Table 1. Thermal denaturation temperatures (T _m's) and thermal advantages (TA's) of X- and Y-modified DNA duplexes ^a .

ONs	Sequence	M = Monomer X			M = Monomer Y
		T m [ΔT m] (°C)			T m [ΔT m] (°C)
		Invader	5′-Inv:cDNA	TA (°C)	Invader	5′-Inv:cDNA	TA (°C)
			3′-Inv:cDNA			3′-Inv:cDNA
M1	5′-GGMATATATAGGC	36.5 [–1.0]	44.5 [+7.0]	+18.0	33.5 [–4.0]	45.5 [+8.0]	+22.0
M2	3′-CCAMATATATCCG		47.5 [+10.0]			47.5 [+10.0]
M3	5′-GGTAMATATAGGC	36.5 [–1.0]	47.5 [+10.0]	+22.0	40.5 [+3.0]	48.5 [+11.0]	+21.5
M4	3′-CCATAMATATCCG		48.5 [+11.0]			51.0 [+13.5]
M5	5′-GGTATAMATAGGC	36.5 [–1.0]	48.5 [+11.0]	+22.0	38.5 [+1.0]	49.5 [+12.0]	+22.5
M6	3′-CCATATAMATCCG		47.5 [+10.0]			49.0 [+11.5]
M7	5′-GGTATATAMAGGC	35.5 [–2.0]	47.5 [+10.0]	+21.0	36.5 [–1.0]	48.0 [+10.5]	+22.0
M8	3′-CCATATATAMCCG		46.5 [+9.0]			48.0 [+10.5]
M9	5′-GGMAMATATAGGC	40.0 [+2.5]	51.5 [+14.0]	+29.5	43.5 [+6.0]	51.5 [+14.0]	+25.0
M10	3′-CCAMAMATATCCG		55.5 [+18.0]			54.5 [+17.0]
M11	5′-GGMATAMATAGGC	49.0 [+11.5]	53.5 [+16.0]	+23.5	48.0 [+10.5]	56.0 [+18.5]	+29.0
M12	3′-CCAMATAMATCCG		56.5 [+19.0]			58.5 [+21.0]
M13	5′-GGMATATAMAGGC	49.0 [+11.5]	52.5 [+15.0]	+21.5	45.0 [+7.5]	55.5 [+18.0]	+32.0
M14	3′-CCAMATATAMCCG		55.5 [+18.0]			59.0 [+21.5]
M15	5′-GGTAMAMATAGGC	45.0 [+7.5]	55.5 [+18.0]	+28.5	38.5 [+1.0]	55.5 [+18.0]	+35.0
M16	3′-CCATAMAMATCCG		55.5 [+18.0]			55.5 [+18.0]
M17	5′-GGTATAMAMAGGC	47.5 [+10.0]	54.5 [+17.0]	+24.0	46.5 [+9.0]	56.0 [+18.5]	+28.0
M18	3′-CCATATAMAMCCG		54.5 [+17.0]			56.0 [+18.5]
M19	5′-GGMAMAMAMAGGC	50.0 [+12.5]	65.5 [+28.0]	+45.5	39.5 [+2.0]	66.5 [+29.0]	+56.5
M20	3′-CCAMAMAMAMCCG		67.5 [+30.0]			67.0 [+29.5]

^aΔT _m = change in T _m relative to unmodified dsDNA (T _m = 37.5 °C); thermal denaturation curves were recorded in medium salt buffer ([Na⁺] = 110 mM, [Cl^–] = 100 mM, pH 7.0 (NaH₂PO₄/Na₂HPO₄), [EDTA] = 0.2 mM) and [ON] = 1.0 μM; see main text for definition of TA. A = adenin-9-yl DNA monomer, C = cytosin-1-yl DNA monomer, G = guanin-9-yl DNA monomer, T = thymin-1-yl DNA monomer.