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Oligo modifications

A wide variety of modifications can be incorporated into an oligo at the time of synthesis. Some modifications, however, must be attached after synthesis, using NHS Ester chemistry. These post-synthesis modifications often result in lower yields, as they require HPLC purification.

For detailed information about the modifications we offer, click on any of the categories below. Note that not all modifications are available for all types of products and sequences. If the modification you need is not listed, please contact

Fluorophores and dark quenchers »

Fluorescent dyes re-emit light upon excitation while dark quenchers absorb the emitted light and release heat. These modifications are added to oligos that are used in a variety of molecular biology applications. Browse our Freedom™ Dyes, which have no patent licensing restrictions, or the full catalog of fluorophores and dark quenchers.

Attachment chemistry and linkers »

Link an oligonucleotide with another molecule or a particular surface. Subcategories include biotins, amino-modifiers, alkynes, and thiol Modifiers, as well as Azide, Digoxigenin, and Cholesteryl-TEG.

Spacers »

Create distance between a functional moiety and the hybridizing region of your oligo. This category includes the commonly used C3 Spacer, as well as Spacer 9, Spacer 18, and dSpacer.

Phosphorylation »

Use if your oligo is being used as a substrate for DNA ligase. 3′ phosphorylation will inhibit degradation by some 3′ exonucleases and can be used to block extension by DNA polymerase.

Phosphorothioate bonds »

Include these bonds in your oligo sequence for increased inter-nucleotide resistance to nuclease degradation. These modified bonds are especially beneficial when incorporated into antisense oligos.

Modified bases »

A variety of modifications that can serve a range of functions, including cross-linking, duplex stabilization, and nuclease resistance.

Click chemistry modifications »

Learn about the two-step process that uses quantitative chemical reactions of alkyne and azide moieties to create covalent carbon-heteroatom bonds between biochemical species. See available modifications.