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Background: Colorectal cancer (CRC) has high mortality, and 5-fluorouracil (5-FU) is a common clinical chemotherapeutic drug. The current study aimed to investigate the role of FAT4 in chemosensitivity of CRC cells treated by 5-FU. Methods: The immunohistochemistry and qRT-PCR was conducted to measure the FAT4 expression in CRC and adjacent tissues. The FAT4 expression was determined by qRT-PCR and Western blot, comparison of FAT expression between normal and several CRC cell lines was then made, so as to identify cell lines with the highest (LS174T) and the lowest (SW-620) expressions of FAT4 . The effects of 5-FU stimulation at various doses on cell viability were determined by CCK-8, and the level of FAT4 was also measured. After FAT4 knockdown in LS174T or FAT4 overexpression in SW-620 with or without pretreatment of 5-FU (30 µg/mL), cell growth, colony formation, cell migration and invasion, angiogenesis were determined by flow cytometry, wound-healing, transwell assay and tube formation assay, respectively. The expression levels of epithelial-mesenchymal transition (EMT) markers were detected by qRT-PCR and Western blot. Results: FAT4 was down-regulated in CRC tissues and cells, cell viability of CRC cells was decreased. The level of FAT4 was increased with the increase of 5-FU concentrations. Moreover, 5-FU stimulation increased FAT4 expression, and reduced cell proliferation, migration, invasion, angiogenesis and cell EMT process, furthermore, such effects of 5-FU stimulation could be enhanced by FAT4 overexpression but reversed by FAT4 knockdown. Conclusions: Upregulation of FAT4 could increase the sensitivity of CRC cells to 5-FU.

Exploration of the biological effects of transition metal ions in acupuncture points is essential to clarify the functional mechanism of acupuncture treatment. Here we show that in the SP6 acupuncture point (Sanyinjiao) the Fe ions are in a high-spin state of approximately t2g4.5eg1.5 in an Fe-N(O) octahedral crystal field. The Fe K-edge synchrotron radiation X-ray absorption fine structure results reveal that the Fe-N and Fe-O bond lengths in the SP6 acupuncture point are 2.05 and 2.13 A, respectively, and are 0.05-0.10 A longer than those in the surrounding tissue. The distorted atomic structure reduces the octahedral symmetry and weakens the crystal field around the Fe ions by approximately 0.3 eV, leading to the high-spin configuration of the Fe ions, which is favorable for strengthening the magnetotransport and oxygen transportation properties in the acupuncture point by the enhanced spin coherence. This finding might provide some insight into the microscopic effect of the atomic and electronic interactions of transition metal ions in the acupuncture point. Graphical Abstract ᅟ.

Direct and efficient photocatalytic water splitting is critical for sustainable conversion and storage of renewable solar energy. Here, we propose a conceptual design of two-dimensional C3N4-based in-plane heterostructure to achieve fast spatial transfer of photoexcited electrons for realizing highly efficient and spontaneous overall water splitting. This unique plane heterostructural carbon ring (Cring)–C3N4 nanosheet can synchronously expedite electron–hole pair separation and promote photoelectron transport through the local in-plane π-conjugated electric field, synergistically elongating the photocarrier diffusion length and lifetime by 10 times relative to those achieved with pristine g-C3N4. As a result, the in-plane (Cring)–C3N4 heterostructure could efficiently split pure water under light irradiation with prominent H2 production rate up to 371 μmol g–1 h–1 and a notable quantum yield of 5% at 420 nm.

Enhancing catalytic water-splitting activity under mild environments is significant to solve the long-standing cost, safety and stability issues in photoelectrochemical cells. Here, we demonstrate the crucial role of improving surface H transfer in achieving efficient water-splitting catalytic activity of Co3O4 nanowire arrays in near-neutral pH working electrolytes. Under weak OH circumstances, the impedance of mass transfer quickly multiplies and the catalytic current declines to a current plateau in the region of 1.7–2.1 V vs. RHE, due to the surface H concentration approaching a threshold value in the range of 10−3–10−4 M. The proper choice of buffering agents to facilitate the mass transfer, with 0.1 M KPi as a prototype, would decrease the overpotential by 500 mV for neutral electrolyte and favors to achieve a catalytic current comparable to that under strong alkali environments (pH > 13). These results also provide a solid guideline for extending the electrocatalytic utility of other transition metal catalysts to near-neutral pH environments.

