THE HYDROLYSIS OF SUBSTITUTED METHYL BENZENESULFONATES IN WATER

1966 ◽  
Vol 44 (6) ◽  
pp. 685-688 ◽  
Author(s):  
R. E. Robertson ◽  
A. Stein ◽  
S. E. Sugamori
Keyword(s):  
Negligible Effect ◽  
Rate Data ◽  
The Difference ◽  
Hydrolysis Of

Rate data and derived parameters for the hydrolysis of a series of para-substituted methyl benzenesulfonates are given. The introduction of such substituents has negligible effect on ΔCp≠, and the difference in rate is largely reflected in δXΔS≠.

SOLVOLYSIS IN DEUTERIUM AND HYDROGEN OXIDE

1956 ◽  
Vol 34 (12) ◽  
pp. 1714-1718 ◽  
Author(s):  
P. M. Laughton ◽  
R. E. Robertson
Keyword(s):  
Heavy Water ◽  
Rate Ratio ◽  
Methyl Chloride ◽  
Rate Data ◽  
Methyl Ethyl ◽  
Butyl Chloride ◽  
Initial States ◽  
The Difference ◽  
Hydrogen Oxide ◽  
Hydrolysis Of

Rate data for a series of benzenesulphonates, halides, and methyl methanesulphonate were determined in light and heavy water. The rate ratio [Formula: see text] varied with the nature of the anion being formed from 0.94. for the hydrolysis of methyl methanesulphonate to 0.78 for methyl chloride. This difference in ratio was attributed to differences in the nature of the solvation of the initial states. No appreciable differences arose, however, through the alkyl series methyl, ethyl, isopropyl benzenesulphonates, and the difference for the ratio [Formula: see text] between MeCl and t-butyl chloride was small, contrary to recently published work.

scholarly journals Propranolol Inhibits Hyphal Development in Candida albicans

2002 ◽  
Vol 46 (11) ◽  
pp. 3617-3620 ◽  
Author(s):  
Carol A. Baker ◽  
Kevin Desrosiers ◽  
Joseph W. Dolan
Keyword(s):  
Growth Rate ◽  
Candida Albicans ◽  
Phosphatidic Acid ◽  
Rate Data ◽  
Dimorphic Transition ◽  
Hyphal Development ◽  
Germ Tubes ◽  
Hydrolysis Of

ABSTRACT Propranolol was used to investigate the role of phosphatidic acid (PA) and diacylglycerol in the dimorphic transition in Candida albicans. Propranolol was able to inhibit the appearance of germ tubes without decreasing growth rate. Data suggest that inhibition of morphogenesis may be due to binding by propranolol of PA derived from PLD1 hydrolysis of phosphatidylcholine.

Bioenergetics of Na+ transport across frog skin: chemical and electrical measurements

1983 ◽  
Vol 245 (6) ◽  
pp. F691-F700 ◽  
Author(s):  
M. M. Civan ◽  
K. Peterson-Yantorno ◽  
D. R. DiBona ◽  
D. F. Wilson ◽  
M. Erecinska
Keyword(s):  
Free Energy ◽  
Frog Skin ◽  
Atp Hydrolysis ◽  
Transepithelial Transport ◽  
Base Line ◽  
Free Energies ◽  
Electrical Measurements ◽  
Far From Equilibrium ◽  
The Difference ◽  
Hydrolysis Of

Enzymatically prepared split frog skins consisted purely of epithelial cells. Electrical parameters and the cell contents of ATP, ADP, phosphocreatine (PCr), creatine, inorganic phosphate, protein, and water were measured in skins maintained at room temperature. Studies were conducted under base-line conditions, 15 and 60 min after adding vasopressin, and 30 min after adding amiloride. Intracellular ionic activities and concentrations were obtained from previous results. The data demonstrated that 1) the base-line concentration ratio of PCr/ATP was 0.53 +/- 0.03; 2) the average molar free energy of hydrolysis of intracellular ATP was approximately 15.0 kcal X mol-1 under control conditions, changing by less than or equal to 3% with changes in transport; and 3) the free energy of extruding 3 mol of Na+ and accumulating 2 mol of K+ was approximately 9.8 kcal X mol-1 under base-line conditions; the difference between the molar free energies of ATP hydrolysis and of transport work remained large, despite large changes in transepithelial transport. The simplest conclusion is that the Na+ pump of frog skin operates far from equilibrium.

