scholarly journals Dynamics of cetyltrimethylammonium bromide mediated reaction of phenylsulfinylacetic acid with Cr(VI): Treatment of pseudo-phase models

2015 ◽  
Vol 80 (8) ◽  
pp. 1019-1034 ◽  
Author(s):  
Perumal Subramaniam ◽  
Thamil Selvi
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Initial Rate ◽  
Intermediate Formation ◽  
Oxidative Decarboxylation ◽  
Micellar Phase ◽  
Cooperative Model ◽  
Rate Acceleration ◽  
Rate Retardation ◽  
Phase Models ◽  
Rate Profile

micellar effect % Hammett correlation % Piszkiewicz cooperative model KR nema The influence of cetyltrimethylammonium bromide, CTon the oxidative decarboxylation of phenylsulfinylacetic acid, PSAA and several meta- and para-substituted PSAAs by Cr(VI) was investigated in 95 % H2O-5 % CH3CN medium. The rate profile displayed a peculiar trend with an initial rate increase at low [CTAB] followed by sharp rate inhibition at higher [CTAB]. The initial rate acceleration can be explained by strong binding of SO42- on the positively charged micellar surface. The specific partitioning of PSAA in micellar phase by hydrophobic interaction and the oxidizing species, HCrO3+ in aqueous phase by electrostatic repulsion accounted the rate retardation at higher [CTAB]. The Hammett plot with different substituted PSAAs showed an excellent correlation affording negative ? value which supports the proposed mechanism involving a sulfonium cation intermediate formation. The obtained ? value in CTmedium is found to be slightly lower than that in aqueous medium. The quantitative analysis of rate data for the inhibition shown by CTwas performed using Menger-Portnoy and Piszkiewicz pseudo-phase models. The binding constant for PSAA with micelle was evaluated from Piszkiewicz cooperative model.

Effect of stimulation with light on synthesis and release of acetylcholine by an isolated mammalian retina

1976 ◽  
Vol 39 (6) ◽  
pp. 1210-1219 ◽  
Author(s):  
R. H. Masland ◽  
C. J. Livingstone
Keyword(s):  
Initial Rate ◽  
Horizontal Cells ◽  
High Rate ◽  
Cholinergic Synapse ◽  
Pharmacological Agents ◽  
Choline Incorporation ◽  
Rate Acceleration ◽  
Mammalian Retina ◽  
Release Of Acetylcholine ◽  
Stimulation Of

1. Acetylcholine synthesis and release were studied in rabbit retinas isolated from the eye and incubated under conditions in which their electrophysiological function is maintained. ACh synthesized from exogenous [14C] choline appeared in the retina at an initial rate of 16 nmol/g wet wt-h. Incorporation of labeled choline into ACh was accelerated by stimulation of the retina with light. 2. Retinas incubated for 40 min in the presence of labeled choline and then superfused with a medium containing an anticholinesterase released radioactive ACh into the perfusate. The rate of release increased approximately fourfold during stimulation with light. 3. When retinas were incubated with labeled choline and then superfused with medium containing no pharmacological agents, stimulation with light caused an increased release of choline into the perfusate. The recovery of labeled choline following stimulation was enhanced by hemicholinium 3. 4. Neither the light-induced release of ACh (in perfusate containing anticholinesterase) nor the light-induced release of choline (in perfusate containing no anticholinesterase) occurred if the perfusate contained 20 mM Mg2+ and 0.2 mM Ca2+. 5. Synthesis of ACh by the retina at a high rate, acceleration of choline incorporation by stimulation, and Ca2+-dependent release of ACh by stimulation are each presumptive evidence that the retina contains a cholinergic synapse. If this presumption is correct, one such synapse mayx be of an amacrine or bipolar cell since these cells can depolarize during illumination, whereas the predominant response of receptor and horizontal cells is hyperpolarization.