The MFI/MCM-41 composite material with bimetallic Fe and Co incorporation was prepared using templating method via a two-step hydrothermal crystallization procedure. The obtained products were characterized by a series of techniques including powder X-ray diffraction, N2 sorption, transmission electron microscopy, scanning electron microscope, H2 temperature programmed reduction, thermal analyses, and X-ray absorption fine structure spectroscopy of the Fe and Co K-edge. The catalytic properties of the products were investigated by residual oil hydrocracking reactions. Characterization results showed that the FeCo-MFI/MCM-41 composite simultaneously possessed two kinds of stable meso- and micro-porous structures. Iron and cobalt ions were incorporated into the silicon framework, which was confirmed by H2 temperature programmed reduction and X-ray absorption fine structure spectroscopy. This composite presented excellent activities in hydrocracking of residual oil, which was superior to the pure materials of silicate-1/MCM-41.

In this study, we investigated the Cr(VI) uptake mechanism in an indigenous Cr(VI)-tolerant bacterial strain - Bacillus cereus through batch and microscopic experiments. We found that both the cells and the supernatant collected from B. cereus cultivation could reduce Cr(VI). The valence state analysis revealed the complete transformation from Cr(VI) into Cr(III) by living B. cereus. Further X-ray absorption fine structure and Fourier transform infrared analyses showed that the reduced Cr(111) was coordinated with carboxyl and amido functional groups from either the cells or supernatant. Scanning electron microscopy and atomic force microscopy observation showed that noticeable Cr(III) precipitates were accumulated on bacterial surfaces. However, Cr(111) could also be detected in bacterial inner portions by using transmission electron microscopy thin section analysis coupled with energy dispersive X-ray spectroscopy. Through quantitative analysis of chromium distribution, we determined the binding ratio of Cr(111) in supernatant, cell debris and cytoplasm as 22%, 54% and 24%, respectively. Finally, we further discussed the role of bacterium-origin soluble organic molecules to the remediation of Cr(Vi) pollutants. (C) 2011 Elsevier Ltd. All rights reserved.

Si 1− x Mn x diluted magnetic semiconductor films were deposited on the p-Si (100) single crystal wafer using magnetron sputtering method. Post-rapid thermal annealing treatments were performed at temperatures of 700 °C, 800 °C, and 900 °C in an argon atmosphere for approximately 5 min. Alternating gradient magnetometer, scanning electron microscope, atomic force microscope, X-ray diffraction and X-ray absorption near-edge structure spectra were employed to characterize magnetic properties and structure of the as-grown and annealed films. The films were about 2.8 μm thick and the RMS roughness of the surface was about 5–10 nm. All samples exhibit ferromagnetism at room temperature and the saturation magnetization reaches at the maximum value for the sample annealed at 700 °C. The silicide MnSi 1.7 was observed in the annealed samples. X-ray absorption near-edge structure spectra indicated that Mn atoms preferred to occupy substitutional or interstitial sites instead of precipitating to form silicide when annealing at 700 °C. It is inferred that the observed ferromagnetism is attributed to the interstitial and substitutional Mn dimers, which existed mostly in the sample annealed at 700 °C. The weaker ferromagnetism of the 900 °C annealed sample was closely related to the increased content of Mn 4 Si 7 compound.

