Table 2.

Summary of modification strategy used to evaluate structure–activity relationship for single strand and duplex siRNAs

Oligos were prepared with or without 5′ phosphate (5′p). Additionally, oligos containing a 5′PO4 were tested and with or without three abasic residues at the 5′ end of the guide strand (5′aba). Unmodified ribose (2′OH) is compared to 2′-fluoro (2′F), 2′-deoxy (2′H), and 2′-methoxy (2′OMe) modifications assigned to pyrimidines (Pyr) or purines (Pur). Key column lists nomenclature used in subsequent figures. Structures are shown with adenosine as the representative nucleotide. A total of 30 different siRNAs were designed for each target site. Sequences and modification patterns are listed in Supplementary Table S3.