SOME ASPECTS OF THE ENZYMIC HYDROLYSIS OF URINARY 17-KETOSTEROID CONJUGATES

1960 ◽  
Vol 38 (1) ◽  
pp. 769-776
Author(s):  
R. Hobkirk ◽  
J. J. Cohen
Keyword(s):  
Liver Enzymes ◽  
Striking Difference ◽  
Degree Of Hydrolysis ◽  
Enzyme Preparations ◽  
Bacterial Preparation ◽  
Bacterial Enzyme ◽  
The Difference ◽  
Normal Urine ◽  
High Degree ◽  
Hydrolysis Of

Four enzyme preparations containing β-glucuronidase, of bacterial, mammalian, and molluscan origin, have been shown to be equally effective in liberating 17-ketosteroids (17-KS) of the 5β-(etiocholane) configuration in normal urine. The bacterial preparation releases steroids of the 5α-(androstane) configuration more rapidly than do the molluscan enzymes and with much greater ease than does the liver enzyme. In view of the data obtained it seems unlikely that the striking difference between the bacterial and liver enzymes can be due to the hydrolysis of some labile conjugate, such as sulphate, by the former and not by the latter. Possibilities that the difference is due to the hydrolysis of an unknown type of urinary conjugate by the bacterial preparation, or to the low specificity of the bacterial β-glucuronidase, are discussed. The high degree of hydrolysis of 17-KS conjugates by the bacterial enzyme followed by solvolysis suggests this as a most useful hydrolytic procedure.

The log kexovs. log kendo correlation as a mechanistic criterion; on the mechanisms of solvolysis of norbornyl derivatives and base-catalyzed isotope exchange of norbornanones

1976 ◽  
Vol 54 (5) ◽  
pp. 678-684 ◽  
Author(s):  
Sujit Banerjee ◽  
Nick Henry Werstiuk
Keyword(s):  
Transition State ◽  
Exchange Rates ◽  
Isotope Exchange ◽  
Transition States ◽  
Substituent Effects ◽  
Proton Exchange ◽  
Hydrogen Deuterium Exchange ◽  
Rate Data ◽  
Hydrogen Deuterium ◽  
The Difference

Rate data for the acetolysis of exo-norbornyl-sulfonates have been correlated with those for the corresponding endo isomers. It is shown that the slopes of the log kexovs. log kendo plots reflect the difference in delocalization between the transition states derived from the exo and endo isomers, respectively. The log kexovs. log kendo plot, which is comprised of the parent norbornyl sufonate and its derivatives substituted at the 5, 6, and 7 positions, has a slope of 1.11 ± 0.08, which establishes that σ bridging is absent in the transition state obtained from the exo isomer. A similar analysis of base-catalyzed hydrogen–deuterium exchange rates of norbornanones reveals that exo proton exchange is more sensitive to substituent effects than the corresponding endo process.

scholarly journals Activation of muscarinic receptors in PC12 cells. Stimulation of Ca2+ influx and redistribution

1986 ◽  
Vol 234 (3) ◽  
pp. 547-553 ◽  
Author(s):  
T Pozzan ◽  
F Di Virgilio ◽  
L M Vicentini ◽  
J Meldolesi
Keyword(s):  
Pc12 Cells ◽  
Muscarinic Receptor ◽  
Muscarinic Receptors ◽  
Differentiated Cells ◽  
Low Concentrations ◽  
Before And After ◽  
Voltage Dependent ◽  
The Difference ◽  
Free Media ◽  
Hydrolysis Of

