Phosphorothioate DNA and RNA

Phosphorothioate oligonucleotides are isoelectronic analogues of natural oligonucleotides in which one of the non-bridging internucleotide oxygen atoms is replaced by a sulphur atom. These analogues are more resistant to endonuclease degradation in vivo than their phosphodiester counterparts and are therefore useful in antisense studies. Phosphorothioate bonds can be placed in specific positions or throughout the whole oligonucleotide.