In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the re...In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.展开更多
A novel ellipsoidal helical antenna is proposed and studied in this letter. As a special in-stance,the hemispherical helical antennas are analyzed firstly,which indicates that the characteristics of a two-arm unit are...A novel ellipsoidal helical antenna is proposed and studied in this letter. As a special in-stance,the hemispherical helical antennas are analyzed firstly,which indicates that the characteristics of a two-arm unit are better than that of a single-arm unit. Based on this,the ellipsoidal helical antenna,formed by changing the axial direction’s dimension of the two-arm hemispherical helical antenna,is analyzed by the moment method with curved basic and testing function. The effects to VSWR (Voltage Standing Wave Ratio),gain,polarization and patterns by the axial direction’s dimensions are inves-tigated. The study results provide dependable gist to the choice of antenna format according to the practical requirements.展开更多
文摘In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.
文摘A novel ellipsoidal helical antenna is proposed and studied in this letter. As a special in-stance,the hemispherical helical antennas are analyzed firstly,which indicates that the characteristics of a two-arm unit are better than that of a single-arm unit. Based on this,the ellipsoidal helical antenna,formed by changing the axial direction’s dimension of the two-arm hemispherical helical antenna,is analyzed by the moment method with curved basic and testing function. The effects to VSWR (Voltage Standing Wave Ratio),gain,polarization and patterns by the axial direction’s dimensions are inves-tigated. The study results provide dependable gist to the choice of antenna format according to the practical requirements.
