Transition of Chromatin from the “10 nm” Lower Order Structure, to the “30 nm” Higher Order Structure, as Followed by Small Angle X-Ray Scattering

Greulich, Karl Otto; Wachtel, Ellen; Ausió, Juan; Seger, Dalia; Eisenberg, Henryk

doi:10.1007/978-1-4612-4600-8_13

Cited by 7 publications

(6 citation statements)

References 33 publications

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“…Thus there was little evidence for aggregation. This result has been found for other types of chromatin at much higher concentrations (e.g., Suau et al, 1979;Gerchman and Ramakrishnan, 1987;Greulich et al, 1987;Koch et al, 1988).…”

Section: Radii Of Gyrationsupporting

confidence: 70%

Small angle x-ray scattering of chromatin. Radius and mass per unit length depend on linker length

Williams

Langmore

1991

Biophysical Journal

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Analyses of low angle x-ray scattering from chromatin, isolated by identical procedures but from different species, indicate that fiber diameter and number of nucleosomes per unit length increase with the amount of nucleosome linker DNA. Experiments were conducted at physiological ionic strength to obtain parameters reflecting the structure most likely present in living cells. Guinier analyses were performed on scattering from solutions of soluble chromatin from Necturus maculosus erythrocytes (linker length 48 bp), chicken erythrocytes (linker length 64 bp), and Thyone briareus sperm (linker length 87 bp). The results were extrapolated to infinite dilution to eliminate interparticle contributions to the scattering. Cross-sectional radii of gyration were found to be 10.9 +/- 0.5, 12.1 +/- 0.4, and 15.9 +/- 0.5 nm for Necturus, chicken, and Thyone chromatin, respectively, which are consistent with fiber diameters of 30.8, 34.2, and 45.0 nm. Mass per unit lengths were found to be 6.9 +/- 0.5, 8.3 +/- 0.6, and 11.8 +/- 1.4 nucleosomes per 10 nm for Necturus, chicken, and Thyone chromatin, respectively. The geometrical consequences of the experimental mass per unit lengths and radii of gyration are consistent with a conserved interaction among nucleosomes. Cross-linking agents were found to have little effect on fiber external geometry, but significant effect on internal structure. The absolute values of fiber diameter and mass per unit length, and their dependencies upon linker length agree with the predictions of the double-helical crossed-linker model. A compilation of all published x-ray scattering data from the last decade indicates that the relationship between chromatin structure and linker length is consistent with data obtained by other investigators.

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Section: Radii Of Gyrationsupporting

confidence: 70%

Small angle x-ray scattering of chromatin. Radius and mass per unit length depend on linker length

Williams

Langmore

1991

Biophysical Journal

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“…The absolute mass per unit lengths of the fully compacted Thyone and Necturus models are in excellent agreement with STEM (Williams et al, 1986) and solution scattering results (Williams and Langmore, manuscript submitted for publication) obtained from isolated fibers prepared under conditions identical to those used for this diameter study. Other studies indicate consistently lower values for the mass per unit length (e.g., Suau et al, 1979;Greulich et al, 1987). However, as shown in Fig.…”

Section: The Crossed-linker Models Predict Fiber Diameters That Incresupporting

confidence: 56%

The diameters of frozen-hydrated chromatin fibers increase with DNA linker length: evidence in support of variable diameter models for chromatin.

Athey

Smith

Rankert

et al. 1990

The Journal of Cell Biology

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Abstract. The diameters of chromatin fibers from Thyone briareus (sea cucumber) sperm (DNA linker length, n = 87 bp) and Necturus maculosus (mudpuppy) erythrocytes (n = 48 bp) were investigated. Soluble fibers were frozen into vitrified aqueous solutions of physiological ionic strength (124 mM), imaged by cryo-EM, and measured interactively using quantitative computer image-processing techniques. Frozenhydrated Thyone and Necturus fibers had significantly different mean diameters of 43.5 nm (SD = 4.2 nm; SEM = 0.61 nm) and 32.0 nm (SD = 3.0 nm; SEM = 0.36 nm), respectively. Evaluation of previously published EM data shows that the diameters of chromatin from a large number of sources are proportional to linker length. In addition, the inherent variability in fiber diameter suggests a relationship between fiber structure and the heterogeneity of linker length. The cryo-EM data were in quantitative agreement with space-filling double-helical crossed-linker models of Thyone and Necturus chromatin. The data, however, do not support solenoid or twisted-ribbon models for chromatin that specify a constant 30 nm diameter. To reconcile the concept of solenoidal packing with the data, we propose a variable-diameter solid-solenoid model with a fiber diameter that increases with linker length. In principle, each of the variable diameter models for chromatin can be reconciled with local variations in linker length.

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“…This peak corresponds to a spacing greater than 400 A, far larger than the linker length between nucleosomes. Similar peaks have been observed in x-ray data and used to support a loose three-dimensional model (12,13) but the assignment of this peak is uncertain (28). Because the peak observed in this work was more pronounced along the fiber axis, it is unlikely that it is due to an interfiber distance.…”

Section: Discussionsupporting

confidence: 73%

Orienting rigid and flexible biological assemblies in ferrofluids for small-angle neutron scattering studies

Sosnick

Charles

Stubbs

et al. 1991

Biophysical Journal

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Small-angle scattering from macromolecules in solution is widely used to study their structures, but the information content is limited because the molecules are generally randomly oriented and hence the data are spherically averaged. The use of oriented rodlike structures for scattering, as in fiber diffraction, greatly increases the amount of structural detail that can be obtained. A new technique using a ferromagnetic fluid has been developed to align elongated structures independent of their intrinsic magnetic properties. This technique is ideal for small-angle neutron scattering because the scattering from the ferrofluid particles can be reduced significantly by matching the neutron scattering length density of the particles to a D(2)O solvent ("contrast matching"). The net result is scattering primarily from the ordered biological assembly in a solution environment that can be adjusted to physiological pH and ionic strength. Scattering results from ordered tobacco mosaic virus, tobacco rattle virus, and chromain fibers are presented.

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Transition of Chromatin from the “10 nm” Lower Order Structure, to the “30 nm” Higher Order Structure, as Followed by Small Angle X-Ray Scattering

Cited by 7 publications

References 33 publications

Small angle x-ray scattering of chromatin. Radius and mass per unit length depend on linker length

Small angle x-ray scattering of chromatin. Radius and mass per unit length depend on linker length

The diameters of frozen-hydrated chromatin fibers increase with DNA linker length: evidence in support of variable diameter models for chromatin.

Orienting rigid and flexible biological assemblies in ferrofluids for small-angle neutron scattering studies

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