Thiophosphoramidites are reagents used to synthesize internucleotide linkages that contain two non-bridging sulfurs in place of the oxygens. These PS2 linkages when used in aptamers can result in significantly increased binding affinity and much slower off-rates (See Improve Existing Aptamers & siRNA). When used in siRNA, PS2 linkages can result in increased gene silencing.
AM Biotech sells thiophosphoramidites in 1g, 2g, 5g, 10g, and 20g packages.
IMPORTANT: thiophosphoramidites required non-standard synthesis protocols for best results.