Polyurethane-functionalized graphene oxide (MGO) was fabricated by surface modification of graphene oxide (GO) with a self-made waterborne polyurethane. MGO/polyurethane (MGO/PU) elastomer was ...produced by in situ polymerization. The structure and properties of GO and MGO and their effect on polyurethane elastomer were investigated. The results show that after the waterborne polyurethane successfully grafted and modified, the ordered crystal structure of GO transforms into the disordered structure, as well as its interlayer spacing becomes larger and the lipophilicity of GO improves greatly. The addition of MGO could promote the formation of hydrogen bonding of the PU and reduce the breaking speed of the hydrogen bonding. In addition, the results of thermogravimetric analysis and temperature-dependent mechanical properties indicate that the thermal stability and mechanical properties of MGO/PU are better than PU and GO/PU.
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A reagentless and single-step electrochemical aptasensor with separation-free fashion and rapid response is developed for the Hg2+ assay in dairy products. Herein, the sensing strategy is established ...on Hg2+-induced structural transition of the methylene-blue-tagged single-stranded DNA (ssDNA) from a flexible manner to rigid hairpin-shaped double-stranded DNA (dsDNA), generating an improved peak current for the Hg2+ assay with a detection limit of 0.62 fM. Importantly, the best signal-to-noise ratio value can be obtained by exploiting Au flowers as sensing material and the optimal ssDNA concentration. The proposed sensor also exhibits high selectivity as a result of the specific thymine–Hg2+–thymine (T–Hg2+–T) coordination chemistry and can be applied to detect Hg2+ in dairy products. With the use of the electric “signal-on” switch, the electrochemical aptasensor has the advantages of simplicity, ease of operation, and high sensitivity and specificity, offering a promising method to assess the safety of dairy products polluted with Hg2+.
Srv2p/CAP1 is an essential regulator of actin turnover, but its exact function in regulating actin polymerization, particularly the contribution of its actin nucleotide exchange activity, remains ...incompletely understood. We found that, although Arabidopsis CAP1 is distributed uniformly in the cytoplasm, its loss of function has differential effects on the actin cytoskeleton within different regions of the pollen tube. Specifically, the F-actin level increases in the shank but decreases in the apical region of cap1 pollen tubes. The reduction in apical F-actin results mainly from impaired polymerization of membrane-originated actin within cap1 pollen tubes. The actin nucleotide exchange activity of CAP1 is involved in apical actin polymerization. CAP1 acts synergistically with pollen ADF and profilin to promote actin turnover in vitro, and it can overcome the inhibitory effects of ADF and synergize with profilin to promote actin nucleotide exchange. Consistent with its role as a shuttle molecule between ADF and profilin, the cytosolic concentration of CAP1 is much lower than that of ADF and profilin in pollen. Thus, CAP1 synergizes with ADF and profilin to drive actin turnover in pollen and promote apical actin polymerization in pollen tubes in a manner that involves its actin nucleotide exchange activity.
The opening and closing of stomata are crucial for plant photosynthesis and transpiration. Actin filaments undergo dynamic reorganization during stomatal closure, but the underlying mechanism for ...this cytoskeletal reorganization remains largely unclear. In this study, we identified and characterized Arabidopsis thaliana casein kinase 1-like protein 2 (CKL2), which responds to abscisic acid (ABA) treatment and participates in ABA- and drought-induced stomatal closure. Although CKL2 does not bind to actin filaments directly and has no effect on actin assembly in vitro, it colocalizes with and stabilizes actin filaments in guard cells. Further investigation revealed that CKL2 physically interacts with and phosphorylates actin depolymerizing factor 4 (ADF4) and inhibits its activity in actin filament disassembly. During ABA-induced stomatal closure, deletion of CKL2 in Arabidopsis alters actin reorganization in stomata and renders stomatal closure less sensitive to ABA, whereas deletion of ADF4 impairs the disassembly of actin filaments and causes stomatal closure to be more sensitive to ABA. Deletion of ADF4 in the ckl2 mutant partially recues its ABA-insensitive stomatal closure phenotype. Moreover, Arabidopsis ADFs from subclass I are targets of CKL2 in vitro. Thus, our results suggest that CKL2 regulates actin filament reorganization and stomatal closure mainly through phosphorylation of ADF.
Actin filaments are often arranged into higher-order structures, such as the longitudinal actin cables that generate the reverse fountain cytoplasmic streaming pattern present in pollen tubes. While ...several actin binding proteins have been implicated in the generation of these cables, the mechanisms that regulate their dynamic turnover remain largely unknown. Here, we show that Arabidopsis thaliana ACTIN-DEPOLYMERIZING FACTOR7 (ADF7) is required for turnover of longitudinal actin cables. In vitro biochemical analyses revealed that ADF7 is a typical ADF that prefers ADP-G-actin over ATP-G-actin. ADF7 inhibits nucleotide exchange on actin and severs filaments, but its filament severing and depolymerizing activities are less potent than those of the vegetative ADF1. ADF7 primarily decorates longitudinal actin cables in the shanks of pollen tubes. Consistent with this localization pattern, the severing frequency and depolymerization rate of filaments significantly decreased, while their maximum lifetime significantly increased, in adf7 pollen tube shanks. Furthermore, an ADF7-enhanced green fluorescent protein fusion with defective severing activity but normal G-actin binding activity could not complement adf7, providing compelling evidence that the severing activity of ADF7 is vital for its in vivo functions. These observations suggest that ADF7 evolved to promote turnover of longitudinal actin cables by severing actin filaments in pollen tubes.
