Recognition of centimeter-level length changes using the intensity of probe light in BOTDA.

We proposed a method based on the Brillouin optical time domain analysis (BOTDA) system to demodulate the length changes of the heating region using the intensity of probe light, under the premise that the temperature in the heating region does not change and the Brillouin frequency shift (BFS) of the heating region is known. This method can realize the recognition of small length under the condition of wide pulse width. The theoretical analysis shows that the different lengths of the heating region will lead to different gains when the spatial resolution corresponding to the pulse width of the pulsed light is larger than the length of the heating region. And through theoretical derivation and simulation, it is concluded that the relationship between the intensity of probe light and the length of the heating region satisfies the exponential growth. Further experiments verify that the exponential growth is approximately linear in the range of small length changes. The length of the heating region can be inversely deduced by using the linear relationship by detecting the intensity of probe light. When the length of sensing fiber is 100 m and the heating region changes from 2 cm to 8 cm, 1 cm heating region changes can be identified.

Early Detection of SARS-CoV-2 Seroconversion in Humans with Aggregation-Induced Near-Infrared Emission Nanoparticle-Labeled Lateral Flow Immunoassay.

An outbreak of coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses great threats to human health and the international economy. To reduce large-scale infection and transmission risk of SARS-CoV-2, a simple, rapid, and sensitive serological diagnostic method is urgently needed. Herein, an aggregation-induced emission (AIE) nanoparticle (AIE810NP, λem = 810 nm)-labeled lateral flow immunoassay was designed for early detection of immunoglobulin M (IgM) and immunoglobulin G (IgG) against SARS-CoV-2 in clinical serum samples. Using a near-infrared (NIR) AIE nanoparticle as the fluorescent reporter (△λ = 145 nm), the autofluorescence from the nitrocellulose membrane and biosample and the excitation background noise were effectively eliminated. After optimization, the limit of detection of IgM and IgG is 0.236 and 0.125 µg mL-1, respectively, commensurate with that of the enzyme-linked immunosorbent assay (ELISA) (0.040 and 0.039 µg mL-1). The sensitivity of the proposed AIE810NP-based test strip for detecting IgM and IgG is 78 and 95% (172 serum samples), commensurate with that of ELISA (85 and 95%) and better than that of a commercial colloidal gold nanoparticle (AuNP)-based test strip (41 and 85%). Importantly, the time of detecting IgM or IgG with an AIE810NP-based test strip in sequential clinical samples is 1-7 days after symptom onset, which is significantly earlier than that with a AuNP-based test strip (8-15 days). Therefore, the NIR-emissive AIE nanoparticle-labeled lateral flow immunoassay holds great potential for early detection of IgM and IgG in a seroconversion window period.

Separation and determination of estrogen in the water environment by high performance liquid chromatography-fourier transform infrared spectroscopy.

The components for connecting high-performance liquid chromatography (HPLC) with Fourier-transform infrared spectroscopy (FTIR) were investigated to determine estrogen in the water environment, including heating for atomization, solvent removal, sample deposition, drive control, spectrum collection, chip swap, cleaning and drying. Results showed that when the atomization temperature was increased to 388 K, the interference of mobile phase components (methanol, H2O, acetonitrile, and NaH2PO4) were completely removed in the IR measurement of estrogen, with 0.999 of similarity between IR spectra obtained after separation and corresponding to the standard IR spectra. In experiments with varying HPLC injection volumes, high similarity for IR spectra was obtained at 20 ul injection volume at 0.01 mg/L BPA while a useful IR spectrum for 10 ng/L BPA was obtained at 80 ul injection volume. In addition, estrogen concentrations in the natural water samples were calculated semi-quantitatively from the peak intensities of IR spectrum in the mid-infrared region.

Ligand-induced conformational change of Plasmodium falciparum AMA1 detected using 19F NMR.

We established an efficient means of probing ligand-induced conformational change in the malaria drug target AMA1 using 19F NMR. AMA1 was labeled with 5-fluorotryptophan (5F-Trp), and the resulting 5F-Trp resonances were assigned by mutagenesis of the native Trp residues. By introducing additional Trp residues at strategic sites within a ligand-responsive loop, we detected distinct conformational consequences when various peptide and small-molecule ligands bound AMA1. Our results demonstrate an increase in flexibility in this loop caused by the native ligand, as inferred from, but not directly observed in, crystal structures. In addition, we found evidence for long-range allosteric changes in AMA1 that are not observed crystallographically. This method will be valuable in ongoing efforts to identify and characterize therapeutically relevant inhibitors of protein-protein interactions involving AMA1 and is generalizable to the study of ligand-induced conformational change in a wide range of other drug targets.

