Structural stability for surface display of antigen 43 and application to bacterial outer membrane vesicles production.

Antigen 43 (Ag43) proteins, found on the outer membrane of Escherichia coli, are ß-sheets that fold into a unique cylindrical structure known as a ß-barrel. There are several known structural similarities between bacterial Ag43 autotransporters and physical components; however, the factors that stabilize the barrel and the mechanism for Ag43 passenger domainmediated translocation across the pore of the ß-barrel remain unclear. In this study, we analyzed Ag43ß-enhanced green fluorescent protein chimeric variants to provide new insights into the autotransporter Ag43ß-barrel assembly, focusing on the impact of the α-helical linker domain. Among the chimeric variants, Ag43ß700 showed the highest surface display, which was confirmed through extracellular protease digestion, flow cytometry, and an evaluation of outer membrane vesicles (OMVs). The Ag43ß700 module offered reliable information on stable barrel folding and chimera expression at the exterior of the OMVs. [BMB Reports 2024; 57(8): 369-374].

The Effects of a Gate Bias Condition on 1.2 kV SiC MOSFETs during Irradiating Gamma-Radiation.

We investigated the effects of gate bias regarding the degradation of electrical characteristics during gamma irradiation. Moreover, we observed the punch through failure of 1.2 kV rated commercial Silicon Carbide (SiC) Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) due to the influence of gate bias. In addition, the threshold voltage (VT) and on-resistance (Ron) of the SiC MOSFETs decreased significantly by the influence of gate bias during gamma irradiation. We extracted the concentration of carriers and fixed charge (QF) in oxide using N-type SiC MOS capacitors and Transmission Line Measurement (TLM) patterns to analyze the effects of gamma irradiation. The Total Ionizing Dose (TID) effect caused by high-energy gamma-ray irradiation resulted in an increase in the concentration of holes and QF in both SiC and oxide. To analyze the phenomenon for increment of hole concentration in the device under gate bias, we extracted the subthreshold swing of SiC MOSFETs and verified the origin of TID effects accelerated by the gate bias. The QF and doping concentration of p-well values extracted from the experiments were used in TCAD simulations (version 2022.03) of the planar SiC MOSFET. As a result of analyzing the energy band diagram at the channel region of 1.2 kV SiC MOSFETs, it was verified that punch-through can occur in 1.2 kV SiC MOSFETs when the gate bias is applied, as the TID effect is accelerated by the gate bias.

Bovine Colostrum Exosomes Are a Promising Natural Bacteriostatic Agent against Staphylococcus aureus.

Bioactive molecules and immune factors in the bovine colostrum (BC) are important elements of passive immunity that prevent bacterial infection. However, the mechanisms underlying the antimicrobial activity of BC are not fully understood. We assessed the antibacterial properties of BC-derived exosomes (BC-Exo) and found that they had bacteriostatic, anti-hemolytic, and biofilm-eradication effects on Staphylococcus aureus. Moreover, cell surface deformation and reduced ATP production were observed following BC-Exo treatment. The most reasonable explanation for this finding is that BC-Exo has a strong inhibitory effect on the oxidative phosphorylation pathway in S. aureus. We demonstrated, for the first time, that BC-Exo can exhibit clear antimicrobial activity against S. aureus. Our findings constitute an important basis for future antibiotic discovery.