Theoretical Study of the Adsorption/Dissociation Reactions of Formic Acid on the α‑Al₂O₃(0001) Surface

Formic acid was used as the model of lauric acid to investigate the microscopic mechanism of the anti-icing behavior and was checked to find out if it can be catalyzed to produce H₂ for fuel cells by the α-Al₂O₃(0001) 2 × 2 supercell slab model. The density functional theory with the all-electron double numerical polarized basis sets was employed. The results show that when it involves the carboxyl O and hydroxyl H atom the 1,2-dissociated adsorbate is the most stable intermediate on the dry Al₂O₃(0001) surface and is energetic barrier free to form the fairly stable ROCO- and HO-covered surface with the binding energy of 59.5 kcal/mol, and this dissociation mode has the lowest energy barrier of 14.9 kcal/mol to form the HOCO- and H₂O-covered surface after the surface is fully hydroxylated. The energetic barrier of the HCOOH dehydrogenation and dehydration reactions on the alumina surface decreased considerably from 65.3 to 30.6 kcal/mol and from 62.1 to 26.8 kcal/mol, respectively, in comparison with the gaseous decomposition. The dissociated configuration of lauric acid was tested, and it was found that it dissociated with free energy barrier through 1,2-hydrogen migration into the C₁₁H₂₃OCO- and HO-covered surface with a binding energy of 60.7 kcal/mol. The present theoretical work is useful to gain some new insights on the microscopic interaction mechanism of the superhydrophobic alumina surface fabrication procedure and on the heterogeneous catalysis reactions of the H₂ production

Molecular Dynamics Simulation of a RNA Aptasensor

Single-stranded RNA aptamers have emerged as novel biosensor tools. However, the immobilization procedure of the aptamer onto a surface generally induces a loss of affinity. To understand this molecular process, we conducted a complete simulation study for the Flavin mononucleotide aptamer for which experimental data are available. Several molecular dynamics simulations (MD) of the Flavin in complex with its RNA aptamer were conducted in solution, linked with six thymidines (T6) and, finally, immobilized on an hexanol-thiol-functionalized gold surface. First, we demonstrated that our MD computations were able to reproduce the experimental solution structure and to provide a meaningful estimation of the Flavin free energy of binding. We also demonstrated that the T6 linkage, by itself, does not generate a perturbation of the Flavin recognition process. From the simulation of the complete biosensor system, we observed that the aptamer stays oriented parallel to the surface at a distance around 36 Å avoiding, this way, interaction with the surface. We evidenced a structural reorganization of the Flavin aptamer binding mode related to the loss of affinity and induced by an anisotropic distribution of sodium cationic densities. This means that ionic diffusion is different between the surface and the aptamer than above this last one. We suggest that these findings might be extrapolated to other nucleic acids systems for the future design of biosensors with higher efficiency and selectivity

Highly Sensitive Strategy for Hg²⁺ Detection in Environmental Water Samples Using Long Lifetime Fluorescence Quantum Dots and Gold Nanoparticles

The authors herein described a time-gated fluorescence resonance energy transfer (TGFRET) sensing strategy employing water-soluble long lifetime fluorescence quantum dots and gold nanoparticles to detect trace Hg²⁺ ions in aqueous solution. The water-soluble long lifetime fluorescence quantum dots and gold nanoparticles were functionalized by two complementary ssDNA, except for four deliberately designed T–T mismatches. The quantum dot acted as the energy-transfer donor, and the gold nanoparticle acted as the energy-transfer acceptor. When Hg²⁺ ions were present in the aqueous solution, DNA hybridization will occur because of the formation of T–Hg²⁺–T complexes. As a result, the quantum dots and gold nanoparticles are brought into close proximity, which made the energy transfer occur from quantum dots to gold nanoparticles, leading to the fluorescence intensity of quantum dots to decrease obviously. The decrement fluorescence intensity is proportional to the concentration of Hg²⁺ ions. Under the optimum conditions, the sensing system exhibits the same liner range from 1 × 10^–9 to 1 × 10^–8 M for Hg²⁺ ions, with the detection limits of 0.49 nM in buffer and 0.87 nM in tap water samples. This sensor was also used to detect Hg²⁺ ions from samples of tap water, river water, and lake water spiked with Hg²⁺ ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. In comparison to some reported colorimetric and fluorescent sensors, the proposed method displays the advantage of higher sensitivity. The TGFRET sensor also exhibits excellent selectivity and can provide promising potential for Hg²⁺ ion detection

Analysis of migration and invasion of CpG-ODN treated HB cells.

