溶剂和外电场下N-羟乙酰神经氨酸的理论光谱研究

Theoretical spectroscopy study of N-glycolylneuraminic acid in solvent and external electric field

通过密度泛函理论对非人源性的红肉危害因子N-羟乙酰神经氨酸(Neu5Gc)在溶剂和外电场下的分子光谱性质进行研究.以M062X/6-311+G(d,p)水平在不同介电常数溶剂(苯ε=2.27,乙酸ε=6.2528,乙醇ε=24.85,甲酸ε=51.10,水ε=78.35)和气相条件下完成几何结构优化、红外、拉曼光谱模拟,相应的,在M062X/6-311G(d,p)水平进行笛卡尔坐标X轴正方向不同强度外电场(0,0.005,0.01,0.015,0.02,0.025 a.u.)下的对比计算.基于各自优化后结构在PBE1PBE/TZVP水平模拟了Neu5Gc在溶剂和外电场下的紫外光谱.结果表明,溶剂下Neu5Gc因溶液极性和与溶质分子间相互作用使其结构稳定性降低,红外和拉曼光谱均产生一定蓝移,在乙醇、甲酸、水相下O-H红外收缩振动频率增高;紫外最大吸收波长为乙酸时183.26 nm,其主要是HOMO到LUMO+1轨道的跃迁.电场下Neu5Gc的红外和拉曼光谱因诱导偶极效应差异较大,在0.025 a.u.时C-H键拉曼活性达到最大,伴随红外光谱蓝移;0.025 a.u.时,紫外激发能最低,紫外最大吸收波长为189.63 nm,主要是HOMO-4和HOMO-1到LUMO+1轨道的跃迁.

The molecular spectral properties of the non-human red meat harmful factor N-glycolylneuraminic acid(Neu5Gc)in solvent and external electric field were studied by density functional theory.The Neu5Gc geometric optimization,infrared and Raman spectra simulations were simultaneously performed at the M062X/6-311+G(d,p)level,under solvents with different dielectric constants(benzeneε=2.27,acetic acidε=6.2528,ethanolε=24.85,formic acidε=51.10,waterε=78.35)and the gas phase.Correspondingly,for comparison,the infrared and Raman spectra of Neu5Gc under the external electric field with different intensities(0,0.005,0.01,0.015,0.02,0.025 a.u.)on Cartesian coordinates X-axis positive direction was calculated at the M062X/6-311G(d,p)levels.The UV spectra under solvent and external electric field were simulated at the PBE1PBE/TZVP level based on the optimized structure.The results show that the structural stability of Neu5Gc was reduced due to the polarity and intermolecular interaction with solvent molecule,and the blue-shift phenomenon occurs on infrared and Raman spectra of Neu5Gc in the solvent..The frequency of O-H infrared shrinkage vibration increases under ethanol,formic acid and water.The maximum absorption wavelength of ultraviolet light is 183.26 nm when acetic acid is used,which is mainly the transition from HOMO to LUMO+1 orbital.The infrared and Raman spectra of Neu5Gc under the electric field are greatly different due to the induced dipole effect.The C-H bond Raman activity reaches the maximum at 0.025 a.u.,followed by the infrared sepctra blue-shifted.The lowest ultraviolet excitation energy happens at 0.025 a.u.,the maximum ultraviolet absorption wavelength is 189.63 nm at 0.025 au,which is a transition of HOMO-4 and HOMO-1 to LUMO+1 orbital.