scholarly journals The kinetics of the reduction of the lipophilic quinone avarone by N-alkyl-1,4-dihydronicotinamides of various lipophilicities

1999 ◽  
Vol 64 (11) ◽  
pp. 647-654 ◽  
Author(s):  
Mario Zlatovic ◽  
Dusan Sladic ◽  
Miroslav Gasic
Keyword(s):  
Cationic Surfactants ◽  
Reaction Rate ◽  
Anionic Surfactants ◽  
Reaction Rates ◽  
Biologically Active ◽  
Ionic Surfactants ◽  
Protic Solvent ◽  
Model Compounds ◽  
Kinetics Of ◽  
Long Chain

Several NADH model compounds, N-alkyl-1,4-dihydronicotinamides, some of them possessing amphiphilic properties, have been synthesized, and the kinetics of their reaction with a biologically active liphophilic quinone, avarone, has been studied in a protic solvent both in the presence and absence of cationic, anionic or non-ionic surfactants. In the absence of micellar agents, the medium- and long-chain N-dodecyl (3) and N-heptadecyl (4) derivatives show a significant increase in the reaction rates compared to other model compounds, due to the stabilization of the semiquinone intermediate. Anionic surfactants retard the reaction, non-ionic surfactants slightly accelerate the reaction with the short-chain derivatives, and retard the reaction with the medium- and long-chain derivatives, and the cationic surfactants increase the reaction rate with all derivatives except the long-chain 4. The results support the e-p-e mechanism of the reduction of lipophilic quinones byNADHmodels in protic medium.

A KINETICS AND MECHANISTIC STUDY OF THE OXIDATION OF L-ARGININE BY QDC IN DMF-WATER MEDIUM

2021 ◽  
pp. 11-12
Author(s):  
Deepika Jain ◽  
Shilpa Rathor
Keyword(s):  
Perchloric Acid ◽  
Reaction Rate ◽  
Main Product ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Mechanistic Study ◽  
Water Medium ◽  
Volume Percentage ◽  
Kinetics Of Oxidation ◽  
Kinetics Of

The present paper describes the kinetics of oxidation of l-Arginine by QDC in the presence of perchloric acid in 30% DMF-H O(v/v) medium at 2 + 40⁰C spectrophotometrically at λ =354nm. The reaction is rst order with respect to [QDC], [H ], and [substrate]. The reaction rate increased with max increasing volume percentage of DMF in reaction mixture. Michaelis- Menten type kinetic was observed with l-Arginine. The reaction rates were studied at different temperature and the activation parameters has been computed. The main product was identied as Cr (III) and 4-Guanidino buteraldehyde.

scholarly journals Enzymatic Kinetics of Enzymatically Extruded Degerminated Maize Using Glucamylase

2018 ◽  
Vol 7 (2) ◽  
pp. 10 ◽  
Author(s):  
Chengye Ma ◽  
Shuangshuang Yu ◽  
Yuyan Fan ◽  
Shuhua Wu ◽  
Zhehao Zhang ◽  
...  
Keyword(s):  
Incubation Time ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Enzyme Concentration ◽  
Kinetics Equation ◽  
Enzymatic Kinetics ◽  
Substrate Ph ◽  
Kinetics Of

In this study, the reaction rates of native degerminated maize, extruded degerminated maize and enzymatically extruded degerminated maize using glucoamylase were evaluated and the extrudate models were investigated. The effects of enzyme concentration, substrate pH, temperature and incubation time on the reaction rates were studied. The Lineweaver–Burk equation was used in order to obtain the parameters of the kinetics equation of catalysed hydrolysis. The results show that NDM’s vm is 0.0845g/(mL·min) and km is 0.0032, EDM’s vm is 0.6251g/(mL·min) and km is 0.0167, EEDM’s vm is 1.897g/(mL·min) and km is 0.0240. The reaction rate of EEDM is quicker than those of NDM and EDM. The kinetics equation of EEDM is in accordance with the Michaelis–Menten equation.

Kinetics of precipitation of surfactants. I. Anionic surfactants with calcium and with cationic surfactants

2001 ◽  
Vol 4 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Cheryl H. Rodriguez ◽  
Lori H. Lowery ◽  
John F. Scamehorn ◽  
Jeffrey H. Harwell
Keyword(s):  
Cationic Surfactants ◽  
Anionic Surfactants ◽  
Kinetics Of Precipitation ◽  
Kinetics Of

The Opacification of the Bovine Isolated Cornea by Surfactants and Other Chemicals—A Process of Protein Denaturation?