Self-assembly of an azobenzene-containing polymer prepared by a multi-component reaction: supramolecular nanospheres with photo-induced deformation properties.

In this article, we have synthesized a polymer containing regulated azobenzene groups by one-pot multi-component polymerization (MCP) based on Passerini reaction, and investigated its self-assembly behavior and photo-induced deformation properties. We found that this molecule can form spherical structures with sizes ranging from hundreds of nanometers to several micrometers when dissolved in THF. NMR and FTIR studies indicate that there are associated hydrogen bonds among the molecules in the aggregates, which are responsible for the formation of the nanospheres. By controlling the stirring rate as the THF suspension is dropped into water, the nanospheres can be sorted according to their size. In this way, we have obtained nanospheres with relatively uniform diameter. When irradiated by UV light in the aqueous medium, the nanospheres tend to aggregate into large clusters, while in dry state they are ready to merge into island-like structures, showing a good photo-induced deformation property.

The role of the hybridization between Mn 3d and O 2p orbitals in the existence of the Griffiths phase in La0.85Ca0.15MnO3.

Favourable conditions for the existence of the Griffiths phase in the La0.85Ca0.15MnO3 compound are experimentally investigated in terms of electronic and lattice structure by temperature-dependent x-ray absorption spectroscopy, valence band photoemission spectroscopy, and x-ray diffraction experiments. The chemical shifts of Mn L-edge and O K-edge x-ray absorption lines in the Griffiths phase are understood to be related to the hybridization between Mn 3d and O 2p states instead of the variation of Mn valence states. Valence band spectra also indicate that the hybridization of O 2p with Mn 3d is enhanced in the Griffiths phase. From a 2D diluted Ising ferromagnet model, this hybridization between Mn 3d and O 2p orbitals surely enhances the Griffiths phase feature.

Overcoming antigenic diversity by enhancing the immunogenicity of conserved epitopes on the malaria vaccine candidate apical membrane antigen-1.

Malaria vaccine candidate Apical Membrane Antigen-1 (AMA1) induces protection, but only against parasite strains that are closely related to the vaccine. Overcoming the AMA1 diversity problem will require an understanding of the structural basis of cross-strain invasion inhibition. A vaccine containing four diverse allelic proteins 3D7, FVO, HB3 and W2mef (AMA1 Quadvax or QV) elicited polyclonal rabbit antibodies that similarly inhibited the invasion of four vaccine and 22 non-vaccine strains of P. falciparum. Comparing polyclonal anti-QV with antibodies against a strain-specific, monovalent, 3D7 AMA1 vaccine revealed that QV induced higher levels of broadly inhibitory antibodies which were associated with increased conserved face and domain-3 responses and reduced domain-2 response. Inhibitory monoclonal antibodies (mAb) raised against the QV reacted with a novel cross-reactive epitope at the rim of the hydrophobic trough on domain-1; this epitope mapped to the conserved face of AMA1 and it encompassed the 1e-loop. MAbs binding to the 1e-loop region (1B10, 4E8 and 4E11) were ∼10-fold more potent than previously characterized AMA1-inhibitory mAbs and a mode of action of these 1e-loop mAbs was the inhibition of AMA1 binding to its ligand RON2. Unlike the epitope of a previously characterized 3D7-specific mAb, 1F9, the 1e-loop inhibitory epitope was partially conserved across strains. Another novel mAb, 1E10, which bound to domain-3, was broadly inhibitory and it blocked the proteolytic processing of AMA1. By itself mAb 1E10 was weakly inhibitory but it synergized with a previously characterized, strain-transcending mAb, 4G2, which binds close to the hydrophobic trough on the conserved face and inhibits RON2 binding to AMA1. Novel inhibition susceptible regions and epitopes, identified here, can form the basis for improving the antigenic breadth and inhibitory response of AMA1 vaccines. Vaccination with a few diverse antigenic proteins could provide universal coverage by redirecting the immune response towards conserved epitopes.

[Coupling AFM fluid imaging with micro-flocculation filtration process for the technological optimization].

Atomic force microscope (AFM) fluid imaging was applied to the study of micro-flocculation filtration process and the optimization of micro-flocculation time and the agitation intensity of G values. It can be concluded that AFM fluid imaging proves to be a promising tool in the observation and characterization of floc morphology and the dynamic coagulation processes under aqueous environmental conditions. Through the use of AFM fluid imaging technique, optimized conditions for micro-flocculation time of 2 min and the agitation intensity (G value) of 100 s(-1) were obtained in the treatment of dye-printing industrial tailing wastewater by the micro-flocculation filtration process with a good performance.

