Molecular Dynamics Simulation On The Interactions Of Plasma And Bacterial Cell Structure

Cold Atmospheric Plasma has been widely used in plasma sterilization and disinfection,especially in the sterilization of medical equipment,due to its advantages of safety,high efficiency,non-toxicity and no residue and temperature close to room temperature.Existing experiments have proved that the active particles in plasma play an important role in the killing of microorganisms.However,due to the lack of existing observation methods,it is difficult to explore the mechanism of action of plasma on the specific components of bacteria from the microscopic perspective,and the specific mechanism of how plasma causes cell death remains unclear.Therefore,it is very important to study the mechanism of plasma action on bacterial cells from molecular and atomic level by reasonable computer simulation.In this paper,reactive molecular dynamics simulation method is adopted to study the microscopic mechanism of plasma sterilization and disinfection from the microscopic level.The research work on this mechanism mainly includes:Construct representative biomolecular models of pathogenic bacteria cell wall,cell membrane and macromolecular substances in cells,and explore the effects of Reactive Oxygen Species(ROS)in plasma on cell wall and cell membrane.As well as the destruction of key biological macromolecular components in cells after entering cells through cell wall and membrane,the inactivation mechanism of bacteria by different reactive oxygen particles was explored.The main research results are as follows:(1)To explore the active particles in plasma of cell wall and cell membrane effect,build the cell walls of candida albicans main component polymer chitin and gram-negative bacteria cell’s outer membrane is an important structure of the lipopolysaccharide Kdo2-A part of the structure of molecular model,using molecular dynamics simulation method to study different ROS and reaction mechanism of the two structures.The results show that ROS can lead to the fracture of the two chain structures through hydrogen capture reaction of chitin polymer and Kdo2-A.There are two kinds of hydrogen snatching reactions.One is the snatching of hydrogen by OH and O for two molecular structures,forming H2O after the snatching of hydrogen.The other is that the molecular structure snatches the H from the H2O2 molecule,which then snatches the hydrogen to form O2.In addition,the O atom is more active in the three ROS,followed by OH,and H2O2 is the least active due to its own decomposition.The hydrogen capture of chitin polymer molecules by ROS mainly focuses on the destruction of N-H bonds,as well as some destruction of O-H and C-H bonds.Hydrogen capture of Kdo2-A mainly focuses on C-H break,which leads to subsequent C-O bond break,resulting in Kdo2-A lipid chain and glycoside bond break.The destructive effect of plasma on chitin polymer and Kdo2-A molecule indicates that plasma acts on cell wall and cell membrane,oxidizing these two cell barrier structures,and causing defects and holes in cell barrier structure is a way for plasma to enter the cell interior.The simulation results were consistent with other experiments in which cell walls were destroyed,cell morphology was changed and cell membranes were disintegrated under the action of plasma.(2)Four ribonucleotide and RNA fragment models were established based on molecular dynamics simulation to simulate the destruction of intracellular RNA by O,OH and H2O2.The results show that the plasma mainly acts on the base part of ribonucleotide,and the action of O oxygen atom and OH radical is mainly targeted at the capture of H atom on C-H,N-H and OH of ribonucleotide.The capture of H atom on C-H bond can also lead to the rupture of C-O bond and lead to the opening of ribonucleotide.The rupture of the junction and the breakdown of the phosphate diester bond.In addition,the C=O addition reaction of H2O2 to pyrimidine structure,especially uracil,is also one of the important reasons for the rupture of bonds between ribonucleotides.In addition,according to the damage result of ROS on the single chain structure of RNA,it is found that the main target of ROS on RNA is the damage of bases,accounting for more than 60%of the reaction proportion.The damage of C-H bond is the largest,and the damage of N-H bond is the largest.These reactions will cause great damage to the integrity of RNA structure,resulting in the loss of genetic information in the transmission process of RNA,which affects the transcription and translation process of cells,thus making normal life activities of cells unable to carry out,resulting in the death of bacterial cells.