Maleimides are among the most frequently used reagents for thiol modification. In most proteins, the sites of reactions are at cysteine residues that either are intrinsically present or result from reduction of cystines. Unlike iodoacetamides, maleimides do not react with histidines and methionines under physiological conditions. Tetramethylrhodamine-5-(and-6)-maleimide is an excellent reagent for thiol modifications of peptides, nucleotides, nucleic acids and proteins.
Geibel S, et al. (2003). Conformational dynamics of the Na+/K+-ATPase probed by voltage clamp fluorometry. Proc Natl Acad Sci USA 100, 964-9; Cha A and Bezanilla F (1998). Structural implications of fluorescence quenching in the Shaker K+ channel. J Gen Physiol 112, 391-408.