118 



SHIRO AKABORI 



tJie surface of kaolinite was suspended in water and treated with formaldehyde 

 or acetaldehyde in the presence of a basic catalyst. The reaction product was 

 washed with alcohol, dried and hydrolysed with 6N-hydrochloric acid. The 

 hydrolysate was dinitrophenylated and analysed by siHca gel chromatography. 

 The results of these experiments are shown in Table i. 



Table i 



Abbreviations: PGK: Polyglycine-kaolinite. 

 PG: Polyglycine. 

 TEA: Triethylamine. 



In the reaction with formaldehyde, 2-3% of glycyl residues of polyglycine 

 were converted to seryl residues and in the case of acetaldehyde the rate of the 

 conversion of glycyl to threonyl residues was about 1-5%. The degree of poly- 

 merization of polyglycine dispersed on kaolinite was from 140 to 170. It is, 

 therefore, clear that not only the N-terminal residue but other glycyl residues 

 reacted with the aldehydes. When polyglycine without supporter was used, 

 practically no side chains were introduced into polyglycine under the same 

 reaction conditions. 



The conversion of seryl residue to cysteinyl or cystinyl residue in the fore- 

 protein could have taken place as follows. 



li: 



H 



NH 



NH 



I + CH2O 1 



CH2 



cic 



CH- 



I 

 CO 



-CH20H 



CH2 



+ H2S 



I 



NH 



CH— CH2— SH 



CO 



I 



do 



I 



This hypothesis was then experimentally tested. For the purpose of experimental 

 convenience we used polyserine synthesized by Okawa [6], one of my associates, 

 according to the method shown in Fig. 2. The formation of cystinyl and 

 cysteinyl residue has not yet definitely been confirmed, but when polyserine 

 was treated with benzyl mercaptan in an alkaline solution, the presence of 

 5-benzylcysteine in the hydrolysate of the reaction product was clearly 

 demonstrated. 



