Zone electrophoresis and chromatography 

 as methods for the purification and 

 characterization of proteins 



A. TISELIUS 



Biochemical Institute, Uppsala University, Sweden 



The Commission on Proteins was created at the lUPAC Congress in New 

 York and Washington 1951 and had as its first task to investigate the possi- 

 bility of finding a standard protein preparation which would meet reason- 

 able requirements of purity and homogeneity. This is not the time to discuss 

 the very valuable work of this commission. I think, however, that I am right 

 in saying that the task proved much more difficult than could be foreseen. 

 Still, I believe that if nothing else had come out of the work than a realiza- 

 tion of the difficulty of defining a pure protein, this would have been well 

 worth the eff"ort spent. 



Some may perhaps ask how far we should go in our demands as to the 

 purity of proteins, and if there is not a danger that we might become protein 

 'purists', interested in purity for its own sake. Such an argument neglects, 

 however, several facts of importance in protein research to-day. One is that 

 the very character of the modern sequence analysis methods, developed by 

 Sanger, assumes a high degree of homogeneity. It would be an almost hope- 

 less task to fit the puzzle of peptide fragments together, if these residues 

 come from more than one homogeneous protein. Secondly, the high resolu- 

 tion of modern methods of protein separation has in an increasing number 

 of cases revealed a complexity or micro-heterogeneity which appears to be 

 extremely interesting. I am thinking now not only of the various patho- 

 logical varieties of hemoglobin which were first demonstrated by Pauling, 

 Itano, Singer and Wells (1949), but also of a number of enzyme proteins 

 which appear to consist of mixtures of closely similar but distinctly different 

 components. We cannot yet judge the significance of these results — for ex- 

 ample, how these differences are reflected in specificity or activity — but this 

 is certainly an important field for further investigations. In some cases this 

 variation appears to be genetically controlled. Besides the pathological 

 hemoglobins this complexity has now also been established for normal 



