Syntheses and spectral properties of fluorescent trimethine sulfo-3H-indocyanine dyes

Novel fluorescent sulfo-3H-indocyanine dyes containing at least one p-carboxybenzyl group on the nitrogen atoms in 3H-indocyanine rings were synthesized. Their lambda(abs) are in the range of 547-551 nm and lambda(em) 562-567 nm in water. When solvents change from water to ethanol or DMF, the lambda(abs) and lambda(em) of the dyes exhibit red shifts. Because of the presence of sulfonate groups and carboxyl groups, these dyes have good aqueous solubility. The p-carboxybenzyl group let the dyes have better photo-stability than commercial 5-carboxylpentynyl- containing dyes. The carboxyl groups can be converted into their N-hydroxylsuccinimidyl esters to label proteins, oligonucleotides or other bio-chemicals. (C) 2002 Elsevier Science Ltd. All rights reserved.