ASPECTS OF PROTEIN STRUCTURE 



BARBARA W. LOW, Department of Biological Chemistry^ Harvard 



Medical School, Boston, Massachusetts 



JOHN T. EDSALL, Biological Laboratories, Harvard University, 



Cambridge, Massachusetts 



We propose here to inquire into the configuration of a few 

 important protein molecules. The inquiry is still preliminary 

 and tentative, but it can proceed at a level which would have 

 been unattainable only a few years ago. The last ten years, and 

 more especially the last five, have seen the most remarkable 

 advances ever recorded in our knowledge of protein structure. 

 These advances have illuminated the difficult problems of the 

 configuration of polypeptide chains in space, and of the 

 sequences of amino acid residues in the peptide chains found in 

 natural proteins. 



The complete structural formulas of the insulins of beef, 

 sheep, and pig have been deduced by Sanger and his associates 

 (21,92-96) by a powerful chain of detailed circumstantial 

 evidence. The structure of each of the many peptides derived 

 by partial breakdown from either the A or the B chain of the 

 insulin molecule is compatible with one, and only one, sequence 

 in the amino acid residues in each of these chains. It is true 

 that the original insulin used as starting material was not 

 quantitatively accounted for in the split products; conceivably 

 some material in the latter which escaped detection might have 

 represented peptides arising from other sequences than those 



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