SESSION II. DISCUSSION 183 



S. Akabori (Osaka, Japan) : 



A Comment to the Paper of Prof. Klabunovskiî 



Asymmetric catalysis is important not only from the standpoint of biochemistry but 

 from that of synthetic organic chemistry. As it is well known, many enzymes are metaUo- 

 proteins and, on the other hand, metallic palladium is a good catalyst for the hydrogéna- 

 tion of organic compounds. Based on these facts we devised a hydrogenase model which 

 was prepared as follows. When silk fibroin was warmed in an aqueous solution of palla- 

 dium chloride, the former absorbed effectively palladivim ion. Brown-coloured Pd-silk- 

 fibroin thus formed was shaken under hydrogen at 50°, whereby black coloured Pd- silk- 

 fibroin was obtained. This Pd-silk is capable of catalysing asymmetrical hydrogénation 

 as applied to various unsaturated compounds. The experimental results are represented 

 in the Bakh memorial volume of Biokhimiya [i]. 



It is interesting that natural silk fibroin produces asymmetric catalyst, but if silk 

 fibroin was once dissolved in copper-ammonia solution and reprecipitated, it loses this 

 specific character. It seems, therefore, the asymmetric property of an enzyme depends 

 not only on the asymmetric structure of individual component amino acids but also on 

 the asymmetric structure of the whole enzyme-protein molecule. 



REFERENCE 



I. S. Akabori, S. Sakurai, Y. Izumi & Y. Fujii, Biokhimiya, 22, 154, 1957. 



C. Reid (Canada) : 



I believe that we have paid insufficient attention to small molecules, other than amino 

 acids, which may have appeared under the supposed early atmospheric conditions. 



If we accept Dr Miller's view of a sea containing comparatively high concentration of 

 ammonia, and also the view that formaldehyde may have appeared either from CO2 or 

 from methane, it implies that hexamethylenetetramine must have formed in large quan- 

 tities, since this substance is formed exothermically and in high yield even without hght 

 under all conditions in aqueous solutions, except at unreasonably low pH. The formation 

 of large quantities of this substance would provide a 'pre-coacervation' concentration 

 stage on subsequent evaporation of water. 



That such a step might be a useful one towards amino acids, we have tested by long 

 irradiation of hot hexamethylenetetramine solutions with Hg 1850 A light. Glycine and 

 alanine have been identified in the products, and a third substance of uncertain identity 

 is also formed. 



A second molecule which may have appeared as the ammonia atmosphere slowly 

 became oxidized is hydroxylamine. This is an interesting molecule, since its absorption 

 of fight extends to considerably longer wavelengths than does that of H2O or NH3. We 

 have found that the ultraviolet synthesis of amino acids using the Hg 1850 A line is, in 

 fact, more efficient when hydroxylamine rather than ammonia is used as the source of 

 nitrogen. 



D. Sapozhnikov (U.S.S.R.): 



The Screening of Ultraviolet Rays before the formation 



of the Ozone Layer 



We believe that the products of gaseous dissociation brought about by ultraviolet 

 radiation might have acted as a screen against short-wave ultraviolet rays. Near ultra- 

 violet rays are absorbed by the products of dissociation of compounds of low molecular 

 weight. Thus, at some particular depth, suitable conditions might be produced for the 

 synthesis of compounds of high molecular weight. 



