The flagellar genes fliO, fliP, fliQ, and fliR of Salmonella typhimurium are contiguous within the fliLMNOPQR operon. They are needed for flagellation but do not encode any known structural or regulatory components. They may be involved in flagellar protein export, which proceeds by a type III export pathway. The genes have been cloned and sequenced. The sequences predict proteins with molecular masses of 13,068, 26,755, 9,592, and 28,933 Da, respectively. All four gene products were identified experimentally; consistent with their high hydrophobic residue content, they segregated with the membrane fraction. From N-terminal amino acid sequence analysis, we conclude that fliO starts immediately after fliN rather than at a previously proposed site downstream. FliP existed in two forms, a 25-kDa form and a 23-kDa form. N-terminal amino acid analysis of the 23-kDa form demonstrated that it had undergone cleavage of a signal peptide-a rare process for prokaryotic cytoplasmic membrane proteins. Site-directed mutation at the cleavage site resulted in impaired processing, which reduced, but did not eliminate, complementation of a fliP mutant in swarm plate assays. A cloned fragment encoding the mature form of the protein could also complement the fliP mutant but did so even more poorly. Finally, when the first transmembrane span of MotA (a cytoplasmic membrane protein that does not undergo signal peptide cleavage) was fused to the mature form of FliP, the fusion protein complemented very weakly. Higher levels of synthesis of the mutant proteins greatly improved function. We conclude that, for insertion of FliP into the membrane, cleavage is important kinetically but not absolutely required.In previous work, we have characterized most of flagellar region IIIb of the chromosome of Salmonella typhimurium, from fliE (encoding a basal-body protein) through fliF (basalbody MS ring), fliG (switch), fliH (export), fliI (export and ATPase), fliJ (unknown function), fliK (hook-length control), fliL (unknown function), fliM (switch), and fliN (switch) (4, 7, 10, 12-14, 19, 22, 30). Only fliO, fliP, fliQ, and fliR were left uncharacterized.The fliO, fliP, fliQ, and fliR genes are contiguous within the fliLMNOPQR operon. Their products have not been found in the flagellar structure (11), and there is no evidence that they are regulatory genes. They may therefore play a role in flagellar assembly rather than in flagellar function, perhaps being involved in the export of external components such as the rod proteins, hook protein, and flagellin. The fliP, fliQ, and fliR genes (as well as several other flagellar genes) have homologs in the gene systems for export of virulence factors in a variety of pathogenic bacteria; for example, they correspond to the spa (surface presentation of antigen) genes spaP, spaQ, and spaR in S. typhimurium and to spa24, spa9, and spa29 in Shigella spp. (6). We describe here the characterization of the S. typhimurium fliO, fliP, fliQ, and fliR genes and their products.Of particular interest was the finding...

Plasticity of thermoset polymers has been realized by introducing exchangeable bonds, and the plasticity is mostly triggered via heat or UV light. Visible light is a relatively mild trigger that has not been used to induce plasticity in polymer materials. Herein, thermoset polyurethanes (PUs) containing diselenide bonds are fabricated that possess visible light-induced plasticity along with shape memory behavior. A series of PUs with different diselenide bond contents were tested and their shape memory properties and plasticity varied. With a higher diselenide bond content, both shape memory and light-induced plasticity are achieved. By combining these two properties, reshaping the permanent shapes of the PUs is easier. Compared with heat or UV light, visible light has the advantage of spatial control. For instance, a pattern of visible light was introduced by a commercial projector to demonstrate facile reshaping of the materials. Because visible light can be introduced via various methods, PUs with visible light-induced plasticity have great potential applications.

Substrate‐supported metal–organic frameworks (MOFs) films are desired to realize their potential in practical applications. Herein, a novel substrate‐seeding secondary‐growth strategy is developed to prepare composites of uniform MOFs films on aerogel walls. Briefly, the organic ligand is “pre‐seeded” onto the aerogel walls, and then a small amount of metal‐ion solution is sprayed onto the prepared aerogel. The sprayed solution diffuses along the aerogel walls to form a continuous thin layer, which confines the nucleation reaction, promoting the formation of uniform MOFs films on the aerogel walls. The whole process is simple in operation, highly efficient, and eco‐friendly. The resulting hierarchical MOFs/aerogel composites have abundant accessible active sites and enable excellent mass transfer, which endows the composite with outstanding catalytic activity and stability in both liquid‐phase CO2 cycloaddition and electrochemical oxygen evolution reaction (OER) process.

