SEQUENCE IDENTITY OF THE N-1 PRODUCT OF A SYNTHETIC OLIGONUCLEOTIDE

After synthesis and purification of an oligonucleotide, the final prod uct usually contains a low level of n-1 congeneric species. We have se quenced the n-1 population of a 25mer phosphodiester oligonucleotide. The n-1 band was cut from the gel and eluted. Oligonucleotides were ta iled with dA and annealed to a dT-tailed plasmid. There recombinant pl asmid was ligated and used to transform competent bacteria. Our result s show that the n-1 population was heterogeneous. The frequency of tru ncated nucleotides at the 3'-end was much higher than at the 5'-end of the oligomer. No truncated nucleotides were found in the last four nu cleotides at the 5'-end. Our results also show that the chain of oligo nucleotides can grow on unreacted sites of a controlled-pore glass sup port.