Laser detection devices obtain target information from back-scattered light, such as lidar. The recognition rate can be improved by analyzing intensity and polarization of echo signal. In this paper, ...Monte Carlo method is used to generate a large number of randomly rough surfaces to simulate targets. Every rough surface is discretized into a large number of micro-surface elements. Stokes parameters of back-scattered light are calculated by numerical integration. Incident light is p-, s-, 45° linearly polarized light and right-hand circularly polarized light, respectively. Numerical results show that when s- and p-linearly polarized light incident on a metal rough surface, back-scattered light appears circularly polarized component. Metal rough surface resembles a wave plate with phase difference, with the fast axis parallel or perpendicular to the 45° direction. When linearly polarized light is incident on dielectric rough surface, back-scattered light has no circularly polarized component. Experimental data are consistent with the numerical results. The above research provides a new basis for laser detection device to identify metal targets from the environmental background.
Here, we show that
ADF10 plays an important role in shaping the overall organization of apical actin filaments by promoting their turnover and ordering. ADF10 severs and depolymerizes actin filaments
...and is distributed throughout the entire pollen tube. In
mutants, severing and monomer dissociation events for apical actin filaments are reduced, and the apical actin structure extends further toward the tube base than in wild-type tubes. In particular, the percentage of apical actin filaments that form large angles to the tube growth axis is much higher in
pollen tubes, and the actin filaments are more randomly distributed, implying that ADF10 promotes their ordering. Consistent with the role of apical actin filaments in physically restricting the movement of vesicles, the region in which apical vesicles accumulate is enlarged at the tip of
pollen tubes. Both tipward and backward movements of small vesicles are altered within the growth domain of
pollen tubes. Thus, our study suggests that ADF10 shapes the organization of apical actin filaments to regulate vesicle trafficking and pollen tube growth.
In this study, C-dots were facilely synthesized via microwave irradiation using citric acid and ethylenediamine as carbon precursors. The fluorescence emissions of the C-dots could be selectively ...quenched by Fe3+, and the degree of quenching was linearly related to the concentrations of Fe3+ presented. This phenomenon was utilized to develop a sensitive fluorescence assay for Fe3+ detection with broad linear range (0–250, 250–1200 μmol/L) and low detection limit (1.68 μmol/L). Most importantly, the assay demonstrated high reliability towards samples in deionized water, tap water and lake water, which should find potential applications for Fe3+ monitoring in complicated environments.
Angiogenin (ANG) is a secreted ribonuclease (RNase) with cell-type- and context-specific roles in growth, survival, and regeneration. Although these functions require receptor-mediated endocytosis ...and appropriate subcellular localization, the identity of the cell surface receptor remains undefined. Here, we show that plexin-B2 (PLXNB2) is the functional receptor for ANG in endothelial, cancer, neuronal, and normal hematopoietic and leukemic stem and progenitor cells. Mechanistically, PLXNB2 mediates intracellular RNA processing that contribute to cell growth, survival, and regenerative capabilities of ANG. Antibodies generated against the ANG-binding site on PLXNB2 restricts ANG activity in vitro and in vivo, resulting in inhibition of established xenograft tumors, ANG-induced neurogenesis and neuroprotection, levels of pro-self-renewal transcripts in hematopoietic and patient-derived leukemic stem and progenitor cells, and reduced progression of leukemia in vivo. PLXNB2 is therefore required for the physiological and pathological functions of ANG and has significant therapeutic potential in solid and hematopoietic cancers and neurodegenerative diseases.
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•PLXNB2 is the receptor of ANG in physiological and pathological cell types•ANG acts through PLXNB2 to either restrict or promote cell proliferation•PLXNB2 mediates cell-type-specific signaling and RNA-processing activities of ANG•Anti-PLXNB2 therapy is relevant in cancer, neurodegeneration, and stem cells
Plexin-B2 acts as a functional angiogenin receptor in a variety of physiological and pathological contexts, suggesting that the ANG-PLXNB2 axis could be harnessed for therapeutic applications.
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•Microbial carbonates record ambient seawater chemistry.•Exact formation ages of microbialites offers new insights into microbial habitats.•Advances in LA-ICP-MS make low U carbonates ...accessible for U-Pb geochronology.•Bio-sedimentary layering of microbialites traps detrital grains high in Th and Al.•LA-(TOF)-ICP-MS maps help to preselect areas high in U and low in Th and Al.
Some of the earliest bio-sedimentary records of life on Earth are represented by microbial carbonates, which are also critical geochemical archives of ancient seawater chemistry and the environmental circumstances in which they precipitated. Reconstructing paleo-microbial environments on Earth and potentially other planets requires precise determination of the depositional ages of these materials. The (abiogenic) carbonate geochemistry communities can now use developments in in-situ laser ablation U-Pb dating using inductively coupled plasma mass spectrometry (LA-ICP-MS). Due to the effects of impurity mixing and diagenesis, microbial carbonates have received little geochronological study despite their broad relevance for understanding ancient seawater's environmental conditions and geochemical compositions. This study demonstrates using time-of-flight mass spectrometry (TOF-MS) to perform quick, quantitative elemental mapping before U-Pb spot dating to improve experiment success rates and data reliability and offers four practical application examples.
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