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FSEUDONUCLEINS. 177
washed and purified by alternately dissolving in very faintly alkaline
water and reprecipitating with an acid, washing with water, and treating
with alcohol and ether. A nuclein may be prepared more simply by the
digestion of a nucleoprotein. In the detection of nucleins we make use
of the above-described method, testing for phosphorus in the product
after fusing with saltpeter and soda. Naturally the phosphates and
phosphatides must first be removed by treatment with acid, alcohol,
and ether, respectively. No exact methods are known for the quanti-
tative estimation of nucleins in organs or tissues.
Pseudonucleins or Paranucleins. These bodies are obtained as
an insoluble residue on the digestion of certain nucleoalbumins or phospho-
glycoproteins with pepsin-hydrochloric acid. Attention is called to
the fact that the pseudonuclein may be dissolved by the presence of too
much acid or by a too energetic peptic digestion. If the relation between
the degree of acidity and the quantity of substance is not properly selected,
the formation of pseudonucleins may be entirely overlooked in the
digestion of certain nucleoalbumins. Pseudonucleins contain phosphorus,
which, as shown by Liebermann,1
is split off as metaphosphoric acid
by mineral acids.
The pseudonucleins are amorphous bodies insoluble in water, alcohol,
and ether, but readily soluble in dilute alkalies and barium hydroxide
solution. They are readily split by barium hydroxide solution with the
splitting off of phosphoric acid, and according to Giertz 2
they differ
in this regard from the true nucleins, which are neither dissolved nor
decomposed by baryta. They are not soluble in very dilute acids, and
may be precipitated from their solution in dilute alkalies by adding
acid. They give the protein reactions very strongly, but do not yield
purine bases.
In preparing a pseudonuclein, dissolve the mother-substance in hydro-
chloric acid of 1-2 p. m., filter if necessary, add pepsin solution, and
allow the mixture to stand at the temperature of the body for about
twenty-four hours. The precipitate is filtered off, washed with water,
and purified by alternately dissolving in very faintly alkaline water and
reprecipitating with acid.
Cleavage Products of the Xucleoproteins.
1. The Nucleic Acids.
All nucleic acids are rich in phosphorus and yield phosphoric acid,
purine bases and a carbohydrate or carbohydrate derivative as cleavage
products; most of them also contain pyrimidine bases. The older
1
Ber. d. d. chem. Gesellsch., 21, and Centralbl. f. d. med. Wissensch., 1889.
2
Zeitschr. f. physiol. Chem., 28.
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