Nucleoproteins

NUCLEOPROTEINS (nucleoproteids), complex proteins in which nucleic acids are included as the non-protein part (prosthetic group), in the form of which all the phosphorus of the nucleoproteins is found. Nucleoproteins are contained primarily in cell nuclei, constituting the main mass of them. Nucleoproteins are compounds built on the salt type and can consist of various relative amounts of nucleic acid and one or another protein. Under the influence of various effects (boiling, digestion by enzymes, change in reaction), part of the protein originally bound by nucleic acid can be split off, and then compounds are obtained that contain relatively less protein and more phosphorus, so-called nucleins. Further splitting off of the remaining part of the protein leads to the production of free nucleic acid.

Nuclein protein.

Nucleic acid. As the protein component, nucleoproteins can contain either ordinary proteins or, for the most part, proteins of a basic character, protamines and histones. Nucleoproteins can be isolated from various tissues, especially from those rich in cell nuclei, for example, from the thymus gland, pancreas, nucleated erythrocytes of birds, spermatozoa of fish, and from leukocytes of pus (from which they were first obtained by Miescher in 1871). Nucleoproteins are usually soluble in water and in weak solutions of neutral salts and precipitate upon acidification of their solutions with acetic acid; methods for their preparation and isolation are based on this. If the tissue is subjected to heating to 100° before extraction, part of the proteins coagulates and a product containing less protein is obtained, the so-called β-nucleoprotein. The non-protein component of nucleoproteins, nucleic acids, gives insoluble precipitates with proteins, especially in an acidic solution. Therefore, the opinion has been expressed that the nucleoproteins usually obtained do not pre-exist in tissues but are artifacts and are formed during the very process of extraction from the nucleic acids and proteins extracted from the cell. Nucleoproteins obtained by ordinary methods are white, amorphous substances of an acidic character that give ordinary protein reactions. Upon heating, they denature.

Almost all rotate the plane of polarization to the right. The phosphorus content in nucleoproteins is 0.5–6.1%, and in nucleins, up to 5% and more.

V. Engelhardt. NUCLEOPHAGA, minute parasitic organisms belonging to the chytrid fungi (Chytridiaceae); they infect the nuclei of various free-living and parasitic amoebae (Figure 1). Among the latter, these nuclear parasites have been found in Endolimax nana, Iodamoeba bütschlii (= Nucleophaga williamsi), Entamoeba blattae, in amoebae of the Entamoeba coli type, Naegleria, and others. In the initial stage of infection, in the light (peripheral) zone of the nucleus, there are 1–2 spherical bodies 1–1.5 µm in diameter. They stain well with various nuclear stains. The number of bodies increases, and they push the karyosome to the periphery, where it flattens and atrophies. The nucleus, filled with coccoid bodies, enlarges, and simultaneously the protoplasm hypertrophies. In the nucleus, the membrane is preserved the longest; it can rupture, and the parasites enter the

protoplasm of the amoeba. The destruction of the nucleus does not immediately affect the vital activity of the infected amoeba. Doflein observed the amoeboid movement of Amoeba vespertilio, in which the entire nucleus was destroyed by Nucleophaga (Fig. 2). Cases of the karyosome being affected by the parasite have been observed. Several forms of Nucleophaga have been described, but their species independence is not clear. Examples: Nucleophaga amoebae, Nucleophaga intestinalis, etc. In cases where Nucleophaga is found in parasitic amoebae, one can speak of the phenomenon of hyperparasitism.