Dedifferentiation of human epidermal melanocytes into melanoblasts in vitro.

Melanoblasts (MB) are also called melanocyte (MC) precursor cells. In recent years, people have successfully cultivated human and mouse MB. Previous studies have shown that EDN3 induces cultivated bird MC to re-differentiate into double potential progenitor cells of MB. However, no study has reported whether in vitro cultivated human MC can be dedifferentiated. Our research on MC that were purified and cultivated in vitro found that adding 10 nm endothelin 1 (EDN1) (ET-1) to the MC medium without phorbol 12-myristate 13-acetate (PMA) induced a few MC to dedifferentiate and become a new type of cell. This new cell type was separated, purified, cloned and identified using multiple approaches. The results show that 88.7%, 8.69% and 2.5% of this new cell type were cells in the G(0) -G(1) , G(2) -M and S stages, respectively. The new cell type did not exhibit an apparent apoptotic peak, and its apoptotic rate was 0.09%. Stage I melanosomes were observed in the cytoplasm and were negative for the DOPA reaction. The cell surface antigen expression was positive for tyrosinase-related protein 2, negative or positive for c-kit and negative for S-100 and HMB45, showing that these cells were dedifferentiated MB of MC. Our findings provided evidence for atavism of mature human MC under certain conditions.

[Effects of pH value on the adsorption and degradation of 2, 4-DCP by nanoscale zero-valent iron].

To evaluate the effect of pH on the degradation of 2,4-DCP by zero-valent iron nanoparticles (with the particle size of 30-40 nm in diameter) samples were taken for TEM, SEM-EDX, and ICP-OES analysis and investigated on the particle morphology changes and 2,4-DCP removal under different pH conditions. It is shown that iron nanoparticles agglomerate from individual particles and tiny clusters into massive aggregate assemblies with their surfaces oxidized and coated by the needle-like rotten iron oxide products (FeOOH) in the degradation process, which will block up a further reaction of 2,4-DCP dechlorination, while the low pH value condition in acidic system can effectively suppress particles aggregation and the surface oxidation, although iron loss in the solid phase is somehow inevitable. Large quantity of Fe2+ ions soaked out from iron nanoparticles significantly promote 2,4-DCP removal by reduction, and the solution pH tends to go up in the reaction process. Acidic conditions facilitate 2,4-DCP dechlorination, and the removal efficiency became higher with the pH reduced, in which 90% of 2,4-DCP removal is reached in 24 h under the pH value of 3.

Distribution of heavy metals in the water column, suspended particulate matters and the sediment under hydrodynamic conditions using an annular flume.

Sediment resuspension plays an important role in the transport and fate of heavy metals in the aquatic environment. In the present study, the release and binding forms of Cr, Cu, Zn, Pb under hydrodynamic conditions were investigated using an annular flume. Two sediments located at YLZ and GBD from Liangshui River, Beijing were resuspended for 10 hr at 0.159 and 0.267 m/sec, respectively. The concentrations of suspended particulate matters of YLZ were higher than those of GBD during resuspension, indicating that the former sediment is more sensitive to the velocity. Cr in the dissolved phase stayed nearly constant at about 2.25 and 1.84 micro/L for YLZ and GBD, respectively, due to the high percentage of its stable binding fractions in both sediments, while Cu, Zn, and Pb showed a fast release in the initial period of time. However, their concentrations in SPM generally decreased with time and were higher at the lower velocity of 0.159 m/sec, which resulted from the entrainment and depressing effect of larger size particles with lower heavy metal content, commonly referred to as the "particle concentration effect". In addition, the binding form and heavy metal fractions were also found to vary during the resuspension event. A decrease in the sulphide/organic matters bounded form in GBD sediment was observed, whereas no visible changes were perceived in YLZ site samples. This phenomenon is due to the oxidation of heavy metal-sulphide binding forms, which originated from its high acid volatile sulphide content in GBD sediment.

[Comparative study on the coagulation of PACl with different contents of aluminum polymeric species].

