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Bioconjug Chem. 2002 May-Jun;13(3):387-91.

Facile synthesis of thiol-reactive Cy3 and Cy5 derivatives with enhanced water solubility.

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Department of Cell Biology, Scripps Research Institute, 10550, N. Torrey Pines Road, BCC162, La Jolla, California 92037, USA.


The cyanine dyes Cy3 and Cy5 have proven valuable in numerous applications involving conjugation with proteins. Practical syntheses of lysine-selective, succinimidyl ester derivatives of these dyes have been published, and succinimidyl esters are commercially available. However, the published syntheses of cysteine-selective derivatives produce relatively low yields from expensive starting materials, or produce molecules with marginal water solubility for protein labeling. We report here facile syntheses (four steps, >50% overall yield) of iodoacetamide, sulfhydryl-reactive derivatives of the Cy3 and Cy5 fluorophores. These novel derivatives have good water solubility (>2.5 mM) and bear only one reactive side chain, reducing possible protein cross-linking encountered with previous derivatives.

[Indexed for MEDLINE]

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