Table 2.

Melting temperatures and extent of RNA:RNA duplex destabilization by modified UNA^a

ID	Sequence 5′-UACAGXCUAUGU-3′	T m [°C]	(ΔTm) [°C]
ON 1	X = U	61.1
ON 4	X = UNA	43.6	−17.5
ON 5	X = 5′-(S)-Me-UNA	43.3	−17.8
ON 6	X = 5′-(R)-Me-UNA	42.5	−18.6
ON 7	X = 2′-(S)-Me-UNA	42.4	−18.7
ON 8	X = 2′-(R)-Me-UNA	42.6	−18.5
ON 9	X = 3′-(S)-Me-UNA	42.1	−19.0
ON 10	X = 3′-(R)-Me-UNA	43.3	−17.8
ON 11	X = 4′-(β)-methoxy-UNA	45.4	−15.7

^aThe absorbances of hybridized duplexes formed by indicated sequence with 3′-AUGUCAGAUACA)-5′ (2.5 μM each strand) at 260 nm were determined as a function of temperature in PBS. The T_m was determined as the maximum of the first derivative of the melting curve. Values are reported as the average of two independent experiments. ΔT_m was calculated with respect to the unmodified RNA duplex. Reported values are an average of six determinations using the Varian Cary Bio-300 built-in software, with standard deviation reported.