Antisense oligonucleotides (ASOs) are DNA oligos, typically 15–25 bases long, designed in antisense orientation to the RNA of interest. Hybridization of the ASO to the target RNA mediates RNase H cleavage of the RNA, which can inhibit the function of non-coding RNAs (e.g., miRNAs, siRNAs, piRNAs, snoRNAs, snRNAs, exRNAs, scaRNAs and lncRNAs) or prevent protein translation of mRNAs. To increase nuclease resistance, we recommend adding phosphorothioate (PS) modifications to the oligo. In the IDT ordering system, use an asterisk to indicate the the position of a phosphorothioate internucleoside linkage. Consider adding modified bases, such as 2′-O-methoxy-ethyl (2′-MOE) or Affinity Plus Locked Nucleic Acid bases, in chimeric antisense designs to increase nuclease stability and affinity (Tm) of the antisense oligo to the target mRNA . Substitution of 5-methyl dC for dC in CpG motifs will slightly increase the Tm of the antisense oligo.