Feb 1, 1976

Molar absorptivities of beta-NADH and beta-NADPH

Clinical Chemistry
J ZiegenhornT Bücher


Re-investigating the accuracy of the commonly used values for molar absorptivities (epsilon) of beta-NADH and beta-NADPH at Hg 334, Hg 365, or 340 nm, we obtained the following results: The maximum of absorbance of NADH is shifted from about 340 nm at 0 degrees C to about 338.5 nm at 38 degrees C; the corresponding maxima of NADPH are located at about 0.5-nm longer wavelengths. In addition, the absorption curves of both coenzymes broaden with increasing temperature. For these reasons, the epsilon-values of NADH and NADPH are generally different from each other, and are temperature-dependent. Only at 334 nm are they almost identical and nearly independent of temperature. Therefore this wavelength is recommended for precise measurements. The epsilon-values of these coenzymes are influenced by ionic strength and pH. To determine the absolute values of the molar absorptivities, we performed the glutamate dehydrogenase or lactate dehydrogenase assay with carefully purified 2-oxoglutaric acid or pyruvic acid in the presence of excess coenzyme. The purity of the substrates was checked through differential scanning calorimetry, moisture analysis, gas-liquid chromatography, gas chromatography in combination with mass spectrometry, and n...Continue Reading

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Mentioned in this Paper

Process of Absorption
Ketoglutaric Acids
Spectrophotometry, Ultraviolet
Hydrogen-Ion Concentration
Glutamate Dehydrogenase

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