Low angle X-ray scattering studies of chromatin in different solvents; analysis by comparison with computer-simulated scattering curves

Notbohm, Holger; Hollandt, H.; Meissner, Joseph; Harbers, Eberhard

doi:10.1016/0141-8130(79)90046-1

Cited by 12 publications

(9 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6 R t (the square of the radius of gyration of the cross-section of the sum of quaternary and tertiary structure) is plotted against k (the ratio of the extrapolated scattering intensities, both from Guinier plots as shown in Fig.3 for chromatin solutions with a high content of quaternary structure). From the measured points a straight line can be approximated [56]. Extrapolation of the line to k = x and assuming x = 0.02 results in RQ = 11.7 nm corresponding to 33 nm for the outer diameter of the quaternary structure, a value in good accordance with the 32nm deduced from the shoulder in the scattering curve in Fig.…”

Section: For Chromatin From F K T I O T Zsupporting

confidence: 60%

“…2 shows the desmeared scattering curve of chromatin from fraction pool I in comparison to a calculated curve obtained by computer simulation. The idealized model corresponds to a nucleosome solenoid [56] with an outer diameter of about 33 nm. Although the curves are not really congruent, there are obviously strong similarities.…”

Section: Resultsmentioning

confidence: 99%

“…For the quaternary structure a cylinder without an inner hole seems to be a better approximation; the reasons in support of the assumption are discussed later. Defining k as the ratio of the above two values derived directly from the Guinier plot [56] :…”

Section: For Chromatin From F K T I O T Zmentioning

confidence: 99%

See 2 more Smart Citations

Structural Investigations on Isolated Chromatin of Higher‐Order Organisation

Brust

Harbers

1981

European Journal of Biochemistry

View full text Add to dashboard Cite

Chromatin of a high structural order was prepared by a method avoiding drastic mechanical stress, as well as strong changes of the ionic strength, and was investigated by small-angle X-ray scattering. The results obtained support the idea that the quaternary structure of completely hydrated chromatin in solution is a solenoid with a diameter of about 32-34 nm. Gel chromatography of this chromatin yields solutions containing mainly quaternary structures with differing portions of tertiary structure. Decrease of the ionic strength results in an increase of loosening and unfolding of quaternary structures. Reconstitution by readjustment of the physiological ionic strength indicates slight differences between reconstituted and original higher-order structures.Chromatin structure appears to be a hierarchical one. The elementary subunit is the nucleosome [I -61 of which the over all shape is well known now. Some details about the arrangement of D N A and histones within the nucleosome are established [7-111 and several models of primary organization of nucleosomes are discussed [8,12 -The next level of organization is the tertiary structure of chromatin which appears to be an arrangement of nucleosomes like 'beads on a string' or tightly packed like a rod with a diameter of about 10-11 nm in solvents of low ionic strength [1,16]. In solvents of higher ionic strength part of the chromatin is organized in a higher-order conformation [ 16 -321 forming a quaternary structure. In electron micrographs this sometimes appears as a 'knobby' fiber of about 25 -30 nm in diameter. However, whether the quaternary structure is organized in the form of 'superbeads' [26,27, 32-34] containing 6-12 nucleosomes or as a solenoid [17,[29][30][31] is still an open question [16].In order to investigate chromatin in solution it has first to be isolated. Even with mild methods avoiding shear and mechanical stress, one can obtain isolated chromatin only as a fragmentary material. A procedure often applied is the lysis of the cell nuclei in 0.2 mM EDTA [38]. In this solvent chromatin appears as a string of nucleosomes, i.e. the tertiary structure. Increasing the ionic strength of the solvent leads to reconstitution of higher-order structures. These quaternary structures appear to be very similar to the original ones in intact cell nuclei; however, it is not known how far they are really identical. By avoiding drastic changes of ionic strength during lysis of the nuclei it is possible to obtain solutions of chromatin having a highly preserved structural order [39,40]. For our structural studies applying small-angle X-ray scattering higher-order chromatin was obtained by a modification of the method of Rees et al. [39,41]. By enzymatic autolysing of the cell nuclei chromatin with a very high sedimentation coefficient can be isolated. Purification of this chromatin by gel chromatography results in solutions containing native quaternary structure and still a certain amount of tertiary structure. This accumulation of quaternary structure material ...

show abstract

Section: For Chromatin From F K T I O T Zsupporting

confidence: 60%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Structural Investigations on Isolated Chromatin of Higher‐Order Organisation

