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Oligo Modifications List | Oligo Modifications Reference Category
Modification : pseudoiso dC (pidC)
Reference Catalog Number 26-6605
Category Minor Bases
Modification Code pidC
5 Prime Y
3 Prime Y
Internal Y
Molecular Weight (mw) 303
Extinction Coeficient (ec) 7.4
Technical Info (pdf) PS26-6605.pdf
Catalog NoScalePrice
26-6605-0550 nmol$610.00
26-6605-02200 nmol$610.00
26-6605-011 umol$825.00
26-6605-032 umol$1,237.50
26-6605-032 umol$1,237.50
26-6605-1010 umol$6,600.00
26-6605-1515 umol$8,250.00

Discounts are available for pseudoiso dC (pidC)!
Modification* Discount Price Structure
1 site/order List price
2 sites/order 10% discount
3 sites/order 20% discount
4 sites/order 30% discount
5-9 sites/order 50% discount
10+ sites/order 60% discount
*Exceptions apply

Related Modifications
5-Me iso dC
iso dG
iso dC

Deoxypseudoisocytidine (PidC) is an isostere of dC that offers an additional hydrogen-bond donor at the N3 position, compared with the natural dC base. Because of this property, PidC-modified oligonucleotides are primarily used to enhance triple-helix formation between single-stranded polypyrimidine oligonucleotides and duplex DNA. Under standard conditions, protonation of the N3 position of the single (Hoogsteen) strand is required in order to stabilize triple-helix formation within the C-GC pyrimidine-purine-pyrimidine binding motif. Acidic conditions are required to convert C-GC into (C+)-GC, which drives the Hoogsteen base pairing between the N3-protonated cytidine and G (2). However, under physiological conditions (which are neutral/slightly basic), deprotonation of this cytidine occurs, and Hoogsteen base pairing is disrupted, destabilizing the triple helix. Substitution of PidC for dC in the polypyrimidine single strand allows for the formation of PidC-dG Hoogsteen base pairs via hydrogen bonding between the N3 of PidC and dG at neutral pH.

1. Ono, A., Ts’o, P.O.P., Kan, L.S. Triplex formation of an oligonucleotide containing 2’-O-methylpseudoisocytidine with a DNA duplex at neutral pH. J. Org. Chem. (1992), 57: 3225-3230.
2. Rich, A. DNA comes in many forms. Gene (1993), 135: 99-109.

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