Bifunctional Receptor. Rate-acceleration of Oxidative Decarboxylation of Pyruvate by Thymine-Thiazolium and Zn2+in the Presence of a Melamine Derivative Bearingα-Bipyridine Moiety in Chloroform-Acetonitrile

1997 ◽  
Vol 26 (10) ◽  
pp. 1081-1082 ◽  
Author(s):  
Katsuhiro Utsumi ◽  
Yasuaki Nishihara ◽  
Kazuhiko Hoshino ◽  
Shin-ichi Kondo ◽  
Tatsuya Nabeshima ◽  
...  
Keyword(s):  
Oxidative Decarboxylation ◽  
Rate Acceleration

scholarly journals The superoxide-generating oxidase of leucocytes. NADPH-dependent reduction of flavin and cytochrome b in solubilized preparations

1984 ◽  
Vol 223 (2) ◽  
pp. 337-344 ◽  
Author(s):  
A R Cross ◽  
J F Parkinson ◽  
O T G Jones
Keyword(s):  
Cytochrome B ◽  
Cetyltrimethylammonium Bromide ◽  
Methyl Viologen ◽  
Initial Rate ◽  
Cell Extract ◽  
Temperature Sensitive ◽  
O2 Uptake ◽  
Sharp Maximum ◽  
Low Concentrations ◽  
O2 Production

An NADPH-dependent O2.-−generating oxidase was solubilized from phorbol 12-myristate 13-acetate-activated pig neutrophils by using a mixture of detergents. Recovery of oxidase was approx. 40%. The extract contained cytochrome b-245 (331 pmol/mg of protein) and FAD (421 pmol/mg of protein); approx. 30% of each was reduced within 60s when NADPH was added to anaerobic incubations. Three different additives, quinacrine, p-chloromercuribenzoate and cetyltrimethylammonium bromide, strongly inhibited O2.- generation; they also inhibited the reduction by NADPH of cytochrome b at the same low concentrations. In the presence of p-chloromercuribenzoate cytochrome b reduction was strongly inhibited and flavin reduction was less inhibited. A detergent extract prepared from non-stimulated neutrophils also contained flavin and cytochrome b, but its rate of O2.- production was less than 1% of that from activated cells; its initial rate of cytochrome b and flavin reduction was low, although the state of reduction at equilibrium was similar to that of extracts of activated cells. Even in the non-activated cell extract the reduction of flavin and cytochrome was made fast and complete when Methyl Viologen was added to the anaerobic incubations. The oxidase was temperature-sensitive, with a sharp maximum at 25 degrees C; temperatures above this caused loss of O2.- generation, and this coincided with loss of the characteristic cytochrome b spectrum, indicate of denaturation of the cytochrome. The cytochrome b formed a complex with butyl isocyanide (close to 100% binding at 10mM); butyl isocyanide also inhibited the oxidase activity of stimulated whole neutrophils (22.5% inhibition at 10mM). Photoreduced FMN stimulated O2 uptake by the oxidase. The results support a scheme of electron transport within the oxidase complex involving NADPH, FAD, cytochrome b-245 and O2 in that sequence.

Transition state stabilization by micelles: thiolysis of p-nitrophenyl alkanoates in cetyltrimethylammonium bromide micelles

2000 ◽  
Vol 78 (8) ◽  
pp. 1100-1108 ◽  
Author(s):  
Oswald S Tee ◽  
Ogaritte J Yazbeck
Keyword(s):  
Transition State ◽  
Cetyltrimethylammonium Bromide ◽  
Substrate Binding ◽  
Mercaptoacetic Acid ◽  
Passive Component ◽  
Dynamic Component ◽  
Micellar Phase ◽  
Hydrophobic Binding ◽  
Dynamic Components ◽  
Ester Chain

