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K Karawajew

Publications and source records attributed to K Karawajew.

4 recordsLinked to original sources
PubMed1982

Physicochemical properties of salt-soluble, unsheared chromatin. Molecular weight studies.

A chromatin fraction, which can reproducibly be extracted from rat liver nuclei at moderate salt concentration (0.1 M (NH4)2SO4, 0.1 M Tris-HCl, 2 mM MnCl2, pH 7.9), was analyzed with regard to changes of its molecular weight in the range of (NH4)2SO4 concentrations between 0.1 M and 0.4 M. With the transition from 0.1 M to 0.2 M (NH4)2SO4 histone H1 is released and the molecular weight obtained from both sedimentation-viscosity and light scattering is reduced by approximately one-half. A spatial expansion of the resulting half-molecules is observed with further increasing salt concentration. On the basis of these results a double-fibrillar structure of this chromatin fraction is proposed.

Animals↗
PubMed1981

Ionic strength dependent structural changes of nucleosomes.

Rat thymus nucleosomes were studied as to their sedimentation behaviour and molecular weight Mr in NaCl and (NH)2SO4 solutions of different ionic strengths. The sedimentation coefficient s20,w decreases in two steps at ionic strengths of about 0.45-0.6 and of 1-1.2 and amounts to 11.0 S in salt-free buffer and to 5.5 S in 2 M NaCl-solution. This decrease in s20,w is paralleled by an analogous decrease in Mr. There is, however, an additional decline in Mr from 233 000 to 200 000 between the ionic strengths of 0.005 and 0.4. These changes are accompanied by conformational changes of nucleosomes as shown by varying molar frictional ratios f/f0. The decrease in Mr could be attributed to the successive release of histones as checked by electrophoretic analysis. Furthermore, nucleosomes in (NH4)SO4-solution proved to be more stable against increasing salt concentration than nucleosomes in NaCl-solution.

Ammonium Sulfate↗