Protein splicing is a unique post-translational process in which an intein excises itself from a precursor with the concomitant ligation of flanking sequences. The binding of zinc to intein inhibits protein splicing reversibly and EDTA relieves the inhibition. Copper was found to inhibit protein trans splicing; however, the recovery of intein splicing required both EDTA and TCEP, suggesting a different inhibition mechanism for copper compared to zinc. In this work, we have investigated the binding properties and inhibition effects of copper ions on the RecA intein from Mycobacterium tuberculosis. Both Cu(+) and Cu(2+) exhibited high binding affinity to inteins, while different binding sites were identified. Cu(2+) coordinates to Cys1, the key residue involved in the mechanism of protein splicing, however, Cu(+) does not coordinate to cysteine. An in vitro inhibition assay indicated that monovalent Cu(+) demonstrates reversible inhibition to protein splicing, and the inhibitory efficiency is comparable to Zn(2+). Redox reaction between Cu(2+) and cysteine in inteins were observed and the rate constants were determined. The results suggested a dual role for Cu(2+) in the inhibition of intein splicing: strong coordination of Cu(2+) to key residues (including Cys1) in the intein, and subsequent oxidation of Cys1, the residue required for the N-->S acyl shift step in protein splicing. A kinetic study suggested that the coordination could be the major cause of inhibition effect of Cu(2+) initially, whereas the redox reaction could play an additional role in inhibition at a later stage.

The interfacial and surface structures of CeO2−TiO2 mixed oxides prepared by the sol−gel method have been investigated in detail by means of X-ray diffraction (XRD), BET surface area measurement, X-ray absorption spectroscopy (XAS), high-resolution transmission electron microscope (HRTEM), and selective chemisorption of methyl orange. TiO2 and CeO2 are in the anatase phase and the cubic fluorite phase in CeO2−TiO2 mixed oxides, respectively. The mixed oxides exhibit much higher surface areas than the individual oxides and are with both mesopores and micropores. XAS results suggest that Ce atoms nucleate as cubic [CeO8] polyhedrons with the formation of a Ce−O−Ti interface in mixed oxides. With the increasing Ce/TiO2 weight ratio, the cubic fluorite CeO2 crystallites gradually develop. TiO2 anatase forms ultrafine particles in mixed oxides, whose local structure is stabilized by the presence of CeO2. HRTEM results reveal that the exposed surfaces of mixed oxides depend on the Ce concentration. Chemisorptio...

Endowing transition-metal oxide electrocatalysts with high water oxidation activity is greatly desired for production of clean and sustainable chemical fuels. Here, we present an atomically thin cobalt oxyhydroxide (γ-CoOOH) nanosheet as an efficient electrocatalyst for water oxidation. The 1.4 nm thick γ-CoOOH nanosheet electrocatalyst can effectively oxidize water with extraordinarily large mass activities of 66.6 A g(-1), 20 times higher than that of γ-CoOOH bulk and 2.4 times higher than that of the benchmarking IrO2 electrocatalyst. Experimental characterizations and first-principles calculations provide solid evidence to the half-metallic nature of the as-prepared nanosheets with local structure distortion of the surface CoO(6-x) octahedron. This greatly enhances the electrophilicity of H2O and facilitates the interfacial electron transfer between Co ions and adsorbed -OOH species to form O2, resulting in the high electrocatalytic activity of layered CoOOH for water oxidation.

X-ray absorption fine structure (XAFS) has experienced a rapid development in the last three decades and has proven to be a powerful structural characterization technique nowadays. In this review, the XAFS basic principles including the theory, the data analysis, and the experiments have been introduced in detail. To show its strength as a local structure probe, the XAFS applications in semiconductors are summarized comprehensively, that is, thin films, quantum wells and dots, dilute magnetic semiconductors, and so on. In addition, certain new XAFS-related techniques, such as in-situ XAFS, micro-XAFS, and time-resolved XAFS are also shown.

Fluorescence x-ray absorption fine structure and x-ray diffraction are used to study the structures of super-hard TiN/Si3N4 multilayer films deposited by reactive magnetron sputtering at temperatures of 20, 200, 500 and 800 °C. The results clearly reveal the presence of interfacial intermixing between adjacent TiN and Si3N4 layers. And the interlayer is composed of TiSixN1−x solid solution with an NaCl-like structure. Increasing the growth temperature from 20 to 500 °C, the crystalline quality of the pure TiN layer improves significantly, and the thickness of the interlayer rises from 2.5 to 5.0 A. For the TiN/Si3N4 multilayer film grown at 500°C, the interfacial layer is composed of TiSi0.24N0.76 solid solution, where the Ti–N bond length (2.07 A) is largely shrunk as compared with the value (2.12 A) in the pure TiN layer. When growth temperature rises to 800°C, the composition of the interfacial layer becomes TiSi0.3N0.7 and reaches a thickness of 7.8 A. We propose that the TiSixN1−x interlayer with obviously contracted Ti–N bond length is an important hardening factor for the crystalline/amorphous TiN/Si3N4 multilayer films grown at high temperatures.

