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GLOBULINS. 103
precipitated by the addition of large quantities of mineral acids or metallic
-alts. Their solution in water coagulates on boiling in the presence of
neutral salts, but a weak saline solution does not. If NaCl or MgS< ’4
is added to saturation to a neutral solution in water at the normal tem-
perature or at 30° C. no precipitate is formed; hut if acetic acid i> added
to this saturated solution the albumins readily separate. When ammonium
sulphate is added to one-half saturation the albumin solutions are not
precipitated at ordinary temperatures. Of all the native proteids the
albumins are the richest in sulphur, containing from 1.6 per cent to 2.2
per cent. So far as they have been investigated they do not yield any
glycocoll on acid hydrolysis.
Globulins. These substances are, as a rule, insoluble in water, but
dissolve in dilute neutral salt solutions. The globulins are precipitated
unchanged from these solutions by sufficient dilution with water, and
on heating they coagulate. The globulins dissolve in Avater on the addi-
tion of very little acid or alkali, and on neutralizing the solvent they
precipitate again. The solution in a minimum amount of alkali is pre-
cipitated by carbon dioxide, but the precipitate may in certain cases be
redissolved by an excess of the precipitant. The neutral solutions of the
globulins containing salts are partly or completely precipitated on satura-
tion with NaCl or MgSC>4 in substance at normal temperatures, depending
upon the kind of globulin. The globulins are completely precipitated
by half-saturating with ammonium sulphate. The globulins contain an
average amount of sulphur generally not below 1 per cent. As a differ-
ence between the albumins and globulins the latter yield glycocoll among
the hydrolytic cleavage products, and according to Obermayer and
"Willheim l
they contain fewer NH2 groups at the end of the chain, as
determined by formol titration, as compared to the total number of N-
atoms.
A sharp line cannot be drawn between the albumins and globulins
from their properties and this is shown from the researches of Moll,2
which showr
that by the action of dilute alkalies and warmth upon
seralbumin it attains the properties of serglobulin. It is evident that
we are here dealing with a change of the external properties of the
albumins to a greater similarity to those of the globulins, and not with
a true transformation of the albumin, which is free from glycocoll, into
globulin which contains glycocoll. The same follows from the observa-
tions of others.3
This is an instructive example of the subordinate impor-
tance the solubility and precipitation properties have in the differentia-
tion of various groups of proteids.
1
Bioch. Zeitschr., 38.
2 Moll, Hofmeister’s Beitrage, 4 and 7; also Breinl, Arch. f. exp. Path. u. Pharm., 65.
•Obermayer and Willheim, 1. c; R. Gibson, Journ. of biol. Chem., 12.
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