Corilagin is a member of polyphenolic tannins. Its antimicrobial activity and action mechanism against Escherichia coli, Staphylococcus aureus and Candida albicans were investigated through membrane permeability. Crystal violet staining determination, outer membrane (OM) and inner membrane (IM) permeability, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and atomic force microscopy (AFM) were used as methods for our investigation. The minimum inhibitory concentrations were 62.5, 31.25 and 62.5 µg/mL for E. coli, S. aureus and C. albicans, respectively. Crystal violet results and SDS-PAGE of supernatant proteins showed that corilagin dose-dependently affected membrane permeability of E. coli and C. albicans but not of S. aureus. OM and IM permeability assays revealed comparable results for E. coli. By using AFM, we demonstrated extensive cell surface alterations of corilagin-treated E. coli and C. albicans. SDS-PAGE of precipitated proteins revealed possible targets of corilagin, i.e. Fib, Sae R, Sar S in S. aureus and Tye 7p in C. albicans. In conclusion, corilagin inhibited the growth of E. coli and C. albicans by disrupting their membrane permeability and that of S. aureus by acting on Fib, Sae R and Sar S but not on membrane integrity.
SUMMARYThis paper investigates the application of a recently proposed higher-order Cauchy-Born rule in the continuum simulation and multiscale analysis of carbon nanotubes (CNTs). A mesh-free computational framework is developed to implement the numerical computation of the hyper-elastic constitutive model that is derived from the higher-order Cauchy-Born rule. The numerical computation reveals that the buckling pattern of a single-walled carbon nanotube (SWCNT) can be accurately displayed by taking into consideration the second-order deformation gradient, and fewer mesh-free nodes can provide a good simulation of homogeneous deformation. The bridging domain method is employed to couple the developed mesh-free method and the atomistic simulation. The coupling method is used to simulate the bending buckling of an SWCNT and the tensile failure of an SWCNT with a single-atom vacancy defect, and good computational results are obtained.
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