Carbohydrates in protein. 4. The determination of mannose in hen's-egg albumin by radioisotope dilution

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Abstract
Earlier results based on colorimetric techniques for the mannose content of hen''s-egg albumin are critically discussed. The mannose content of egg albumin by the orcinol-sulphuric acid method is about 2%. The effect of borate on this method has been examined. A new procedure for the determination of mannose in a glycoprotein by radioisotope dilution has been developed and applied to egg albumin. The maximum quantity of mannose liberated from the protein by 2N-hydrochloric acid by this method is about 2%. The possibility that this may not be the true content of mannose in the protein has been discussed. The minimum mannose content of the protein by direct isolation as the phenylhydrazone has been shown to be 1.77%.