scholarly journals Kinetic studies with the use of proton-magnetic-resonance spectroscopy of the specific α-deuteration of amino acids by Escherichia coli aspartate aminotransferase

1978 ◽  
Vol 171 (3) ◽  
pp. 719-723 ◽  
Author(s):  
E Gout ◽  
S Chesne ◽  
C G Beguin ◽  
J Pelmont
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Aspartate Aminotransferase ◽  
Proton Magnetic Resonance ◽  
Reaction Rate ◽  
Kinetic Studies ◽  
Bond Breaking ◽  
Resonance Spectroscopy ◽  
First Order ◽  
Reaction Rate Constants

Escherichia coli aspartate aminotransferase was exposed to aspartate or phenylalanine without oxo acid in buffered 2H2O. The alpha-hydrogen of the amino acids underwent first-order exchange with respect to both substrate and enzyme. P.m.r. spectroscopy gave consistent reaction-rate constants. The deuterium-exchange rate was only moderately increased by addition of oxo acids and was of the same order as the transamination rate. No beta-deuteration was observed. The C(alpha)-H-bond-breaking step is discussed as a part of the entire transamination mechanism.

Kinetics of the Ozonation of Tetrabromobisphenol-A in Wastewater

2011 ◽  
Vol 383-390 ◽  
pp. 2945-2950 ◽  
Author(s):  
Jie Zhang ◽  
Shi Long He ◽  
Mei Feng Hou ◽  
Li Ping Wang ◽  
Li Jiang Tian
Keyword(s):  
Rate Constants ◽  
Apparent Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Kinetic Studies ◽  
Tetrabromobisphenol A ◽  
First Order ◽  
Reaction Rate Constants ◽  
Pseudo First Order ◽  
Kinetics Of

The kinetics of TBBPA degradation by ozonation in semi-batch reactor was studied. The reaction rate constants of TBBPA with O3 and •OH were measured by means of direct ozone attack and competition kinetics, and the values of which were 6.10 l/(mol•s), 4.8×109 l/(mol•s), respectively. Results of kinetic studies showed that TBBPA degradation by ozonation under the different conditions tested followed the pseudo-first-order. The values of apparent rate constant of TBBPA degradation increased with the increase of ozone dosage and pH, but decreased with the increase of initial TBBPA concentration.

scholarly journals Reactivity and kinetic studies of benzofuran hydrodeoxygenation over a Ni2P-O/MCM-41 catalyst

2019 ◽  
Vol 44 (4) ◽  
pp. 307-315 ◽  
Author(s):  
Xueya Dai ◽  
Hua Song ◽  
Hualin Song ◽  
Jing Gong ◽  
Feng Li ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Time Analysis ◽  
Liquid Ratio ◽  
Order Model ◽  
Free Products ◽  
First Order ◽  
Reaction Rate Constants ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Mcm 41

A nickel phosphide hydrodeoxygenation catalyst (Ni2P-O/MCM-41) was prepared using a new synthetic method. The as-prepared catalyst was evaluated in the hydrodeoxygenation of benzofuran, and the effects of reaction temperature, pressure, and the H2/liquid ratio were investigated. A pseudo first-order model was employed to describe the reaction kinetics of benzofuran hydrodeoxygenation over the Ni2P-O/MCM-41 catalyst. The reaction rate constants ( k1– k5) at different temperatures were determined according to this model. At 533 K, the conversion of 2-ethylphenol in to ethylbenzene began to increase dramatically, and the yield of O-free product, ethylcyclohexane, started to increase rapidly. At 573 K, 3.0 MPa, and a H2/liquid ratio of 500 (V/V), the conversion of benzofuran over Ni2P-O/MCM-41 reached 93%, and the combined yield of O-free products was 91%. Contact time analysis indicated that demethylation was not favored over the Ni2P-O/MCM-41 catalyst.

