Rate constant

The objective of this study was to establish a standard experimental model to determine the removal rate constants of wastewater pollutants in subsurface flow–constructed wetlands. This result shows the applicability of the proposed experimental model and procedure to determine the contaminant removal rate constants in constructed wetlands uniformly.

9p vibecca 01-10-2024 2 1   Download

In this study, a series of Consolidated–Undrained triaxial compression tests were conducted at a constant axial strain rate, with a small unloading and reloading during the monotonic loading to investigate the effect of various densities and curing times on the mechanical properties of Liquefied Stabilized Soil (LSS).

6p vibecca 01-10-2024 0 0   Download

The results showed that the overall diffusioncontrolled rate constant is equal to 4.82×109 M-1 s -1 at 298.15K. The zwitterionic form is the main existing form that plays an essential role in the HO - initiated oxidation of Ile (99.98%). The most preponderant reactions are found at C6-H (36.19%) and C8-H (37.77%) positions. Finally, the influence of temperature on the overall rate is also evaluated.

8p dianmotminh02 03-05-2024 7 2   Download

Using ab-initio calculations at the MP2/6-311G(3df, 2pd), a very high level theory, we obtained minimum energy structures for the C2H5O radical, products and transition states of reactions on the potential energy surface.

7p tamynhan9 02-12-2020 17 1   Download

In this study, a single product is considered which starts to deteriorate with constant rate of replenishment and demand rate is time and price dependent exponential function.

12p tocectocec 24-05-2020 16 1   Download

The evaporation of I2 was observed to follow primarily first order kinetics, depending on the I2 concentration. The evaporation rate constant increased rapidly with increase in temperature. The presence of Ie slightly reduced the evaporation rate of I2 by forming relatively stable I 3 . The effect of Cle at

7p minhxaminhyeu4 26-06-2019 14 2   Download

The main objective of nuclear reactor safety is to maintain the nuclear fuel in a thermally safe condition with enough safety margins during normal operation and anticipated operational occurrences. In this research, core flow bypass is studied under the conditions of the unavailability of safety systems. As core bypass occurs, the core flow rate is assumed to decrease exponentially with a time constant of 25 s to new steady state values of 20, 40, 60, and 80% of the nominal core flow rate.

6p minhxaminhyeu3 12-06-2019 19 2   Download

In the presence of suitable inhibitors, the experimental results show that free radical
OH was generated in the H2O-Mn(II)-ethylenediamine-indigocarmine-H3BO3-H2O2 system. Hydroxyl radical
OH has hight oxidation capability and its reaction rate constant with a substrate as indigocarmine kOH+Ind was determined by using the concurent reactions. The calculations were done by method of least square after programming on PC and by graphic method.

4p uocvong04 24-09-2015 51 5   Download

The high-pressure stopped-flow technique is applied to study the CO binding in cytochrome P450cam (P450cam) bound with homologous substrates (1R-camphor, camphane, norcamphor and norbornane) and in the substrate-free protein. The activation volume DV # of the CO on-rate is positive for P450cam bound with substrates that do not contain methyl groups. The kon rate constant for these substrate complexes is in the order of 3 · 106 M)1Æs)1. In contrast, P450cam complexed with substrates carrying methyl groups show a negative activation volume and a low kon rate constant of % 3 · 104 M)1Æs)1. ...

8p system191 01-06-2013 38 4   Download

A comparative study of thermodynamic and kinetic aspects of Cu(II) and Ni(II) binding at the N-terminal binding site of human and bovine serum albumins (HSA and BSA, respectively) and short peptide analogues was performed using potentiometry and spectroscopic techniques. It was found that while qualitative aspects of interaction (spectra and structures of complexes, order of reactions) could be reproduced, the quantitative parameters (stability and rate constants) could not.

9p research12 01-06-2013 38 4   Download

Y238, oneof thevery fewconservedresidues in theactive site ofD-amino acid oxidases (DAAO), was mutated to phe-nylalanine and serine in the enzyme from the yeastRhodo-torula gracilis. The mutated proteins are catalytically competent thus eliminating Tyr238 as an active-site acid/ base catalyst. Y238FandY238Smutants exhibit a threefold slower turnover on D-alanine as substrate, which can be attributed to a slower rate of product release relative to the wild-type enzyme (a change of the rate constants for sub-strate binding was also evident). ...

10p research12 29-04-2013 58 5   Download

The interactions between photosystem I and five charge mutants of plastocyanin from the cyanobacteriumPhormi-dium laminosumwere investigatedin vitro. The dependence of the overall rate constant of reaction,k2, on ionic strength was investigated using laser flash photolysis. The rate con-stant of the wild-type reaction increased with ionic strength, indicating repulsion between the reaction partners. Remov-inganegativechargeonplastocyanin(D44A) acceleratedthe reactionandmade it independentof ionic strength; removing a positive charge adjacent to D44 (K53A) had little effect....

