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Interaction of Thionine with Triple‑, Double‑, and Single-Stranded RNAs
Ist Teil von
The journal of physical chemistry. B, 2013-01, Vol.117 (1), p.38-48
Ort / Verlag
Washington, DC: American Chemical Society
Erscheinungsjahr
2013
Link zum Volltext
Quelle
MEDLINE
Beschreibungen/Notizen
The interaction of thionine with triple, double, and single RNA helices has been fully characterized by thermodynamic and kinetic methods. The nature of the interaction of thionine with the synthetic polynucleotides poly(rU), poly(rA)·poly(rU), and poly(rA)·2poly(rU) has been studied at pH = 7.0 and 25 °C by UV absorbance, fluorescence, circular dichroism spectroscopy, viscometry, differential scanning calorimetry, and T-jump kinetic measurements. The results show that at I = 0.1 M thionine binds to a single poly(rU) strand, destabilizes the poly(rA)·2poly(rU) triplex by external binding, and intercalates into poly(rA)·poly(rU) with similar affinity to the thionine/DNA intercalated complex ( Paul P. ; Kumar G. S. J. Fluoresc. 2012, 22, 71−80 ). On the other hand, the differential scanning calorimetry measurements performed with thionine display a point in which the heat capacity remains unaltered, revealing the equilibrium of isothermal denaturation: thionine/poly(rA)·2poly(rU) + thionine ⇌ thionine/poly(rA)·poly(rU) + thionine/poly(rU), an outcome supported by the other techniques used. The denaturation equilibrium constant, K D (25 °C) = 522 M–1, was evaluated from the affinity with the single, duplex, and triplex RNA.