Purification and kinetic studies of the hemolysin from Escherichia coli

1971 ◽  
Vol 17 (6) ◽  
pp. 741-745 ◽  
Author(s):  
Peter Zwadyk Jr. ◽  
I. S. Snyder
Keyword(s):  
Escherichia Coli ◽  
Ammonium Sulfate ◽  
Reaction Rate ◽  
Kinetic Studies ◽  
Ammonium Sulfate Precipitation ◽  
Complex Curve ◽  
Sheep Erythrocytes

The hemolysin of Escherichia coli has been concentrated 23-fold by ethanol and ammonium sulfate precipitation. Further evidence has been presented that the hemolysin is a protein or peptide. Kinetic studies of the hemolytic reaction reveal a complex curve which consists of a lag, an area of accelerated reaction rate, and a plateau. Kinetic studies also show that the hemolytic reaction can be best demonstrated at a pH of 7.9 and a temperature of 30 °C using a 1% suspension of sheep erythrocytes.

scholarly journals Kinetic analysis of myoglobin autoxidation by isoelectric-focusing electrophoresis

1981 ◽  
Vol 193 (1) ◽  
pp. 181-185 ◽  
Author(s):  
A Tomoda ◽  
T Takizawa ◽  
A Tsuji ◽  
Y Yoneyama
Keyword(s):  
Isoelectric Focusing ◽  
Superoxide Anion ◽  
Reaction Rate ◽  
Ph Dependence ◽  
Acid Base ◽  
First Order ◽  
Reaction Rate Constants ◽  
Ph Values ◽  
Ph Dependent ◽  
Three State Model

The autoxidation of horse myoglobin was studied in the presence or absence of catalase (EC 1.11.1.6) and/or superoxide dismutase (EC 1.15.1.1) at various pH values (6.6-7.8). Changes in the percentages of oxymyoglobin and metmyoglobin during the reaction were analysed by means of isoelectric focusing on Ampholine gel plates. Oxymyoglobin was decreased in a first-order manner, with an accompanying increase in metmyoglobin, under the various conditions studied. The observed reaction rate constants obtained under these conditions were pH-dependent; however, they were also greatly affected by the presence of the enzymes. The pH-dependence of the overall reaction was explained by the acid-base three-state model of myoglobin proposed by Shikama & Sugawara [(1978) Eur. J. Biochem. 91, 407-413]. The reaction process of myoglobin autoxidation was explained by the model suggested by Winterbourn, McGrath & Carrell [(1976) Biochem. J. 155, 493-502], indicating that superoxide anion and hydrogen peroxide are involved in the reaction mechanism.

PENGARUH KONSENTRASI KATALIS ASAM DAN KECEPATAN PENGADUKAN PADA HIDROLISIS SELULOSA DARI AMPAS BATANG SORGUM MANIS

EKUILIBIUM ◽  
2013 ◽  
Vol 12 (1) ◽  
Author(s):  
Enny Kriswiyanti
Keyword(s):  
Hydrochloric Acid ◽  
Sweet Sorghum ◽  
Reaction Rate ◽  
Acid Catalyst ◽  
Agitation Speed ◽  
First Order ◽  
Reaction Rate Constants ◽  
Glucose Levels ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of

<p>Abstract : Sweet sorghum stem residues contains high enough cellulose (36.92%)so it can be<br />hydrolyzed to glucose. In this research, hydrolysis of cellulose is carried out using hydrochloric<br />acid catalyst. This research aims to determine the effect of acid catalyst concentration and<br />agitation speed on the resulting reduction of glucose levels and determine the reaction rate<br />constant of hydrolysis of sweet sorghum stem residues. The observed variables were the<br />concentration of hydrochloric acid catalyst (0.5 N, 1 N, 1.5 N, 2 N) and the agitation speed (150<br />rpm, 200 rpm, 250 rpm, 300 rpm). Glucose samples were analyzed by using the Lane-Eynon<br />method. Data analysis showed the higher concentration of hydrochloric acid (HCl) and the<br />agitation speed, the levels of reduced glucose that is formed is also higher. In this study by<br />assuming a first order reaction, the reaction rate constants obtained at variable concentrations of<br />hydrochloric acid catalyst ranged from 0.0010 to 0.0033 / minute and at agitation speeds variable<br />ranged from 0.0023 to 0.0030 / minute.<br />Keywords : sweet sorghum stem residues, hydrochloric acid, hydrolysis, cellulose</p>

scholarly journals Study on Cecropin B2 Production via Construct Bearing Intein Oligopeptide Cleavage Variants

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 1005
Author(s):  
Yi-Ting Fang ◽  
Si-Yu Li ◽  
Nien-Jen Hu ◽  
Jie Yang ◽  
Jyung-Hurng Liu ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Fusion Protein ◽  
Md Simulation ◽  
Cleavage Reaction ◽  
Chitin Binding Domain ◽  
First Order ◽  
C Terminus ◽  
Efficient Performance ◽  
Order Rate Equation

