Internal labeling of oligonucleotide probes by Diels-Alder cycloaddition

A new method of adding fluorescent labels to the middle of oligonucleotides is reported. Diets-Alder cycloaddition was used to add five fluorescent maleimides to an oligonucleotide containing a 2'-deoxyuridine modified at the 5-position with a spaced furan. This is a new approach to internal oligonucleotide chemistry that opens Lip a large range of possibilities for further conjugation. (C) 2002 Elsevier Science Ltd. All rights reserved.