Conformational behaviour of 1,4-dihydronicotinamide and protonated nicotinamide in vacuo and in solvent: a density functional study

摘要

Conformations of 1,4-dihydronicotinamide (NH) and protonated nicotinamide (N~+), considered models for the NADH and NAD~+ systems, have been studied in vacuo by using the density functional method employing gradient corrected and hybrid exchange-correlation non local potentials. Solvent effects have been investigated using Perdew and Wang and Perdew potential in the framework of self consistent reaction field approximation. In vacuo, the amide group adopts, preferentially, a cis conformation for both N~+ and NH systems. The cis form is retained by N~+ also in water, while, in the case of NH, we found that the trans conformer is more stable than cis by about 2.5 kcal/mol. Rotational barriers for cis → trans interconversion in N~+ and NH undergo, in the presence of water, a slight increase with respect to the in vacuo values.