PubMed Health⌕ Search

Biomedical subjects

M Böttger

Publications and source records attributed to M Böttger.

At least 55 records · Page 3Linked to original sources
PubMed1981

Physicochemical properties of salt-soluble, unsheared chromatin. The mass per unit length by light scattering.

The mass per unit length of 7 X 10(3) (formula: see text) and the corresponding DNA packing ratio of about 14 for the chromatin soluble at moderate ionic strengths has been determined by light scattering. With the increase in ionic strength and corresponding release of histone H1 the DNA packing ratio has been found to decrease down to 4.4. The data obtained are consistent with the idea suggested previously that the salt-soluble chromatin is organized in double nucleosome chains arranged side-by-side and stabilized by H1. With salt-induced H1 release the double chain dissociates and the nucleosomal DNA partially unravels.

Animals↗
PubMed1981

Interaction of histone H1 with superhelical DNA. Sedimentation and electron microscopical studies at low salt concentration.

Complexes of histones H1 with superhelical SV40 DNA obtained by direct mixing were studied in 0.1 SSC buffer corresponding to 0.02 M Na+. Depending on the molar input ratio H1/DNA three classes of sedimenting species were observed: (1) a component sedimenting similar to superhelical DNA with a sedimentation coefficient s2o,w of 25 S observable up to 335 Mol H1/Mol DNA (w/w = 2); (2) a component with s2o,w = 120 S appearing at 135 Mol H1/Mol DNA and (3) growing amounts of heterogeneous aggregates greater than 1000 S. Electron micrographs revealed the 25 S component to consist of double-fibers formed from one DNA molecule and the 120 S component to consist of bundles of several such double-fibers. The aggregates represent cable-like structures. The addition of ethidium bromide to 25 S complexes induces the formation of bundles, if H1 is present in a quantity which alone is not sufficient to bring about this effect. This result indicates that ethidium bromide effects a redistribution of H1 molecules and that H1 is responsible for the bundle formation.

DNA, Superhelical↗
PubMed1981

Physicochemical properties of salt-soluble, unsheared chromatin. Salt-dependent structural changes.

Salt-dependent structural changes of rat liver chromatin isolated by an extraction procedure not involving shear and exogenous nucleases were investigated by sedimentation and light scattering methods. The effects observed are complex involving changes in the molecular weight and expansion. Between 0.1 M and 0.2 M (NH4)2SO4 where histone H1 is released, a fragmentation into molecules of half molecular weight is found which is accompanied by an expansion into a more extended conformation gradually increasing to 0.4 M (NH4)2SO2. The H1-free chromatin does not exhibit the reduction in molecular weight but undergoes this expansion. The original conformation is not reversible on re-decreasing the salt concentration to 0.1 M (NH4)2SO4.

Ammonium Sulfate↗
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↗
PubMed1980

Isolation and characterization of salt-soluble, unsheared chromatin.

From rat liver nuclei depending on the extraction time, 10 to 20% of total chromatin has been extracted with a solution containing 0.1 M ammonium sulfate, 2 mM MnCl2, 0.1 M Tris-HCl, pH 7.9. We term this chromatin chromatin S. It has a protein: DNA ratio of 1.3, the full amount of the 5 histones in an undegraded state, and a RNA: DNA ratio of approximately 0.2. Its nonhistone protein pattern, obtained by gel electrophoresis exhibits a rich spectrum of proteins in a broad range of molecular weights. Electrophoretic analysis of the DNA fragments obtained by micrococcus nuclease digestion of chromatin S yields the same digestion pattern as that of nuclei. Thus, chromatin S fulfils an essential criterion of unsheared chromatin. In contrast to other chromatin preparations described so far, this chromatin is soluble at a salt concentration of 0.1 M ammonium sulfate. We have shown previously that it exhibits a compact conformation, low intrinsic viscosity and low radius of gyration obtained by light scattering measurements. Its mean molecular weight was determined to be nearly 10(8).

