ROUTINE PREPARATION OF THIOL OLIGONUCLEOTIDES - APPLICATION TO THE SYNTHESIS OF OLIGONUCLEOTIDE-PEPTIDE HYBRIDS

Oligonucleotide-peptide hybrids have potential for use as antisense in hibitors of gene expression, with the peptide helping to increase the intracellular concentration of the active oligonucleotide. The prepara tion of such hybrids can be achieved by the coupling of thiol-derivati zed oligonucleotides with maleimido-peptides. We have developed reliab le methods for preparing 5'-thiol oligonucleotides in good yields usin g phosphoramidite chemistry and coupling 6-(tritylthio)hexyl phosphora midite as the 5'-terminal residue. The use of highly pure thiol phosph oramidite as well as a manual iodine treatment after this coupling wer e found to be important. Oligonucleotide-peptide hybrids were prepared in high yield (85%) by reacting freshly purified 5'-thiol oligonucleo tides with peptides derivatized at their N-terminus with a maleimido f unctionality.