Nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+) are two important cofactors found in cells. NADH is the reduced form of NAD+. NAD forms NADP with the addition of a phosphate group to the 2' position of the adenyl nucleotide through an ester linkage. The traditional NAD/NADH and NADP/NADPH assays are based on monitoring the changes in NADH or NADPH absorption at 340 nm. The short UV wavelength of NAD/NADH and NADP/NADPH assays makes the traditional methods suffer low sensitivity and high interference. Due to the weak absorption of NAD and NADH, the UV absorption method requires large sample sizes, making NAD and NADH measurements unpractical for limited sample size. AAT Bioquest's Amplite® Colorimetric NADH and NADPH Assay Kit provides a convenient method for the detection of NADPH. The NADPH probe is a chromogenic sensor that has its maximum absorbance at ~460 nm upon NADH reduction. The absorbance increase at ~460 nm is directly proportional to the concentration of NADPH in the solution. The NADPH probe can recognize NADPH in an enzyme-free reaction, and the signal can be easily read by an absorbance microplate reader at ~ 460 nm. The Amplite® Colorimetric NADH and NADPH Assay Kit provides a sensitive assay to detect as little as 3 µM NADPH in a 100 µL assay volume. The assay can be performed in a convenient 96-well or 384-well microtiter-plate format.