In a recent paper, 4 we proposed an alternative procedure for labelling RNA targets, called 'post-amplification labelling'. The approach first involves enzymatic incorporation of a nucleotide triphosphate previously modified so as to carry a reactive functional group X. The resulting amplified RNA sequences are then labelled by reaction with a fluorophore functionalised by a Y group complementary to X. Severe limitations exist as to the nature of X and Y. The conjugation ...