Based on the Ferron assay of aluminum species, jar test and filterability index, four types of PACl products of Al(a),, Al(b), Al(c), and Al(abc) are investigated on raw water samples from settling tank of water plant, which denote the different dominant aluminum species of AlCl3 for monomer or oligomer, PACl with high Al13 contents for mediate polymer of Al(b), PACl with high Al(c) contents for aluminum high polymer or Al (OH)3 sol, and industrial PACl for the mixed aluminum polymeric species with variety of alkalinity of Al(a), Al(b) and Al(c), respectively. Multiple parameters including the residual turbidity, UV254, particles removal, filterability index as well as the floc formation kinetics are monitored to make a comprehensive evaluation of their coagulation and settling-filtration performance. It indicates that PACl with high Al(b) contents demonstrate their predominant ability in the turbidity removal, whereas PACl with high Al(c) contents prefer to cutting down the particles and UV254.

Effect of speciation transformation on the coagulation behavior of Al(13) and Al(13) aggregates.

Flocculation of kaolin suspension with aluminium fractal polycations was investigated as a function of aluminium concentration and pH. Aluminium flocculants included Al(13) and Al(13) aggregates with OH/Al ratio of 2.6 and 2.8, respectively. The flocculation kinetics and floc size distribution were monitored by light scattering. The characterization of flocculants showed that the tridecatmer Al(13) and bridged [Al(13)](n) with out-sphere structure were the dominant species for all flocculants in a wide pH range. The coagulation results indicated that the pre and in situ-formed [Al(13)](n) play a key role in removing particles. With the increasing concentration of [Al(13)](n), coagulation mechanisms were transformed from charge-neutralization, electro-patch coagulation to bridge-aggregation. Moreover, sweep-flocculation was involved at higher dosage besides other three mechanisms when amorphous aluminium oxides formed. Hence, chemical interaction between particles and flocculants evolved from surface adsorption to surface precipitation for aluminium polycations by virtue of species transformation.

Optimized coagulation of high alkalinity, low temperature and particle water: pH adjustment and polyelectrolytes as coagulant aids.

The Yellow River in winter as source water is characterized as high alkalinity, low temperature and low particle concentrations, which have brought many difficulties to water treatment plants. This study fully examines the optimized coagulation process of the Yellow River by conventional and pre-polymerized metal coagulants, pH adjustment and polyelectrolytes as the primary coagulants or coagulant aids. For all the metal coagulants, polyaluminum chlorides are superior to traditional metal coagulants due to their stable polymeric species and low consumption of alkalinity. The removal of natural organic matter by monomeric metal coagulants can be improved through pH adjustment, which is in accordance with the higher concentration of polymeric species formed at corresponding pH value. With the addition of polyelectrolytes as coagulant aids, the coagulation performance is significantly improved. The effective removal of dissolved organic matter is consistent with high charge density, while molecular weight is relatively important for removing particles, which is consistent with polyelectrolytes as primary coagulants. These results suggest that the coagulation mechanisms in the removal of dissolved organic matter and particles are different, which may be exploited for optimized coagulation for the typical source water in practice.

Characteristic features of Bacillus cereus cell surfaces with biosorption of Pb(II) ions by AFM and FT-IR.

In order to elucidate the potential mechanisms involved in the biosorption of metal ions, atomic force microscopy (AFM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the interaction between Pb2+ and Bacillus cereus. AFM imaging of the biomass surfaces exposed to different concentrations of lead ions solution showed a major morphological change occurred after Pb2+ biosorption. The FT-IR spectra indicated the binding characteristics of the lead ions involved the carboxyl, hydroxyl and amino groups in the biomass. Equilibrium biosorption experiments of Pb2+ were carried out to investigate the effects of pH values and the initial metal concentrations. The experimental isotherm data were then modeled using Langmuir, Freundlich, and Redlich-Peterson isotherm equations. As a result, the Redlich-Peterson model yielded the best fit of experimental data. Kinetics experiments showed the biosorption was a rapid process and the pseudo-second-order model was successfully applied to predict the rate constant of biosorption.

Comparative study on the removal technologies of 2-methylisoborneol (MIB) in drinking water.

Removal of 2-methylisoborneol (MIB) in drinking water by ozone, powdered activated carbon (PAC), potassium permanganate and potassium ferrate was investigated. The adsorption kinetics of MIB by both wood-based and coat-based PACs show that main removal of MIB occurs within contact time of 1 h. Compared with the wood-based PAC, the coat-based PAC evidently improved the removal efficiency of MIB. The removal percentage of trace MIB at any given time for a particular carbon dosage was irrelative to the initial concentration of MIB. A series of experiments were performed to determine the effect of pH on the ozonation of MIB. The results show that pH has a significant effect on the ozonation of MIB. It is conclusive that potassium permanganate and potassium ferrate are ineffective in removing the MIB in drinking water.