Spectrophotometric Determination Of Tryptophan Research Articles

Determination of tryptophan by high-performance liquid chromatography of alkaline hydrolysates with spectrophotometric detection

A procedure for quantitation of tryptophan in feedstuff is described. It consist of hydrolysis in sodium hydroxide at 100 °C for 4 h, neutralization of the resulting hydrolysate to pH 7, dilution with sodium borate buffer (pH 9), and analysis by reverse-phase high-performance liquid chromatography with spectrophotometric determination of tryptophan at 280 nm. The recovery of tryptophan from lysozyme, added to some feedstuff before hydrolysis, ranges from 98.6 to 100%. A reduction of the time of analysis has been achieved as compared to previous methods for analysis of tryptophan.

Spectrophotometric determination of tryptophan in intact proteins by the acid ninhydrin method

The interaction of tryptophan, lysozyme and tyrosine with ninhydrin in strong acid media has been investigated at 20, 25, 30, and 35°C by spectrophotometry. Second-order rate constants and molar absorptivity values have been evaluated from an analytical point of view. Optimum conditions for the selective estimation of tryptophan, tryptophan residues in intact proteins, and indoles—without the disturbing affect of tyrosine—have been given. Under optimum conditions, in the concentration range from 2.5 × 10 −8 to 3.0 × 10 −7 m, molar absorptivity values and reproducibility data for various reactants have been reported. Molar absorptivity values ( A m × 10 −3/ m × cm) of tryptophan (21.35), lysozyme (19.33), bovine serum albumin (21.05), human serum albumin (21.00), casein (17.85), α-chymotrypsin (18.28), trypsin (14.43), indole (5.03), and indole-3-acetic acid (13.75) have been measured with a standard error of 2.3% or less for any particular reactant.

Spectrophotometric determination of tryptophan by reaction with nitrous acid

The heterocyclic nucleus in tryptophan is oxidised by nitrous acid at elevated temperature to produce a phenolic intermediate which further reacts with nitrous acid to form a nitro compound that has a golden yellow colour in alkaline medium. The maximum absorbance is obtained at 400 nm with maximum molar absorptivity of 9.44 × 10 3 l.mole −1. cm −1. Derivatives of tryptophan such as indole-3-acetic acid, tryptamine and tryptophanamide, as well as indole, produce the same colour, but some others, e.g., 5-hydroxytryptamine and 5-hydroxyindole-3-acetic acid do not give the colour reaction. A plausible mechanism is proposed to explain this behaviour.

Spectrophotometric determination of tryptophan and tyrosine in peptides and proteins based on new color reactions

A new spectrophotometric method for quantitative determination of tryptophan and tyrosine in peptides and proteins is described. It is based on two specific color reactions, the reaction of tryptophan with formaldehyde and the reaction of tyrosine and tryptophan with hydroxylamine and ceric cations. By combination of these two reactions both tyrosine and tryptophan can be determined simultaneously. Tyrosine and/or tryptophan bound in peptides and/or proteins react independently of the rest of the peptide or protein molecule. The method is simple, accurate, and sensitive. Hydrolysis is not necessary.

High-performance liquid chromatography and ultraviolet spectrophotometry for quantitation of tryptophan in barytic hydrolysates

A procedure for quantitation of tryptophan in feedstuffs is described. It is based on barytic hydrolysis of material at 125°C for 16 h, acidification of hydrolysate to pH 3 with HCl, high-performance liquid chromatography on Nova Pak C 18 (Waters Assoc.), and spectrophotometric determination of tryptophan at 280 nm. The recovery of tryptophan from lysozyme added to samples ranges from 98.7 to 100%.

Spectrophotometric Determination of Tryptophan and Tyrosine in Atp-Creatine Phosphotransferase

Abstract A recent paper by Edelhoch1 has presented a spectrophotometric method for the rapid determination of the tryptophan and tyrosine content of unhydrolyzed proteins.

Spectrophotometric determination of tryptophan with mercuric chloride

Spectrophotometric determination of tryptophan with mercuric chloride

The chemical determination of tryptophan in foods and mixed diets

A description is given of a colorimetric method for the determination of tryptophan in foods and mixed diets. The method is based on enzymic hydrolysis of the material, extraction of the hydrolyzed protein with a mixture of diluted potassium hydroxide and carbon tetrachloride, and spectrophotometric determination of tryptophan after the addition of p-dimethylaminobenzaldehyde to an aliquot of the extract.

Spectrophotometric determination of tryptophan by the method of Roth and Schuster: some sources of error.

IN Roth and Schuster's method1 for colorimetric determination of tryptophan in vegetable matter, the measurement of the yellow colour is made with a Pulfrich Stufenfotometer with filter S 43. The method has often been used, but I have been unable to find any published account of the measurements made spectrophotometrically. I have therefore tested the method for some cereals, etc., by means of a Beckman spectrophotometer, model D.U.