Terbium(3 +) as a probe of nucleic acids structure. Does it alter the DNA conformation in solution? |
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Authors: | D. Gersanovski P. Colson C. Houssier E. Fredericq |
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Affiliation: | Laboratoire de Chimie Physique, Université de Liège, Sart-Tilman (B6), B 4000 Liège Belgium |
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Abstract: | At low ionic strength, Tb3+ binding strongly alters the secondary structure of DNA. Circular dichroism and electro-optical techniques are more sensitive than fluorescence to study these alterations in double-stranded DNA, at low Tb3+/DNA phosphate () ratios. Both techniques yield the following conclusion: as is increased, native and sonicated DNA undergo a transition from the B- to ψ-form, the latter being a compact structure characteristic of aggregated DNA. Our study of alkylated DNA establishes that the accessibility of N-7 guanine to Tb3+ is clearly required for structural alterations in an aggregated state to occur. The chelation of the phosphate group and of the N-7 guanine by Tb3+ simultaneously alters the geometry of the sugar-phosphate backbone and the stacking interaction between the bases in double-stranded DNA. |
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Keywords: | DNA structure Structural transition Circular dichroism Electric dichroism To whom correspondence should be addressed. |
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