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Need a non-standard modification?

Need a modification you don’t find on our website? IDT offers over 100 modifications that are not listed in our online catalog. A few of the more popular ones are described along with information on how to order them. IDT will consider most of the modifications that you have in mind.

Not finding the modification you need on the IDT website? No worries. IDT currently offers 100 modifications not listed in our online catalog. We have experience synthesizing these “off-catalog modifications”, but they are not in high demand like our other 210 catalog options (see the Standard IDT Oligonucleotide Modifications section below, for a summary of those listed on our oligo modification catalog page).

The main difference between catalog and off-catalog modifications is that off-catalog modifications are not typically kept in stock. Therefore, these special modifications need to be prepared before oligonucleotide synthesis. This may increase turnaround time by 1–3 business days.

Off-catalog modifications we can synthesize for you

Here are a few examples of the off-catalog modifications we can provide:

Internal NHS ester modifications. We can provide several internal NHS ester modifications as off-catalog orders (Table 1). All internal NHS ester modifications are attached post-synthesis to an amino modifier, C6 dT. Thus, such modifications will require a dT base at the position modified in your final oligo (for further explanation, see the article, When dT is required for modification attachment).

Table 1. Modification codes for off-catalog NHS esters.

Off-catalog modification Modification code
DIG NHS ester /iDigN/
Cy® 5 NHS ester /iCy5N/
Cy® 3 NHS ester /iCy3N/
Most Alexa Fluor® Dye NHS esters Varies*

*For Alexa Dye mod codes, contact us.

Representative internal NHS ester modifications

Digoxigenin NHS ester.

Figure 1. Internal DIG NHS Ester.

Dibenzocyclooctyl (DBCO). DBCO (Figure 2) is used for copper-free click reactions. We can place this modification on the 5′ or 3′ ends of an oligo. To order, use the 5′ modification code /5DBCON/ and the 3′ modification code /3DBCON/.

Figure 2. Dibenzocyclooctyl (DBCO).

DBCO-TEG, (Figure 3), offers a longer linker arm. Unlike DBCO, DBCO-TEG is only available for modification of the 5′ ends of oligos. To order, use the 5′ modification code /5DBCOTEG/.

 Dibenzocyclooctyl (DBCO)-TEG.

Puromycin. We can synthesize oligos with puromycin on the 3′ end (Figure 4). This modification is an antibiotic that mimics transfer RNA (tRNA). It is commonly added to the end of RNA oligos to facilitate binding in the ribosome’s A site. From there, it can attach to the growing peptide to ultimately stop elongation. To order this modification, use the code /3Puro/.

Figure 4. Puromycin.

How to order off-catalog modified oligos

The codes used to order off-catalog modifications can be obtained from our Customer Care department. Contact us online by visiting Once you receive the modification codes for your off-catalog modifications, you can order them through the website just like standard catalog modifications. These oligos receive yield guarantees, and pricing will be provided in the website shopping cart.

IDT will consider any modification you have in mind. Please contact us with questions.

Standard IDT oligonucleotide modifications

You can find a list of 210 standard modifications we make to oligonucleotides on the Modifications page of our online catalog. These include modifications of the following types:

  • Phosphorylation
  • Spacers
  • Fluorophores
  • Iowa Black® Dark Quenchers
  • Dark quenchers
  • Attachment chemistry/linkers
  • Modified bases
  • Phosphorothioate bonds
  • Click chemistry

For research use only. Not for use in diagnostic procedures.
 Unless otherwise agreed to in writing, IDT does not intend these products to be used in clinical applications and does not warrant their fitness or suitability for any clinical diagnostic use. Purchaser is solely responsible for all decisions regarding the use of these products and any associated regulatory or legal obligations. RUO22-1597_001

Published Mar 5, 2015
Revised/updated Nov 23, 2022