Mesomorphic behaviour of new azomethine liquid crystals having terminal bromo substituent

A homologous series of azomethine esters,4-n-alkanoyloxybenzylidene-4’-bromoanilines possessing even number of carbon atoms at the terminal alkanoyloxy chain(C_n-1H_2n-1COO- n = 8,10,12,14,16,18) was synthesized and characterized.Whilst n-octanoyloxy to n-dodecanoyloxy derivatives exhibited enantiotropic smectic A and smectic B phases,n-tetradecanoyloxy to n-octadecanoyloxy derivatives possessed enantiotropic smectic A and monotropic smectic B properties.n-Decanoyloxy derivatives demonstrated the optimum exhibition for both smectic A and smectic B phases.It was found that the length of terminal alkanoyloxy chain has an influence on mesomorphic properties.     

Charge-transfer guest interactions in luminescent MOFs: implications for solid-state temperature and environmental sensing

One of the ongoing goals in the field of porous materials is the design and synthesis of materials that possess chemical structures amenable for use in sensing applications. We describe the preparation, luminescence characteristics, and environmental sensing properties of variants of the aluminum-based MOF [Al(OH)(O(2)C-C(10)H(6)-CO(2))](∞). Careful activation of the open framework complex, 1, yielded a dynamic structural transformation to a non-porous form, 2, that exhibited strong inter-linker interactions and red-shifted emission characteristics indicative of dimer formation. We also demonstrate the formation of highly luminescent ground-state charge-transfer (CT) complexes between 1 and the electron-donating amines dimethylamine (DMA) (1a), and N,N-diethylaniline (DEA) (1b), both of which exhibit dual-emission characteristics and a ratiometric luminescence response that is sensitive to temperature and solvent polarity. Steady-state and time-resolved measurements on 1a, 1b, and 2 indicate that the MOF structures stabilize ground-state CT interactions that are distinct from the weakly-bound exciplexes formed in comparable mixtures of purely organic components. The spectra for 1a and 1b also indicate different temperature dependencies that correspond to thermally-activated complex formation (ΔH(f) = +1.1 ± 0.2 kcal mol(-1)) in 1a and static quenching effects (ΔH(f) = -2.2 ± 0.3 kcal mol(-1)) in 1b. The addition of ethanol, isopropanol, toluene, or chloroform to suspensions of 1b indicate destabilization of the CT state with increasing solvent polarity, which suggests the generalized application of this or related materials in sensor applications.     

NATURAL CONVECTION FROM A VERTICAL RECTANGULAR FIN

An experimental investigation of steady-state natural convection from vertical rectangular mild steel and aluminum fins was conducted using laser holographic interferometry. Infinite-fringe interferograms demonstrate the effect of fin base heating. Depending on the fin material and base temperature, the local heat transfer coefficients vary along the fin with maximum values at positions about 22-48% of the fin height measured from the base. Temperature measurements along the fin show good agreement with the classical one-dimensional corwective and adiabalic tip solutions. Hence, in the thermal design of vertical aluminum fins of low Biot numbers, the classical one-dimensional fin solutions may be used together with an average heat transfer coefficient obtained from established correlations for natural convection from an isothermal flat plate.     

Reciprocal Response of Human Oral Epithelial Cells to Internalized Silica Nanoparticles

Silica nanoparticles (SiO₂ NPs) are one of the most widely used engineered nanoparticles and can been found in a wide range of consumer products. Despite their massive global production scale, little is known about their potential effects in the context of unintended exposure or ingestion. Using TR146 cells as an in vitro model of the human oral buccal mucosa, the uptake, spatial intracellular distribution, reactive oxygen species (ROS) production, inflammatory response, and cytotoxic effects of commercial SiO₂ NPs are examined. SiO₂ NPs are shown to dock and cross the cellular membrane barrier in a dose–time‐dependent manner. Confocal sectioning reveals translocation of SiO₂ NPs into the cell nucleus after 12 h of exposure. A concentration threshold of more than 500 × 10^?6 m is observed, above which SiO₂ NPs are shown to exert significant oxidative stress with concomitant upregulation of inflammatory genes IL6 and TNFA. Further analysis of the p53 pathway and a series of apoptotic and cell cycle biomarkers reveals intracellular accumulation of SiO₂ NPs exert marginal nanotoxicity. Collectively, this study provides important information regarding the uptake, intracellular distribution, and potential adverse cellular effects of SiO₂ NPs commonly found in consumer products in the human oral epithelium.     

Ageing and collapse of bentonite gels—effects of Li,Na, K and Cs ions

The state of bentonite gels at the start of the ageing experiment must be well-defined, and this required the gels to be at a constant surface chemistry condition. This is achieved by allowing the freshly prepared gels to rest for a day. At this state, the yield stress is constant, provided that the gel is at an equilibrium breakdown state after stirring prior to each measurement. This point is also the yield stress at zero aged time. Ageing study then commenced, and the behaviour is generally characterised by an increasing yield stress with wait time. Alkali metal ion type and concentration affect the gel ageing and stability behaviour significantly. The ageing behaviour is most pronounced at low salt concentrations for the smallest and most strongly hydrated cations, Li ⁺and Na ⁺. The yield stress at any given aged time and its rate of increase are generally larger. Coarsening of these suspensions was observed. The opposite is true for the weakly hydrated K ⁺and Cs ⁺ions. At high concentrations of 0.5 and 1.0 M Cs, K and Na ions, the gels became unstable over time and phase-separated. The stability time of these weak gels was found to increase with decreasing cation size, Na > K > Cs. This stability time displayed a very strong quantitative correlation with the hydration bond length. Coarsening was also expected, but not observed due to the lack of integrity of these weak aggregates during particle size measurement. The recovery or ageing behaviour was fitted with both the Nguyen–Boger and Leong models.     

