Modelling the adsorption of phospholipid vesicles to a silicon dioxide surface using Langmuir kinetics

2022 ◽  
Author(s):  
Iad Alhallak ◽  
Peter J. N. Kett
Keyword(s):  
Silicon Dioxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Lipid Vesicles ◽  
Phospholipid Vesicles ◽  
Adsorption And Desorption ◽  
Langmuir Kinetics

The rate constants and equilibrium constant for the adsorption and desorption of lipid vesicles from a SiO2 surface have been determined.

The reaction of nickel(II) bis(diethyldithiocarbamate) with N,N,N',N'-tetraethyl thiuramdisulphide

1985 ◽  
Vol 50 (8) ◽  
pp. 1648-1660 ◽  
Author(s):  
Ernest Beinrohr ◽  
Andrej Staško ◽  
Ján Garaj
Keyword(s):  
Equilibrium Constant ◽  
Rate Constants

The oxidation of nickel(II) bis(diethyldithiocarbamate) (NiL2) by N,N,N',N'-tetraethyl thiuramdisulphide (tds) can be described by the equation 2 NiL2 + tds ⇄ 2 NiL3 (NiL3 = tris(diethyldithiocarbamate) nickel(III)). The equilibrium constant of the reaction depends on the polarity of the solvent (4.4 . 10-3 in toluene, 1.3 . 10-3 in chloroform, and 8 . 10-4 in acetone and methanol). The rate constants k1 and k-2 and the ratio k2/k-1 were found for the reaction steps NiL2 + tds ⇄ NiL3 + L. and NiL2 + L. ⇄ NiL3, where L. is the (C2H5)2NCS2. radical.

scholarly journals The Lantibiotic Nisin Induces Transmembrane Movement of a Fluorescent Phospholipid

1998 ◽  
Vol 180 (24) ◽  
pp. 6565-6570 ◽  
Author(s):  
Gert N. Moll ◽  
Wil N. Konings ◽  
Arnold J. M. Driessen
Keyword(s):  
Antimicrobial Peptide ◽  
Rate Constant ◽  
Lipid Vesicles ◽  
Phospholipid Vesicles ◽  
Nisin Concentration ◽  
Outer Leaflet ◽  
Target Membrane

ABSTRACT Nisin is a pore-forming antimicrobial peptide. The capacity of nisin to induce transmembrane movement of a fluorescent phospholipid in lipid vesicles was investigated. Unilamellar phospholipid vesicles that contained a fluorescent phospholipid (1-acyl-2-{6-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]caproyl}-sn-glycero-3-phosphocholine) in the inner leaflet of the bilayer were used. Nisin-induced movement of the fluorescent phospholipid from the inner leaflet to the outer leaflet of the membrane reached stable levels, which were dependent on the concentration of nisin added. The rate constant k of this nisin-induced transmembrane movement increased with the nisin concentration but was not dependent on temperature within the range of 5 to 30°C. In contrast, the rate constant of movement of fluorescent phospholipid from vesicle to vesicle strongly depended on temperature. The data indicate that nisin transiently disturbs the phospholipid organization of the target membrane.

scholarly journals STUDY OF CARBON DIOXIDE ADSORPTION ON CHROMIUM OXIDE AND GALLIUM OXIDE CATALYSTS ON BASIS OF NON-LINEAR RELAXATION TIMES

2018 ◽  
Vol 61 (2) ◽  
pp. 46 ◽  
Author(s):  
Nikolay I. Kol'tsov
Keyword(s):  
Carbon Dioxide ◽  
Relaxation Time ◽  
Chromium Oxide ◽  
Rate Constants ◽  
Gallium Oxide ◽  
Relaxation Times ◽  
Oxide Catalysts ◽  
Linear Relaxation ◽  
Adsorption And Desorption ◽  
Non Linear

