Table 2. Thermal melting points for DNA 1–DNA 2 5 µM duplexes measured in 10 mM phosphate buffer pH 7.0 and either 100 or 500 mM NaCl_a.

DNA 1 sample	Tm (°C)	ΔTm	Tm (°C)	ΔTmb
	100 mM NaCl	100 mM NaCl	500 mM NaCl	500 mM NaCla
O-Propyl	54.2	+1.8	59.7	+1.6
O-Methoxyethyl	57.9	+2.2	67.1	+2.3
O-Aminopropyl	39.7	+0.3	43.4	∼0
Control (P=O)	36.3	–	43.7	–
Fluoro (P=S)	50.0	+1.3	58.4	+2.0
Control (P=S)	36.8	–	38.7	–

aMaximum error in reported T_m values: ± 1.5°C.

^bΔT_m refers to [T_m(modified duplex) – T_m(control duplex)]/10, i.e. the difference in T_m per modification.