An ultracentrifugal investigation of the serum proteins

THE extensive researches into the molecular dimensions of the proteins carried out in recent years by Svedberg and collaborators2 by means of the ultra- centrifuge have hitherto been conducted mainly on dilute protein solutions. This has been necessitated by the fact that the sedimentation velocity in the centrifugal field is independent of the protein concentration only in dilute solu- tion. In addition to this, various practical difficulties arise when it is desired to examine protein solutions, such as serum, which contain more than 1-2 % of protein. For instance, the light absorption in the ultraviolet of such solutions is generally too great to permit the use of the absorption method of following the protein sedimentation. Also, in the case of serum, the absorption over the whole cell would not be due to the proteins alone, as. is desirable, but also to the serum pigments.