Thiolysis of p-nitrophenyl esters (acetate to decanoate) by the anion of 2-mercaptoethanol (ME) is catalyzed by micelles of cetyltrimethylammonium bromide (CTAB) in aqueous solution. At fixed [ME], the observed rate constants (kobs) show saturation with respect to added [CTAB], consistent with ester binding in the micelles. Plots of kobs vs. [ME] are linear in the absence and in the presence of the CTAB, and analysis of the slopes of the plots afford rates constants for thiolate ion attack on the esters in the aqueous phase (kN) and in the micellar phase (kcN). The strengths of substrate binding and transition state binding to the micelles are strongly correlated, with a slope of unity, because they have the same dependence on the ester chain. Consequently, the catalytic ratios (kcN/kN) are independent of the length of the ester. Similar behaviour is found for thiolysis by the dianions of mercaptoacetic acid, 3-mercaptopropionic acid, and cysteine, and also for ester cleavage by the anions of glycine and 2,2,2-trifluoroethanol, as earlier for cleavage by hydroxide ion. The results are consistent with Kirby's dissection of transition state binding into "passive" and "dynamic" components. The passive component involves hydrophobic binding of the ester chain which is more or less the same as in the substrate binding. The dynamic component is associated with reaction in the Stern layer of the micelle, and its magnitude varies with the nucleophiles because of differences in their ease of exchange between the aqueous medium and the Stern layer.Key words: catalysis, esters, thiolysis, micelles.

scholarly journals 4-Methyl-2-oxopentanoate oxidation by rat skeletal-muscle mitochondria

1979 ◽  
Vol 182 (2) ◽  
pp. 353-360 ◽  
Author(s):  
V W M Van Hinsbergh ◽  
J H Veerkamp ◽  
J F C Glatz
Keyword(s):  
Skeletal Muscle ◽  
Intermediate Formation ◽  
Inhibitory Effect ◽  
Oxidative Decarboxylation ◽  
Rat Skeletal Muscle ◽  
Mitochondrial Inner Membrane ◽  
Skeletal Muscle Mitochondria ◽  
Intact Muscle ◽  
Km Value ◽  
Branched Chain

1. Oxidative decarboxylation of 4-methyl-2-oxopentanoate (2-oxoisocaproate) by mitochondria of rat skeletal muscle showed biphasic kinetics. Two apparent Km values of 9.1 micronM and 0.78 mM were established. In broken mitochondria the rate of oxidation was lower and only the higher apparent Km value was found. 2. Isovalerylcarnitine inhibited 4-methyl-2-oxopentanoate oxidation in the presence and absence of carnitine, but isovaleryl-CoA had no inhibitory effect. 3. Addition of ADP enhanced 4-methyl-2-oxopentanolate oxidation. Malate, succinate and 2-oxoglutarate additionally increased the rate of oxidation, but in the absence of ADP succinate and 2-oxoglutarate inhibited. 4. Addition of rotenone and simultaneous addition of carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP) and valinomycin markedly decreased 4-methyl-2-oxopentanoate oxidation. 5. These observations indicate that the branched-chain 2-oxo acid dehydrogenase complex is situated on the inner side of the mitochondrial inner membrane. 6. In mitochondria and homogenates CO2 was only produced by oxidative decarbosylation of 4-methyl-2-oxopentanoate. In intact muscle oxidation of this oxo acid proceeds more to completeness. 7. The physiological significance of intermediate formation during oxidation of branched-chain amino acids is discussed.

The Effect of Searching Versus Surfing on Cognitive and Emotional Responses to Online News

2009 ◽  
Vol 21 (2) ◽  
pp. 49-59 ◽  
Author(s):  
Kevin Wise ◽  
Hyo Jung Kim ◽  
Jeesum Kim
Keyword(s):  
Heart Rate ◽  
Skin Conductance ◽  
Skin Conductance Level ◽  
Emotional Responses ◽  
Online News ◽  
Self Report ◽  
Mixed Design ◽  
Information Need ◽  
News Stories ◽  
Rate Acceleration

