The Applications Of ABEEM??/MM And Molecular Face Theory On The Interactions Of Na⁺/K⁺ With N-methylacetamide And H₂O

Metal ions play diverse and indispensible roles in many life activities.For example,they help to keep osmotic balance in multi phase system and maintain biomolecular conformational stability.And the catalysis of many enzymes also need metal ions as part of the enzyme activity center.Scientists are paying more attention to the role of metal ions in the process of life.Therefore,it is of great scientific and practical significance to explore the interactions of metal ions with H2O and NMA(N-methylacetamide).This paper contains two parts:Firstly,select[M(H2O)n]+/2+(n=1-6;M=Li,Na,K,Be,Mg,Ca)systems were studied using molecular face theory(MFT)to examine shapes,bonding between metals and coordinated atoms,and the surface charge distributions of the complexes.Secondly,for the[Na/K(N/L)n]+(n=3-8;N=H20/L=NMA),[NaNnLm]+(n+m=4;N=H2O/L=NMA)and[KNnLm]+(n+m=6;N=H2O/L=NMA)complexes,a high level quantum chemical methods and atom-bond electronegativity equalization fluctuating charge model(ABEEM??/MM)were employed to explore the structures and binding energies.For the complexes studies by MFT,the structure optimization,frequency calculation,binding energy as well as the first ionization energy are calculated on the level of MP2/6-311G(d,p).The potential acting on an electron within a molecule(PAEM),and the volume and surface area determined by the molecular face are calculated using the ab initio MELD program with a theoretical level of CISD/6-31G.Because of the systems studied by ABEEM??/MM,which are much larger,we used B3LYP/6-31+G(d,p)for the structure optimizations and frequency calculations,and MP2/6-311++G(2d,2p)to obtain binding energies.According to these results together with the HF/STO-3G Mulliken charge distributions,were referred to the ABEEM??/MM interaction potential functions and relative parameters were constructed an determined.Results show that when Na+/K+ interact with water and NMA molecular,if with the same ligand,Na+demonstrates stronger binding ability.For all complexes studied containing Na+and K+,the linear correlation coefficient between the charge distributions of ABEEM and QM is 0.9739 for Na+,0.9633 for K+,respectively.