Double strand compositions comprising differentially modified strands for use in gene modulation

A composition comprising first and second chemically synthesized oligomeric compounds wherein:

• at least a portion of the first oligomeric compound is complementary to and capable of hybridizing to a selected nucleic acid target;
• a portion of from about 12 to about 24 nucleosides of the first oligomeric compound is complementary to the second oligomeric compound;
• one of the first and second oligomeric compounds is an asymmetric gapped oligomeric compound;
• the other of the first and the second oligomeric compounds comprises nucleosides linked by internucleoside linking groups wherein the sequence of linked nucleosides defines an alternating motif having the formula:
• 5′-A(-L-B-L-A)n(-L-B)nn-3′
• wherein:
• each L is, independently, an internucleoside linking group;
• one of each A or each B is a β-D-ribonucleoside;
• the other of each A or each B is a sugar modified nucleoside wherein each sugar modified nucleoside is identical;
• n is from about 7 to about 11;
• nn is 0or 1;
• the composition optionally further comprises one or more overhangs, phosphate moieties, conjugate groups or capping groups.