22 EXPERIMENT STATION RECORD. 



The analysis of proteins by determination of the chemical groups charac- 

 teristic of the different amino acids, D. D. Van Slyke {Jour. Biol. Chem., 

 10 {1911), No. 1, pp. 15-55, figs. 2).-^This quantitative method, which was 

 designed for the purpose of obtaining with small amounts of material an in- 

 sight into the composition of proteins, was previously reported (E. S. R., 23, 

 p. 303) in the form in which it was developed originally. 



The author has now so modified the procedure that it is possible to indi- 

 cate the nature of from 98 to 100 per cent of the nitrogenous products of hydrol- 

 ysis with 24 to 3 gm. of protein, " to follow the course of protein hydrolysis 

 and detect the time at which it is complete, and for determining the ammonia 

 (amid nitrogen), arginin, histidin, lysin, cystin, amino nitrogen not precipi- 

 tated by pbosphotungstic acid (the group of ordinary primary amino acids, 

 leucin, alanin, etc.), and the nonamino nitrogen not precipitated by pbospho- 

 tungstic acid (prolin, oxyprolin, one-half the tryptophan nitrogen). . . . The 

 results of hydrolyses of wheat gliadin, edestin from hemp seed, dog's hair, 

 gelatin, fibrin, hemocyanin (the protein from the blood of the king crab corre- 

 sponding to the hemoglobin of higher animals), and of ox hemoglobin are 

 summarized. . . . 



" Comparison of the amounts of amino acids' of the different groups present 

 in proteins, found by the quantitative group determination method, with the 

 amounts isolated in previous hydrolyses, indicates that the losses of isolation 

 have fallen chiefly on the primary mouo-a-amino acids, containing all their 

 nitrogen in the — CH(NH2) — COOH group. So far as can be judged from the 

 analyses available for comparison, the presence of unknown amino acids out- 

 side of this group seems improbable. Whether the losses of isolating those 

 of this group arise from the presence of new, as yet unreco.gnized jnono-amino 

 acids, or from the unavoidable losses connected with the methods of isolation, 

 can not at present be stated." 



Some factors influencing' the quantitative determination of gliadin, J. E. 

 Greaves {Univ. Cal. Pubs., Physiol., 4 {1911), No. 6, pp. Sl-l't; Jour. Biol. 

 Chem., 9 {1911), No. 3-4, pp. 271-293).— This, work was done with 6 different 

 flours obtained from wheats having a high, medium, and low gluten content 

 and grown at the dry-farming substations of the Utah Station. The work is 

 summarized as follows : 



The concentration of solutions of the alcohol-soluble proteins is decreased on 

 filtering through layers of animal charcoal or on being clarified by shaking with 

 this substance and then filtering, but clear filtrates can be obtained without 

 materially changing the concentration of the solution by filtering through care- 

 fully prepared asbestos filters. When 7.985 gm. of flour was treated with 100 cc. 

 of alcohol 0.05 per cent more alcohol-soluble protein nitrogen was extracted 

 than when twice this amount of flour was used, and greater accuracy was also 

 obtained in the gliadin determinations by means of the polariscope. The extrac- 

 tion of the alcohol-soluble proteins does not seem to be complete, especially with 

 70 per cent alcohol, when the proportion of flour to alcohol exceeds 2 gm. of 

 flour to 100 cc. of alcohol. The amount of protein nitrogen extracted was found 

 to be greatest with 65 per cent alcohol by volume, with a decrease as the strength 

 of the alcohol increased. The specific rotation of alcohol-soluble proteins varies 

 but little if any with the concentration of the solution, but alcohol of 74 per cent 

 by volume more nearly extracts pure gliadin than does other strengths, and with 

 a charge of 7,985 gm. of flour to 100 cc. of alcohol it extracts as much gliadin 

 as does 70 per cent alcohol. The ratio of per cent nitrogen extracted from flour 

 by alcohol to the polariscope reading for the solution varies with the strength 

 of the alcohol. 



