In some cases, applications such as sequencing or PCR probes require the 3' terminus of an oligonucleotide to be blocked from allowing polymerase extension. This can be achieved by modifying the 3'-terminus with, for example, a phosphate group, a phosphate ester, or using an inverted 3'-3' linkage. Commonly, the 3'-propyl phosphate formed using 3'-Spacer C3 CPG has been used as an effective non-nucleosidic blocker of the 3'-terminus.
In other situations, where having the four nucleobases available is desired, the use of 3'-deoxynucleoside supports can effect 3'-termination. Although the 2'-hydroxyl group is still present in the final oligonucleotide, it is not a substrate for the commonly used polymerases. We offer all four 3'-deoxynucleoside supports, along with their phosphoramidite analogues, and a 5-Me-dU variant.
Further, these products can be used to synthesise oligonucleotides which have 2'-5' linkages. A unique feature of these is their ability to bind selectively to complementary RNA, with applications in RNA specific probes or in antisense oligos.