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INTEGRATEDDNATECHNOLOGIESPRODUCTSMODIFICATIONSModified BasesIso-dG MW: 329.25’ INT. 3’a a —IE-HPLC purification requiredONHNHNHNNHONNNIso-dGHNNHNOHONHNNNdGNHH5-Me-Iso-dC5-Me-dCTrimer-20Mix of 20 Trimers:(AAA+AAC+ACT+ATC+ATG+CAG+CAT+CCG+CGT+CTG+GAA+GAC+GCT+GGT+GTT+TAC+TCT+TGC+TGG+TTC)It is common practice to insert random N-base domains into oligonucleotides to perform mutagenesis or to evolve novelproteins (random sequence libraries). Unfortunately, inserting serial N bases gives rise to all 64 possible codons and thus doesnot produce an equal representation of the 20 amino acids (AAs). It will also insert unwanted stop codons. A set of trimerphosphoramidites has been developed which comprises a single codon for each of the 20 AAs. The set is available as a 20Trimer Mix for creating better N-domains into oligonucleotides intended to encode proteins. Each trimer addition inserts 3bases into a DNA sequence. It is also possible to obtain custom mixes with more limited AA content. Note that the use oftrimer mixes will not be useful to create N-base domains for aptamer evolution libraries.5’ INT. 3’a a —Phosphorothioate BondThe phosphorothioate (PS) bond substitutes a sulfur atom for a non-bridging oxygen in the phosphate backbone of an oligo.This modification renders the internucleotide linkage resistant to nuclease degradation. Phosphorothioates can be introducedat either the 5’- or 3’-end of the oligo to inhibit exonuclease degradation. In antisense oligonucleotides, phosphorothioatesare also introduced internally to limit attack by endonucleases. Phosphorothioate bonds are indicated using the * symbol(A* for example) in the IDT ordering system.NH2NN'5NNOONH 2NOOPS -NOOOOOPS -O3'©2008 Integrated DNA Technologies 80 www.idtdna.com