A method of incorporating iron onto the mesoporous silica network using potassium ferricyanide (K 3 Fe (CN) 6 ) as the iron source was established. The Fe (CN) 6 3 + ions interact with the template and attached onto the silica network after the as-synthesized sample calcined at 823 K. FT-IR spectroscopy provided a clear evidence for the interaction between cyanide ligands and template. XANES spectroscopic displayed that the Fe 3 + changed from octahedral to tetrahedral coordinated during thermal treatment. XRD and HRTEM results indicated that the iron ions incorporated onto the silica network without destroying the lattice structure of the parent MCM-41. The synthesized material exhibited a good activity for phenol hydroxylation.

The driving mechanism of the metal-insulator transition (MIT) in VO(2) has always attracted attention, in particular with regards to understanding if and how the doping mechanism may tune the MIT transition temperature. However, due to the lack of detailed local structural information, in this oxide the underlying MIT mechanism is still matter of debate. In this contribution on the V(1-x)W(x)O(2) system, we attempt to clarify the origin of the MIT induced by tungsten doping. Combining W L(3)-edge and V K-edge extended X-ray absorption fine-structure (EXAFS) spectroscopy, the local structures around both V and W have been obtained. The data point out the occurrence of internal stress along the V-V chains induced by doping. It reaches a critical value that remains constant during the transition. The main effect of the internal stress on the vanadium local structure has also been identified. Actually, upon increasing the dopant concentration, the tilt of the V-V pairs towards the apex oxygen atoms in the VO(6) octahedron decreases while the V-V bond lengths remain unchanged. The electronic structure has also been investigated by O K-edge X-ray absorption near-edge structure (XANES) spectroscopy. Actually, at high doping concentrations the interaction of O(2p) and the V d(∥) state increases, while the hybridization of O(2p) and V π* decreases. The O(2p)-V(3d) hybridization is therefore an essential parameter correlated with the decreasing transition temperature in the V(1-x)W(x)O(2) system.

Understanding the formation process in the controlled synthesis of nanocrystals will lead to the effective manipulation of the morphologies and properties of nanomaterials. Here, in-situ UV-vis and X-ray absorption spectroscopies are combined to monitor the tracks of the nucleation pathways in the solution synthesis of platinum nanocrystals. We find experimentally that the control over nucleation pathways through changing the strength of reductants can be efficiently used to manipulate the resultant nanocrystal shapes. The in-situ measurements show that two different nucleation events involving the formation of one-dimensional "Pt(n)Cl(x)" complexes from the polymerization of linear "Cl(3)Pt-PtCl(3)" dimers and spherical "Pt(n)(0)" clusters from the aggregation of Pt(0) atoms occur for the cases of weak and strong reductants; and the resultant morphologies are nanowires and nanospheres, respectively. This study provides a crucial insight into the correlation between the particle shapes and nucleation pathways of nanomaterials.

The mesoporous ferrisilicates (MFS) with high iron content were synthesized by pH-modification method, and the iron content could be up to 10.5 wt.% (Si/Fe = 8). The pH was kept less than 2 at pre-hydrothermal synthesis step and was adjusted to 11 during hydrothermal step. The samples were characterized by XRD, HRTEM, N2-sorption, XRF, FTIR, DRUV–vis, Fe K-edge EXAFS, EPR, and DSC. The results suggested that the MFS materials were ordered 2D hexagonal mesophase of MCM-41, and the iron atoms were tetrahedral coordinated in the silica framework. This material could efficiently catalyze the hydroxylation of phenol in water medium using H2O2 as an oxidant, and the phenol conversion could be up to 52% under the optimal experimental conditions.

