Comparative studies in the field of 

 protein microstructure 



F. SORM 



Institute of Chemistry, 

 Czechoslovak Academy of Science, Prague 



Work in the field of protein microstructure is at present being directed along 

 two fundamental lines : the first of these is characterized by efforts to deter- 

 mine the complete structure of the simplest proteins; work along the second 

 line seeks to discover general regularities in protein structure on the basis 

 of comparative studies of lower fission products of the proteins. Practical 

 difficulties at present limit the scope of the first line of research to the higher 

 natural peptides and proteins of very low molecular weight. In spite of these 

 limitations, a number of notable successes has, as is generally known, been 

 achieved in this field, culminating at present in the determination of the 

 complete structure of ribonuclease.^ The exact determination of the amino 

 acid sequence in the peptide chains of the simpler proteins and of natural 

 peptides undoubtedly also contributes valuable information to our know- 

 ledge of the general laws governing protein structure. The results of the 

 work carried out so far must, however, for the present be evaluated with 

 some caution in this respect, since the compounds concerned are mostly 

 possessed of highly specific biological activities which very probably reflect 

 a corresponding specificity of chemical structure. For these reasons, the 

 second fundamental line of protein research, which is not limited by the 

 molecular weight of the materials studied, is gaining increasing importance. 

 The aim of such research may be either the elucidation of regularities in 

 the arrangement of amino acids within the protein chains — a line hitherto 

 pursued mainly in work on the fibrous proteins — or a search for resemblances 

 in the chemical structure of proteins related in their biological function or 

 origin. The search for such resemblances in protein structure has up to the 

 present more particularly involved those parts of the peptide chains whose 

 nature makes them amenable to direct comparison at the present level of 

 experimental technique. Such is the case, for instance, with the amino acid 

 groupings terminating the peptide chains, which may be exactly determined 

 by identification of the terminal amino acids or peptide sequences, A second 



