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NUCLE0PE0TEIN8. 175
In certain cases this is histone, and the combinations between nucleic
acid and protamines are also sometimes classified as nucleoproteins.
The combination between protamine and nucleic acid is, it seems, a
salt-like combination, and entirely different from the combination of the
proteins with nucleic acid in the nucleoproteins. The following facts,
given in connection with the nucleoproteins, do not apply to the nucleo-
protamines. The nucleoproteins differ not only according to the protein
component they contain, but also as to the nucleic acids, which vary
among themselves. There are essentially different nucleic acids, some
among which contain a pentose carbohydrate while others contain a
hexose carbohydrate. The nucleic acids also differ in regard to the
amount of purine and pyrimidine bases they contain (sec below).
The native nucleoproteins contain a variable, but not a high percentage
of phosphorus, which in most of the nucleoproteins investigated, ranges
between 0.5 and 1.6 per cent. They also regularly contain iron, and in
Octopodes, Henze i
has observed an iron-free nucleoprotein with 0.96
per cent copper. The nucleoproteins behave like weak acids, especially
those having considerable protein in the molecule. They therefore
give the ordinary protein reactions and behave in this regard like the
proteins. The nucleoproteins prepared from organs rich in cell nuclei
seem to be characterized by containing more phosphorus and having a
stronger acid character. All nucleoproteins are bodies that are insoluble
in water, but whose alkali combination is soluble in water. From
such a solution the nucleoprotein can be precipitated by acetic acid, and
in an excess of the acid, the precipitate dissolves with more or less
difficulty and in some cases not at all. It dissolves, on the contrary, in
very dilute hydrochloric acid. In this respect nucleoproteins are similar
to the nucleoalbumins and the mucin substances, but differ from these
two groups in that they yield purine bases on hydrolysis. According
to Plimmer and Scott 2
the nucleoproteins differ from the nucleo-albu-
mins by the fact that with sodium hydroxide in 1 per cent solution the
nucleoalbumins split off phosphoric acid while the nucleoproteins do not.
The nucleoproteins give the color reactions of the proteins, but those
which have been investigated are dextrorotatory and not laevorotatory
(Gamgee and Jones 3
).
The nucleoproteins are readily modified. The alkali combination
scluble in water suffers a decomposition on heating its solution, when
as neutral as possible, and coagulated protein separates while a protein
rich in phosphorus and poor in protein with strong acid character remains
1
Zeitschr. f. physiol. Chem., 55.
2
Plimmer and Scott, cited in Biochem. Centralbl., 8, p. 109.
3
Hofmeister’s Beitrage, 4.
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