Fluorescein-5-maleimide is an activated fluorescent molecule (excitation: 494 nm, emission: 519 nm) that is used to easily conjugate fluorescein to proteins.1,2,3 The maleimide group reacts optimally with sulfhydryl groups on cysteine side chains at pH 7, forming a stable thioether bond.4 The compound can be used to label proteins for the detection of conformational changes, assembly of multisubunit complexes, and ligand-binding processes.5
1.Curtis, S.K., and Cowden, R.R.Demonstration of sulfhydryl and disulfide groups by a fluorescent maleimide procedureHistochemistry68(1)23-28(1980) 2.Elliott, J.T., Tona, A., and Plant, A.L.Comparison of reagents for shape analysis of fixed cells by automated fluorescence microscopyCytometry52(2)90-100(2003) 3.Lepedda, A.j., Zinellu, A., Nieddu, G., et al.Protein sulfhydryl group oxidation and mixed-disulfide modifications in stable and unstable human carotid plaquesOxid. Med. Cell. Longev.403973(2013) 4.Bigelow, D.J., and Inesi, G.Frequency-domain fluorescence spectroscopy resolves the location of maleimide-directed spectroscopic probes within the tertiary structure of the Ca-ATPase of sarcoplasmic reticulumBiochemistry30(8)2113-2125(1991) 5.Taraska, J.W., and Zagotta, W.N.Fluorescence applications in molecular neurobiologyNeuron66(2)170-189(2010)