Sambucus nigra lectin, isolated from elderberry bark, binds preferentially to sialic acid attached to terminal galactose in α-2,6 and to a lesser degree, α-2,3 linkage. Binding is also inhibited to some extent by lactose or galactose. This lectin does not appear to bind sialic acid linked to N-acetylgalactosamine. SNA has been reported to inhibit cell-free protein synthesis. Fluorescein labeled Sambucus nigra lectin has an appropriate number of fluorochromes bound to provide the optimum staining characteristics for this lectin. This conjugate is supplied essentially free of unconjugated fluorochromes. The excitation maximum is at 495 nm and the emission maximum is at 515 nm.