Description_x000D_ General description_x000D_ Maleimide is an unsaturated imide used in protein conjugation reactions. The direct measurement of maleimide moieties following conjugation reactions by spectrophotometric analysis at 302 nm is insensitive due to the small extinction coefficient (620M-1 cm-1) and complicated by protein absorbance at this wavelength._x000D_ Suitability_x000D_ Suitable for quantifying maleimide groups_x000D_ Principle_x000D_ The colorimetric maleimide quantiation kit provides a simple and direct procedure for measuring maleimide groups. The sample is first reacted with a known amount of excess thiol and then the remaining unreacted thiol is assayed using 4,4′-DTDP (4,4′-Dithiodipyridine). The amount of maleimide is calculated as the difference between the initial amount of thiol and the amount of unreacted thiol after the complete reaction of all maleimide groups.