Terbium(3+) as a probe of nucleic acids structure. Does it alter the DNA conformation in solution?
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 (I/P) ratios. Both techniques yield the following conclusion: as I/P is increased, native and sonicated DNA undergo a transition from the B- to psi-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.
D002413:Cations, Divalent; D002942:Circular Dichroism; D003300:Copper / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D006147:Guanine / Q000378:metabolism; D006358:Hot Temperature; D008345:Manganese / Q000494:pharmacology; D009690:Nucleic Acid Conformation / Q000187:drug effects; D009691:Nucleic Acid Denaturation; D012996:Solutions; D013057:Spectrum Analysis; D013725:Terbium / Q000378:metabolism*; D014461:Ultracentrifugation
D002413:Cations, Divalent; D012996:Solutions; D013725:Terbium; D008345:Manganese; D006147:Guanine; D003300:Copper; D004247:DNA