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LECITHALBUMINS. 105
The nucleoallmmins arc often confounded with nucleoproteina and
also with phosphorized glucoproteins. From the first class, they differ
by not yielding any purine bases when boiled with acids, and from the
second group by not yielding any reducing substance on the same treat-
ment. The best studied member of this group is the casein of milk,
which will be discussed, in detail in chapter XIII.
Neuberg and Pollak ’ have artificially prepared phosphoproteins by the
action of phosphorus oxychloride upon an alkaline solution of lactalbumin or blood
globulin. The product obtained from lactalbumin was rather close to casein
in regard to composition and other properties.
Lecithalbumins. In the preparation of certain protein substances,
products are often obtained containing lecithin, and this lecithin (see
the phosphatides, Chapter IV) can be removed only with difficulty or in-
completely by a mixture of alcohol and ether. Ovovitellin (Chapter XII)
is such a protein body containing considerable lecithin, and Hoppe-Seyler
considers it a combination of proteid and lecithin. Similar substances
occur in fish-eggs. These last lecithalbumins often have the solubilities
of the globulins and are readily soluble in dilute salt solutions. The
behavior of the nucleoalbumin of the eggs of the perch shows how easily
this solubility may be changed. This nucleoalbumin, which contains con-
siderable amounts of lecithin, is readily soluble in dilute NaCl solution,
but at ordinary temperatures it is changed by 0.1 per cent HC1 almost
instantaneously and without splitting off lecithin, so that it becomes in-
soluble in dilute salt solutions (Hammarsten) . Liebermann 2
has obtained
];roteids containing lecithin as an insoluble residue on the peptic digestion
of the mucous membrane of the stomach, liver, kidneys, lungs, and spleen.
He considers them as combinations of proteid and lecithin and calls them
lecithalbumins. Further investigation of these bodies is desirable.
Mayer and Terroine ’ have shown that from lecithin emulsified in water and
a dialyzed solution of ovalbumin or dialyzed blood serum a precipitate can be
obtained which has some similarity to the lecithalbumins, but which in other
respects is so strikingly different that we are not justified in calling this pre-
cipitate lecithalbumin.
Nothing characteristic has thus far been found which differentiates
this group from others in the quantity of amino-acids split off on hydrol-
ysis. The members of this group differ essentially among themselves,
e.g., vitellin yields glycocoll while casein does not.
In order to give a review of the three above-mentioned groups of pro-
teids we give (page 106) a tabulation of the amounts of the amino-acids
1
Ber. d. d. chem. Gesellsch., 43 and Bioch. Zeitschr., 26.
2
Hoppe-Seyler, Med. chem. Untersuch., 1868; also Zeitschr. f. physiol. Chem., 13,
479; Hammarsten, Skand. Arch. f. Physiol., 17; Liebermann, Pfluger’s Archiv, 50
and 54.
3
Compt. rend. soc. biol., 62.
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