Molecular Simulation Of The Interactions Between Mineral Dusts And Structural Molecules Of Microbial Cell Wall

Molecular simulation has been an important tool in the study of interface interaction due to its visibility at the scale of molecule. Simulation methods including Monte Carlo, molecular dynamics, quantum chemistry were introduced to simulate the interactions between air-pollutant minerals(calcite, quartz, montmorillonite) and the biomolecules(glycine, serine, glutamic acid, arginine, peptidoglycan, lipid A, phospholipid) contained in the microbial cell wall. Moreover, the electron transfer between the minerals and biomolecules was calculated. The study was aimed to provide some evidences that why microorganism could adhere to mineral surface and grow on it.The results of Monte Carlo calculation showed that all the biomolecules were adsorbed stablely on surface of the minerals. As a whole,the adsorption of biomolecules on calcite was stronger than on montmorillonite, and montmorillonite was stronger than quartz. For biomolecules, when adsorbed on montmorillonite, the adsorption of lipid A was strongest, then the amino acids and peptidoglycan which were almost the same, phospholipid was the weakest. The strong-weak sequence of biomolecules adsorption on quartz was in accordance with montmorillonite. The adsorption of biomolecules on calcite differed quite a lot in strength. Pecking order of each biomolecule was Gly> PDG> Lipid A> Arg> Phospholipid> Ser> Glu.Molecular dynamics calculation indicated that montmorillonite and quartz interacted with biomolecules mainly by the side-surface oxygen atoms. Then, calcite by calcium ions and oxygen atoms of carbonates. As for biomolecules, the interaction groups were amino, carboxyl and methylene of amino acids clusters; phosphate and ester groups of phospholipid; phosphate groups and methylene of lipid A; peptide bond in the tetrapeptide tail and N- acetylglucosamine of peptidoglycan.The main acting forces in the interaction process were determained by the change of non-bond interaction energy. The calculation results showed that when interacted with montmorillonite and quartz, neutral amino acids(glycine, serine), lipid A and phospholipid interacted by Van del Waals forces, non-neutral amino acids(glutamic acid, argine) by electronstatic forces. When interacted with calcite, electronstatic force always played an improtant role.Quantum chemistry calculation results showed that there were some delocalized electrons in the mineral structure and some groups of biomolecules which were easy to lose. The delivery of electrons were existed between the active groups in the interaction process. There was an positive correlation between number of transfer electrons and intercation strenght.