The use of fluorescence anisotropy decay of poly d(A-T) ethidium bromide complex to estimate the unwinding angle of the double helix. |
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Authors: | J L Tichadou D Genest P Wahl G Aubel-Sabron |
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Affiliation: | Centre de Biophysique Moleculaire, C.N.R.S., 45045 Orléans Cedex, France |
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Abstract: | We measured the fluorescence decay under polarized light, of ethidium bromide bound to the poly d(A-T) isolated from Cancer Pagurus. The decay of the whole fluorescence is a single exponential function revealing a good homogeneity of the binding sites. The anisotropy decay due to energy transfers between the ethidium bromide molecules bound to a same poly d(A-T) molecule has been analysed, with a Monte Carlo calculation. We found the dye unwinds the poly d(A-T) duplex by an angle of 17 degrees plus or minus 2 degrees. This result is in agreement with the value previously found in the case of calf thymus DNA-ethidium bromide complex, although the base compositions of the two nucleic acids are different. |
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Keywords: | Present address: Centre de Recherches de Biochimie et de Génétique Cellulaires 31077 Toulouse Cedex France. |
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