10p tumor12 22-04-2013 38 4   Download

One-electron oxidation of six different c-type lysozymes from hen egg white, turkey egg white, human milk, horse milk, camel stomach and tortoise was studied by gamma-and pulse-radiolysis.In the first step, one tryptophan side chain is oxidized to indolyl free radical, which is produced quantitatively.As shown already, the indolyl radical subse-quently oxidizes a tyrosine side chain to the phenoxy radical in an intramolecular reaction.However this reaction is not total and its stoichiometry depends on the protein.Rate constants also vary between proteins, from 120Æs )1 to 1000Æs )1 at pH 7.

7p tumor12 20-04-2013 40 2   Download

Thermobifida fusca xyloglucan-specific endo-b-1,4-gluca-nase (Xeg)74 and the Xeg74 catalytic domain (CD) were cloned, expressed inEscherichia coli, purified and charac-terized.This enzymehas aglycohydrolase family-74CDthat is a specific xyloglucanase followed by a family-2 carbo-hydrate binding module at the C terminus.The Michaelis constant (Km) andmaximal rate (Vmax) values for hydrolysis of tamarind seed xyloglucan (tamXG) are 2.4lMand 966lmol xyloglucan oligosaccharides (XGOs) min )1 Ælmol protein )1 ....

9p tumor12 20-04-2013 48 5   Download

Incubation of an NAD + -dependent succinic semialdehyde dehydrogenase from bovine brain with 4-dimethylamino-azobenzene-4-iodoacetamide (DABIA) resulted in a time-dependent loss of enzymatic activity. This inactivation followed pseudofirst-order kinetics with a second-order rate constant of 168M )1 Æmin )1 .The spectrumofDABIA-labeled enzyme showed a characteristic peak of the DABIA alkyl-ated sulfhydryl group chromophore at 436 nm, which was absent from the spectrum of the native enzyme.

0p awards 05-04-2013 31 2   Download

Escherichia colifatty acid cyclopropane synthase (CFAS) was overproduced and purified as a His6 -tagged protein. This recombinant enzyme is as active as the native enzyme with aKmof 90lMforS-AdoMet and a specific activity of 5·10 )2 lmolÆmin )1 Æmg )1 . The enzyme is devoid of organic or metal cofactors and is unable to catalyze the wash-out of themethyl protons ofS-AdoMet to the solvent, data that do not support the ylidemechanism. Inactivationof the enzyme by 5,5¢-dithiobis-(2-nitrobenzoic acid) (DTNB), a pseudo first-order process with a rate constant of 1.

10p awards 05-04-2013 32 2   Download

The signal transducer and activator of transcription (STAT) proteins have initiallybeendescribedas cytoplasmicproteins that enter the nucleus only after cytokine treatment of cells. Contrary to this assumption, it was demonstrated that STATs are constantly shuttling between nucleus and cyto-plasm irrespective of cytokine stimulation. This happens both via carrier-dependent as well as carrier-independent transportation. Moreover, it was also recognized that cyto-kine stimulation triggers nuclear retention of dimeric STATs, rather than affecting the rate of nuclear import. ...

7p awards 05-04-2013 36 3   Download

The different effects of pH and NaCl on individual O2-binding properties ofaandbsubunits within liganded tetramer and dimer of human hemo-globin (HbA) were examined in a number of laser time-resolved spectro-scopic measurements. A previously proposed approach [Dzhagarov BM & Lepeshkevich SV (2004)Chem Phys Lett390, 59–64] was used to determine the extent of subunit dissociation rate constant difference and subunit affinity difference from a single flash photolysis experiment.

11p dell39 27-03-2013 48 4   Download

TheispC gene of Arabidopsis thalianawas expressed in pseudomature form without the putative plastid-targeting sequence in a recombinant Escherichia colistrain. The recombinant protein was purified by affinity chromatography and was shown to catalyze the formation of 2C-methyl-d-erythritol 4-phosphate from 1-deoxy-d-xylulose 5-phosphate at a rate of 5.6lmolÆmin )1 Æmg )1 (kcat 4.4 s )1 ). The Michaelis constants for 1-deoxy-d-xylulose 5-phosphate and the cosubstrate NADPH are 132 and 30lm, respectively. ...

13p inspiron33 25-03-2013 36 5   Download

Prostacyclin synthase (PGIS) is a member of the cytochrome P450 family in which the oxyferrous complexes are generally labile in the absence of substrate. At 4C, the on-rate constants and off-rate constants of oxygen binding to PGIS in solution are 5.9·10 5 m )1 Æs )1 and 29 s )1 , respectively.

10p media19 06-03-2013 39 3   Download