric enzyme, the reaction schemes are considered on the basis of the KNF model. For each of the ten possible schemes, the rate equation is derived on the basis of the combined steady-state and rapid-equilibrium assumptions. The curves of the plots of initial velocity v versus the substrate concentration [S] and the Hill coefficients h calculated from the rate equations depend strongly on the reaction scheme and the parameter X1. This parameter is defined by log (KS2/KS1) and is a measure of the relative affinities of the first and second protomers for the substrate. When X1 less than 0, v-[S] curves for some schemes exhibit negative co-operativity (h less than 1.0) and v-[S] curves for other schemes are similar to that of the Michaelis-Menten scheme, indicating that, even if there is interaction between the distinct protomers, sigmoidal rate behaviour is not necessarily observed. When X1 greater than 0, all the reaction schemes except one, which shows substrate-inhibition kinetic behaviour, exhibit sigmoidal kinetic behaviour (h greater than 1.0), and at the limit of X1 much greater than 0 the Hill coefficients attain the maximum possible value of 2.0. Furthermore, we have found that, even if X1 = 0, the v-[S] curve for almost all the schemes considered in the present work does not necessarily agree with that for the Michaelis-Menten scheme. This means that the deviation of the v-[S] curve from a hyperbola can be observed even if there is no interaction between the distinct protomers.

scholarly journals Influence of Water Activity on Protease Adsorbed on Biochar in Organic Solvents

2017 ◽  
Vol 6 (4) ◽  
pp. 96 ◽  
Author(s):  
Hidetaka Noritomi ◽  
Jumpei Nishigami ◽  
Nobuyuki Endo ◽  
Satoru Kato ◽  
Katsumi Uchiyama
Keyword(s):  
Thermal Stability ◽  
Catalytic Activity ◽  
Organic Solvents ◽  
Water Activity ◽  
Initial Rate ◽  
Butyl Ester ◽  
Nitrogen Atmosphere ◽  
Bamboo Charcoal ◽  
Influence Of Water ◽  
Hydrolysis Of

We have found that the organic solvent-resistance of Alpha-chymotrypsin (Alpha-CT) is enhanced by adsorbing Alpha-CT onto bamboo charcoal powder (BCP), which is obtained by pyrolyzing bamboo waste under nitrogen atmosphere, and is markedly dependent on the thermodynamic water activity (aw) in organic solvents. When BCP-adsorbed　Alpha-CT was immersed in acetonitrile at an appropriate water activity, it effectively enhanced the transesterification of N-acetyl-L-tyrosine ethyl ester (N-Ac-Tyr-OEt) with n-butanol (BuOH) to produce N-acetyl-L-tyrosine butyl ester (N-Ac-Tyr-OBu), compared to the hydrolysis of N-Ac-Tyr-OEt with water to give N-acetyl-L-tyrosine (N-Ac-Tyr-OH). When the water activity was 0.28, the initial rate of transesterification catalyzed by BCP-adsorbed Alpha-CT was about sixty times greater than that catalyzed by free Alpha-CT. Regarding the reaction selectivity which is defined as a ratio of the initial rate of transesterification to that of hydrolysis, BCP-adsorbed α-CT was much superior to free Alpha-CT. The catalytic activity of BCP-adsorbed Alpha-CT was markedly dependent on the reaction temperature. Furthermore, concerning the thermal stability at 50 oC, the half-life of BCP-adsorbed Alpha-CT exhibited 3.8-fold, compared to that of free Alpha-CT.

scholarly journals Thermal fractionation of soil organic matter produces fine-scale distributions of SOM age

2021 ◽  
Author(s):  
Shane Stoner ◽  
Carlos Sierra ◽  
Marion Schrumpf ◽  
Sebastian Dötterl ◽  
Susan Trumbore
Keyword(s):  
Thermal Stability ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Chemical Oxidation ◽  
Fine Scale ◽  
Mineral Association ◽  
Density Fractions ◽  
Chemical Complexity ◽  
Wide Range ◽  
Carbon Release

<p>Soil organic matter (SOM) is a complex collection of organic molecules of varying origin, structure, chemical activity, and mineral association. A wide array of laboratory methods exists to separate SOM based on qualitative, biological, chemical, and physical characteristics. However, all present conceptual and logistical limitations, including the requirement of a substantial amount soil material.</p><p>An newly applied alternative method of fractionation relies on a conceptual analogue between biochemical stability in soil and thermal stability, e.g. more persistent SOM will require higher temperatures (greater energy inputs) to decompose than less persistent SOM. This accounts for both chemical complexity and mineral association as main factors in determining SOM persistence.</p><p>In this method, carbon is released by heating SOM to 900°C at a constant rate. The peaks of carbon release are grouped into activation energy pools, CO<sub>2 </sub>is collected, and analyzed for <sup>13</sup>C and <sup>14</sup>C. We seek to describe in finer detail the distribution of soil radiocarbon by adding another fractionation step following a different paradigm of SOM stability, and explore mineralogical effects on SOM quality and stability using thermal analysis, radiocarbon, and gas chromatography.</p><p>Here, we analyzed bulk soil and soil fractions derived from density separation and chemical oxidation, as well as mineral horizons dominated by diverse mineralogies. Density fractions contained a wide range of radiocarbon activities and that young SOM is stabilized across multiple fractions, likely due to organomineral complexation. Initial results showed that soil minerals with limited stabilization potential released C at lower temperatures than those with diverse stabilization mechanisms. High-temperature sub-fractions contained the oldest carbon across fractions and minerals, thus supporting the assumption that thermal stability can be used as a limited analogue for stability in soil. We present a fine-scale distribution of radiocarbon in SOM and discuss the potential of this method for comparison with other fractionation techniques.</p>

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