Photocleavable biotin phosphoramidite for 5′-end-labeling, affinity purification and phosphorylation of synthetic oligonucleotides

We report the design, synthesis and evaluation of a non-nucleosidic photocleavable biotin phosphorami-dite (PCB-phosphoramidite) which provides a simple method for purification and phosphorylation of oligo-nucleotides. This reagent introduces a photocleavable biotin label (PCB) on the 5′-terminal phosphate of synthetic oligonucleotides and is fully compatible with automated solid support synthesis. HPLC analysis shows that the PCB moiety is introduced predominant-ly on full-length sequences and is retained during cleavage of the synthetic oligonucleotide from the solid support and during subsequent deprotection with ammonia. The full-length 5′-PCB-labeled oligo-nucleotide can then be selectively isolated from the crude oligonucleotide mixture by incubation with immobilized streptavidin. Upon irradiation with 300–350 nm light the 5′-PCB moiety is cleaved with high efficiency in <4 min, resulting in rapid release of affinity-purified 5′-phosphorylated oligonucleotides into solution. 5′-PCB-labeled oligonucleotides should be useful in a variety of applications in molecular biology, including cassette mutagenesis and PCR. As an example, PCB-phosphoramidite has been used for the synthesis, purification and phosphorylation of 50-and 60mer oligonucleotides