1987 ◽  
Vol 15 (1) ◽  
pp. 8-19
Author(s):  
Haruyoshi Igarashi
Keyword(s):  
Cationic Surfactants ◽  
Anionic Surfactants ◽  
Protein Denaturation ◽  
Egg White ◽  
Ionic Surfactants ◽  
Anionic Group ◽  
Ionic Compounds

An attempt has been made to determine whether anionic, cationic and non-ionic surfactants and other chemicals opacify the various layers of bovine isolated corneas to the same or to differing degrees. In the intact cornea the opacifying ability of surfactants was in the following order: cationic>anionic>non-ionic. The chemicals tested spanned the range from virtually inactive to very active. However, in the isolated stroma, the anionic surfactants caused considerably more opacity than either the cationic or non-ionic compounds. The results indicate that cationic surfactants primarily opacify the epithelium. It is suggested that opacification of the cornea is due to precipitation of protein in its various layers. The surfactants opacify egg white solutions in the same order of potency as in the cornea, but within the anionic group the order of opacification produced was the reverse of that in the cornea.

scholarly journals Kinetic Explanations for the Sequence Biases Observed in the Nonenzymatic Copying of RNA Templates

2021 ◽  
Author(s):  
Dian Ding ◽  
Lijun Zhou ◽  
Constantin Giurgiu ◽  
Jack W. Szostak
Keyword(s):  
Nucleic Acid ◽  
Origin Of Life ◽  
Reaction Rate ◽  
Nearest Neighbor ◽  
Reaction Rates ◽  
Primer Extension ◽  
Extension Rate ◽  
The Origin Of Life ◽  
Noncanonical Nucleotides ◽  
Kinetics Of

ABSTRACTThe identification of nonenzymatic pathways for nucleic acid replication is a key challenge in understanding the origin of life. We have previously shown that nonenzymatic RNA primer extension using 2-aminoimidazole (2AI) activated nucleotides occurs primarily through an imidazolium-bridged dinucleotide intermediate. The reactive nature and preorganized structure of the intermediate increase the efficiency of primer extension but remain insufficient to drive extensive copying of RNA templates containing all four canonical nucleotides. To understand the factors that limit RNA copying, we synthesized all ten 2AI-bridged dinucleotide intermediates and measured the kinetics of primer extension in a model. The affinities of the ten dinucleotides for the primer/template/helper complexes vary by over 7,000-fold, consistent with nearest neighbor energetic predictions. Surprisingly, the reaction rates at saturating intermediate concentrations still vary by over 15-fold, with the most weakly binding dinucleotides exhibiting a lower maximal reaction rate. Certain noncanonical nucleotides can decrease sequence dependent differences in affinity and primer extension rate, while monomers bridged to short oligonucleotides exhibit enhanced binding and reaction rates. We suggest that more uniform binding and reactivity of imidazolium-bridged intermediates may lead to the ability to copy arbitrary template sequences under prebiotically plausible conditions.

Eclogitization kinetics of continental granulites : quantification and implications

2020 ◽  
Author(s):  
Marie Baisset ◽  
Loic Labrousse ◽  
Alexandre Schubnel
Keyword(s):  
Rheological Behavior ◽  
Reaction Rate ◽  
Experimental Studies ◽  
Reaction Rates ◽  
First Order ◽  
Piston Cylinder ◽  
Ductile Flow ◽  
Convergence Zones ◽  
Kinetics Of ◽  
Type Apparatus

<p><span>When implicated in convergence zones, granulites of the lower continental crust are expected to eclogitize at depth.When exposed in the field such units show a bimodal rheological behavior between fracturing of the protolith rock (granulites) and ductile flow of the transformed parts (eclogites). It seems therefore that a competition exists between the rate at which the rocks are loaded in stress and the rate at which they transform, i.e. the overall eclogitization kinetics. The aim of the work presented here is to quantify the kinetics of the metamorphic reactions involved in eclogitization by estimating the reaction rates in plagioclase-bearing assemblages<span>  </span>submitted to different P-T conditions over different time spans. For this, experiments have been performed in piston-cylinder apparatus on aggregates derived from natural granulites. Special attention is paid to the location where nucleation starts and how it propagates in and between the grains. In this prospect, the presence of garnet and cpx in the plagioclase matrix is a first order control on the reaction process. This work follows previous experimental studies (e.g. Shi et al., 2017, Incel et al., 2018) which show that reaction-enhanced embrittlement may be key for fracturing at high pressure. It has been proposed that transient properties of the rocks induced by the very beginning of the reaction (e.g. volume change, small grain size nucleation products) can lead to brittle instabilities. As we assume that the rheological behavior of the crust is controlled by a competition between reaction rate and strain rate, experiments involving deformation of granulites while undergoing eclogitization are required. Preliminary results performed on Griggs-type apparatus, which constitutes the best tool for that, will also be presented.</span></p>

