Der Einfluß des pH, der Temperatur und der Polarität des Lösungsmittels auf die Absorption des reduzierten und oxidierten Nicotinamidadenin-dinucleotids bei 260 nm / Influence of pH, Temperature and Polarity of the Solvent on the Absorption of NADH+ and NADH at 260 nm

Assuming a reversible equilibrium of an unfolded and a base-stacked conformation of both NADH and NAD+ the influence of pH, temperature and methanol on this equilibrium was studied as indicated by the UV-absorption of the adenine, band at 260 nm. By the addition of methanol as well as by an increase of temperature the equilibrium is shifted to the unfolded conformation. An increase of the H+ concentration seems to favor the unfolded conformation in the case of NAD+ while for NADH a decrease of the absorption coefficient is pointing to a higher percentage of the stacked conformation at lower pH. From the temperature variation of the absorption coefficients the enthalpies for the conformational change were calculated and compared with data obtained by different methods.