Spectral properties Excitation/absorption maximum, nm: 675 ε, L⋅mol−1⋅cm−1: 211000 Emission maximum, nm: 694 Fluorescence quantum yield: 0.21 CF260: 0.09 CF280: 0.11 The dye is well-suitable for non-invasive in vivo NIR imaging and applications requiring low fluorescent background. sulfo-Cyanine5.5 NHS ester is an amine-reactive activated ester of sulfonated far-red Cyanine5.5 fluorophore, an analog of Cy5.5. This is a reagent of choice for the labeling of antibodies, sensitive proteins, and others which require reactions in a purely aqueous environment or without any significant additions of organic co-solvents. Application： The dye is well-suitable for non-invasive in vivo NIR imaging and applications requiring low fluorescent background.