Understanding the initial nucleation mechanism of monodisperse nanocrystals (NCs) during synthesis process is an important prerequisite to control the desired sizes and to manipulate the properties of nanoscale materials. The acquisition of information for the small nanocluster nucleation process, however, still remains challenging. Here, using a continuous-flow in situ X-ray absorption fine structure (XAFS) spectroscopy for time-resolved studies, we have clarified the initial kinetic nucleation of Au clusters under the grain size of 1 nm for the classical Au NCs synthesis via the reduction of AuCl(4)(-) in aqueous solution. The in situ XAFS results present the experimental revelation of the formation of intermediate Cl(3)(-)Au-AuCl(3)(-) dimer and the subsequent higher complexes 'Au(n)Cl(n+x)' in the initial nucleation stage. We propose a kinetic three-step mechanism involving the initial nucleation, slow growth, and eventual coalescence for the Au NCs formation, which may be helpful for the synthesis of metallic nanomaterials.

First-principles study on the energetic stability, electronic structure, and magnetic coupling in Mn-doped silicon with various configurations has been performed systematically. The results show that the poly-Mn atoms prefer to aggregate in the Mn-doped silicon dilute magnetic semiconductor. It is found that the tetrahedral interstitial Mn $({\text{Mn}}_{T})$ atoms assemble together via an intervening substitutional Mn $({\text{Mn}}_{\text{Si}})$ ion, subsequently forming the generally favored ${\text{Mn}}_{T}{\text{-Mn}}_{\text{Si}}{\text{-Mn}}_{T}$-type complexes. The dominant $d\text{\ensuremath{-}}d$ exchange interactions between the ${\text{Mn}}_{\text{Si}}$ and ${\text{Mn}}_{T}$ make all Mn ions in the ${\text{Mn}}_{T}{\text{-Mn}}_{\text{Si}}{\text{-Mn}}_{T}$ structures interact ferromagnetically with each other.

The local structure of dilute Ge impurity in the Si host has been studied by fluorescence x‐ray absorption fine structure spectra through multiple‐scattering data analysis method. Contrary to the elongation of 0.029 A for the Ge‐Si distance in the first shell, the Ge‐Si interatomic distance in the second shell shows a contraction of about 0.013 A relative to the corresponding Si‐Si distance in the Si host. This coincides with the theoretical prediction by Mousseau and Thorpe [Phys. Rev. B 46, 15887 (1992)] which includes both the bond length mismatch and bond‐angle deviation. It turns out that the contraction of the second‐shell Ge‐Si distance is due to the deviation of Ge–Si–Si bond‐angle from the ideal tetrahedral angle. From the Ge‐Si distances within the first three shells, it is revealed that the dilute Ge doped into Si host can lead to the local distortion rather than the average lattice change.

Electrochemical impedance spectroscopy has been used for the characterisation of electrodes modified with different polythiophenes, namely poly[4,4′-bis(butylsulfanyl)-2,2′-bithiophene], poly[4,4′-bis(methylsulfanyl)-2,2′-bithiophene] and poly(3-methylthiophene), at different applied potentials, using different supporting electrolytes. By comparison of the results obtained under experimental conditions in which n-doping is prevented and those obtained from tests where it does occur, some general features have been deduced, all of them being coherently described by a recently proposed ‘generalised transmission line circuit’ model: impedance plots at different applied potentials exhibit progressive changes which are well accounted for by the ‘evolving’ model. The results obtained on the n-doping process of S -alkyl substituted polymers suggest a behaviour interestingly similar to that exhibited in the p-doping; this supports a symmetry that was also found by us in a previous work, with respect to the incorporation and release of counterions during the n- and p-charge–discharge processes.

