The amino-groups of the proteins of human serum. Action of formaldehyde and ninhydrin

Abstract

Proteins from human serum were purified from ammo-acids by repeated trichloroacetic acid precipitations, and by ultrafiltration. Using the S0rensen titra-tion, the average content of amino-N for total proteins was 0.635 mg per 100 cc of proteins (weighed as desiccated trichloroacetic acid precipitates). Globulins contain about 0.5 mg, albumins about 0.85 mg of amino-N per 100 cc. The existence of a protein-ninhydrin compound with definite physical and chemical properties is described. It has lost the property of reacting with formaldehyde.