Morgan-Elson test

The amino sugar gives a reaction similar to that of 2-amino-2-deoxy-D-glucose in the Elson-Morgan test. 

Recently, in seeking a colorimetric method more sensitive than the Elson-Morgan test (20y), Dische and Borenfreund88 have developed a technique needing only 5y of the amino sugar. The method is based on the deamination of the hexosamine to give the corresponding 2,5-anhydro-hexose with Walden inversion at C2. The anhydro derivatives yield stable characteristic colors when treated with indole in dilute hydrochloric acid, well suited to quantitative colorimetric estimation. 

The ninhydrin reagent (No. 178) is the most sensitive for detection of the free amino sugars (lower limit of detection, 0.5 (xg), whereas a periodic acid reagent, followed by thiobarbituric acid, although less sensitive (3 to 5 (Xg), gives characteristic colors (red for the N-acetyl compounds). The Elson-Morgan test can be used on cellulose MN 300 A but the characteristic color formation is hindered on cellulose MN 300 [39]. 

Whilst there appears to be limited scope at present for the utilization of these observations in determinations of polysaccharide structures, they can be of value when the Morgan-Elson test is applied to oligosaccharides containing amino sugar residues, as the work on the oligosaccharides from human milk2 has shown. Obviously, no simple relation exists between a positive test and the presence of free 2-acetamido-2-deoxyhexose, but much information may be culled by a consideration of all the factors outlined above. 

Morgan-Elson Test.—The color intensity produced by the 2-acetamido sugars in the Morgan-Elson test is significantly affected by substitution... 

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