L. Messineo
Dec 1, 1966
Citations
3
Influential Citations
58
Citations
Journal
Archives of Biochemistry and Biophysics
Abstract
Abstract 2,4-Dichloro-1-naphthol in alkaline solution becomes red on standing. It becomes red also upon addition of small concentrations of NaOCl and fades when higher concentrations of NaOCl are added. This instability of an alkaline solution of naphthol (probably due to its oxidation) has been interpreted as one of the reasons for the nonlinearity present in the Spectrophotometric determination of arginine with previous modifications of the Sakaguchi reaction. Another reason for this nonlinearity has been found in the fact that all amino acids react with alkaline solutions of 2,4-dichloro-1-naphthol, thus interfering with the spectrum specifically due to the guanidino group of arginine. These interferences are eliminated with the reagent suggested here which is obtained by dissolving 100 mg of 2,4-dichloro-1-naphthol in 100 ml of 5.0 n KOH and 180 ml of absolute alcohol, and then bringing it to a full color development by adding a small concentration of NaOCl. It was also found that the addition to the reaction mixture of 2 moles of KI for each mole of naphthol stabilizes the reaction products. Thus the reaction of naphthol with arginine is made stable; the plot of optical density (O.D.) versus concentration of arginine is linear and the slope passes through the origin. This method for the determination of arginine has been tested with solutions of various proteins without previous hydrolysis. The arginine content of these proteins has been found to be close to the values reported in the literature.