Development And Applications Of ABEEMσπ/MM In The Study Of The Interactions Of Alkali-earth Metal Ions With H₂O And N-methylacetamide

Metal ions play an irreplaceable role in multitudinous chemical and life processes.To accurately and reasonably represent the interactions of divalent metal cations-water,metal cations-protein is significant to the study on the structures and properties of the electrolyte aqueous solution and biomolecular system containing divalent cations.In this thesis,the structures,binding energies and charge distributions of [Mg（H₂O）n]²⁺（n=6-8）and [Mg（NMA）m]²⁺（m=6-8）were studied in terms of four popular quantum chemical methods,namely B3 LYP,B3PW91,M06-2X and MP2 respectively.Based on the results of QM calculations,developed and applied the atom-bond electronegativity equalization fluctuating charge force field（ABEEMσπ/MM）,constructed the interaction potential energy of the clusters of Magnesium ion complex with both water and NMA to adjusting and determining the ABEEMσπ/MM potential energy function and related parameters which is including charge parameters and force field parameters.Then used to study the [Mg（H₂O）n（NMA）m]²⁺（n+m=6）system.The geometries and charge distributions of the above clusters were calculated by the ABEEMσπ/MM,and the results are in reasonably agreement with those from QM method,in which the average absolute deviations（AADs）of the distances between Mg²⁺-ligand（H₂O/NMA）are less than 0.04 ?,and the relative root mean square deviations（RRMSDs）are less than 2.0%.The linear correlation coefficients of the charge distributions obtained by ABEEMσπ/MM and QM are above 0.97.In the same way,the ABEEMσπ/MM potential energy function of Ca²⁺-H2 O was constructed,and it was used to calculate the structures and charge distributions of [Ca（H₂O）n]²⁺（n=6-8）.The results are in great agreement with those of QM.The AAD of the distances between Ca²⁺-ligand is about 0.01 ?,and the RRMSD is about 0.8%.The linear correlation coefficients of the charge distributions obtained by ABEEMσπ/MM and QM are above 0.98.In conclusion,the ABEEMσπ/MM of Mg²⁺/Ca²⁺constructed in this thesis can reasonably represent the interactions between Mg²⁺/Ca²⁺ and H₂O/NMA.