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SCIENCE PROGRESS 



phenylalanine ester fraction is hydrolysed by evaporating with 

 concentrated hydrochloric acid, when the hydrochloride is 

 obtained. 



The ester method can be combined with the methods for 

 obtaining tyrosine and the diamino acids. The protein is 

 therefore hydrolysed by sulphuric acid, the tyrosine separated 

 by crystallisation, and the diamino acids precipitated by 

 phosphotungstic acid. The filtrate, after removal of phospho- 

 tungstic acid, is treated as above described for the separation 

 of the monoamino acids. 



From the above it is obvious that a mixture of amino acids 

 is still present ; their final separation, as they result from the 

 various fractions, has still to be carried out. The methods 

 employed are best described by taking a particular protein as 

 illustration, e.g. crystallised oxyhsemoglobin, which was hydro- 

 lysed by Abderhalden by the above method, and gave five 

 fractions of esters from which the appended weights of amino 

 acids were isolated : 



Oxyhaemoglobin contains no glycine, so that its separation 

 was not necessary, but as ester hydrochloride four-fifths can 

 be isolated when the protein contains 20 per cent, in its 

 molecule; the remainder is distilled as ester, and passes into 

 the first fraction with alanine ester, from which it is separated 

 by conversion into its ester hydrochloride. The alanine is then 

 separated by crystallisation, after removal of the hydrochloric 

 acid, and is characterised by conversion into its benzoyl deriva- 

 tive. Owing to partial racemisation occurring during the 