Recently the analysis of transient regimes of chemical reactions is paid much attention. This is due to the fact that the time-dependent relaxation modes prior to achieving steady states contain important information about the features of the reactions. During unsteady mode the changes in reactant concentrations and rate of the reaction in time are observed. These changes are due to their own relaxation processes, depending on the structure of the reaction mechanism. A complete study of the reaction mechanism involves the study of the relaxation characteristics both near and away from the stationary state. Linear relaxation time describes the local transient modes near the steady state and it is calculated as the time decrease deviations of reactant concentrations from steady-state values in the e-times. Non-linear relaxation time describes the overall behavior reactions and it can be evaluated through the reaction time from the initial state to a stationary. Depending on the structural features of reactions ratio to determine the non-linear relaxation time through of reactions parameters (rate constants stages and reactant concentrations) differ significantly. The establishment of such ratio for a particular reaction allows getting more information to identify the mechanism and the constituent rate constants of its stages. The mechanism of any catalytic reaction involves stages adsorption of one or more of the starting materials on the catalyst surface. As a rule these stages are initial remaining stages of chemical transformation of reactants adsorbed forms follow them. Therefore, it is necessary to have the data on these stages and rate constants of adsorption of reagents on the catalyst surface. Earlier by author the method for estimating the values of the rate constants of adsorption and desorption by linear relaxation times was described. This method was used for determine of mechanism and kinetic parameters of process of adsorption of carbon dioxide on the chromium oxide and gallium oxide catalysts. In this article the method for estimating the values of the rate constants of adsorption and desorption by non-linear relaxation times for this process is described. The previously found CO2 dissociative adsorption mechanism was proved by the obtained results. The intervals of values changes of the rate constants of adsorption and desorption of carbon dioxide on the gallium oxide and chromium oxide catalysts were defined.Forcitation:Kol’tsov N.I. Study of carbon dioxide adsorption on chromium oxide and gallium oxide catalysts on basis of non-linear relaxation times. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 46-52

scholarly journals The study of phosphate ions sorption from silicon dioxide solutions obtained by using acid decomposition of nepheline

2021 ◽  
Vol 12 (2-2021) ◽  
pp. 42-47
Author(s):  
Yu. O. Velyaev ◽  
◽  
D. V. Maiorov ◽  
Keyword(s):  
Experimental Data ◽  
Silicon Dioxide ◽  
Equilibrium Constant ◽  
Municipal Wastewater ◽  
Adsorption Equilibrium ◽  
Sorption Process ◽  
Acid Decomposition ◽  
Phosphate Ion ◽  
Phosphate Ions ◽  
Adsorption Monolayer

The process of sorption of phosphate ion by silicon dioxide obtained by acid decomposition of nepheline is studied. The experimental data were processed using the Freundlich and Langmuir sorption equations, which showed that the sorption process is fairly accurately described by both equations, while the use of the Langmuir monomolecular adsorption equation is preferable in the calculations. The capacity of the adsorption monolayer of the synthesized sample relative to the РО43–-ion and the adsorption equilibrium constant are calculated. Based on the obtained data, various options for sorption treatment of municipal wastewater from РО43--ion to normalized MPC values were evaluated.

Dynamics of the Bis-Tris and High Spin-Low Spin Equilibria of 2-(2′-Pyridyl)imidazoleiron(II) Complexes in Dimethyl Sulfoxide Solutions

1988 ◽  
Vol 41 (9) ◽  
pp. 1315 ◽  
Author(s):  
JK Beattie ◽  
KJ Mcmahon
Keyword(s):  
Relaxation Time ◽  
Dimethyl Sulfoxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Temperature Jump ◽  
Free Ligand ◽  
Relaxation Curve ◽  
Dissociation Equilibrium ◽  
Laser Temperature Jump ◽  
Equilibrium Transition

Ultrasonic and temperature-jump relaxation kinetics have been used to observe, respectively, the spin equilibrium and tris-bis ligand dissociation equilibrium of the 2-(2′-pyridyl) imidazoleiron (II) complexes in dimethyl sulfoxide solutions. In the ultrasonic experiments a single relaxation curve describes the excess sound absorption with a relaxation time of 73�3 ns. This was identified as perturbation of the singlet-quintet spin equilibrium by comparison with previous laser temperature-jump measurements in other solvents and by the temperature dependence of the relaxation amplitude. The equilibrium constant for the singlet-quintet transition was determined by the Evans n.m.r . method to be 0.48 at 298 K. From the relaxation time and the equilibrium constant the rate constants for the spin-equilibrium transition can be calculated to be k15 of 4.5×106 s-1 and k51 of 9.4×106s-1. In the temperature-jump experiments a millisecond relaxation time was observed. The dependence of the relaxation time on the concentration of the free ligand is of the form kobs = a + b[L]. From the ratio b/a an equilibrium constant for the perturbed process can be calculated. An independent measure of this equilibrium constant was obtained from spectrophotometric measurements. The rate constants for the formation and dissociation of the tris complex are calculated to be 2.8 × 104 dm3 mol-1 s-1 and 2.1 × 102 s-1, respectively, at 298 K.

