Full resolution (JPEG) - On this page / på denna sida - II. The Protein Substances - I. Simple Proteins - A. True Albuminous Bodies - Synopsis of the Most Important Properties of the Different Groups of Albuminous Bodies - B. Albuminoids or Albumoids
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112 THE PROTEIN SUBSTANCES.
to Kossel and Weiss l
depends at least in part, to a racemisation of the
hexone bases, especially arginine within the protamine molecule. They
give the biuret test beautifully, but with the exception of cyclopterine,
/3-cyprinine and crenilabrine do not give Millon’s reaction. The pro-
tamine salts are precipitated in neutral or even faintly alkaline solutions
by phosphotungstic acid, picric acid, chromic acid, and alkali ferrocy-
anides.
The protamines are prepared, according to Kossel, by extracting
the heads of the spermatozoa, which have previously been extracted
with alcohol and ether, with dilute sulphuric acid (1-2 per cent), filtering,
and precipitating with 4 vols, of alcohol. The sulphate may be purified
by repeated solution in water and precipitation with alcohol, and if
necessary, conversion into the picrate. For more details see the works
of Kossel and Malenuck. The double-platinum salt is best suited
for analysis and can be obtained, according to Goto, by precipitating
the methyl-alcohol solution of the protamine hydrochloride with plat-
inum chloride. Miescher also precipitates the base as a double-plat-
inum salt.
B. Albuminoids or Albumoids.
Under this name we collect into a special group all those protein
bodies which cannot be placed in either of the other groups. Most and
best studied of the bodies belonging to this group are important con-
stituents of the animal skeleton or the cutaneous structure. Some are
hardened secretions, and all occur as a rule in an insoluble state in the
organism, and they are distinguished in most cases by a pronounced
resistance to reagents which dissolve proteins, or to chemical reagents
in general, and it is due to these external properties that they are put
in a special group. From a purely chemical standpoint there is no
reason why they should be separated from the true proteids in a special
group. Most of the bodies belonging to the albuminoids have been
given on page 92.
The Keratins. Keratin is the chief constituent of the horny struc-
ture of the epidermis, of hair, wool, of the nails, hoofs, horns, feathers,
of tortoise shell, etc., etc. Keratin is also found as neurokeratin (Kuhne)
in the brain and nerves. The shell membrane of the hen’s egg seems
also to consist of keratin, and according to Neumeister 2
the organic
matrix of the eggshells of various vertebrate animals belongs in most
cases to the keratin group.
1
Zeitschr. f. physiol. Chem., 59, 60, and 78.
2
Kuhne and Ewald, Verh. d. naturhistor.-med. Vereins zu Heidelberg (N. F.) ;
1;
also Kuhne and Chittenden, Zeitschr. f. Biologie, 26; Neumeister, ibid., 31.
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