Human Transferrin

Human transferrin was isolated by two different methods from both fresh plasma and outdated blood bank plasma. The resulting preparations were shown to be homogeneous by the criteria of polyacrylamide electrophoresis, immunoelectrophoresis, absorption spectra between the wave lengths of 400 mµ and 460 mµ, sedimentation velocity, and concurrence of the weight and number average molecular weights. The molecular weights of these preparations were all between 73,200 and 76,000 by sedimentation equilibrium, sedimentation and diffusion, osmotic pressure, and maximum iron-binding capacity. This molecular weight is significantly lower than the usually accepted value of 90,000. The sedimentation coefficient was found to decrease below pH 5.0 from 4.92 S to 2.75 S at pH 2.1. The molecular weight was independent of pH in the pH range of 2 to 8.