Improved Thermodynamic Parameters and Helix Initiation Factor to Predict Stability of DNA Duplexes

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Abstract
To improve the previous DNA/DNA nearest-neighbor parameters, thermodynamic parameters (Δ H °, Δ S ° and Δ G °) of 50 DNA/DNA duplexes were measured. Enthalpy change of a helix initiation factor is also considered though the parameters reported recently did not contain the factor. A helix initiation factor for DNA/DNA duplex determined here was the same as that of RNA/RNA duplex (ΔG° 37 = 3.4 kcal/mol). The improved nearest-neighbor parameters reproduced not only these 50 experimental values used here but also 15 other experimental values obtained in different studies. Comparing Δ G ° 37 values of DNA/DNA nearest-neighbor parameters obtained here with those of RNA/RNA and RNA/DNA, RNA/RNA duplex was generally the most stable of the three kinds of duplexes with the same nearest-neighbor sequences. Which is more stable between DNA/DNA and RNA/DNA duplexes is sequence dependent.