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AKB: Biologische Physik

AKB 6: DNA Mechanics

AKB 6.5: Vortrag

Montag, 27. März 2006, 15:30–15:45, ZEU 260

Electrostatic interactions of DNA can quantize azimuthal orientations of nucleosome core particles in bilayers — •Andrey Cherstvy and Ralf Everaers — Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden, Germany

We propose that DNA charge distribution can affect electrostatic interactions of nucleosome core particles (NCP) in bilayers and crystals. The bilayers of NCPs are formed by densely packed columns of NCPs, stacked on top of each other with axes nearly parallel to columnar axis. We suggest that mutual azimuthal orientations of NCPs in neighboring columns across the NCP bilayer are quantized with the angle of about 45 degrees. The reason for that is the helical symmetry of DNA charge distribution, with its phosphates and cations adsorbed in the grooves. This results in azimuthal charge No-dqoscillationsNo-dq on outer circumference of NCPs, along a No-dqringNo-dq of wrapped DNA. When two NCPs are close to each other, these charge patterns can establish an electrostatic zipper, similarly as for two parallel DNA molecules [1]. Our predictions can be tested experimentally, provided a better statistics and resolution of cryoelectron micrographs [2] will be achieved. This can provide new information about inter-nucleosomal electrostatic interactions that influence DNA compactification in chromatin fibers, the phenomenon which is still poorly understood. [1] A. G. Cherstvy, A. A. Kornyshev, and S. Leikin, J. Phys. Chem. B, 106, 13362 (2002); ibid., 108, 6508 (2004) and references therein [2] A. Leforestier, J. Dubochet, and F. Livolant, Biophys. J., 81 2414 (2001).