scholarly journals Investigation of ribonuclease-catalysed kinetics by a micro-calorimetric method

1976 ◽  
Vol 153 (1) ◽  
pp. 89-91 ◽  
Author(s):  
M Tribout ◽  
S Paredes ◽  
J Léonis
Keyword(s):  
Ribonuclease A ◽  
Calorimetric Method ◽  
Published Data ◽  
Enzymic Hydrolysis ◽  
Cyclic Phosphates ◽  
Hydrolysis Of ◽  
Cyclic Cmp ◽  
Step Mechanism ◽  
Good Agreement

A rapid micro-calorimetric method for the simultaneous determination of the Michaelis-Menten parameters and the enthalpy of enzymic reactions is developed. The hydrolysis of 2‘: 3’-cyclic CMP by ribonuclease A is studied to test the proposed method; values obtained are in good agreement with already published data. Enzymic hydrolysis of yeast RNA, unlike that of cyclic phosphates, is shown to be endothermic. This result is explained by the two-step mechanism of this reaction.

A simple procedure using trinitrobenzenesulphonic acid for monitoring proteolysis in cheese

1988 ◽  
Vol 55 (4) ◽  
pp. 585-596 ◽  
Author(s):  
Anna Polychroniadou
Keyword(s):  
Simple Procedure ◽  
Water Soluble ◽  
Acid Solutions ◽  
Amino Groups ◽  
Total N ◽  
Cheese Ripening ◽  
Amino Acid Solutions ◽  
Hydrolysis Of ◽  
Good Agreement

SummaryA simple, rapid and sensitive spectrophotometric assay was developed and evaluated for monitoring proteolysis during cheese ripening, based on the fact that α-amino groups released by hydrolysis of cheese proteins react with trinitrobenzenesulphonic acid to form products that absorb strongly at 420 nm. A linear relationship was shown to exist between A420 and concentration of free α amino groups up to 0·5 HIM (r = 0·999, 38 df, P < 0·001). Repeatability of the method was satisfactory. The coefficient of variance was 0·53% for amino acid solutions and 1·19% for cheese extracts. Average recovery of glycine added to the cheese was 104 ± 2·9%. A comparison of the above method with that of determination of water-soluble N to total N ratio showed that there was good agreement between these two methods of assessment of proteolysis in cheese (r = 0·857, 32 df, P < 0·001). Mainly Feta and Teleme cheese were examined, but a similar correlation was obtained with hard Greek cheeses. Analytical conditions of the procedure are discussed.

Determination of Sevin Insecticide Residues in Fruits and Vegetables

1964 ◽  
Vol 47 (2) ◽  
pp. 283-286
Author(s):  
D P Johnson
Keyword(s):  
Fruits And Vegetables ◽  
Collaborative Study ◽  
Colorimetric Determination ◽  
Average Recovery ◽  
Insecticide Residues ◽  
Chromogenic Agent ◽  
Hydrolysis Of ◽  
Concentration Levels ◽  
Good Agreement

Abstract Collaborative study of a method for Sevin insecticide residues was repeated with apples and lettuce as test crops. The method is based on alkaline hydrolysis of Sevin and colorimetric determination of the resulting 1-naphthol with p-nitrobenzenediazonium fluoborate as chromogenic agent. Data from 5 collaborators were in good agreement with an average recovery of 87.8% at 2 concentration levels. It is recommended that the method be adopted as official, first action.

Instability of Propyl Lactate Prepared by Boron Trifluoride-Catalyzed Esterification of Lactic Acid

1972 ◽  
Vol 55 (4) ◽  
pp. 888-889
Author(s):  
Walter F Staruszkiewicz ◽  
John F Bond
Keyword(s):  
Lactic Acid ◽  
Ethyl Ether ◽  
Boron Trifluoride ◽  
Chromatographic Method ◽  
Published Data ◽  
Chromatographic System ◽  
Propyl Esters ◽  
Gas Chromatographic Method ◽  
Hydrolysis Of

The official first action gas chromatographic method for the determination of lactic, β-hydroxyhutyric, and succinic acids, 17.034–17.038, requires the formation of their propyl esters with boron trifluoride-1-propanol and extraction of the esters into an organic solvent prior to chromatography. Previously published data showed that the solutions of propyl esters were stable for as long as 4 weeks when they were extracted into chloroform and stored at 40°F. However, when ethyl ether is substituted for chloroform, propyl lactate is no longer stable during storage. The ether apparently extracts some unreacted boron trifluoride which eventually causes the hydrolysis of propyl lactate. The propyl esters of β-hydroxybutyric, levulinic, and succinic acids were stable in ether as well as in chloroform. The method has been revised to include the use of ethyl ether, if required by the gas chromatographic system, and to specify analysis of the ether solutions within 24 hr of esterification.

