Fluorescent labelling of sequencing primers for automated oligonucleotide synthesis

A fluorescein derivative is described which can be used as a normal phosphoramidite in oligonucleotide synthesis, giving high yields of fluorescein labelled sequencing primers. The labelled primers were used in automated DNA-sequence analysis without modification of existing protocols, the computer-processed sequences being reproducibly readable up to 400 bases. The procedure described makes the fluorescent labelling of oligonucleotides much easier, and the time of labelling can be significantly reduced. It speeds up the "primer walking" approach of automated DNA sequencing.