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Core Concepts
Scientific Fundamentals Explained

Increase oligo stability with phosphorothioate modifications

Quick facts:

Availability: DNA or RNA

Scales: 100 nmol-Large Scale

Purification: HPLC or PAGE

Symbol (for ordering through IDT): * placed between 2 nucleotides

Phosphorothioate bond

Phosphorothioate bonds substitute a sulfur atom for one of the non-bridging oxygen atoms in the phosphate backbone of an oligonucleotide. Phosphorothioates are primarily incorporated to prevent nuclease degradation. Substituting a sulfur atom for an oxygen atom renders the internucleotide linkage resistant to both endo- and exonucleases. Placing this modification between nucleotides at either terminus of an oligonucleotide sequence will provide exonuclease protection, while using the modification internally will inhibit endonuclease degradation. To order, place an asterisk (*) between two nucleotides, indicating the bond you would like to modify (e.g., A*CTG*ATCG*A).

See what other modifications are available from IDT. You can find a list of standard modifications we make to oligonucleotides on the Modifications page of our online catalog. And if you don’t find what you are looking for, just send us a request. We often synthesize special, non-catalog requests. Contact us at noncat@idtdna.com

Product focus—Oligos, oligo modifications, dsDNA fragments

Custom oligonucleotides and primers

You can order up to 1 µmol desalted, custom synthesized DNA oligonucleotides and they will be shipped to you the next business day (larger scales are shipped within 5 business days). You can also specify whether to receive them dried down or hydrated, and whether you want them already annealed. Every IDT oligonucleotide you order is deprotected and desalted to remove small molecule impurities. Your oligos are quantified twice by UV spectrophotometry to provide an accurate measure of yield. Standard oligos are also assessed by mass spectrometry for quality you can count on.


Learn more or order now.


Oligo modifications

Review a list of the common modifications IDT can add to oligonucleotides here. Not finding a modification you need on the IDT website? IDT will consider any modification you need. Just send your request to noncat@idtdna.com.


Custom dsDNA fragments

Rather than annealing oligonucleotides to obtain dsDNA fragments, when your fragment size is 125 bp or longer, it might make more sense to order gBlocks® Gene Fragments. gBlocks Gene Fragments are double-stranded, sequence-verified, DNA genomic blocks, 125–2000 bp in length, that can be shipped in 2–5 working days for affordable and easy gene construction or modification. These dsDNA fragments have been used in a wide range of applications including CRISPR-mediated genome editing, antibody research, codon optimization, mutagenesis, and aptamer expression. They can also be used for generating qPCR standards.


Learn more about gBlocks Gene Fragments at www.idtdna.com/gblocks.

Additional reading

DNA oligonucleotide resuspension and storage—You just received your newly synthesized oligonucleotides. Now what? Here are some guidelines and recommendations on how to resuspend and store your oligos.

Oligonucleotide modifications: Choosing the right mod for your needs—Learn about our broad family of oligonucleotide modifications, and get suggestions for selecting modifications that can help you in your research.

Modifications that block nuclease degradation—Are you working with your oligos in cells culture or in vivo? Find out which modifications can be added to an oligo to limit nuclease degradation.

Need a non-standard modification?—Need a modification you don’t find on our website? IDT offers 89 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 any modification you have in mind. Just make a request at noncat@idtdna.com.


Author: Jeremy Pritchard is a Technical Support Representative at IDT.

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1 Comment

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