Nucleoproteins VOLUME

An active bending of the DNA induced by regulatory proteins is of particular importance when a defined arrangement of the DNA in a small volume within a larger nucleoprotein complex is required. 

There has been a steady accumulation of evidence to support the Idea that the most Important damage to a cell that leads to mitotic failure Is a macromolecular lesion of DMA in the nucleoprotein system.Cellular radlosensltlvlty In 120 diverse organisms ranging from viruses to higher plants and animals was a direct function of the chromosome volume and nucleic acid content. In the Intact cell of bacteria, protection by thiols appears to be protection of a functional repair mechanism rather than prevention of DNA degradation, but the need for more information about damage to DMA remains moot. 

Table 13. Further experimental specific volumes of some selected typical conjugated proteins (hemo-, metaUo-, phospho-, glyco-, lipo-, and nucleoproteins proteoglycans) from different sources and under varying environmental conditions. In a few cases, calculated volumes (, 0(. ) were added. Some values presented in this table were taken from [86D1]. Note that a great number of volumes for conjugated proteins are given in Table 12.

Fig. 1. Schematic representation of isopotential specific volumes, Vj, and partial specific volumes,, of non-conjugated proteins and nucleic acids in an aqueous solution containing inorganic salt (from [89D1]). The difference between isopotential and isomolal specific volumes (Vj > V2 ) i more pronounced with nucleic acids than with proteins. Open circles show V2 C3 = 0, and filled circles indicate Vj at C3 = 0.2 M salt (e.g., NaCl). Since a solvent component concentration of C3 = 0.05 - 0.2 M is usually applied in biochemical experiments, and Vj is the proper volume quantity usually needed in experimental work, v should be used preferably. Because of the slight difference between Vj and V2, in the case of nonconjugated proteins Vj may be used instead of Vj. For nucleic acid studies, however, only use of Vj makes sense. It is obvious that conjugated proteins with pronounced electrolyte character (e.g., nucleoproteins) will show an intermediate behavior, though sufficient data are not available at present. Reprinted from Colloid Polymer Science, Vol. 267, H. Durchschlag, Determination of the partial specific volume of conjugated proteins, pp. 1139-1150, 1989, with permission finm Steinkopff, Darmstadt.

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