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Microcin C7 (McC) as a viable form of antimicrobial has gained substantial attention due to its distinctive antimicrobial activity, by targeting aspartyl tRNA synthetase. McC can be a potential solution against pathogenic microbial infections in the postantibiotic era. However, considering that degradation by digestive enzymes can disrupt the function of this peptide in the gastrointestinal tract, in this study, we attempt to design McC variants to overcome several barriers that may affect its stability and biological activity. The mccA gene encoding the McC peptide precursor was mutated and 12 new McC variants with trypsin resistance were found. The Yej+rimL− strain was used as an indicator to determine the minimum inhibitory concentrations (MICs). The results showed that three variants, including R2A, R2T and R2Q, among 12 variants formed by the replacement of the second arginine of the McC peptide with different amino acids, were resistant to trypsin and had an outstanding antimicrobial ability, with MIC values of 12.5, 25, and 25 μg/mL, respectively. Taken together, our findings show that the engineering of the site-directed mutagenesis of McC significantly enhances McC trypsin resistance and maintains a great antimicrobial activity.

Abstract Smad5 (small mothers against decapentaplegic 5) protein is a receptor-regulated member of the Smad family proteins, mainly participating in the bone morphogenetic protein (BMP) signaling pathway in its phosphorylated form. This article will provide a detailed review of Smad5, focusing on its gene characteristics, protein structure, and subcellular localization properties. We will also explore the related signaling pathways and the mechanisms of Smad5 in respiratory diseases, including chronic obstructive pulmonary disease (COPD), bronchial asthma, pulmonary arterial hypertension(PAH), lung cancer, and idiopathic pulmonary fibrosis (IPF). Additionally, the review will cover aspects such as proliferation, differentiation, apoptosis, anti-fibrosis, and mitochondrial function metabolism. In addition, the review will cover aspects of proliferation, differentiation, apoptosis, anti-fibrosis and functional mitochondrial metabolism related to the above topics. Numerous studies suggest that Smad5 may play a unique and important role in the pathogenesis of respiratory system diseases. However, in previous research, Smad5 was mainly used to broadly determine the activation of the BMP signaling pathway, and its own function has not been given much attention. It is worth noting that Smad5 has distinct nuclear-cytoplasmic distribution characteristics different from Smad1 and Smad8. It can undergo significant nuclear-cytoplasmic shuttling when intracellular pH (pHi) changes, playing important roles in both the classical BMP signaling pathway and non-BMP signaling pathways. Given that Smad5 can move intracellularly in response to changes in physicochemical properties, its cellular localization may play a crucial role in the development of respiratory diseases. This article will explore the possibility that its distribution characteristics may be an important factor that is easily overlooked and not adequately considered in disease research.

Off-line high-power tests of the fundamental power couplers prior to their on-line operations are of importance for ensuring their operating reliability and stability. To test the couplers using a limited power supply effectively, a movable standing wave (SW) resonant test system with an extraordinary power gain has been developed at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). The system consists of a movable resonator having two movable shorts for the enhancement and movement of the SW field, and a tunable secondary coupler for feeding power into the resonator without reflection. The proof-of-principle structure of the system has been built and tested both at the low-power and at the high-power levels. The low-power test demonstrates that the moving range of the SW resonant field is over half a wavelength which ensures that the fundamental couplers can be tested by SW field at all reflected phases, and the system can provide a power gain ranging from 50 to 94, corresponding to 200–376 (4×50–4×94) of power gain in the case of traveling wave resonant ring system. Two types of multipacting inside the couplers were observed during the high-power tests and the mechanism of their influences on the power gain was analyzed. This movable and high-power-gain solution can be beneficial for the promotion of SW resonant test systems for fundamental couplers.