Analysis of carbohydrates in glycoproteins

If a protein does not contain hexosamines, one other test for the presence of neutral sugars should be made. This can be done by paper chromatography (Carsten and Pierce 1963 Spiro 1965) or gas chromatography ( 2.13.3) after appropriate hydrolysis ( 2.13.2), or a simple colorimetric reaction, such as the orcinol method (below), may be used. 

Proteins to be analyzed for hexoses by the orcinol method (Winzler 1955) should be free of extraneous carbohydrate. The protein (2-10 mg) is dissolved in 0.1 N NaOH (1.0 ml), and a blank of 0.1 N NaOH (1.0 ml) and a standard of galactose and mannose (0.1 mg of each in 

An alternate colorimetric method for hexoses is the anthrone procedure (Spiro 1965). 

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Chaplin used methanolysis for the analysis of carbohydrates in glycoproteins. His method was a variation of the foregoing procedures, with an improvement of using tert-hvAyX alcohol to remove hydrogen chloride by coevaporation, instead of prolonged trituration with silver carbonate. His method is useful for samples containing uronic acids and lipids. Mononen studied methanolysis, followed by deamination and reduction with borohydride, for determination of the monosaccharide constituents of glycoconjugates. This method was applied to a lipid-free, protein fraction of rat brain. 

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