386 CARNEGIE INSTITUTION OF WASHINGTON. 



tion potentials, both still and flowing. The results are of considerable 

 interest and bid fair to throw light upoti the mechanism of the con- 

 duction of electricity from one part of a liquid cell to another. 



(8) Adsorption on Glass Surfaces. 



Dr. Emmett K. Carver, Rockefeller Research Fellow, continued his 

 investigations of the adsorption of vapors on glass surfaces with the 

 help of the very accurate pressure-gage mentioned in the previous 

 report. The precautions necessary for the use of this highly sensitive 

 instrument were further studied; and at the time of writing systematic 

 experiments upon the adsorption of toluene on glass are being prose- 

 cuted and will be continued during the summer. 



During the winter several of the investigations described in previous 

 reports have been published in detail. References to these publi- 

 cations will be found in the bibliography. 



Sherman, H. C, Columbia University, New York, New York. Chemical 

 investigation of amylases and related enzymes. (For previous reports see- 

 Year Books Nos. 11-19.) 



The experimental studies of the influence of the amino acids, glycine, 

 alanine, phenylalanine, and tyrosine, outlined briefly in the report of 

 last year, have been completed and prepared for publication. As 

 pointed out in last year's report, the uniformly favorable influence of 

 these amino acids (as well as of asparagine and aspartic acid as re- 

 ported in 1919) may conceivably be due to one or more of several 

 causes. Frequently, no doubt, the "buffer effect" of an amino acid 

 aids the activity of an enzyme by assisting in the maintenance of a 

 favorable hydrogen-ion concentration. In our experiments the opti- 

 mum hydrogen-ion concentration for each of the three kinds of amylase 

 chiefly used has been determined by previous studies and is regularly 

 insured by the addition of pure salts (chloride and primary or second- 

 ary phosphate) ; also, frequent determinations of the concentration of 

 hydrogen-ion in actual digestion mixtures have shown that this is not 

 appreciably influenced by our additions of carefully neutralized amino 

 acids, whose effects are therefore due to some more specific cause. 



Since the action of a hydrolytic enzjone is frequently retarded by the 

 accumulation of the products resulting from the hydrolysis, experi- 

 ments have been performed to determine whether the amino acid 

 favors the activity of the enzyme by combining with products which 

 might otherwise have an inhibitory influence. Such experiments, 

 made both with pure maltose and with a digestion mixture resulting 

 from the action of the amylase upon soluble starch, have shown that 

 this is not the explanation of the favorable influence exerted by the 

 amino acids in our experiments. 



On the other hand, we have found that the amino acid may have a 

 pronounced effect in protecting the enzyme from the action of a ilele- 

 terious substance, such as copper, and also in retarding the deteriora- 



