| Autor: |
Grigoriev SV; Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, 188300, Russia.; Saint-Petersburg State University, Ulyanovskaya 1, Saint-Petersburg, 198504, Russia., Iashina EG; Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, 188300, Russia., Bairamukov VY; Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, 188300, Russia., Pipich V; Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, 85748 Garching bei München, Germany., Radulescu A; Heinz Maier-Leibnitz Zentrum, Lichtenbergstraße 1, 85748 Garching bei München, Germany., Filatov MV; Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, 188300, Russia., Pantina RA; Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, 188300, Russia., Varfolomeeva EY; Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, 188300, Russia. |
| Abstrakt: |
The small-angle neutron scattering (SANS) on the chicken erythrocyte nuclei demonstrates the bifractal nature of the chromatin structural organization. Use of the contrast variation (D_{2}O-H_{2}O) in SANS measurements reveals the differences in the DNA and protein arrangements inside the chromatin substance. It is the DNA that serves as a framework that constitutes the bifractal behavior showing the mass fractal properties with D=2.22 at a smaller scale and the logarithmic fractal behavior with D≈3 at a larger scale. The protein spatial organization shows the mass fractal properties with D≈2.34 throughout the whole nucleus. The borderline between two fractal levels can be significantly shifted toward smaller scales by centrifugation of the nuclei disposed on the dry substrate, since nuclei suffer from mechanical stress transforming them to a disklike shape. The height of this disk measured by atomic force microscopy (AFM) coincides closely with the fractal borderline, thus characterizing two types of the chromatin with the soft (at larger scale) and rigid (at smaller scale) properties. The combined SANS and AFM measurements demonstrate the stress induced switch of the DNA fractal properties from the rigid, but loosely packed, mass fractal to the soft, but densely packed, logarithmic fractal. |
