The free amino groups of haemoglobins

Abstract

Several 2,4-dinitrophenyl amino acids were prepared and characterized. Several modifications of the method of measuring the free amino groups of proteins with 1,2,4-fluorodinitrobenzene were described. The method was applied to several hemoglobins. Horse and donkey hemoglobins contain 6 terminal valyl residues/molecule, adult human hemoglobin 5 terminal valyl residues, and cow, sheep and goat hemoglobins 2 terminal valyl and 2 terminal methionyl residues. If a molecular wt. of.66,000 is assumed, human fetal hemoglobin contains 2.6 terminal valyl residues. Horse myoglobin has 1 terminal glycyl residue/molecule of molecular wt. 17,000. The epsilon-amino groups of the lysine residues are free in the above proteins. The significance of these results in relation to the structure of the hemoglobins and the correlation between structure and immunologic specificity of proteins is discussed.