The retroaldol reaction of 3-methyl-2-butenal

1983 ◽  
Vol 61 (1) ◽  
pp. 171-178 ◽  
Author(s):  
J. Peter Guthrie ◽  
Brian A. Dawson
Keyword(s):  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Aqueous Sodium Hydroxide ◽  
Initial Increase ◽  
Aqueous Sodium ◽  
Rate Determining Step ◽  
Kinetics Of

In aqueous sodium hydroxide solutions at 25 °C, 3-methyl-2-butenal, 1c, undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics of the retroaldol reaction were followed spectrophotometrically at 242 nm and showed simple first order behavior. When 3-methyl-3-hydroxybutanal, 2c, was added to aqueous sodium hydroxide solutions at 25 °C, there was an initial increase in absorbance at 242 nm, attributed to formation of 1c, followed by a 20-fold slower decrease; the rate of the slow decrease matches the rate of disappearance of 1c under the same conditions. Analysis of the kinetics allows determination of the three rate constants needed to describe the system: khyd = 0.00342; kdehyd = 0.00832; kretro = 0.0564; all M−1 s−1. The equilibrium constant for enone hydration is 0.41. Rate constants for the analogous reactions for acrolein and crotonaldehyde could be obtained from the literature. There is a reasonable rate–equilibrium correlation for the retroaldol step. For the enone hydration step, rate and equilibrium constants respond differently to replacement of hydrogen by methyl. It is proposed that this results from release of strain after the rate-determining step by rotation about a single bond; this decrease in strain is reflected in the equilibrium constant but not in the rate constant.

Isothiazole chemistry. IV. Cyanide cleavage of the S-N bond in 3-hydroxyisothiazole

1967 ◽  
Vol 20 (12) ◽  
pp. 2729 ◽  
Author(s):  
WD Crow ◽  
I Gosney
Keyword(s):  
Equilibrium Constant ◽  
Rate Constants ◽  
Nucleophilic Attack ◽  
Effect Of Temperature ◽  
Cyanide Ion ◽  
Equilibrium Studies ◽  
Conjugate Acid ◽  
Ph Range ◽  
Rate Profile ◽  
Direct Attack

Nucleophilic attack on 3-hydroxyisothiazole by cyanide ion, yielding cis-3-thiocyanoacrylamide, has been investigated over the pH range 0.00-5.50. Rate constants have been measured both for direct attack by cyanide ion and from the effect of cyanide ion in retarding the cyclization of the thiocyanoacrylamide; in both cases the derived rate constants agree. The pH-rate profile of the reaction reveals the existence of two kinetically discrete mechanisms. Within the range 5.50-4.00 the dominating mechanism is one involving a slow direct attack on 3-hydroxyisothiazole itself, while at pH less than 3.50 the conjugate acid of this molecule is subjected to a much faster attack. Equilibrium studies have been made for the system, and the effect of temperature on the equilibrium constant has been used to derive thermodynamic parameters.

Inhibition of Factor Xa in Prothrombinase Is Enhanced by Covalent Linkage of Antithrombin to Heparin.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1613-1613
Author(s):  
Sanjay Patel ◽  
Leslie R. Berry ◽  
Lesley Smith ◽  
Anthony Chan
Keyword(s):  
Rate Constants ◽  
Thrombin Generation ◽  
Factor Xa ◽  
Complex Mixtures ◽  
Free State ◽  
Phospholipid Vesicles ◽  
Covalent Linkage ◽  
Rate Difference ◽  
Prothrombinase Complex ◽  
Factor Va

Abstract The rate of prothrombin to thrombin conversion by factor Xa (Xa) is enhanced when Xa is incorporated into the surface-bound prothrombinase complex. However, in comparison to the free state, Xa within the prothrombinase complex is afforded protection from antithrombin + heparin (AT+H) inactivation. We have shown that, unlike AT+H, a covalent conjugate of AT and H (ATH) can neutralize fibrin-bound thrombin. In this study, AT+H and ATH were compared in their reaction with Xa +/− prothrombinase complex. Mixtures of CaCl2, phospholipid vesicles, factor Va (Va) and prothrombin in TSP buffer, were combined with Xa. Following addition of either AT+H or ATH, time samples were neutralized with Na2EDTA + polybrene + substrate (S-2222) and residual Xa activity measured. Second order rate constants (k2) were calculated from plots of activity versus time. Results were compared to corresponding experiments with Xa alone. AT+H inactivation of Xa in prothrombinase occurred at a k2 (x 107 M−1min−1) of 2.34 +/− 0.09. In contrast, neutralization of free Xa by AT+H was significantly faster (k2 = 8.34 +/− 0.18, p = 0.03). Reaction with ATH showed no significant rate difference for Xa inhibition in either the complexed or free states (18.5 +/− 3.3 and 16.3 +/− 3.7, respectively). Intriguingly, the rates achieved for ATH inhibition of complexed and free Xa were significantly greater than that for AT+H with free Xa (p=0.03 and p=0.02, respectively). We conclude that covalent complexes of AT and H do not encounter resistance in the inhibition of Xa in prothrombinase, as seen for non-covalent AT+H mixtures. Thus, it is possible for ATH to effectively inhibit the propagation phase of thrombin generation and thus dampen thrombin production via neutralization of Xa in prothrombinase.

Sign in / Sign up

Export Citation Format

Share Document