<p>(<b>A</b>) Evaluation of cell migration by scratch wound healing assay: Cells were allowed to migrate with and without 0.8 μM CpG-ODN. Cell migration into the wound surface was then monitored by microscopy after 24 h of the CpG-ODN treatment and reported as the width of remaining wounded area relative to the initial wound area. (<b>B</b>)Evaluation of cell invasion by transwell assay. Representative photomicrographs of the membrane-associated cells (jacinth part) were assayed by Eosin staining (×400). (<b>C</b>)Graphical representation of scratch wound assay. The average distance of cell invasion was significantly greater in the CpG-ODN treated sample. **P<0.01. (<b>D</b>)Semi-quantitative analysis of the stimulate-invasion effects of CpG-ODN on HB cells. “% of control” denotes the mean number of the cells expressed as a proportion of the control group and the average of three independent experiments ± S.D. **p<0.01, compared with the lane 2; ^★p<0.05, compared with the lane 3. (<b>E</b>)Colorimetric analysis of CpG-ODN modulation of HB cell invasiveness with different concentrations (0∼0.8 μM) for 48 h by the CytoSelect cell invasion assay. *p<0.05; **p<0.01, compared with lane 1.</p

Effect of CpG-ODN on NF- κB and AP-1 activity.

<p>(<b>A</b>) Effects of CpG-ODN on the expression of NF- κB subunit. HB cells were treated with 0.8 μM CpG-ODN at indicated time period (0∼24 h) and the protein levels were determined using Western blot. β-actin was used as an internal control. (<b>B</b>) Changes in NF- κB subunit protein levels compared with the control as determined by densitometric scanning of the immunoreactive bands. (<b>C</b>) Effects of CpG-ODN on the expression of AP-1 subunit. (<b>D</b>) Changes in AP-1 subunit protein levels compared with control as determined by densitometric scanning of the immunoreactive bands. (*P<0.05; **P<0.01, compare with the control) (<b>E</b>) Electrophoretic mobility shift analysis (EMSA) analysis of AP-1 in HB cell lines before and after treatment with 0.8 μM CpG-ODN at indicated time period (0∼24 h). (*P<0.05; **P<0.01, compared with the panel 1), (^★★P<0.01, compared with the panel 5). (<b>F</b>) CpG-ODN treatment enhances the DNA-binding activity of AP-1(c-Fos/Jun-D) to the promoter of MMP-2 in a time-dependent manner.</p

Role of MMP-2 in TLR-9/AP-1 mediated cancer cell invasion.

<p>(<b>A</b>) Expression of TLR-9 protein in HB cells before and after 48 hr of transfection. β-actin was used as an internal control. (<b>B</b>) CpG-ODN treatment does not enhance AP-1 activity in HB cells transfected with special siRNA against TLR-9. (**P<0.01, NS: no significant) (<b>C</b>) The interferon effect of AP-1 inhibitor and/or TLR-9-RNAi on the CpG-ODN induced MMP-2 expression/activity as well as subsequent cancer cell invasion. (**P<0.01, compared with the panel 1), (^★★P<0.01, compared with the panel 2)</p

Effects of CpG-ODN on MMP-2 and MMP-9 expressions.

<p>(<b>A</b>) Analysis of MMP-2 and -9 protein expression in cells treated with indicated doses of CpG-ODN and harvested at 24 h. β-actin served as an internal control. (<b>B</b>) Determined secretion of MMP-2 and -9 was subsequently quantified by ELISA analysis, and presented as means ± S.D. of three repeats from one independent study. (<b>C</b>) HB cells in serum-free medium were treated with various concentrations (0∼0.8 μM) of CpG-ODN for 24 h. The culture medium of cells after treatment was subjected to gelatin zymography to analyze the activity of MMP-2 and -9; *p<0.05; **p<0.01, compared with the control.</p

Fractal Reconstruction of Microscopic Rough Surface for Soot Layer during Ceramic Filtration Based On Weierstrass–Mandelbrot Function

The microscopic surface of soot layer on the external surface of filtration elements is rather hard to reconstruct. In this study, an incinerator–filter setup was designed to mimic the capture of soot particles in flue gas to achieve the samples to construct the rough soot-layer surface. The specific velocities around the ceramic cartridge were determined by particle image velocimetry (PIV) measurement. Resorting to a box-counting method, the fractal dimensions (FDs) were determined by Richardson–Mandelbrot method with binary images of samples. Accordingly, the in situ thickness of soot layer was constructed with consideration of particle deposit and the microscopic rough surfaces were modeled by employing Weierstrass–Mandelbrot (W-M) function. Additionally, a comparison between the constructed surface and real surface achieved from the image taken by atomic force microscopy (AFM) was performed. The results suggest that all roughness deviations of constructed surface from real surface of soot layer not exceed 5%