In this study, genetic engineering was applied to the overexpression of the antimicrobial peptide (AMP) cecropin B2 (cecB2). pTWIN1 vector with a chitin-binding domain (CBD) and an auto-cleavage Ssp DnaB intein (INT) was coupled to the cecB2 to form a fusion protein construct and expressed via Escherichia coli ER2566. The cecB2 was obtained via the INT cleavage reaction, which was highly related to its adjacent amino acids. Three oligopeptide cleavage variants (OCVs), i.e., GRA, CRA, and SRA, were used as the inserts located at the C-terminus of the INT to facilitate the cleavage reaction. SRA showed the most efficient performance in accelerating the INT self-cleavage reaction. In addition, in order to treat the INT as a biocatalyst, a first-order rate equation was applied to fit the INT cleavage reaction. A possible inference was proposed for the INT cleavage promotion with varied OCVs using a molecular dynamics (MD) simulation. The production and purification via the CBD-INT-SRA-cecB2 fusion protein resulted in a cecB2 yield of 58.7 mg/L with antimicrobial activity.

Effects of Carrageenan and Chitosan as Coating Materials on the Thermal Degradation of Microencapsulated Phycocyanin from Spirulina sp.

2019 ◽  
Vol 15 (5-6) ◽  
Author(s):  
H. Hadiyanto ◽  
Marcelinus Christwardana ◽  
Meiny Suzery ◽  
Heri Sutanto ◽  
Ayu Munti Nilamsari ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Thermal Degradation ◽  
Rate Constants ◽  
Reaction Rate ◽  
Order Reaction ◽  
Coating Materials ◽  
First Order ◽  
Reaction Rate Constants ◽  
Kinetics Of

AbstractPhycocyanin is a natural substance that can be used as an antioxidant and food colorant. The quality of phycocyanin deteriorates when it is exposed to heat, and such deterioration is evidenced by decreases in its antioxidant activity and color. Encapsulation, which introduces a coating material over a substance of interest, has been applied to prevent changes in substance quality. The objective of the present research is to evaluate the kinetics of thermal degradation of phycocyanin coated with carrageenan or chitosan. Encapsulated phycocyanin samples were exposed to temperatures of 40, 50, or 60 °C for 90 min, and kinetics of the resulting degradation was evaluated to determine changes in sample quality. The results showed that the thermal degradation of encapsulated phycocyanin at 40–60 °C follows first-order reaction kinetics with reaction rate constants (k) of 4.67–9.17 × 10–5 s-1 and 3.83–7.67 × 10–5 s-1 for carrageenan and chitosan, respectively, and that the k of encapsulated phycocyanin is slower than that obtained from samples without the coating materials (control). Encapsulation efficiencies (EE) of 68.66 % and 76.45 %, as well as loading capacities of 45.28 % and 49.16 %, were, respectively, obtained for carrageenan and chitosan.

Effect of Mixed-Phase TiO2/PVA Nanofibers on the Degradation on Methyl Orange

2015 ◽  
Vol 1107 ◽  
pp. 353-358
Author(s):  
Norizan Mohammed Lot ◽  
S. Nafisah Md. Rashid ◽  
Umi Sarah Jais ◽  
M. Kamil Abd Rahman
Keyword(s):  
Methyl Orange ◽  
Reaction Rate ◽  
Sol Gel ◽  
Average Diameter ◽  
Mixed Phase ◽  
Electrospinning Technique ◽  
X Ray ◽  
First Order ◽  
Reaction Rate Constants ◽  
Sol Gel Process

We report on the synthesis of nanostructured TiO2for various structural phases and observed the rate of degradation of methyl orange (MO) upon UV irradiation. Mixed phase nanocrystalline TiO2at temperature of 800°C shows higher rate of degradation of MO with the rate of 0.0203/min compared to other phases. This rate corresponds to the percentage of MO degradation of 58.85%, 71.69%, 86.25% and 91.82% for duration of 30, 60, 90 and 120 min of UV irradiations, respectively. The TiO2powder was prepared using titanium (IV) butoxide as the precursor via sol gel process. The samples were characterized using X-ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM). The rate of degradation of MO after UV exposure was measured using UV-Vis spectrophotometer. The first order reaction rate constants (kapp) of anatase; mixed-phase; and rutile phases were 0.0130, 0.0203 and 0.0029, respectively, which shows that mixed-phase TiO2has higherkappvalue indicating higher rate of degradation. The PVA/TiO2nanofibers were produced via electrospinning technique and similar tests on the nanofibers were conducted.Energy dispersive X-ray spectroscopy (EDX) indicates significant presence of TiO2is in nanofibers and the average diameter of the nanofibers was 600 nm.

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