Enzymatic determination

Enzymatic Determination and Microbial Assay. In these methods, only the desired amino acid is detected ia spite of the presence of other amino acids. No expensive tools are needed for these determiaations. The required nutrients for microorganisms and practical operations for the microbial assay of amino acids have been reviewed (134,135). 

Enzymatic determinations of the detection limit where the chromatograms are first sprayed with an enzyme solution Then after appropriate incubation the enzymatically altered components are detected by reaction with a suitable reagent... 

Huidobro, J. F., Estrella, R. M., de Andrade, B. P. C., Sanchez, M. P., Sancho, M. T., Muniategui, S., and Simal-Lozano, J. (1994). Enzymatic determination of primary normal alcohols as apparent ethanol content in honey. /. Agric. Food Chem. 42,1975-1978. 

Tubular electrodes. Blaedel et al.161 were the first to introduce the TBE, a tubular electrode. It was constructed by melting a Pt cylinder in a glass capillary (see Fig. 5.25), the total length of Pt being 25.5 mm and its diameter 0.75 mm. The authors originally used it for an enzymatic determination of glucose by means of differential amperometry based on the following sequential reactions"12 ... 

Maiorino M, Roveri A, Ursini F and Gregolin C. 1985. Enzymatic determination of membrane lipid peroxidation. J Free Radic Biol Med l(3) 203-207. 

Phospholipid concentration was determined using our modification of Bartlett s procedure (49,53). Cholesterol concentration and purity were determined by HPLC or enzymatically by cholesterol oxidase (49,53). Purity of phospholipids as raw materials, and the extent of their hydrolysis during various steps of liposome preparation and liposome storage, were assessed by TLC and enzymatic determination of the increase in level of nonesterified fatty acids (10,38,49-51,53). 

It is often desirable to fix a given factor at some specified level. For example, if an enzymatic determination is always to be carried out at 37°C, we might specify... 

Haining, R. L., Jones, J. R, Henne, K. R., et al. (1999) Enzymatic determinants of the substrate specificity of CYP2C9 role of B -C loop residues in providing the pi-stacking anchor site for warfarin binding. Biochemistry 38, 3285-3292. 

ALTERNATE PROTOCOL 2 ENZYMATIC MEASUREMENT OF CHOLESTEROL Test combination kits for enzymatic determination of cholesterol in food are now commercially available. For the determination of total cholesterol, esterified cholesterol is hydrolyzed to free cholesterol and fatty acid under mild alkaline conditions. Cholesterol oxidase oxidizes free cholesterol to cholest-4-en-3-one to generate hydrogen peroxide, which further oxidizes methanol to formaldehyde. Formaldehyde then reacts with acetyl acetone in the presence of NH4+ ions to form yellow lutidine dye, which is subsequently determined spectrophotometric al 1 y. 

Several methodologies are known as effective tools for the determination of cholesterol in food and foodstuffs, e.g., colorimetry using the Libermann-Burchard reaction (Naito and David, 1984), Iatroscan thin-layer chromato-graphy/flame ionization detection (Indrasena et al., 1991), enzymatic determination (Shen et al., 1982), GC determination (Karkalas et al.,... 

HPLC determination (Osada et al., 1999), and HPLC/MS (Redden and Huang, 1991). In general, enzymatic determination is superior to colorimetry to obtain true cholesterol content. When food such as shellfish contains sterols other than cholesterol, the GC determination is the most adequate method. Although GC/MS also accomplishes good separation between and identification of all sterol analogs, the instrument is too expensive to use for routine analyses of cholesterol. 

The adaptation of methods for lipid extraction and quantification by colorimetric determination of either ester or cholesterol in egg yolk with some contamination of egg white is described. Results are compared with those obtained by a conventional enzymatic determination. 

An effort to reduce the analytical time for enzymatic determination of starch. 

Some important technical details for the enzymatic determination of starch in cereal flours. 

Cation exchange chromatography Automatic enzymatic determination... 

Wu M, Lin Z, Durkop A, Wolfbeis OS. Time-resolved enzymatic determination of glucose using a fluorescent europium probe for hydrogen peroxide. Analytical and Bioanalytical Chemistry 2004, 380, 619-626. 

In cases where standardized methods are used in clinical laboratories to indicate bias, repeatability, or sensitivity, (for instance in enzymatic determinations) the measurement result is traceable to a reference method only if all the instruments involved in the method are appropriately calibrated against the proper physical standard. 

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