Determination of 15N isotope effects on the acid-base equilibria of amino groups in amino acids by carbon-13 NMR

1993 ◽  
Vol 58 (16) ◽  
pp. 4487-4489 ◽  
Author(s):  
Dallas L. Rabenstein ◽  
S. V. S. Mariappan
Keyword(s):  
Amino Acids ◽  
Isotope Effects ◽  
Amino Groups ◽  
15N Isotope ◽  
Acid Base

Steroids and steroidases. IX. Activation parameters and the mechanism of base- and enzyme-catalyzed isomerizations of androst-5-ene-3,17-dione. The nature of the active center of the Δ5 → Δ4-3-ketosteroid isomerase of Pseudomonas testosteroni

1969 ◽  
Vol 47 (23) ◽  
pp. 4459-4466 ◽  
Author(s):  
J. Bryan Jones ◽  
Donald C. Wigfield
Keyword(s):  
Amino Acids ◽  
Active Center ◽  
Activation Parameters ◽  
Circumstantial Evidence ◽  
Kcal Mole ◽  
Acid Base ◽  
Ketosteroid Isomerase ◽  
Enzyme Action ◽  
Enthalpy Of Activation

Determination of the activation parameters for the acid-, base-, and enzyme-catalyzed isomerizations of androst-5-ene-3,17-dione has revealed that the facility of the enzymic process is mainly due to an extremely low enthalpy of activation of 5.0 kcal mole−1. Further circumstantial evidence regarding the nature of the reacting groups at the active center has also been obtained, and a mechanism of enzyme action is proposed employing tyrosine and histidine as the principal amino acids responsible for catalyzing the isomerization.

Automated Determination of Free Amino Groups in Serum and Plasma Using 2,4,6-Trinitrobenzene Sulfonate

1969 ◽  
Vol 15 (9) ◽  
pp. 891-901 ◽  
Author(s):  
D W Palmer ◽  
T Peters
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Clinical Applications ◽  
Amino Groups ◽  
Automated Method ◽  
Total Free Amino Acids ◽  
Colored Complexes ◽  
Automated Determination

Abstract A simple automated method is described for determining the level of total free amino acids in the blood. The method utilizes the AutoAnalyzer, and is based on the formation of colored complexes by uniting free amino groups with 2,4,6-trinitrobenzene sulfonate (TNBS). Proteins do not interfere because the free amino acids are first separated by dialysis. Characteristics of the reaction and potential clinical applications of the procedure are discussed.

Determination of isotope effects on acid–base equilibria by 13C NMR spectroscopy

1997 ◽  
pp. 445-450 ◽  
Author(s):  
Tonis Pehk ◽  
Ene Kiirend ◽  
Endel Lippmaa ◽  
Ulf Ragnarsson ◽  
Leif Grehn
Keyword(s):  
Nmr Spectroscopy ◽  
13C Nmr ◽  
Isotope Effects ◽  
13C Nmr Spectroscopy ◽  
Acid Base

scholarly journals The Free Amino Groups of the Proteus Flagella Protein. Determination of Dinitrophenyl Amino Acids Using Paper Chromatography.

1953 ◽  
Vol 7 ◽  
pp. 335-339 ◽  
Author(s):  
Claes Weibull ◽  
Artturi I. Virtanen ◽  
J. K. Miettinen ◽  
Artturi I. Virtanen ◽  
Nils Andreas Sörensen
Keyword(s):  
Amino Acids ◽  
Paper Chromatography ◽  
Free Amino ◽  
Amino Groups ◽  
Protein Determination

Measurement of proteolysis in cheese: relationship between phosphotungstic acid-soluble N fraction by Kjeldahl and 2,4,6- trinitrobenzenesulphonic acid-reactive groups in water-soluble N

