Question

Does the reduced or oxidized form of the molecule nicotinamide adenine dinucleotide absorb at 340 nm? Explain

Answer 1

NAD: nicotinamide adenine dinucleotide

NAD⁺ oxidized form

NADH⁺ reduced form

Both NAD⁺ and NADH strongly absorb ultraviolet light because of the adenine. For example, peak absorption of NAD⁺ is at a wavelength of 259 nanometers (nm), with an extinction coefficient of 16,900 M⁻¹cm⁻¹. NADH also absorbs at higher wavelengths, with a second peak in UV absorption at 339 nm with an extinction coefficient of 6,220 M⁻¹cm⁻¹. This difference in the ultraviolet absorption spectra between the oxidized and reduced forms of the coenzymes at higher wavelengths makes it simple to measure the conversion of one to another in enzyme assays – by measuring the amount of UV absorption at 340 nm using a Uv-Vis spectrometer.

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