Influence of a Hairpin Loop on the Thermodynamic Stability of a DNA Oligomer

Table 1

Thermodynamic parameters^a obtained from fitting the model functions ((14) and (18)) to the duplex (D) and hairpin (HP) DSC thermograms presented in Figure 2.

Transition	𝑇1/2	Δ𝐻^0(𝑇1/2)	Δ𝐻^cal(𝑇1/2)	Δ𝑐^0𝑃 ^b	Δ𝑐^0𝑃 ^c	Δ𝑛Na^+
HP → I	59.2	37			0.34	0.9
I → S	75.0	74		0.37	0.25	1.5
HP → S		117^d	111		0.59	2.4
D → 2S	56.5	71	71	0.25	0.30	1.7
Error	±0.2	±2	±2	±0.05	±0.05	±0.2

^aUnits: ^∘C(𝑇_1/2), kcalmol⁻¹ (▵𝐻⁰_(𝑇1/2),▵𝐻^cal_(𝑇1/2)), kcalmol⁻¹K⁻¹(▵𝑐⁰_𝑃); unless stated otherwise the values are those obtained at [Na⁺]=0.13M;
^bobtained from fitting the model function;
^cobtained as the slope of ▵𝐻⁰_(𝑇1/2) versus 𝑇_1/2 curves (Figure 3(a));
^d the total enthalpy of the of the I→S transition was calculated as ▵𝐻⁰_{HS(𝑇1/2,IS)}=▵𝐻⁰_{HI(𝑇1/2,HI)}+▵𝑐⁰_𝑃HI(𝑇_1/2,IS−𝑇_1/2,HI)+▵𝐻⁰_{IS(𝑇1/2,IS)} where 𝑇_1/2,IS and 𝑇_1/2,HI are the melting temperatures of the I→S and H→I transitions and ▵𝐻⁰_{IS(𝑇1/2,IS)} and ▵𝐻⁰_{HI(𝑇1/2,HI)} are the corresponding enthalpies of transition.