Pt-based alloys have recently triggered a lot of attentions due to their important potential industrial applications. They provide great opportunities for the development of low-cost and high-performance fuel-cell catalysts. Many studies have already pointed out the excellent physico-chemical properties of Pt-based alloys, intimately related to their internal structure. Great efforts have been spent to characterize shape, homogeneity, dispersion, alloying extent and kinetic growth of Pt-based nano-particles. Here, we present Cu-Pt bimetallic nano-particles synthesized by the thermal decomposition method under oleylamine and OE coordination. HRTEM images show that Cu-Pt nanostructures having size of about 1.2 nm includes about 35 atoms capped by the surfactant with OA. Accurate structural information of this system has been obtained by XRD and XAFS. A charge transfer mechanism has been observed and Pt occupied Cu sites in these Cu-Pt nanoparticles.

Understanding the kinetic mechanism during ligand adsorption on gold nanocrystals is important for designing and fine-tuning their properties and implications. Here, we report a kinetic study on the adsorption process of dodecanethiol ligands on Au nanocrystals of 3.3 nm by an in situ time-resolved X-ray absorption fine structure technique. A two-step process of dodecanethiol adsorption on Au NC surfaces is proposed based on the obtained ligand coverage, which shows a quick increase from 0 to 0.40 within the first 20 min, followed by a much slower increase to the limiting value of 0.94. In-depth analysis suggests that the first stage involves the quick adsorption of dodecanethiol to the corner and edge sites of Au NCs surfaces, leading to remarkable surface Au-Au bond length relaxation (from 2.79 to 2.81 angstrom) and pronounced gold-to-ligand charge transfer. The second step that corresponds to the much slower adsorption process to the surface facets could be described by the Langmuir kinetics equation with an adsorption rate constant of 0.0132 min(-1) and an initial coverage of 0.41, in good agreement with the initially preferable adsorption of thiols to the most favorable sites.

The controllable synthesis route of Co doped GaN nanowires was developed and the structural and magnetic properties of Co doped GaN nanowires were studied. The results indicate that Co atoms substitute Ga sites in GaN lattice, suggesting the intrinsic nature of ferromagentism at room temperature.

The complicated three-dimensional interior structures of the polycrystalline hollow zinc oxide microspheres were clearly obtained by the nondestructive nanocomputed tomography (nano-CT) technique. The parameters such as diameter, volume, porosity, and surface area were calculated by the quantitative analysis of reconstructed data. Especially, three single selected particles with different typical structures were separated and compared. With these results, the distinction of the particles can be clearly understood in nanoscale. This study reveals that nano-CT is an effective and competent tool for investigating the three-dimensional interior structures of nanomaterials in the natural environment.

Cu and Co ions co-doped Zn0.95?xCuxCo0.05O (0 ? x ? 0.08) diluted magnetic semiconductors (DMSs) prepared by the sol?gel method were investigated by x-ray absorption fine structure (XAFS). Although the Co K-edge XAFS data indicate that the doped Co ions are located substitutionally at the Zn sites for all the Zn0.95?xCuxCo0.05O DMSs, the CuK-edge XAFS analysis combined with XRD results reveals that the doped Cu ions are separated to form a CuO phase for samples calcined at 1073?K. After being sintered at a higher temperature of 1473?K, the Cu ions with low Cu concentration (x ? 0.02) are substantially incorporated into the ZnO host lattice, while a small proportion of CuO clusters still coexist in the samples with a higher Cu concentration (x ? 0.05). The solubility of the doped Cu ions in Zn0.95Co0.05O DMS is estimated as about 0.04. The results provide experimental guidance in the synthesis of the co-doped ZnO based DMSs.

X-ray absorption fine structure (XAFS) and first-principles calculations were employed to study the structure and ferromagnetism origin of Zn0.97Mn0.03O thin film grown by metal organic chemical vapor deposition. The magnetization measurements indicate that this sample is ferromagnetic at room temperature. The Mn ions are located at the substitutional Zn sites as revealed by the Mn K-edge XAFS spectroscopy. Moreover, the O K-edge XAFS analysis indicated the existence of numerous Zn vacancies. Based on first-principles calculations, the authors propose that the Zn vacancy can induce the room-temperature ferromagnetism in Mn-doped ZnO.