Knowledge of the structural features of carboxy terminal region is very useful in understanding functional properties of tubulin. The goal of this project is to prepare a fluorescently labeled tubulin in which the fluorophore is covalently linked to a single, known site of carboxy terminus, which will prove to be a versatile probe to understand the role of carboxy terminus during tubulin polymerization. Our approach is to enzymatically attach a modified amino acid residue having a unique functional group to the carboxy terminus of alpha- tubulin followed by a chemical reaction with a fluorophore.  From the studies of a series of different molecules, we determined that phenylhydrazine derived fluorophores would possess the best chemical and photo chemical properties for the labeling reaction. Since commercially available hydrazides are least reactive, we synthesized a new fluorophore, 7-hydrazinyl-4-methyl-2H-chromen-2-one. The hydrazone formed with salicylaldehyde was isolated, purified and characterized by NMR (¹H and ¹³C) and HPLC. The kinetics of formation of hydrazone was found to proceed via a reasonable rate at pH 7. The hydrazone of the fluorophore emits and absorbs at a longer wavelength due to the extended conjugation compared to hydrazine fluorophore. This system is successfully used to specifically label carboxy-terminus of alpha-tubulin.