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.

scholarly journals Development of Characterization Techniques of Thermodynamic and Physical Properties Applied to the CO2-DMSO Mixture

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Brice Calvignac ◽  
Elisabeth Rodier ◽  
Jean-Jacques Letourneau ◽  
Jacques Fages
Keyword(s):  
Process Design ◽  
Published Data ◽  
Viscosity Data ◽  
Pressure Measurements ◽  
Co2 Solubility ◽  
Volumetric Expansion ◽  
Characterization Techniques ◽  
Dmso System ◽  
Good Agreement

This work is focused on the development of new characterization techniques of physical and thermodynamic properties. These techniques have been validated using the binary system DMSO-CO2 for which several studies of characterization have been well documented. We focused on the DMSO-rich phase and we carried out measurements of volumetric expansion, density, viscosity and CO2 solubility at 298.15, 308.15 and 313.15 K and pressures up to 9 MPa. The experimental procedures were compared and validated with the available literature data on SC-CO2-DMSO system. We made density and CO2 solubility measurements, using respectively the vibrating tube technology and two static analytical methods. Lastly, we developed an innovative falling body viscosimeter for high pressure measurements. All the measurements made are in good agreement with the already published data in spite of very different experimental techniques. This work is a contribution to the understanding of the DMSO-CO2 binary as it implements new viscosity data. Moreover, it opens new perspectives about the determination of the properties of other systems such as polymers-CO2 and fats-CO2, which are essential for supercritical process design such as extraction, crystallization, chromatography and synthesis reaction.

On the yield stress of geotechnical materials from the slump test

1991 ◽  
Vol 28 (3) ◽  
pp. 457-462 ◽  
Author(s):  
B. Rajani ◽  
N. Morgenstern
Keyword(s):  
Yield Stress ◽  
Undrained Shear Strength ◽  
Bingham Fluid ◽  
Published Data ◽  
Important Class ◽  
Slump Test ◽  
Volcanic Lava ◽  
Undrained Shear ◽  
Good Agreement

There exists an important class of materials, e.g., debris, volcanic lava, sludges, and remoulded sensitive clays, that are known to behave like a Bingham fluid. One of the important properties of a Bingham fluid is the so-called yield stress, and it is usually determined using a coaxial viscometer apparatus. It would be impractical and cumbersome to use this apparatus for many of the materials referred to earlier, and we propose here to examine the use of the slump test. The slump test is used in the concrete industry to evaluate workability and consistency. A statical model is developed to explain the deformation mechanism, and it permits the determination of yield stress. The validity of the statical model is verified using published data on mortar and our own data on Devon silt. The yield stress obtained with the slump test is also compared with the undrained shear strength obtained using the fall cone test. Good agreement is found between the two values. Key words: Bingham fluid, yield stress, slump test, Devon silt.

scholarly journals The hydrolysis of glycosyl fluorides by glycosidases. Determination of the anomeric configuration of the products of glycosidase action

1971 ◽  
Vol 123 (4) ◽  
pp. 607-611 ◽  
Author(s):  
J. E. G. Barnett
Keyword(s):  
Glucose Oxidase ◽  
Galactose Oxidase ◽  
Coffee Bean ◽  
Enzymic Hydrolysis ◽  
Initial Product ◽  
Rapid Assay ◽  
Anomeric Configuration ◽  
Ph Stat ◽  
Hydrolysis Of

The enzymic hydrolysis of glycosyl fluorides is conveniently followed by using a pH-stat. Reactions involving glucosyl or galactosyl fluorides can also be followed by using glucose oxidase or galactose oxidase respectively. The pH-stat allows the rapid assay of intestinal α-glucosidase in crude homogenates. Use of glycosyl fluorides as substrates for glycosidases facilitates the polarimetric or g.l.c. determination of the anomeric nature of the initial product of hydrolysis. Hydrolysis by fungal amyloglucosidase proceeds with inversion of configuration whereas that by yeast and rat intestinal α-glucosidase, coffee-bean α-galactosidase and almond emulsin β-glucosidase proceeds with retention of configuration. β-d-Glucopyranosyl azide was not a detectable substrate for almond emulsin β-d-glucosidase.

Rapid Methods for the Determination of Pregnanediol in Urine

1968 ◽  
Vol 14 (11) ◽  
pp. 1091-1096 ◽  
Author(s):  
P J Brombacher ◽  
A H J Gijzen ◽  
P E Verheesen
Keyword(s):  
Gas Chromatography ◽  
Sulfuric Acid ◽  
Enzymatic Hydrolysis ◽  
Alumina Column ◽  
Rapid Methods ◽  
Urinary Steroids ◽  
Alumina Column Chromatography ◽  
Hydrolysis Of ◽  
Good Agreement

Abstract Pregnanediol determination in urine was performed by alumina-column chromatography followed by reaction with sulfuric acid and by gas chromatography. After enzymatic hydrolysis of the conjugated urinary steroids, there is a very good agreement between both methods.

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