scholarly journals Rate constant of the reaction of the peroxyl radical of 1,4-dioxane with α-Tocopherol and trolox

2020 ◽  
Vol 64 (11) ◽  
pp. 55-60
Author(s):  
Olesya V. Semikasheva ◽  
◽  
Lucia R. Yakupova ◽  
Rustam L. Safiullin ◽  
◽  
...  
Keyword(s):  
Induction Period ◽  
Rate Constant ◽  
Peroxyl Radical ◽  
Practical Interest ◽  
Water Soluble ◽  
Oxygen Absorption ◽  
Initiation Rate ◽  
Radical Chain ◽  
Decay Rate Constant ◽  
Integral Methods

The study of the properties of water-soluble antioxidants is of practical interest. Research is hindered by the fact that such substances are poorly soluble in substrates, which are most widespread in determining the quantitative characteristics of antioxidants. Usually it is cumene, ethylbenzene, styrene. In this work, we used a method based on a model reaction of the radical chain 1,4-dioxane oxidation. This substrate is the most suitable solvent for evaluating the water-soluble substances antioxidant activity. The inhibitory activity of α-tocopherol (vitamin E) and trolox (a water-soluble analogue of α-tocopherol) was studied in a model system of radical chain 1,4-dioxane oxidation. Air oxygen served as the oxidizing agent. The experiments were carried out at 333 K. Initiation was carried out with 2,2'-azo-bis-isobutyronitrile. The reaction kinetics was monitored by the rate of oxygen uptake using a manometric setup. In this work to measure the initiation rate, the inhibitors method is used. The standard α-tocopherol inhibitor was used for this purpose. α-Tocopherol is an effective inhibitor with a known stoichiometric inhibition ratio of two. The method used in our study makes it possible to measure correct the length of the induction period using the kinetics of oxygen absorption. The induction period was determined by graphical and integral methods. The initiation rate was calculated based on the induction period values. The resulting value is in satisfactory agreement with the data based on the literary value of the decay rate constant 2,2'-azo-bis-isobutyronitrile. The rate constant of the reaction of the 1,4-dioxane peroxyl radical with α-tocopherol and trolox (fk7, L mol-1s-1, 333 K) was measured: (1.6 ± 0.1)∙106, (1.2 ± 0.1)∙106. The stoichiometric inhibition coefficient for trolox in the system of radical chain 1,4-dioxane oxidation was determined: f = 2.4 ± 0.2.

Differential antioxidant properties of red wine in water soluble and lipid soluble peroxyl radical generating systems

2004 ◽  
Vol 263 (1/2) ◽  
pp. 211-215 ◽  
Author(s):  
R.S. Faustino ◽  
T.A. Clark ◽  
S. Sobrattee ◽  
M.P. Czubryl ◽  
G.N. Pierce
Keyword(s):  
Red Wine ◽  
Peroxyl Radical ◽  
Antioxidant Properties ◽  
Water Soluble

Determination of the decay rate constant for hepatocytes immobilized in alginate microcapsules

2010 ◽  
Vol 27 (1) ◽  
pp. 86-93 ◽  
Author(s):  
Aldo Leal-Egaña ◽  
Aránzazu Díaz-Cuenca ◽  
Augustinus Bader
Keyword(s):  
Decay Rate ◽  
Rate Constant ◽  
Decay Rate Constant

Synthesis, Applications and Swelling Properties of Poly (Sodium Acrylate-Coacrylamide) Based Superabsorbent Hydrogels

2019 ◽  
Vol 41 (4) ◽  
pp. 668-668
Author(s):  
Saud Hashmi Saud Hashmi ◽  
Saad Nadeem Saad Nadeem ◽  
Zahoor Awan Zahoor Awan ◽  
Adeel ur Rehman Adeel ur Rehman ◽  
Ahsan Abdul Ghani Ahsan Abdul Ghani
Keyword(s):  
Rate Constant ◽  
Polymeric Materials ◽  
Water Soluble ◽  
Ion Concentration ◽  
Copolymer Composition ◽  
Swelling Properties ◽  
Swelling Capacity ◽  
Swelling Rate ◽  
Crosslinker Concentration ◽  
Superabsorbent Hydrogels

