350 SECTIONAL TRANSACTIONS.— p. \ 



Dr. D. M. Wrinch. — Structure of ' globular ' proteins. 



A number of facts relating to proteins suggest that the polypeptides in 

 native proteins are in a folded state : accordingly all types of folding which 

 are geometrically possible are being investigated systematically. The 

 cyclol link =N — C(OH)= is one such possibility. It replaces Fischer's 

 peptide link by multiple peptide links and his polypeptides by cyclol molecules. 

 The Cyclol theory thus presents for consideration a two-dimensional atomic 

 network which, it may be suggested, is the fundamental entity in the protein 

 molecule. 



This theory, originally devised to deal with protein films and laminate 

 proteins, is found to imply the existence of closed space-enclosing struc- 

 tures, which, owing to geometrical exigencies, exist only in certain sizes. 

 It thus predicts in general terms the body of facts relating to the globular 

 proteins established by Svedberg and his collaborators and suggests that 

 each molecular weight class connotes a certain arrangement of amino-acid 

 residues, say a certain closed cyclol, or an association of a number of such 

 structures. Of the closed cyclols so far constructed, the cyclol containing 

 288 residues has been suggested as the structure of the proteins belonging 

 to the 36,000 molecular weight class (egg albumen, insuHn, pepsin . . .). 

 On the basis of this structure, it was predicted that the number of residues 

 per molecule belonging to this class is 288. The number was subsequently 

 put forward by Bergmann and Niemann, on the basis of chemical analysis, 

 as being the number of residues in each molecule of egg albumen. It has 

 also been found that this structure fits the X-ray data for insulin and pepsin. 



Dr. A. Neuberger. — Electrochemistry of proteins and amino-acids. 



One of the most important advances in the electrochemistry of amino- 

 acids and proteins is the zwitterion theory, which explains satisfactorily the 

 physical properties such as solubilities, melting-points and Raman spectra 

 of these polar compounds. The dissociation constants of amino-acids in 

 relation to those of fatty acids, amines and amino-acid esters can be 

 quantitatively interpreted on this basis and estimates of dipol moments 

 of zwitterions can be obtained. For proteins a quantitative relationship can 

 be shown to exist between content of multivalent amino-acids and acid 

 and base-binding capacity. It is further possible to interpret the titration 

 curves of proteins in terms of the chemical composition ; the correctness of 

 such an interpretation can be proved by producing chemical changes in 

 the protein which cause corresponding shifts in the titration curves. 



The isoelectric points of proteins depend also on the chemical com- 

 position of the proteins, and it is possible to separate chemically different 

 proteins by making use of differences in the isoelectric points. 



Mr. J. St. L. Philpot. — Ultracentrifugal investigation of proteins. 



The paper is a summary of the work of Svedberg and his collaborators 

 at Upsala. Size-distributions of dissolved protein particles have been 

 studied by measuring the rates of sedimentation in a centrifugal field 

 300,000 times that of gravity, with the following results : (i) A native 

 protein in solution is ' oligodisperse ' (i.e. its particles have a strictly hmited 

 number of sizes), while inorganic colloids are ' poly disperse ' (i.e. their 

 particles have every possible size within a wide range). This justifies the 

 term ' protein molecule.' (2) Many protein molecules are spherical or 

 nearly so. (3) The molecular weights tend to be simple multiples of 

 18,000, just as the atomic weights of elements tend to be multiples of that 



