98 Dr. 8S. B.Schryver. Some Investigations Dealing | Aug. 12, 
of the precipitate produced when formaldehyde is added to Witte’s peptone 
and their capacity for dissolving the globulins, and this analogy suggested 
an explanation of the chemical character of this class of proteins, and of the 
fact that they are soluble in certain salt solutions, and insoluble in water. 
From general considerations of the chemical characters of proteins and 
their hydrolysis products, it is conceivable that substances of this class can 
‘be either basic or acid in their nature, or that they can be truly amphoteric, 
and combine both acid and basic properties. As members of the basic class, 
which yield on hydrolysis chiefly diamino-derivatives, the protamines may be 
cited as examples. Other proteins of distinctly acid character are also 
known, in which class caseinogen and other phosphoproteins may be 
included, although such substances belong, strictly speaking perhaps, to the 
class of conjugated proteins. The investigations of Hardy on serum 
globulin,* and of Osborne on edestin,f have shown that the globulins have 
both acid and basic functions. If it be assumed that globulins contain both 
basic and acid groups in the molecule, and so situated stereochemically that 
internal neutralisation between these groups cannot take place, then it is 
possible that two molecules can enter into reaction with one another forming 
a complex according to the scheme— 
no precipitate whatever was produced, and no further precipitation occurred until the 
concentration of the zinc salt was twice normal. The precipitate formed at the lower 
limits differed from that formed at the upper limits in that the former was irreversible 
(z.e. did not redissolve on diluting or concentrating the solution), whereas the latter was 
reversible. The precipitate formed at the lower limits is that of the zinc salt of the 
protein, whereas that formed at the upper limits is the ordinary protein precipitation by 
salts. The following is suggested as a possible explanation of this action of zinc salts on 
proteins. If the carboxyl groups in the protein molecule are situated so far apart that 
the salt of the dyad metal cannot be formed by replacement of the hydrogen from two 
carboxyl groups of the same protein molecule, the zinc salt must be formed by the 
replacement from carboxyl groups from two molecules of protein, and be of the type 
Zn (Alb). This would be a larger aggregate than the original protein molecules. If the 
zinc salt could be adsorbed, as well as enter into chemical reaction in the way described, 
it is conceivable the adsorbed molecules would surround the protein molecules and 
inhibit the chemical reaction in which two molecules of protein and one of zinc salt take 
part. The phenomenon of the inhibition of the formation of zinc protein derivatives by 
excess of zinc sulphate is, if the explanation suggested above is correct, analogous to the 
inhibition of formation of complex methyleneimino-peptones, with the difference that the 
adsorbed salt, in addition to its inhibitory action, can also take part in the chemical 
reaction by means of which the formation of larger aggregates is brought about. Other 
similar irregular groups (“unregelmadssige Reichen”) of colloidal reactions have been 
described by Neisser and Friedmann (‘Miinchener Med. Wochenschr.,’ 1903, No. 11) and 
Bechhold (‘ Zeitsch. Physikal. Chem.,’ 1904, vol. 48, p. 355), and others. (For general 
discussion of these phenomena see ‘ Freundlich. Kapillarchemie,’ Leipzig, 1909, p. 462.) 
* ‘Journal of Physiology,’ 1905, vol. 33, p. 251. 
t ‘ Zeitsch. Physiol. Chem.,’ 1901, vol. 33, p. 240. 