1994 ◽  
Vol 61 (3) ◽  
pp. 437-440 ◽  
Author(s):  
Yvette Bouton ◽  
Remy Grappin
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Phosphotungstic Acid ◽  
Water Soluble ◽  
Hydroxyl Groups ◽  
Amino Groups ◽  
Reactive Groups ◽  
Primary Amino

Free amino groups produced during cheese ripening are used to indicate the extent of cheese proteolysis. Several studies have shown a high correlation between the level of free amino acids and the flavour of Gouda (Aston et al. 1983) or Comté (Grappin & Berdagué, 1989). Measurement of the level of free amino acids seems useful for the investigation of flavour chemistry in cheese (Lemieux et al. 1990). The determination of N fractions is often used to estimate the degree of proteolysis in cheese, but since this procedure is laborious and time consuming several attempts have been made to replace it by more rapid methods (Ardö & Meisel, 1991). Since its introduction by Satake et al. (1960), the 2,4,6-trinitrobenzenesulphonic acid (TNBS) method has been widely used for the determination of free amino groups. Because TNBS does not react with the imino groups of histidine and proline or the hydroxyl groups of tyrosine, serine or threonine, it has been accepted as a selective reagent for primary amino groups (Burger, 1974). Measurement of N by Kjeldahl in the phosphotungstic acid (PTA)–sulphuric acid extract (Gripon et al. 1975) estimates the N of free amino acids and low molecular mass peptides. The purpose of this study was to compare the TNBS and PTA-soluble N methods in order to find out whether the TNBS procedure can replace that of PTA-soluble N in the determination of a cheese proteolysis index.

Two different approaches for developing immunometric assays of haptens

1996 ◽  
Vol 42 (9) ◽  
pp. 1532-1536 ◽  
Author(s):  
J Grassi ◽  
C Créminon ◽  
Y Frobert ◽  
E Etienne ◽  
E Ezan ◽  
...  
Keyword(s):  
Amino Acids ◽  
Monoclonal Antibody ◽  
Solid Phase ◽  
Leukotriene C4 ◽  
Amino Groups ◽  
Small Peptides ◽  
Assay Sensitivity ◽  
Primary Amino ◽  
C And N

Abstract To improve immunoassays of small haptens, we developed two different approaches for their measurement in a non-competitive format. We first devised two-site immunometric assays for small peptides (8-11 amino acids) by selecting two sets of antibodies specifically directed against C- and N-terminal moieties of the peptides. In each case, assay sensitivity improved substantially over that of the corresponding competitive assays. More interestingly, all of these new immunometric assays were much more specific than the competitive assays. In a second approach, we developed a new procedure, solid-phase-immobilized epitope immunoassay (SPIE-IA), in which a single monoclonal antibody uses the same epitope for capture and tracer binding and the hapten is covalently cross-linked to solid-phase proteins. To date, SPIE-IA have been successfully applied to the determination of haptens bearing primary amino groups, including substance P, thyroxine, leukotriene C4, endothelin, and angiotensin II. In each case, assay sensitivity was significantly improved.

Titration – a rapid method for the determination of proteolysis in cheese

1990 ◽  
Vol 57 (1) ◽  
pp. 149-150 ◽  
Author(s):  
Pia Ollikainen
Keyword(s):  
Amino Acids ◽  
Rapid Method ◽  
Acid Base ◽  
End Products ◽  
Acid Base Titration ◽  
Lactic Acids ◽  
Titration System

Titration is an old method used for the determination of acidic and basic groups of a molecule. Several metabolic end-products in cheese are compounds with acidic or basic groups, e.g. propionic, acetic and lactic acids, amino acids, amines and ammonia. A number of colorimetric and fluorometric methods have been used to study proteolysis in cheese; some are time-consuming with several steps, and certain of the reagents are hazardous.We have used acid-base titration for analysis of the products of proteolysis in Swiss-type cheese. The titration system was that originally developed for use in silage analysis (Moisio & Heikonen, 1989) and applied to cheese it has proved to be useful, easy and rapid with an accuracy similar to that achieved by colorimetry.

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