Showing papers on "Color reaction published in 1975"

Direct estimation of lysine in corn meals by the ninhydrin color reaction.

Abstract: Since the discovery that opaque-2 (o2) and floury-2 (fl2) mutants of corn have grains high in lysine (Mertz et al., 1964; Nelson et al., 1965), extensive breeding programs have been underway to develop suitable high-lysine hy­ brids. The recent discovery of modifier genes has permit­ ted development of high-lysine corns having vitreous ker­ nels resembling normal dent com in contrast to the floury characteristics of regular o2 and fl2 mutants (Bauman and Aycock, 1970). Breeding programs for high-lysine corn, especially of the vitreous type, have been handicapped by the lack of a simple rapid a.ssay method for lysine content. The use of colorimetric and enzymatic methods, gas and ion-exchange chromatography, and methods of analy­ sis for different proteins has been reviewed by Paulis et al. (1974a,b) and Concon (1972). However, each of these methods for evaluating lysine content lacks either sim­ plicity or accuracy. Recently, !'vlertz et al. (1975) used the ninhydrin re­ agent upon extracts of individual kernels of several cereal grains to detect differences in free amino acid levels. Since high-lysine lines contain much higher levels of free amino acids (Mertz et al., 1975), use of the ninhydrin color reaction permitted them to distinguish normal and high-lysine corns. Prior to the report of their findings, work at this laboratory established that the ninhydrin reaction of total amino groups in the kernel can be corre­ lated with the lysine content of corn. However, if the free amino acids are removed from the meal of corn or other grains, the ninhydrin reagent can be used for a quantitative estimate of lysine content in protein in the grain samples. The production of color by ninhydrin reaction with aand E-amino groups in the grain proteins is facilitated by use of special solvent systems. The reaction is easy to perform and requires only small quantities of sample (10-20 mg).

Use of leuco-dyes in the quantitative colorimetric microdetermination of hemoglobin and other heme compounds.

Abstract: Sensitivity, stability, and specificity of the color-producing reaction of hydrogen peroxide with benzidine, leucomalachite green, or o -dianisidine were tested in numerous systems containing hemoglobin and other hemoproteins. Use of urea or low temperature (to -12 °C), or both, was highly beneficial, especially with leuco-malachite green, for which the color reaction was stable, after about 15 min, for longer than 24 h, with a colorless blank. Absorbance was 0.3 at a final hemoglobin concentration of 0.27 mg/liter. Nonspecific color produced by substances such as FeCl3 and ascorbic acid was completely eliminated. Of the three leuco-dyes studied, only benzidine yielded a completely linear calibration curve, but its relative instability and reported carcinogenicity are serious disadvantages. No system tested eliminated completely the known inhibition by plasma of the peroxidase activity of these leuco dyes.

Color Reaction Streak Test for Catalase-Positive Microorganisms

Abstract: A stable purple color results when a reagent solution is applied to a smear of catalase-positive organisms streaked on a glass slide.

Colour reaction system with metal carboxylate or sulphonate - as developer using org ether cpd as solvent for colour former

Abstract: Colour reaction system, in which metal salts (I) of aliphatic and aromatic carboxylic and sulphonic acids are used as new developer, uses organic cpds (II) contg other gps, pref diphenoxy-diethylformal, as solvent for the colour former (III) Used in colour reaction copying papers (I) give no or only an inadequate colour reaction with (III) in the conventional solvents but give intense colours in (II) (II) are insol in water, as required for microencapsulation, are physiologically harmless and have low volatility Only 05 g (I) m2 or less is needed in the coatings, cf 4-6 g/m2 when clay minerals are employed