Ca2+ homoeostasis was investigated in pheochromocytoma neurosecretory (PC12) cells both before and after treatment with nerve growth factor, which induces a neuronal-like differentiation accompanied by a large increase in the number of muscarinic receptors. The resting concentration of free cytosolic Ca2+, [Ca2+]i, measured by the quin2 technique, was found to be higher and more variable in differentiated cells. Moreover, the [Ca2+]i rises induced by the Ca2+ ionophore ionomycin and by depolarizing concentrations of KC1 were greater and more transient. Exposure to carbachol induced modest, but long-lasting, [Ca2+]i rises, which were faster and greater in differentiated than in non-differentiated cells. These effects were due to the activation of the muscarinic receptor, because they were unaffected by nicotinic blockers (hexamethonium and D-tubocurarine) and completely eliminated by low concentrations of the muscarinic antagonists atropine and pirenzepine [IC50 (concn. causing 50% inhibition) = 2 and 60 nM respectively]. The muscarinic-receptor-dependent [Ca2+]i rises were the result of two concomitant processes: (1) redistribution of Ca2+ from cytoplasmic stores to the cytosol, possibly mediated by generation of inositol 1,4,5-trisphosphate as a consequence of the muscarinic-receptor-coupled hydrolysis of polyphosphoinositides, and (2) increased Ca2+ influx through a pathway of the plasmalemma insensitive to verapamil and thus different from the voltage-dependent Ca2+ channel. The existence of this second process was documented: (a) by the difference of the [Ca2+]i responses brought about by carbachol in Ca2+-containing and Ca2+-free media; (b) by the occurrence of [Ca2+]i rise and increased 45Ca accumulation in cells exposed to 1 mM-CaCl2 after having been treated for 2 min with carbachol in Ca2+-free medium; (c) by typical differences in the quin2 signal kinetics observed in parallel samples of PC12 cells loaded with different concentrations of the dye.

SOME ASPECTS OF THE ENZYMIC HYDROLYSIS OF URINARY 17-KETOSTEROID CONJUGATES

1960 ◽  
Vol 38 (7) ◽  
pp. 769-776 ◽  
Author(s):  
R. Hobkirk ◽  
J. J. Cohen
Keyword(s):  
Liver Enzymes ◽  
Striking Difference ◽  
Degree Of Hydrolysis ◽  
Enzyme Preparations ◽  
Bacterial Preparation ◽  
Bacterial Enzyme ◽  
The Difference ◽  
Normal Urine ◽  
High Degree ◽  
Hydrolysis Of

Four enzyme preparations containing β-glucuronidase, of bacterial, mammalian, and molluscan origin, have been shown to be equally effective in liberating 17-ketosteroids (17-KS) of the 5β-(etiocholane) configuration in normal urine. The bacterial preparation releases steroids of the 5α-(androstane) configuration more rapidly than do the molluscan enzymes and with much greater ease than does the liver enzyme. In view of the data obtained it seems unlikely that the striking difference between the bacterial and liver enzymes can be due to the hydrolysis of some labile conjugate, such as sulphate, by the former and not by the latter. Possibilities that the difference is due to the hydrolysis of an unknown type of urinary conjugate by the bacterial preparation, or to the low specificity of the bacterial β-glucuronidase, are discussed. The high degree of hydrolysis of 17-KS conjugates by the bacterial enzyme followed by solvolysis suggests this as a most useful hydrolytic procedure.

Enzymic determination of free and esterified cholesterol in serum by microcalorimetry.

1982 ◽  
Vol 28 (11) ◽  
pp. 2235-2240 ◽  
Author(s):  
N N Rehak ◽  
D S Young
Keyword(s):  
Cholesterol Oxidase ◽  
Linear Regression Analysis ◽  
Calorimetric Method ◽  
Heat Output ◽  
Flow Modification ◽  
Batch Type ◽  
The Difference ◽  
Hydrolysis Of ◽  
Heat Released