Superabsorbent hydrogels constitute a group of polymeric materials with three-dimensional network structure, which can swell to absorb an enormous amount of water or aqueous solutions. This property enables various commercial applications of hydrogels such as water holding capability in agriculture and superabsorbent material for baby diapers. Several novel superabsorbent hydrogels based on acrylic acid-co-acrylamide copolymers were synthesized under variation of copolymer compositions through free radical polymerization. N,N’methylenebisacrylamide (MBA) was used as a water soluble crosslinker and potassium persulphate (KPS) as an initiator. Effect of varying the copolymer composition, change in crosslinker concentration, and effect of environmental parameters (pH, temperature, and ion concentration) on both swelling capacity and swelling rate were examined. These gel shows maximum swelling at neutral pH-7, whereas increasing salt concentration in water decrease the swelling capacity. It was found interesting that an increase in crosslinker concentration from 0.020% to 0.16%, the swelling capacity decreases up to 70% while the swelling rate increases from 0.007g water/g dry hydrogel sec to 0.024g water/g dry hydrogel sec, respectively because there is a compromise exists between entropic spring forces between network connection points and the hydrostatic pressure of the water diffusing into the gels. Dynamic swelling curve obtained were fitted to the three different kinetic models namely Peleg’s kinetic model, pseudo 1st order as proposed by Lagergen and pseudo 2nd order kinetics. All these models provided a good agreement with the experimental data; However on the bases of statistical parameters (RMSE, R2 and X2) the Peleg’s model was selected as the most appropriate model for this study. Analyzing rate constant for Peleg’s models at different swelling temperatures disclosed that increasing temperature could only increase the swelling rate without affecting the swelling capacity of the hydrogels. Experimental values for rate constant k1 of Peleg’s model at different temperature shows a sharp decrease from 0.57545 at 30 oC to 0.1535 at 75 oC that contemplated the rate of swelling at 75 oC was 65% faster than that of 30 oC. The diffusion mechanisms in hydrogels were proven to be tailorable by increasing cross-linker concentration and temperature, leading towards the Fickian type diffusion behavior. The synthesized superabsorbent hydrogels were also tested for water retention applications in agriculture.

scholarly journals Modification of cardiac sodium channels by carboxyl reagents. Trimethyloxonium and water-soluble carbodiimide.

1993 ◽  
Vol 101 (5) ◽  
pp. 651-671 ◽  
Author(s):  
S C Dudley ◽  
C M Baumgarten
Keyword(s):  
Surface Potential ◽  
Rate Constant ◽  
Transition Rate ◽  
Decay Channel ◽  
Water Soluble ◽  
Adult Rabbit ◽  
Na Channel ◽  
Na Channels ◽  
Unitary Conductance ◽  
Cardiac Sodium Channels

In TTX-sensitive nerve and skeletal muscle Na+ channels, selective modification of external carboxyl groups with trimethyloxonium (TMO) or water-soluble carbodiimide (WSC) prevents voltage-dependent Ca2+ block, reduces unitary conductance, and decreases guanidinium toxin affinity. In the case of TMO, it has been suggested that all three effects result from modification of a single carboxyl group, which causes a positive shift in the channel's surface potential. We studied the effect of these reagents on Ca2+ block of adult rabbit ventricular Na+ channels in cell-attached patches. In unmodified channels, unitary conductance (gamma Na) was 18.6 +/- 0.9 pS with 280 mM Na+ and 2 mM Ca2+ in the pipette and was reduced to 5.2 +/- 0.8 pS by 10 mM Ca2+. In contrast to TTX-sensitive Na+ channels, Ca2+ block of cardiac Na+ channels was not prevented by TMO; after TMO pretreatment, gamma Na was 6.1 +/- 1.0 pS in 10 mM Ca2+. Nevertheless, TMO altered cardiac Na+ channel properties. In 2 mM Ca2+, TMO-treated patches exhibited up to three discrete gamma Na levels: 15.3 +/- 1.7, 11.3 +/- 1.5, and 9.8 +/- 1.8 pS. Patch-to-patch variation in which levels were present and the absence of transitions between levels suggests that at least two sites were modified by TMO. An abbreviation of mean open time (MOT) accompanied each decrease in gamma Na. The effects on channel gating of elevating external Ca2+ differed from those of TMO pretreatment. Increasing pipette Ca2+ from 2 to 10 mM prolonged the MOT at potentials positive to approximately -35 mV by decreasing the open to inactivated (O-->I) transition rate constant. On the other hand, even in 10 mM Ca2+ TMO accelerated the O-->I transition rate constant without a change in its voltage dependence. Ensemble averages after TMO showed a shortening of the time to peak current and an acceleration of the rate of current decay. Channel modification with WSC resulted in analogous effects to those of TMO in failing to show relief from block by 10 mM Ca2+. Further, WSC caused a decrease in gamma Na and an abbreviation of MOT at all potentials tested. We conclude that a change in surface potential caused by a single carboxyl modification is inadequate to explain the effects of TMO and WSC in heart. Failure of TMO and WSC to prevent Ca2+ block of the cardiac Na+ channel is a new distinction among isoforms in the Na+ channel multigene family.

