尼克酰胺核苷构象稳定性的理论研究

A conformation analysis on the nicotinamide riboside(NR) in gas phase and in water as well as chloroform was performed by ab initio(HF and MP2) and density functional theory(DFT) methods at 3 21G and 6 31+G* level. The effects of one water molecule on relative stabilities, conformational parameters of NR were analyzed. The results indicate that there are 36 stable conformers for NR in the gas phase. The south conformer NR S is the most stable form of all conformations in the gas phase. The most stable north puckering is the conformer NAR K’, which is about 10.6 kJ/mol (ΔG298K) above the globle minimain NAR S. The carboxamide group of the NR is preferred in an anti configuration. Varies of the key geometrical parameters ω, P or γ provide about 8.4~23.7 kJ/mol(ΔG298K) relative stabilities for NR. The most stable conformer of NR both for south and north puckering adopts a syn configuration with γ about 63° and by doing so, forms stronger intramolecular hydrogen bond interactions. Solvent effects both in water and chloroform change the order of the relative stability of NR, by decreasing or increasing the relative stabilities of NR molecules. The addition of one water molecule will influence greatly the conformational parameters of NR due to the stronger hydrogen bond interactions with carboxamide group of NR, while this influence will be negligible if the hydrogen bonds formed between water molecule and hydroxy groups of furanose ring.