Assays Morgan-Elson

The Ehrlich reagent, developed originally for the colorimetric assay of pyrrole derivatives, was shown by Ehrlich to give a color with certain glycoproteins, with and without prior alkali treatment (3). The reagent consists of dimethylaminobenzaldehyde in strong hydrochloric acid. This assay later became the basis for the Morgan-Elson reaction for the deter-... 

The Morgan-Elson assay (see Alternate Protocol 2) requires less than 1 hr for the preparation of all the reagents, but a one hour period is required for the reaction of the 2,4-pentadione solution with the amino-sugar samples. In conclusion, without considering the incubation time in the preparation of the reagents, 2 to 4 hrs working time should be enough to determine a sample concentration with any of the procedures. 

Morgan Elson method, 656-659 phenol-sulfuric acid assay, 653-655, 658-659... 

The traditional method of assay of 2-acetamido sugars is the Morgan-Elson reaction. This involves treatment of the sugars in base, which produces furans, and reaction of these furans in situ with Ehrlich s reagent (p-dimethylamino-benzaldehyde in acid), which generates delocalised chromophores, as shown in Figure 7.8." ... 

Figure 7.8 Chromophores from reducing sugar assays, (a) Tetrahedral Cu coordinated by 2,2 -bicinchoninate. (b) A PAHBAH complex of methylgloxal. (c) The Morgan-Elson test for hexosamines. The Morgan-Elson and PAHBAH reactions are of course heterolytic, but are included here for completeness.

K. P. Vercruysse, A. Lauwers, and J. Demeester. Kinetic investigation of the action of hyaluronidase on hyaluronan using the Morgan-Elson and neocuproine assays. Biochem. J. 370 55 (1995). 

The effect of the concentration of tetraborate on the Morgan-Elson reaction for the determination of 2-acetamido-2-deoxy-D-hexoses has been evaluated. Use of optimal concentrations of tetraborate for chromogen formation lower than those previously advocated is suggested. The iV-acetylation of 2-amino-2-deoxy-D-hexoses has been shown to be temperature dependent. Conditions have been chosen for the selective A-acetylation of 2-amino-2-deoxy-D-galactose and not 2-amino-2-deoxy-D-glucose, and have been applied to an assay of mixtures of these two amino-sugars. 

There is one report (Benson, 1975) in which the proposed mechanism of the reaction of a sugar derivative (Morgan-Elson assay for 2-acylamido-2-deoxy-D-hexose sugars) has been tested using the sugar derivative bound to a polymer support. This approach will be discussed in Chapter 11. 

After mild hydrolysis, neomycin has been shown to give a positive Elson-Morgan reaction , a reaction characteristic of amino-sugarsl52 A method involving this reaction has been made the basis of a quantitative assay for neomycinl l which has been used to determine the neomycin content of fermentation broths. ... 

The most specific and frequently used assay to quantify 2-deoxy-2-amino sugars employs the condensation of the carbohydrate with 2,4-pentanedione in basic solution. The product (a pyrrole derivative) is then reacted with p-dimethylaminobenzaldehyde to form a chromogen that has a maximum absorbance at 530 nm (Fig. 11-2). Although both 6-deoxy-6-amino and 3-deoxy-3-amino sugars can also be analyzed using the Elson-Morgan reaction, the chromogens... 

How do the concentrations of D-glucose and D-glucosamine determined in this sodium borohydride reduction experiment compare with the values that you obtained for these two carbohydrates in the hexokinase and Elson-Morgan assays, respectively Discuss the quantitative differences as well as possible explanations for the differences arising from the various assays. 

A sensitive fluorimetric assay for 2-amino-2-deoxy-D-hexoses with increased sensitivity over the Elson-Morgan and Dische-Borenfreund indole methods has been reported. The 2,5-anhydrohexoses produced by nitrous acid deamination of heparin, heparan sulphate, and 2-amino-2-deoxy-D-hexoses have been treated with 3,5-diaminobenzoic acid to give stable derivatives. Neither neutral sugars nor acetamido sugars interfere in the reaction. In a modification of an earlier procedure, equivalent colour complexes were formed by the interaction of 3-methyl 2-benzothiazoline and the 2,5-anhydrohexoses produced by deamination of 2-amino-2-deoxy-D-glucose and 2-amino-2-deoxy-D-galactose. ... 

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