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For detailed information about the modifications IDT offers, click any of the categories on the left. Please note that not all modifications are available for all types of products and sequences.

Please contact IDT Customer Care for modifications not listed

A wide variety of modifications can be incorporated into an oligonucleotide at the time of synthesis. When possible, this is done using a modified solid support (CPG) for 3'-modifications or a specialized phosphoramidite reagent for internal and 5'-modifications.

Certain modifications (notably Digoxigenin and some fluorescent dyes) are not available as a modified-CPG or phosphoramidite and must be attached to the oligo after synthesis using NHS Ester chemistry. NHS Esters react with free primary amines and result in stable, covalent attachment. A primary amine is therefore added to the oligo during synthesis to permit reaction with the desired NHS Ester. Catalog prices for NHS Ester modifications include the amino-modifier:

5' 5' Amino Modifier C6 (phosphoramidite)
Int Internal amino-C6-dT (phosphoramidite)
3' 3' Amino Modifier (CPG)

Post-synthetic chemical modifications made to an oligonucleotide result in lower yields than modifications introduced during synthesis. Further, all NHS Ester modification require HPLC purification. PAGE purification is not offered for NHS Ester modifications as yields are further decreased and certain modifications can be damaged during PAGE purification.

Listed molecular weights correspond to the increase in MW of the oligo upon addition of the modification and includes attachment groups used to incorporate the modification into the sequence. In some cases, the linker, and hence the MW, differs for attachment to the 5' end, internal sites or 3' end.

Absorbance and Emission maxima of fluorescent dyes may vary slightly with oligo composition. Listed Ab/Em Max were measured on a standardized oligo sequence in 10 mM Tris, 50 mM KCl, 5 mM MgCl2, pH 8.3.