Table 2.

Enthalpic and Entropic Contributions of the AT Basepair to DNA Duplex Stabilization

DNA Duplex	Tt °C	$\Delta H_t^{\text{coop}}$ kJ/mol	$\Delta H_{25}^{\text{coop}}$ kJ/mol	$\Delta H_{25}^{AT}$ kJ/mol-bp	$\Delta S_{25}^{\text{coop}}$ J/K⋅mol	$\Delta S_{25}^{AT}$ J/K⋅mol-bp
5′-CGCAAACGC-3′	60.4	251	210		621
3′-GCGTTTGCG-5′
5′-CGCAAAAAACGC-3′	63.0	360	301	30.3	884	87.7
3′-GCGTTTTTTGCG-5′
5′-CGCAAATTTCGC-3′	64.5	350	288	26.0	844	74.3
3′-GCGTTTAAAGCG-5′
5′-CGCTTTAAACGC-3′	60.8	327	271	20.3	801	60.0
3′-GCGAAATTTGCG-5′
5′-CGCATATATCGC-3′	60.3	326	271	20.3	802	60.3
3′-GCGTATATAGCG-5′
5′-CGCAAATTTAAACGC-3′	64.8	440	362	25.3	1058	72.8
3′-GCGTTTAAATTTGCG-5′
5′-CGCAAAAAAAAACGC-3′	65.1	443	365	25.8	1063	73.7
3′-GCGTTTTTTTTTGCG-5′
Averaged				25 ± 3		72 ± 10

Results in this table were obtained by subtracting the 9-bp duplex (top row) from those of the longer six duplexes. All measurements were at a duplex concentration of 283 μM in 0.15 mM NaCl, pH 7.4. Original data was from (10). $\Delta H_t^{\text{coop}}$ represents the total enthalpy of the cooperative transition at the dissociation temperature T_t and $\Delta H_{25}^{\text{coop}}$ is its magnitude corrected to 25°C. $\Delta H_{25}^{AT}$ is the enthalpy of a single AT pair at 25°C. The corresponding entropies are denoted by $\Delta S_{25}^{\text{coop}}$ and $\Delta S_{25}^{AT}$.