Selective Labeling of Extracellular Proteins Containing Polyhistidine Sequences by a Fluorescein−Nitrilotriacetic Acid Conjugate

Abstract
The compound NTA−DCF consists of two components, a dichlorofluorescein (DCF) reporter and a nitrilotriacetic acid (NTA) functionality. The latter binds polyhistidine sequences selectively through a bridging metal ion. The NTA−DCF conjugate has photophysical properties similar to those of the parent DCF fluorophore both by itself and as its nickel(II) complex. The insensitivity of the emission to paramagnetic ions allows the probe to label His6-tagged proteins fluorescently on the extracellular surfaces of HEK 293-T and HeLa cells.