Multiple end labeling of oligonucleotides with terbium chelate-substituted psoralen for time-resolved fluorescence detection.

A new procedure for the photochemical functionalization and the subsequent nonradioactive labeling of synthetic oligonucleotides with psoralen derivatives was developed where a double-stranded poly(A-T) tail is attached to the 5'- or 3'-end of the oligonucleotide to be labeled. The double-stranded poly(A-T) tail is covalently crosslinked by psoralen molecules which carry reactive thiol or amino groups for the attachment of labels. A NH2-specific terbium chelate exhibiting long-lived fluorescence was attached to the functional groups of the intercalated psoralen molecules. Oligonucleotides substituted in this way hybridize readily and can be sensitively detected by time-resolved fluorescence measurements.