Optically tunable plasmonic color filters

We fabricated sub-wavelength patterned gold plasmonic nanostructures on a quartz substrate through the focused ion beam (FIB) technique. The perforated gold film demonstrated optical transmission peaks in the visible range, which therefore can be used as a plasmonic color filter. Furthermore, by integrating a layer of photoresponsive liquid crystals (LCs) with the gold nanostructure to form a hybrid system, we observed a red-shift of transmission peak wavelength. More importantly, the peak intensity can be further enhanced more than 10% in transmittance due to the refractive index match of the media on both sides of it. By optically pumping the hybrid system using a UV light, nematic−isotropic phase transition of the LCs was achieved, thus changing the effective refractive index experienced by the impinging light. Due to the refractive index change, the transmission peak intensity was modulated accordingly. As a result, an optically tunable plasmonic color filter was achieved. This kind of color filters could be potentially applied to many applications, such as complementary metal-oxide-semiconductor (CMOS) image sensors, liquid crystal display devices, light emitting diodes, etc.     

The mechanism of antiparallel <Emphasis Type="Italic">β</Emphasis>-sheet formation based on conditioned self-avoiding walk

By introducing an additional hydrogen bond to hydrogen bond interaction in the force field of the CSAW (Conditioned Self-Avoiding Walk) model, we investigate into the mechanism of antiparallel β-sheet formation based on the folding of a short polyalanine in gas phase. Through our numerical simulation, we detect the possible presence of a transient helix during β-sheet formation, whose presence is shown to have slowed the formation of β-sheets by an order of magnitude. While we observe the mechanisms of nucleation, zipping and induction that drives the formation of a β-sheet, we uncover a new mechanism that involves transient β-turns and short β-sheets during the formation of long β-sheets. Our results have enabled us to provide an overview on the mechanisms of β-sheet formation via two main folding pathways: slow folding through the intermediate state of transient helix, and fast folding from the nucleation of β-turn.     

Prediction of human cytochrome P450 2B6‐substrate interactions using hierarchical support vector regression approach

The human cytochrome P450 2B6 can metabolize a number of clinical drugs. Inhibition of CYP2B6 by coadministered multiple drugs may lead to drug–drug interactions and undesired drug toxicity. The aim of this investigation is to develop an in silico model to predict the interactions between P450 2B6 and novel inhibitors using a novel hierarchical support vector regression (HSVR) approach, which simultaneously takes into account the coverage of applicability domain (AD) and the level of predictivity. Thirty‐seven molecules were deliberately selected and rigorously scrutinized from the literature data, of which 26 and 11 molecules were treated as the training set and the test set to generate the models and to validate the generated models, respectively. The generated HSVR model gave rise to an r² value of 0.97 for observed versus predicted pK_m values for the training set, a q² value of 0.93 by the 10‐fold cross‐validation, and an r² value of 0.82 for the test set. Additionally, the predicted results show that the HSVR model outperformed the individual local models, the global model, and the consensus model. Thus, this HSVR model provides an accurate tool for the prediction of human cytochrome P450 2B6‐substrate interactions and can be utilized as a primary filter to eliminate the potential selective inhibitor of CYP2B6. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009     

pH-sensitive polymer-assisted refolding of urea-denatured fibroblast growth factor

A pH-responsive polymer Eudragit S-100 has been found to assist in correct folding of FGF-2(fibroblast growth factor-2) denatured with 8 mol/L urea and 10 mmol/L dithiothreitol at pH 7.2.The refolding of FGF-2 was performed by directly diluting denatured FGF-2 into a refolding buffer containing Eudragit S-100.The ability of Eudragit S-100 to enhance protein refolding level was investigated using MTr method,fluorescence emission spectroscopy and reverse phase HPLC.On the other hand,the result shows the ab...     

Visualization of Intra‐neuronal Motor Protein Transport through Upconversion Microscopy

Cargo transport along axons, a physiological process mediated by motor proteins, is essential for neuronal function and survival. A current limitation in the study of axonal transport is the lack of a robust imaging technique with a high spatiotemporal resolution to visualize and quantify the movement of motor proteins in real‐time and in different depth planes. Herein, we present a dynamic imaging technique that fully exploits the characteristics of upconversion nanoparticles. This technique can be used as a microscopic probe for the quantitative in situ tracking of retrograde transport neurons with single‐particle resolution in multilayered cultures. This study may provide a powerful tool to reveal dynamic neuronal activity and intra‐axonal transport function as well as any associated neurodegenerative diseases resulting from mutation or impairment in the axonal transport machinery.