Abstract Concentrations of free and esterified cholesterol in serum can be determined simultaneously by measuring, with a batch-type microcalorimeter, the heat released during the coupled cholesterol esterase/cholesterol oxidase/catalase enzymic reaction. To differentiate the two forms of cholesterol, we used kinetic calorimetry: the rate of heat output due to enzymic hydrolysis of esterified cholesterol (the rate-determining reaction) was subtracted from the measured heat, the difference being the heat released during the enzymic oxidation of free cholesterol (the fast reaction). Results obtained by the kinetic calorimetric method agreed with those obtained by separate sequential end-point calorimetric determinations of free and total cholesterol. We also compared the kinetic calorimetric method with the cholesterol method of Abell and Kendall and a continuous-flow modification of the Liebermann-Burchard method (Technicon SMAC). De-biased linear-regression analysis of the data indicates acceptable agreement between the calorimetric and the Abell-Kendall methods (y = 0.98x + 11.5). The correlation between results by calorimetric and SMAC methods shows a significant proportional error (y = 1.17x - 159.4). Bilirubin (up to 200 mg/L) does not interfere with the calorimetry.

Biochemical and biological evidence of the activity of high potencies

1954 ◽  
Vol 44 (01) ◽  
pp. 7-44 ◽  
Author(s):  
W.E. Boyd
Keyword(s):  
Mercuric Chloride ◽  
Soluble Starch ◽  
Distilled Water ◽  
Mechanical Shock ◽  
Significant Difference ◽  
Control Procedures ◽  
Rate Of Hydrolysis ◽  
The Difference ◽  
Hydrolysis Of ◽  
Made In

Summary1. A method is described for investigating the possible action of microdoses of mercuric chloride on the hydrolysis of soluble starch with malt diastase.2. The microdoses of the mercuric chloride used in the latest crucial series carried out in1946, 1948, and 1952, were what are termed “high potencies” made in accordance with the pharmaceutical method of preparation of drugs ordinarily used in the practice of homœotherapy.3. These microdoses were prepared by separate stages of dilution, the solution at each stage being subjected to mechanical shock. The solutions were, theoretically, “dilutions” of the order of 1 in 10−61 and on present physical theory would not contain any molecules of the original mercuric chloride.4. The difference in rate of hydrolysis between flasks containing starch, diastase, and distilledwater (controls) and flasks containing starch, diastase and microdoses of mercuric chloride (tests) were compared colorimetrically by the Spekker absorptiometer, and the frequencies of the differences statistically analysed, as the results obtained showed biological scatter. More than 500 such comparisons were carried out. The differences of means were examined by the Fisher “t” test, the variances tested and Cochrane and Cox's test applied where indicated. All the series gave a highly significant difference in the rate of hydrolysis between controls and tests, the microdoses stimulating the process. Statistically the significance is shown by the fact that a probability of <0·001 was obtained independently in each of the three years 1946, 1948 and 1952. The control results gave an approximately normal distribution.5. The distribution, control methods, and accessory control procedures were considered toexclude, as a cause of the effects, adsorption of the original drug and the presence of extraneous contaminants by chance solely in test flasks. The only difference between control and microdose flasks was the addition of microdose, the distilled water being common to both controls and tests.6. It was concluded that a factor, unidentified, derived from the mercuric chloride used, waspresent in solutions prepared by serial dilution with mechanical shock which could affect the distilled water diluent, that this change was transferable to subsequent “ultramolecular” stages of “dilution”, and that this factor was the source of the activity in the microdose solutions producing the acceleration of the rate of hydrolysis.7. In an addendum there is described recent biological work which is also providing evidence of the presence of an active selective factor in “high potencies” derived from Strophanthus sarmentosus by the same methods of dilution with mechanical shock.

EFFECT OF α-METHYLATION ON THE PARAMETERS CHARACTERIZING HYDROLYSIS IN WATER FOR A SERIES OF HALIDES AND SULFONATES

1966 ◽  
Vol 44 (6) ◽  
pp. 677-684 ◽  
Author(s):  
R. L. Heppolette ◽  
R. E. Robertson
Keyword(s):  
Kinetic Parameters ◽  
Rate Data ◽  
Detailed Mechanism ◽  
Mechanism Of Hydrolysis ◽  
Hydrolysis Of

The aim of this work was to explore the effect of α-methylation on the reactivity and detailed mechanism of hydrolysis. Accordingly, rate data and derived parameters are given for the hydrolysis of a series of halides and sulfonates in water. From the differences in kinetic parameters, an attempt is made to infer further information relating structure and mechanism.

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