The analysis of my purified thiol modified oligonucleotide shows three different species. Are these impurities?
A – No, this is generally not an indication of impurity. A thiol modified oligonucleotide which is not fully reduced will be in three states: free thiol (oligonucleotide-SH), protected thiol (oligonucleotide-S-S-C6-O-DMT) and dimerized oligonucleotide (oligonucleotide-S-S-oligonucleotide). It is recommended to reduce these oligonucleotides just prior to use to ensure that only the free thiol is present. The preferred reductants are either DTT or TCEP.