Brust

Harbers

1981

European Journal of Biochemistry

View full text Add to dashboard Cite

show abstract

“…The solenoid was proposed to be 25-30 nm in diameter with 5-7 nucleosomes per turn. The linker DNA is wrapped in a helical path between the nucleosome cores, leaving a central hole (e.g., Notbohm et al, 1979;McGhee et al, 1983). Although the helical pitch is constrained by the width of the nucleosome, there are no inherent constraints upon fiber diameter, mass per unit length, or handedness of the helix.…”

Section: Models For the Structure Of Chromatin Fibersmentioning

confidence: 99%

“…These data dictate tight packing of nucleosomes (-7.4 nm between the centers of adjacent subunits), Left-Handed Double Helical Chromatin Fibers consistent with nucleosome dimensions of 11 nm diameter and 5.7 nm width (Richmond et al, 1984), but inconsistent with the 11 nm width given by Burlingame et al (1985). The original solenoid model, as detailed by Notbohm et al (1979) and McGhee et al (1983) could not be built using the experimental data because the helically-coiled linker DNA prevented close association of adjacent nucleosomes. By displacing the linker into the center of the fiber, as proposed by Butler (1984), a modified solenoid model could be built.…”

Section: Mass Per Unit Length Of Chromatin Fibersmentioning

confidence: 99%

Chromatin fibers are left-handed double helices with diameter and mass per unit length that depend on linker length

Williams¹,

Athey²,

Muglia³

et al. 1986

Biophysical Journal

232

174

View full text Add to dashboard Cite

Four classes of models have been proposed for the internal structure of eukaryotic chromosome fibers--the solenoid, twisted-ribbon, crossed-linker, and superbead models. We have collected electron image and x-ray scattering data from nuclei, and isolated chromatin fibers of seven different tissues to distinguish between these models. The fiber diameters are related to the linker lengths by the equation: D(N) = 19.3 + 0.23 N, where D(N) is the external diameter (nm) and N is the linker length (base pairs). The number of nucleosomes per unit length of the fibers is also related to linker length. Detailed studies were done on the highly regular chromatin from erythrocytes of Necturus (mud puppy) and sperm of Thyone (sea cucumber). Necturus chromatin fibers (N = 48 bp) have diameters of 31 nm and have 7.5 +/- 1 nucleosomes per 10 nm along the axis. Thyone chromatin fibers (N = 87 bp) have diameters of 39 nm and have 12 +/- 2 nucleosomes per 10 nm along the axis. Fourier transforms of electron micrographs of Necturus fibers showed left-handed helical symmetry with a pitch of 25.8 +/- 0.8 nm and pitch angle of 32 +/- 3 degrees, consistent with a double helix. Comparable conclusions were drawn from the Thyone data. The data do not support the solenoid, twisted-ribbon, or supranucleosomal particle models. The data do support two crossed-linker models having left-handed double-helical symmetry and conserved nucleosome interactions.

show abstract

Neutron‐scattering studies of the structure of chromatin core particles in solution

1981

View full text Add to dashboard Cite

SynopsisThe structure of the nucleosome core particle in solution has been studied by neutron scattering using the full-contrast variation technique, which reduces the experimental spectra to three fundamental scatter functions holding information on shape and structure. Systematic calculations of the fundamental scatter functions expected from proposed core-particle models have been compared with the observed functions and show that the neutron-scattering criteria severely restrict the number of models which can be valid for the structure in solution. The best model for the core particle in solution has a hydrophobic histone core about which 1.7 f 0.1 turns of DNA are wrapped a t a pitch between 3.0 and 3.5 nm. This core contains most of the histone and has an average thickness of 4 nm and diameter 6.4-7.5 nm. While solution scattering is not able to specify uniquely the actual shape of the core to high resolution, all models which are possible for the shape of the core to a resolution justified by the data have been considered. It is clear that cylindrical or wedge shapes compatible with the above dimensions are valid structures. A hole probably penetrates the histone core, but the data do not allow a diameter greater than 1 nm. Available evidence suggests that about a quarter of the total histone is outside the core.

show abstract

Low angle X-ray scattering studies of chromatin in different solvents; analysis by comparison with computer-simulated scattering curves

Cited by 12 publications

References 18 publications

Structural Investigations on Isolated Chromatin of Higher‐Order Organisation

Structural Investigations on Isolated Chromatin of Higher‐Order Organisation

Chromatin fibers are left-handed double helices with diameter and mass per unit length that depend on linker length

Neutron‐scattering studies of the structure of chromatin core particles in solution

Contact Info

Product

Resources

About