Table 4. Van’t Hoff premelting enthalpies and entropies of poly(dA–dT)·poly(dA–dT) and poly(dA)·poly(dT)^a.

Band (cm–1)	Assignmentb	Poly(dA–dT)·poly(dA–dT)			Poly(dA)·poly(dT)
		Tpm (°C)	ΔHvHpm (kcal·mol–1)	ΔSvHpm (cal·°K–1·mol–1)	Tpm (°C)	ΔHvHpm (kcal·mol–1)	ΔSvHpm (cal·°K–1·mol–1)
792	dp	30	14.7 ± 1.9	48.0 ± 5.7	41	18.0 ± 1.9	57.3 ± 6.1
842	dp	30	15.0 ± 1.2	49.5 ± 4.0	38	19.7 ± 1.1	63.3 ± 3.5
924	dr	37	10.5 ± 0.8	33.9 ± 2.6	39	16.4 ± 1.3	52.6 ± 4.2
Average		32 ± 4	13.4 ± 2.5	43.8 ± 8.6	39 ± 1	18.0 ± 1.6	57.7 ± 5.4

^aVan’t Hoff premelting parameters (T_pm, ΔH_vH^pm, ΔS_vH^pm) for poly(dA–dT)·poly(dA–dT) and poly(dA)·poly(dT) are given in the left and right halves of the table, respectively, and are based upon analysis of bands assigned to the DNA backbone as indicated in the second column.

^bdp or dr indicates a band assigned to the deoxyribose-phosphate or deoxyribose moiety, respectively.