Polyoxometalate (POM) oxidation of lignin model compounds

Holzforschung ◽  
2008 ◽  
Vol 62 (1) ◽  
pp. 38-49 ◽  
Author(s):  
Yong Sik Kim ◽  
Hou-min Chang ◽  
John F. Kadla
Keyword(s):  
Reaction Rate ◽  
Model Compound ◽  
Reaction Rates ◽  
Hydroxyl Group ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
First Order ◽  
Resonance Stabilization ◽  
Lignin Model

Abstract Various lignin model compounds were oxidized with polyoxometalate (POM), K5[SiVW11O40]·12 H2O, in sodium acetate buffer (I=0.2 M, pH 5.0) and the reaction kinetics were investigated. The reactions were found to have second order reaction rates, first order with regards to both lignin model compound and POM. A dramatic increase in reactivity was observed upon addition of methoxyl groups in ortho-positions to the phenolic hydroxyl group. Syringyl units reacted faster than guaiacyl units. Reaction rates of para-substituted guaiacyl and syringyl model compounds showed a strong dependency on the nature of the substituents. The reaction rate of a 5-5′ dimer lignin model compound was extremely fast. The addition of the ortho-phenol substituent not only increased the electron density of the aromatic ring, but also helped stabilize the intermediate phenoxy radical through resonance stabilization and delocalization.

scholarly journals Estimation of Reaction Rates of Transesterification Pathways

2021 ◽  
Vol 3 ◽  
Author(s):  
Mario Alberto Pérez-Méndez ◽  
Gladys Jiménez-García ◽  
Rafael Huirache-Acuña ◽  
Rafael Maya-Yescas
Keyword(s):  
Sodium Hydroxide ◽  
Fatty Acid Methyl Esters ◽  
Reaction Rate ◽  
Methyl Esters ◽  
Reaction Rates ◽  
Reaction Engineering ◽  
Reaction Pathways ◽  
Chemical Reactors ◽  
Acid Methyl ◽  
Kinetics Of

Experimental estimation of reaction rates is a common aspect of reaction engineering because reaction kinetics are the base of the design of chemical reactors. However, it is not easy to follow complex reactions as it is the case of transesterification of triglycerides in presence of sodium hydroxide. Identifying the possible reaction pathways taking place as ionic and sequential, starting with the inorganic formation of methoxide, and followed by each one of the three organic transesterification steps of virgin soybean oil, deeper understanding about kinetics of this reacting path has been obtained. Reaction rate evaluations were performed by following the solution’s pH, based on a 24–1 design of experiments, making possible to estimate the rate constants. Additionally, it was observed that there is an optimum amount of sodium hydroxide feed to the process, therefore it is possible to minimize its addition, which favors diminishing the volume of leaching water. The best yield to fatty acid methyl esters, using the minimum amount of sodium hydroxide, was 98.84 wt%, which is highly competitive.

scholarly journals Adsorption of Different Surfactants on Kaolinite

1997 ◽  
Vol 15 (8) ◽  
pp. 619-626 ◽  
Author(s):  
A.A. Atia ◽  
N.R.E. Radwan
Keyword(s):  
Ion Exchange ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Cationic Surfactants ◽  
Anionic Surfactants ◽  
Electrostatic Attraction ◽  
Exchange Mechanism ◽  
Ionic Surfactants

The adsorption of anionic, cationic and non-ionic surfactants on kaolinite has been investigated. Anionic surfactants are widely used in enhanced oil recovery. The lower the adsorption on the oil-bearing rock, the higher the advantage of the surfactant to be used. Whilst the adsorption of anionic and non-ionic surfactants are negligible, that of cationic surfactants is relatively high. For this reason, the use of cationic reagents in the enhanced oil recovery is not recommended. The adsorption of cationic surfactants was found to follow an ion-exchange mechanism, while that of anionic and non-ionic surfactants proceeded through electrostatic attraction and precipitation.

STUDYING THE KINETIC CHARACTERISTICS OF THE EXTRACTION OF ANTHOCYANINS FROM THE SQUEEZE OF KRASNOSTOP ZOLOTOVSKY

2020 ◽  
Author(s):  
M.A. Egyan ◽  
Keyword(s):  
Reaction Rate ◽  
Sugar Content ◽  
Extraction Process ◽  
Efficiency Coefficient ◽  
Kinetic Characteristics ◽  
Reaction Rate Constants ◽  
Solids Content ◽  
Kinetics Of ◽  
Process Speed

The article shows studies characterizing the quality of the squeeze: the mechanical composition of the squeeze is determined, the structural moisture of each component is determined, the sugar content in the formed process of sedimentation of the juice and its acidity are determined refractometrically. The kinetics of anthocyanins extraction was determined in two ways, the solids content in the extract was calculated, and the reaction rate constants of the extraction process and the efficiency coefficient of ultrasonic amplification of the extraction process speed were calculated.

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