Concentrated protein solutions in the analytical ultracentrifuge

Concentrated solutions of transferrin, albumin, immunoglobulin, chymotrypsinogen, transfer‐RNA, dextran, and polystyrene were pelleted in the analytical ultracentrifuge. The proteins developed a solvent/pellet boundary which was chracterized at equilibrium by an asymmetric schlieren peak with a “shoulder”. The schlieren curve was at the same level inside the protein pellet as in the solvent above the pellet, indicating that the protein molecules had been packed homogeneously. The protein concentration in the pellet ranged from 0.6 to 0.7 g/ml. Immediately after deceleration was begun, the “shoulder” of the pellet boundary changed into a very sharp peak, leading to a boundary composed of two schlieren peaks. Sedimentation rates were measured for transferrin solutions at concentrations up to 0.3 g/ml.