The fluorescence anisotropy of ethidium bromide intercalated into the 146 base pairs of DNA on the nucleosome decays due to a combination of rotational diffusion and torsional flexing motions of the DNA. We characterize the internal flexing motions of the DNA by fitting the anisotropy to a mathematical model proposed by Schurr through the variation of two parameters: a torsional coefficient and a frictional coefficient. Using data collected 5°C and 20°C in water, and at 5°C in D{sub}2O, and assuming a model of 146 base pairs clamped at both ends, we have in all cases obtained frictional and torsional coefficients that are higher than the values reported by others.
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