Ion transport mediated by copolymers composed of polyoxyethylene and polyoxypropylene

1988 ◽  
Vol 254 (1) ◽  
pp. C20-C26 ◽  
Author(s):  
T. P. Atkinson ◽  
J. O. Bullock ◽  
T. F. Smith ◽  
R. E. Mullins ◽  
R. L. Hunter
Keyword(s):  
Ion Transport ◽  
Lipid Bilayers ◽  
Practical Interest ◽  
Water Soluble ◽  
Planar Lipid Bilayers ◽  
Monovalent Cations ◽  
Transport Activity ◽  
Experimental Systems ◽  
Surface Active Agents ◽  
Surface Active

Block copolymers composed of polyoxyethylene and polyoxypropylene were found to increase the influx of Na+ and the efflux of K+ from human erythrocytes. They were, however, ineffective at promoting the transport of Ca2+. The size of the ion fluxes induced by the copolymers correlated with their efficacy in stimulating inflammation. These compounds were also found to induce conductance increases in planar lipid bilayers in a nonvoltage dependent and nonstepwise manner. In both experimental systems, ion transport was facilitated only under temperature and ionic-strength conditions in which the polymers form aggregates in aqueous solution. In neither system did the concentration dependence of transport activity exhibit a pronounced cooperativity. These observations are consistent with the view that aqueous monomers of these surface active agents partition into the membrane, where they facilitate the conductive movement of monovalent cations by means of a carrier type mechanism. As a novel class of ionophores, these substances are of practical interest because they can be water soluble and are potentially reversible.

1,1,4-Derivatives of Thiosemicarbazide—New Non-Staining Antiozonants

1973 ◽  
Vol 46 (2) ◽  
pp. 517-523
Author(s):  
L. K. Zolotarevskaya ◽  
A. M. Lipkin ◽  
A. E. Grinberg ◽  
L. G. Angert
Keyword(s):  
Protective Effect ◽  
Rate Constant ◽  
Practical Interest ◽  
Initial Reaction ◽  
Inhibiting Activity ◽  
Thiourea Derivatives ◽  
New Class ◽  
Mechanism Of Reaction ◽  
Thiosemicarbazide Derivatives ◽  
Derivatives Of

Abstract In the nature of non-staining antiozonants, a new class of compounds, 1,1,4-derivatives of thiosemicarbazide, are proposed. The mechanism of reaction of thiosemicarbazide derivatives with ozone is analogous to the mechanism of this reaction with thiourea derivatives. Within this, the rate constant of the initial reaction of the thiosemicarbazide derivatives with ozone is somewhat higher than that of the thiourea derivatives. 1,1,4-Trialkyl-substituted thiosemicarbazides appear to be the most effective antiozonants, not changing the color of light vulcanizates. Of the investigated compounds, 1,1,4-tributylthiosemicarbazide, being distinguished by a large protective effect against ozone, inhibiting activity in the process of heat aging of the vulcanizates, and lesser ability for leaching out of the vulcanizates by water than tributylthiourea, presents the greatest practical interest.

Sign in / Sign up

Export Citation Format

Share Document