DNA motions in the nucleosome core particle.

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Abstract
Time-resolved triplet state anisotropy decay techniques were used to measure the conformational flexibility of DNA in the [chicken] nucleosome. In a nucleosome, the DNA helix experiences substantial internal flexibility, which occurs with a time constant near 30 ns. The data fit well into a modified version of the Barkley-Zimm model for DNA motion, allowing only DNA twisting motions and the overall tumbling of the nucleosome. That fit yields a calculated torsional rigidity equal to 1.8 .times. 10-19 erg.cntdot.cm, a value equal to that measured for uncomplexed DNA. Large, fast twisting motions of the DNA helix persist, nearly unaltered, when DNA is wrapped to form a nucleosome.