One of a family of indocyanine dyes with high fluorescence. Conjugates easily to proteins and oligonucleotides for labelling. Prepn: A. S. Waggoner et al., DE 3912046; eidem, US 5268486 (1990, 1993 both to Carnegie-Mellon). Use with fiber optic biosensors: L. A. Tempelman et al., Proc. SPIE Int. Soc. Opt. Eng. 2293, 139 (1994). Use with neuropeptides for detection of receptors: N. W. Bunnett et al., Histochem. J. 28, 811 (1996); for detection of synaptic vesicle mobility: K. Kraszewski et al., J. Neurosci. 16, 5905 (1996).