A mixed-design experiment was conducted to explore differences between searching and surfing on cognitive and emotional responses to online news. Ninety-two participants read three unpleasant news stories from a website. Half of the participants acquired their stories by searching, meaning they had a previous information need in mind. The other half of the participants acquired their stories by surfing, with no previous information need in mind. Heart rate, skin conductance, and corrugator activation were collected as measures of resource allocation, motivational activation, and unpleasantness, respectively, while participants read each story. Self-report valence and recognition accuracy were also measured. Stories acquired by searching elicited greater heart rate acceleration, skin conductance level, and corrugator activation during reading. These stories were rated as more unpleasant, and their details were recognized more accurately than similar stories that were acquired by surfing. Implications of these results for understanding how people process online media are discussed.

Lipoprotein Fractions and Antithrombin III Consumption During Clotting

1982 ◽  
Vol 47 (03) ◽  
pp. 236-238 ◽  
Author(s):  
J H Winter ◽  
B Bennett ◽  
F McTaggart ◽  
A S Douglas
Keyword(s):  
Blood Clotting ◽  
Antithrombin Iii ◽  
Initial Rate ◽  
Density Lipoprotein ◽  
Normal Subjects ◽  
Lipid Levels ◽  
Antithrombin Activity ◽  
Artery Disease ◽  
Immunological Assays ◽  
Total Triglyceride

SummaryPlasma and serum antithrombin levels were measured in functional (initial rate measurement) and immunological assays together with serum lipid levels in normal subjects and patients with coronary artery disease. Specific antithrombin activity in plasma showed a negative correlation with triglyceride levels. The consumption of antithrombin activity during blood clotting was negatively correlated with both serum total triglyceride and heparin precipitable lipoprotein and positively correlated with serum high density lipoprotein cholesterol. Different blood lipoprotein fractions may influence the activity of the antithrombin III molecule.

Platelet Adhesion to Subendothelium - Effect of Shear Rate, Hematocrit and Platelet Count on the Dynamic Equilibrium Between Platelets Adhering to and Detaching from the Surface

1985 ◽  
Vol 54 (04) ◽  
pp. 857-861 ◽  
Author(s):  
Andrea Remuzzi ◽  
Lucia Raffaella Languino ◽  
Vincenzo Costantini ◽  
Vincenzo Guardabasso ◽  
Giovanni de Gartano ◽  
...  
Keyword(s):  
Platelet Adhesion ◽  
Initial Rate ◽  
Dynamic Equilibrium ◽  
Dynamic Condition ◽  
Platelet Reactivity ◽  
Experimental Conditions ◽  
Platelet Suspension ◽  
Shear Rates ◽  
Platelet Concentration ◽  
Adhesion Rate

SummaryThe adherence of human 3H-adenine-labeled platelets to rat subendothelium was quantitated using a rotating probe device. Platelet adhesion increased in relation to the rotation time, reaching a plateau value in about 4-6 min without any further increase. A non-linear fitting analysis of experimental data allowed calculations of initial rate and plateau value of platelet adhesion. Increasing the shear rates (from 35 to 150 sec-1) or the hematocrit (from 10% to 40%), both the adhesion rate and the plateau value were increased. When different platelet concentrations were used the adhesion rate and the plateau calculated increased with platelet concentration. Different plateau values were obtained in the experimental conditions considered. This suggests that the plateau was not reached for the complete occupation of the subendothelial surface by the adherent platelets. Experiments using two different vessels rotated in the same platelet suspension or, viceversa, the same vessel rotated successively in two fresh platelet suspensions, showed that the plateau was not determined by reduced platelet reactivity. Rotating the same vessel first in radiolabeled platelets, until the plateau was reached, and secondly in non labeled platelets, or viceversa, showed that the plateau was indeed a dynamic condition where the number of platelets adhering and detaching reached equilibrium. These observations suggest that the platelet adhesion to subendothelium is the final equilibrium of two platelet fluxes, one adhering to the surface and another detaching from the surface.

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