GENERAL CHEMICAL CHARACTERS OF PROTEINS 55 

 With bases (B) a similar reaction would take place 



xGB + j;HOH = (GH) y (GB) x _ y + jBOH. 



With increase in the value y\x> the size of the molecules of the 

 globulin salt molecules would increase until finally they are large 

 enough to diffract white light. Such molecules take part in electric 

 transport, and their velocity, as measured indirectly by conductivity 

 and by the " boundary " method, is exceptionally high, much higher, 

 in fact, than, according to Ostwald's law, could be accounted for by 

 ions containing such a large number of atoms. When large mole- 

 cules, such as the globulin salts, become ionised and take part in 

 electrical transport, they are said, according to Hardy, to form " pseudo- 

 ions," and when the magnitude of these latter become sufficiently 

 large, they attain the properties of matter in mass, being defined by 

 a surface, and moving under the influence of a surface contact differ- 

 ence of potential. 



Somewhat similar to the phenomena just mentioned is the forma- 

 tion of opalescent solutions of caseinogen salts. In spite of these 

 peculiarities there is considerable evidence of a true chemical re- 

 action between serum-globulin and acids and bases. It is also 

 possible that globulin forms compounds with salts of the type GNaCl, 

 which readily hydrolyse with water. This would account for the fact 

 that such compounds are only stable in the presence of a large excess 

 of salt, i.e., they are soluble only in comparatively concentrated salt 

 solutions, from which they are reprecipitated on dilution. A globulin 

 acid salt is also but slightly soluble in dilute salt solutions, owing to 

 the double decomposition 



GHAc + NaCl = GNaCl + HAc. 



The globulin alkali salts, however, are more readily soluble in salt 

 solutions than simple globulin. This Hardy considers to be due to 

 the compounds in question being of the following types : 



xNH 2 .HCl /NH 2 .NaCl 



R \ R \ 



\COOH \COOH 



for the compounds of acids and salts. The one could only be formed 

 from the other by double decomposition. The compounds with 

 bases would be formed by the replacement of the hydrogen in the 

 carboxyl group. 



The above chemical considerations go far to explain the peculiar 

 solubility conditions of the globulin type of proteins. 



The Question of Pseudo-acid and Pseudo-base Formation. 



Cohnheim has expressed the opinion that proteins may belong to 

 that class which Hantzsch has termed pseudo-acids and pseudo-bases. 

 Of such a class typical examples are the nitro-paraffins, eg., nitro- 

 ethane. This body can exist in the two forms 



CH 3 . CH 2 . NO 2 True nitro-form which is a neutral body. 



CH 3 . CH : NO . OH Pseudo nitro-form which is an acid body. 



In the presence of alkali the true nitro-form is slowly converted into 

 the pseudo-form 



CH 3 . CH 2 . NO 2 + NaOH = CH 3 . CH : NO . ONa + H 2 O. 



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