Polyoxometalate (POM) has promising antiviral activities.It shows broad-spectrum inhibiting ability,high efficiency,and low toxicity.Experimental assays show that titanium containing polyoxotungstates have anti-influenza-virus activity.In this paper,the binding mechanisms of five isomers of di-Ti-substituted polyoxotungstate,[α-1,2-PTi2W10O40]7– (α-1,2),[α-1,6-PTi2W10O40]7– (α-1,6),[α-1,5-PTi2W10O40]7– (α-1,5),[α-1,4-PTi2W10O40]7– (α-1,4) and [α-1,11-PTi2W10O40]7– (α-1,11),to five subtypes of influenza virus A neuraminidase (FluV-A NA) were investigated in the context of aqueous solution by using molecular docking and molecular dynamics studies.The results show that the isomer α-1,2 is superior to other isomers as a potential inhibitor to neuraminidase.The positively charged arginine residues around the active site of NA could be induced by negatively charged POM to adapt themselves and could form salt bridge interactions and hydrogen bond interactions with POM.The binding free energies of POM/NA complexes range from –5.36 to –8.31 kcal mol–1.The electrostatic interactions are found to be the driving force during the binding process of POM to NA.The conformational analysis shows that POM tends to bind primarily with N1 and N8 at the edge of the active pocket,which causes the conformational change of the pincers structure comprising residue 347 and loop 150.Whereas,the active pockets of N2,N9 and N4 are found to be more spacious,which allows POM to enter into the active pockets directly and anchor there firmly.This study shows that negatively charged ligand as POM could induce the reorganization of the active site of NA and highlights POM as a promising inhibitor to NA despite the ever increasing mutants of NA.
The electronic properties and stabilities of five [Nb2W4O18OCH3]3-isomers have been investigated using a density functional theory method.The results show that the isomer with the methoxy group occupying a bridging position between two tungsten atoms(two tungsten atoms in the plane that contains two niobium atoms) in the [Nb2W4O18OCH3]3-framework is the most stable isomer in acetonitrile.The stability of the one-electron-reduced isomers changes little.The most stable one-electron-reduced isomer has the methoxy group occupying a bridging position between niobium atoms in the [Nb2W4O18OCH3]4-framework.The M-Ob(M = Nb,W;b denotes bridging) bond lengths in anions in which the metal atoms are connected by a methoxy group are longer than those in [Nb2W4O19]4-.The highest occupied molecular orbitals(HOMO) in [Nb2W4O19]4-mainly delocalize over the bridging oxygen atoms of two niobium atoms and two tungsten atoms located in the equatorial plane,and the bridging oxygen atoms on the axial surface.The lowest unoccupied molecular orbitals(LUMO) of [Nb2W4O19]4-are mainly concentrated on the tungsten atoms and antibonding oxygen atoms.Methoxy substitution modifies the electronic properties of the [Nb2W4O18OCH3]3-isomers.The HOMOs in the five isomers formally delocalize over the bridging oxygen atoms,which are distant from the surface containing the methoxy group and four metal atoms.The LUMOs delocalize over the d-shells of the four metal atoms that are close to the methoxy group,and the p-orbitals of oxygen.One-electron reduction occurred at the tungsten atoms,not the niobium atoms.
Transition metal phosphoraniminato derivatives of Keggin-type polyoxometalates(POMs) are important intermediates in N-transfer reactions.Density functional theory(DFT) has been employed to calculate the electronic structures,bonding features and redox properties of the iron and ruthenium phosphoraniminato derivatives of Keggin-type POMs,[PW11O39{MVNPPh3}] 3-(M = Fe,Ru).Our DFT calculations show that both anions have the same qualitative M-N single bond features.However,the calculations predict that the FeN system possesses a lower energy and more accessible metalnitrogen antibonding orbital than the RuN system.This results in a greater weakening of the Fe-N bond in the reduction process,and thus enhances its N-transfer reactivity.
