Reaction Of Ninhydrin Research Articles

The reaction of ninhydrin with keto-acids

The reaction of ninhydrin with keto-acids

Ninhydrin assay in the presence of thiol compounds.

Moore and Stein1 reported that the reaction of cysteine with ninhydrin is an exception to the general reaction of α-amino-acids with this reagent and the absorption curve of the reaction products is somewhat similar to that of proline and hydroxyproline (Fig. 1). They found that if the neutral protein hydrolysates were allowed to stand at room temperature for 24–28 hr. or if they were adjusted to pH 8 with sodium hydroxide and allowed to stand at room temperature for 4 hr. the cysteine–ninhydrin reaction product gave an absorption spectrum identical to that produced by cystine1,2. It is usual to include cysteine, mercaptoethanol, 2,3-dimercaptopropanol-1 or some other thiol compound as an activator for sulphydryl enzymes. When these are used for the activation of proteolytic enzymes such as ficin and papain the thiol compound (10−2 – 10−3 M solutions) is not completely oxidized to the disulphide during the reaction procedure. The presence of the sulphydryl group then interferes with the usual ninhydrin determination as shown in Table 1 (col. 7). The presence of cysteine introduces two errors; first, during the enzymatic reaction it is partially oxidized to cystine (an unpredictable amount), and second, the cysteine remaining reacts with the ninhydrin reagent to give a red colour which interferes with the quantitative reaction of ninhydrin with the amino-groups. The presence of 0.1 µmole of mercaptoethanol in the modified ninhydrin reaction does not affect the quantitative determination of leucine (Table 1, col. 6), but, if the concentration of this reagent is increased to 10 µmole, leucine does not give a characteristic reaction product having a maximum absorption at 570µ but rather a red colour with an absorption maximum around 450 mµ is produced.

Studies on the Reaction of Ninhydrin with Peptides and Dipeptide Esters

Studies on the Reaction of Ninhydrin with Peptides and Dipeptide Esters

158. The reaction of ninhydrin with cyclic α-imino-acids

158. The reaction of ninhydrin with cyclic α-imino-acids

Reaction of ninhydrin in acid solution with straight-chain amino acids containing two amino groups and its application to the estimation of alpha epsilon-diaminopimelic acid.

Reaction of ninhydrin in acid solution with straight-chain amino acids containing two amino groups and its application to the estimation of alpha epsilon-diaminopimelic acid.

AN ULTRAMICRO METHOD FOR QUANTITATIVE DETERMINATION OF AMINO ACIDS

A simple, quantitative method for determination of amino acids in about 300 µgm. protein is described. The amino acids are separated by two-dimensional paper chromatography. The chromatograms are sprayed with 2% ninhydrin and the color is developed under controlled and standardized conditions. The colored areas are cut out, eluted, and the color intensity is read in a photometer. The following factors have been shown to affect the color reaction of ninhydrin with amino acids on paper chromatograms: the quality of the ninhydrin; its concentration; time of color development; and the environmental temperature and humidity. Complete oxidation of the hydrolyzate is necessary for accurate quantitative determinations of cysteine, cystine, glutamic acid, aspartic acid, methionine, and valine. Strict standardization of the length of the solvent run is also important for reproducibility in the analyses of some amino acids.Bovine serum albumin has been analyzed by this method and the results found to be in excellent agreement with previously published values.

Reactions between Cyclic Triketones and Amines. Color Reactions of Ninhydrin and peri-Naphthindane Triones

Reactions between Cyclic Triketones and Amines. Color Reactions of Ninhydrin and peri-Naphthindane Triones

Gasometric Determination of Carboxyl Groups in Amino Acids

Ruhemann1 and Grassmann and von Arnim2 have shown that the color-forming reaction of ninhydrin with amino acids occurs with evolution of CO2. We have found that at pH 5, or somewhat lower, in water solution the CO2 from carboxyl groups adjacent to alpha-amino groups can be quantitatively split off in 3 minutes. The apparatus used is that employed by Van Slyke, Page and Kirk3 for manometric determination of organic carbon. In the combustion tube of this apparatus are placed a few milligrams of amino acid, 100 mg. of KH2PO4, and 50 mg. of ninhydrin made to a volume of 1.0 cc. with water. The tube is connected to the manometric chamber, arranged as for combustions,3 and the solution is boiled gently for 3 minutes. The evolved CO2 is measured as in carbon combustions.3 The reaction appears to be specific for carboxyl groups of amino acids. Other organic acids, such as acetic, lactic, citric, yield no CO2. Each of the naturally occurring amino acids including proline yields 1 mole of CO2, except the dicarboxyl...