Animals↗
PubMed1979

Salt-and histone H1-induced structural changes of reconstituted minichromosomes.

Structural changes of reconstituted SV 40 minichromosomes have been studied in relation to the salt concentration and addition of histone H1 by sedimentation and electron microscopy. Sedimentation data are represented as functions of the NaCl concentration and the Debye-Hückel electrostatic screening radius 1/alpha. The latter representation which proved to provide more information revealed three structural states of the SV 40 reconstitutes which can be additionally characterized by electron microscopy as follows: Expanded or relaxed conformation including free DNA spacers between the nucleosomes at low salt concentration (approx. 0.001 M-0.05 M NaCl), increasing condensation at moderate salt concentration (approx. 0.05 M-0.3 M NaCl) and expansion of this condensed state above approx. 0.3 M NaCl. The condensation of the reconstitutes at moderate salt concentration does not require the presence of histone H1. H1 seems to stabilize the condensed state against electrostatic expansion. The condensation might be promoted by salt-dependent conformational changes of naked superhelical DNA as revealed by sedimentation measurements.

Chromosomes↗
PubMed1976

A sedimentation study of the interaction of superhelical SV40 DNA with H1 histone.

By moving boundary sedimentation it is shown that the interaction of H1 histone with superhelical circular SV40 DNA results in the formation of giant heterogeneous aggregates. The size of these aggregates grows with increasing H1 concentration. s20,w values of some 10 000 S were measured. As compared with open relaxed circular DNA a preferential interaction of superhelical DNA with H1 histone is observed, irrespective of the sign of the superhelical turns which was reversed by the addition to DNA of ethidium bromide. The addition to the H1 complexed aggregates of ethidium bromide effects a progressive breakdown of the aggregates. Furthermore, the superhelicity of DNA is not changed by the addition of small amounts of H1 histone.

Binding Sites↗
PubMed1975

Evidence of altered histone interactions, as investigated by removal of histones, in chromatin isolated from rat liver nuclei by a conventional method.

It is shown that the release of the slightly lysine-rich histones f2a2 and f2b by 0.4 M ammonium sulfate from conventionally isolated chromatin is diminished in comparison to the lysed nuclei. The change in extractability is further demonstrated by the application of ethidium bromide. At a molar input ratio of 0.09 (moles ethidium bromide/moles nucleotide) and 0.4 M ammonium sulfate the slightly lysine-rich histones are released from the chromatin to 70 - 80% if the lysed nuclei are used. At 0.1 M ammonium sulfate ethidium bromide effected also a release of 50 % of histone f1. Comparable effects could not be observed with chromatin prepared in a conventional way but instead a tendency towards loss of histone f3 in the presence of ethidium bromide was observed.

Ammonium Sulfate↗
PubMed1975

Excretion of 2-hydroxyestrone in urine throughout human pregnancies.

Urinary 2-hydroxyesterone was quantitatively determined in the course of several normal human pregnancies. The urine was subjected to hot acid hydrolysis and after chromatographic purification, 2-hydroxyesterone was converted into the corresponding phenazine derivative, which was submitted to a final column chromatogrphy and then quantitated by UV-spectrometry. For correction of procedural losses 2-hydroxyestrone-4-14C was used as internal standard. The urinary 2-hydroxyestrone of different subjects varied within a wide range especially at mid-pregnancy between 100 and 2500 mug/24 h. The day-to-day variation of the excretion of 2-hydroxyestrone was mostly less than 30% of the total value of that day, but sometimes could even reach 60%. The investigation of 2-hydroxyestrone and total estrogens at regular intervals throughout several pregnancies, showed that the excretion of 2-hydroxyesterone generally reached a maximum during the second trimester, while the excretion of the total estrogens steadily increased up to parturition. When analyzing the urines of different subjects during the last 4 months of pregnancy, no correlation appeared to exist for the excretions of the total estrogens and of 2-hydroxyestrone.

Adult↗