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.
Absolute blocking of the 3'-terminus can be achieved using a 2',3'-dideoxynucleoside support. For this purpose we offer ddC CPG. We also offer the analogous 2',3'- dA, dC, dG and dT phosphoramidites.