Duplex Stability and Nuclease Resistance

Duplex Stability Modifications
Modification	Molecular Structure	Duplex Stability	Nuclease Resistance	Chemical Characteristics
Phosphorothioate		Hybridizes to the target sequences with lesser affinity than oligos with phosphodiester backbone	Imparts resistance to nuclease degradation	Modification of the phosphodiester bond by replacing one of the non-bridging oxygens by sulfur
Propyne Analogs		Increased binding affinity to the target sequence and increased stability	Increased nuclease resistance	C-5 propyne analogs of dC and dT

2'-O methyl RNA		Binding similar to DNA bases	Increased	2'O-methyl at the 2' hydroxyl position
5-me-dC		Increased	Similar to DNA	C-5 methylated dC
2-Amino dA		Increased	Similar to DNA	2-amino dA
2'-F bases		Increased	Substantially increased	Fluoro at the 2' position
2'-5' linked oligos		Increased binding efficiency	Increased	2'-5' phosphodiester linkages and 3' deoxy
Chimeric		Substantially increased	Substantially increased	Properties based on modifications used