Structural color materials with reversible stimuli‐responsiveness to external environment have been widely used in sensors, encryption, display, and other fields. Compared with other stimuli, visible light is highly controllable both temporally and spatially with less damage to materials, which is more suitable for structural color patterning. Herein, a new diselenide‐containing shape memory material is prepared and used for creating patterns via visible light stimulus. In this system, the structural color originates from birefringence of stretched materials, whose shapes can be fixed while maintaining the mechanical stress. The fixed stress can be released by diselenide metathesis under visible light irradiation. By regulating the wavelength or irradiation time with a commercial projector, the pattern with tunable structural colors is realized and the structural color pattern can be erased and rewritten arbitrarily. During the patterning process, the optical signal is first stored as mechanical signal and then transformed back to optical signal. It is a new method for preparing visible‐light‐responsive structural color material and has great potential in display devices, anticounterfeiting labels, and data storage.

Wavelength‐controlled dynamic processes are mostly based on light‐triggered isomerization or the cleavage/formation of molecular connections. Control over dynamic metathesis reactions by different light wavelengths, which would be useful in controllable dynamic chemistry, has rarely been studied. Taking advantage of the different bond energies of disulfide and diselenide bonds, we have developed a wavelength‐driven exchange reaction between disulfides and diselenides, which underwent metathesis under UV light to produce Se−S bonds. When irradiated with visible light, the Se−S bonds were reversed back to those of the original reactants. The conversion of the exchange depends on the wavelength of the incident light. This light‐driven metathesis chemistry was also applied to tune the mechanical properties of polymer materials. The visible‐light‐induced reverse reaction was compatible with reductant‐catalyzed disulfide/diselenide metathesis, and could be utilized to develop a dissipative system with light as the energy input.

Loneliness has been found to predict a wide range of physical and mental health problems. It is suggested that China's One-Child Policy places young Chinese people at a particularly high risk for loneliness. Although loneliness is most prevalent in late adolescence and early adulthood, interventions have primarily targeted children or older adults with limited success. The current study examines a pilot randomized controlled trial of a mindfulness training program among Chinese college students. Participants with elevated loneliness (N = 50, ages 17-25) were randomized into either an 8-week mindfulness training or a control group. Self-reported measures of loneliness and mindfulness were administered at baseline and posttest. The training group also completed a program evaluation form and a 3-month follow-up assessment. Results provided preliminary evidence indicating that the intervention was feasible and effective at reducing loneliness among Chinese college students. Limitations and future directions were discussed.

Reactive oxygen species (ROS) play crucial roles in cell signaling and redox homeostasis and are strongly related to metabolic activities. The increase of the ROS concentration in organisms can result in several diseases, such as cardiovascular diseases and cancer. The concentration of ROS in biologically relevant conditions is typically as low as around tens of micromolars to 100 μM H2O2, which makes it necessary to develop ultrasensitive ROS-responsive systems. A general approach is reported here to fabricate an ultrasensitive ROS-responsive system via coassembly between tellurium-containing molecules and phospholipids, combining the ROS-responsiveness of tellurium and the biocompatibility of phospholipids. By using dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and NMR spectra, coassembly behaviors and the responsiveness of the coassemblies have been investigated. These coassemblies can respond to 100 μM H2O2, which is a biologically relevant ROS concentration, and demonstrate reversible redox properties.

Bimetallic organic frameworks (Bi-MOFs) have been recognized as one of the most ideal precursors to construct metal oxide semiconductor (MOS) composites, owing to their high surface area, various chemical structures, and easy removal of the sacrificial MOF scaffolds through calcination. Herein, we synthesized Zn/Ni Bi-MOF for the first time via a facile ion exchange postsynthetic strategy, formed a three-dimensional framework consisting of infinite one-dimensional chains that is unattainable through the direct solvothermal approach, and then transformed the Zn/Ni Bi-MOF into a unique ZnO/NiO heterostructure through calcination. Notably, the obtained sensor based on a ZnO/NiO heterostructure exhibits an ultrahigh response of 280.2 toward 500 ppm n-propanol at 275 °C (17.2fold enhancement compared with that of ZnO), remarkable selectivity, and a limit of detection of 200 ppb with a notable response (2.51), which outperforms state-of-the-art n-propanol sensors. The enhanced n-propanol sensing properties may be attributed to the synergistic effects of several points including the heterojunction at the interface between the NiO and ZnO nanoparticles, especially a one-dimensional chain MOF template structure as well as the chemical sensitization effect of NiO. This work provides a promising strategy for the development of a novel Bi-MOF-derived MOS heterostructure or homostructure with well-defined morphology and composition that can be applied to the fields of gas sensing, energy storage, and catalysis.