The characterization of lower molecular 

 weight proteins by dialysis 



L. C. CRAIG, Wm. KÖNIGSBERG,* 

 A.STRACHERt AND T.P.KING 



The Laboratories of the Rockefeller Institute for Medical Research, New York, N.Y. 



During the course of the fractionation studies required to isolate a new 

 chemical individual from a naturally occurring or synthetic mixture much 

 is usually learned about the nature of the substance. Thus distillation or 

 the ultracentrifuge will set certain limits concerning its size, electrophoresis 

 gives information about its net charge at specific pH levels, countercurrent 

 distribution can tell something of its polarity, etc. In considering the various 

 fractionation techniques now available for isolating relatively large mole- 

 cules it occurred to us that a technique which would separate substances on 

 the basis of their size or shape would not only be a very useful technique 

 supplementing those now used, but could also give very informative data 

 about size and shape. With this idea in mind we have turned to the study 

 of membrane diffusion. 



The viewpoint taken in this work differs from that of the numerous studies 

 on membranes already in the literature in a number of ways. Perhaps most 

 important — much less emphasis has been placed on pore size. Membranes 

 are compared on the basis of the rate they permit standard solutes of known 

 size to pass by diffusion as well as on the basis of total exclusion. An attempt 

 is made to minimize charge efifects. The separate units are designed with 

 fractionation in mind and with the intention of making them part of a 

 countercurrent process. 



Dialysis is one of the earlier separation methods to have been used, and 

 is familiar to everyone for separating dialy sable from nondialy sable solutes. 

 However, few studies attempting to refine the technique beyond this point 

 are to be found in the literature. Probably the most promising were those 

 of Signer^ and co-workers, who experimented with a continuous counter- 

 current dialysis train of unique design. 



* National Science Foundation Fellow. 



j- Fellow of the National Foundation for Infantile Paralysis. 



