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- 2015
尼克酰胺核苷构象稳定性的理论研究
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Abstract:
采用从头算(HF与MP2)和密度泛函理论(DFT)方法, 在3 21G和6 31+G*水平上研究了尼克酰胺核苷(NR)的构象. 分别探讨了在气相及液相(水和氯仿)中NR分子和一水合物异构体的相对稳定性, 分析了溶剂分子的参与对NR异构体的相对稳定性和几何结构参数的影响. 结果表明: 孤立的NR分子在气相中存在36种稳定构象, 其中最稳定的为南式构象NR S, 而最稳定的北式构象为NR K’, 能量比前者高出10.6 kJ/mol (Δ？？G？？？？？？298K？？). NR分子中酰胺基团优势构象为反式, ω, P或γ参数的改变可以为NR分子提供大约8.4~23.7 kJ/mol(Δ？？G？？？？？？298K？？)稳定化能. 不管是南式还是北式褶皱, 最稳定NR分子构象中都存在多根分子内氢键, 且5’ OH基团都为顺式构象(γ ≈ 63°). 溶剂效应使一部分NR分子构象相对稳定性降低, 而一部分则升高, 改变了NR分子各构象的相对稳定性顺序. 水分子的加入与酰胺基团结合形成氢键, 对NR分子的构型影响较大, 而与糖环上羟基结合形成氢键, 则影响较小.
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
