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K Ibel

Publications and source records attributed to K Ibel.

30 records · Page 2Linked to original sources
PubMed1976

New low resolution model for 50S subunit of Escherichia coli ribosomes.

Neutron low angle scattering studies of the 50S subunit of E. coli ribosomes with the contrast variation method reveals large fluctuations in the scattering density. A region of relatively low scattering density, rich in proteins, surrounds an RNA-rich core of higher scattering density. The centers of mass of the RNA and protein parts of the 50S subunit are separated by a distance (20 A) that is considerably smaller than that reported in previous studies.

Escherichia coli↗
PubMed1976

Organisation of subunits in chromatin.

There is considerable current interest in the organisation of nucleosomes in chromatin. A strong X-ray and neutron semi-meridional diffraction peak at approximately 10 nm had previously been attributed to the interparticle specing of a linear array of nucleosomes. This diffraction peak could also result from a close packed helical array of nucleosomes. A direct test of these proposals is whether the 10 nm peak is truly meridional as would be expected for a linear array of nucleosomes or is slightly off the meridian as expected for a helical array. Neutron diffraction studies of H1-depleted chromatin support the latter alternative. The 10 nm peak has maxima which form a cross-pattern with semi-meridional angle of 8 to 9 degrees. This is consistent with a coil of nucleosomes of pitch 10 nm and outer diameter of approximately 30 nm. These dimensions correspond to about six nucleosomes per turn of the coli.

Animals↗
PubMed1975

The subunit structure of the eukaryotic chromosome.

New strucutral data have been obtained from neutron scattering studies of chromatin. The concentration-dependent meridional peak at 10-11 nm comes from the interparticle spacing of a subunit structure. Peaks at 5.5 and 3.7 nm have a different contrast behaviour to those at 11.0 and 3.7 nm showing that histones and DNA have a different spatial arrangement in the subunit. A globular model in which apolar segments of histones from the core surrounded by DNA complexed with the basic segments of histones agrees with the data.

Animals↗
PubMed1975

Quaternary structure of chromatin.

Neutron scattering experiments on chromatin solutions have been carried out at Bragg spacings several times larger than in any previous x-ray work. A new series of very low angle reflections at about 400, 200, and 140 A were observed. These reflections demonstrate the existence of a higher order structure of the 100 A unit fibril. A coiled-coil model with a major pitch of 500 A and a radius of center to fibril center of 130 A is proposed to explain the results.

Animals↗