Analysis photometric, amino acid

The rapid development of biotechnologies, as in biochemistry, requires the analysis of amino acids (proteins hydrolysates) photometric detectors can be used with the condition that prior to passage in the measuring cell a post-column reaction with ninhydrin is carried out (cf. Chapter 8). 

The percentages of amino acids in silk fibroin which Poison et al. (224) found by direct visual and indirect photometric analysis of ninhydrin paper-partition chromatograms are shown in Table VII. The percentages obtained for alanine, glycine, and serine appear to be reasonably accurate, inasmuch as they agree closely with those found by other methods. It would be of interest to determine alanine by the microbiological method reported recently by Sauberlich and Baumann (238), in view of the widely different values found for this amino acid by the described ninhydrin-chromatographic procedure and the selec-... 

Amino Acid Analysis Visual Photometric b Value Method... 

Among the analytical methods presently used for the characterization of natural and synthetic peptides and proteins, the primary value of amino acid analysis is the determination of absolute peptide and protein content in solids and solutions and the quantitation of their amino acid composition and stoichiometry. It involves two steps, i.e. complete hydrolysis of peptides and proteins, followed by photometric determination of the released amino adds. The steps are laborious and time-consuming, and there is a continuous need for improvement of the techniques to increase precision and sensitivity. 

Amino acid analyzers have improved the analysis of free amino acids to a great extent. They offer superior sensitivity, speed, and accuracy to conventional methods. Many such systems are based on IEC. Postcolumn detection is done by ninhydrin derivatization followed by photometric measurement at 570 and 440 nm for primary and secondary amino acids, respectively. Amino acid analyzers are now common and are being manufactured by many companies (e.g., Hitachi, Beckman, PerkinElmer, HP, Pharmacia, etc.). Numerous authors have used amino acid analyzers to monitor proteolysis in several kinds of cheeses (Ardo and Gripon, 1995 Edwards and Kosikowski, 1983 Fenelon et al., 2000 Gardiner et al., 1998 Kaiser et al., 1992 Yvon et al., 1997). A comparison of amino acid analyzers and several other methods for amino acid analysis is available from Biitikofer and Ardo (1999) and Lemieux et al. (1990). 

Lamkin et al. [276] studied in detail the GC analysis of silylated methylthiohydantoins of all protein amino acids. They effected the silylation with BSA-acetonitrile (1 3) at 100°C for 10 min. They separated the products in a simple column packed with 2% of OV-17 on Gas-Chrom Q at 145—230°C, and Fig. 5.20 illustrates the results. The authors used a flame photometric detector, sensitive to sulphur-containing compounds, in order to ensure sensitive and selective detection. Minor incidental peaks that were often noticed during the analysis of the samples obtained by the Edman degradation of proteins with the use of an FID did not appear and the peak of the solvent was not detected. The baseline stability was good and the response was linear over a range of two orders of magnitude of concentration. Asn and Phe were the only unresolved pair Arg, as in previous instances, did not form a volatile derivative. 

T4. Troll, W., and Cannan, R. K., A modified photometric ninhydrin method for the analysis of amino and imino acids. J. Biol. Chem. 200, 803-811 (1953). 

There are several recorded determinations of the absorption curves of the aromatic amino-acids. Most of these were obtained with photographic methods of spectrophotometry which have been superceded by more accurate photoelectric methods. It will be shown that in the spectrophotometric analysis of tyrosine and tryptophan in proteins, the photometric error is magnified in the final estimate of tyrosine and tryptophan contents. This fact is inevitably bound up with the form of the equations of mixture analysis. It is therefore important that the absorption constants be measured as accurately as possible. 

The significance of PED within chemical and biochemical analysis can be best appreciated in view of the commonly held impression, based on attempted detections at constant (dc) applied potential, that polar aliphatic compounds are generally not electroactive. Furthermore, these compounds often do not possess chromophoric or fluorophoric groups and, as a consequence, direct and sensitive detection by photometric techniques is not possible. PED has been applied to the direct, sensitive, and reproducible detection of a large variety of polar ahphatic compounds in foods. These compounds include carbohydrates, amines, amino acids, and thiocompounds. This technique is simple, in that it requires no derivatization. 

The labelled protein is separated by precipitation or by gel filtration and then the 2-NPS-tryptophan content determined spectro-photometrically at 365 nm. Protein concentration is determined by conventional methods, the most accurate being acid hydrolysis of an aliquot of the solution and subsequent quantitative amino acid analysis. 

The chemical immobilization of formylsalicylic acid derivatives on the surface of amino group-containing silica gel phases was reported. The resulting phases were examined for the extraction of Fe(III) and showed an exchange capacity of 0.95-0.96 mmol/g. The other tested metal ions showed lower metal capacity than Fe(lll). The selectivity incorporated into these silica gel phases for the extraction of Fe(III) from a mixture containing several other interfering metal ions was studied and evaluated by atomic absorption spectro-photometric analysis. In addition, a method for the recycling of the immobilized silica gel phases after... 

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