Sambucus nigra Lectin (SNA/EBL I) is an isolectin isolated from elderberry bark and purified by affinity chromatography. SNA I belongs to the group of type 2 ribosome-inactivating proteins and is composed of an A-chain with enzymatic activity and a B-chain with carbohydrate-binding activity. It has specificity for α2,6-linked sialic acid residues, and elutes with the sugar lactose. SNA I can induce apoptosis through the caspase-dependent pathway at low concentrations. This effect depends on the carbohydrate binding of the B-chain and is independent from the catalytic activity of the A-chain.
Cy5, when bound to Sambucus nigra Lectin (SNA/EBL I), can show the binding pattern of this lectin in cellular imaging and flow cytometry. The excitation wavelength required for Cy5 to fluoresce is high enough to avoid overlap with most other fluorochromes, making it useful for dual-labeling experiments. Because of this high excitation, there is typically less background from autofluorescence of biological specimens.