Electrophoresis of a particle at an arbitrary surface potential and double layer thickness: importance of nonuniformly charged conditions

Recent advances in material science and technology yield not only various kinds of nano- and sub-micro-scaled particles but also particles of various charged conditions such as Janus particles. The characterization of these particles can be challenging because conventional electrophoresis theory is usually based on drastic assumptions that are unable to realistically describe the actual situation. In this study, the influence of the nonuniform charged conditions on the surface of a particle at an arbitrary level of surface potential and double layer thickness on its electrophoretic behavior is investigated for the first time in the literature taking account of the effect of double-layer polarization. Several important results are observed. For instance, for the same averaged surface potential, the mobility of a nonuniformly charged particle is generally smaller than that of a uniformly charged particle, and the difference between the two depends upon the thickness of double layer. This implies that using the conventional electrophoresis theory may result in appreciable deviation, which can be on the order of ca. 20%. In addition, the nonuniform surface charge can yield double vortex in the vicinity of a particle by breaking the symmetric of the flow field, which has potential applications in mixing and/or regulating the medium confined in a submicrometer-sized space, where conventional mixing devices are inapplicable.     

Curvature sorting of peripheral proteins on solid-supported wavy membranes

Cellular membrane deformation and the associated redistribution of membrane-bound proteins are important aspects of membrane function. Current model membrane approaches for studying curvature sensing are limited to positive curvatures and often require complex and delicate experimental setups. To overcome these challenges, we fabricated a wavy substrate by imposing a range of curvatures onto an adhering lipid bilayer membrane. We examined the curvature sorting of several peripheral proteins binding to the wavy membrane and observed them to partition into distinct regions of curvature. Furthermore, single-molecule imaging experiments suggested that the curvature sensing of proteins on low-curvature substrates requires cooperative interactions.     

Induction of the Columnar Phase of Unconventional Dendrimers by Breaking the C2 Symmetry of Molecules

Two triazine‐based unconventional dendrimers were prepared and characterized by ¹H and ¹³C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD studies showed that these dendrimers display columnar liquid‐crystalline phases during thermal treatment. This is ascribable to breaking of their C₂ symmetry. The molecular conformations of prepared dendrimers were obtained by computer simulation with the MM3 model of the CaChe program in the gas phase. The simulation showed that the conformations of the prepared dendrimers are rather flat and disfavor formation of the LC phase. However, due to C₂‐symmetry breaking, the prepared dendrimers have structural isomers in the solid state and thus show the desired columnar phases. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks.     

Enantiotropic Nematics From Cross‐Like 1,2,4,5‐Tetrakis(4′‐alkyl‐4‐ethynylbiphenyl)benzenes and Their Biaxiality Studies

The theoretically predicted optimum length/breadth/width ratio for maximizing shape biaxiality was investigated experimentally by the facile and successful synthesis of cross‐shaped compound 3 , which showed enantiomeric nematic phase behavior. This cross‐like core structure could alternatively be viewed as two fused V‐shaped mesogens, which have recently immerged as a new direction in biaxial nematic research, at the bending tips that can act as a new structure for biaxial investigations. Whilst the thermal analysis data of compound 3 did not meet the expected theoretical values for biaxial nematics, surface‐induced biaxiality was evidenced by optical studies. Cluster‐size analysis within the nematic phase of compound 3 revealed the formation of meta‐cybotactic nematics, which approached the cluster sizes of cybotactic nematics. The split small‐angle 2D X‐ray diffraction patterns of magnetic‐field‐aligned samples indicated that the nematic phase was composed of small smectic C‐like clusters with the tilting of molecules within the clusters. The wide‐temperature‐range enantiomeric nematic phase of cross‐like compound 3 enabled the molecular skeleton to serve as an alternative skeleton to bent‐rod mesogens, which exhibited nematic phases with the potential competition of transitions to higher‐order liquid‐crystalline phases and crystallization, for future biaxial investigations.     

Hierarchical Superstructures with Control of Helicity from the Self‐Assembly of Chiral Bent‐Core Molecules

Herein, two asymmetric chiral bent‐core molecules, 3‐[(4‐{[4‐(heptyloxy)benzoyl]oxy}benzoyl)oxy]‐phenyl‐4‐[(4‐{[(1R)‐1‐methylheptyl]oxy}benzoyl)oxy] benzoate (BC7R) and 3‐[(4‐{[4‐(heptyloxy)benzoyl]oxy}benzoyl)oxy]‐phenyl‐4‐[(4‐{[(1S)‐1‐methylheptyl]oxy}benzoyl)oxy] benzoate (BC7S), were synthesized to demonstrate control of the helicity of their self‐assembled hierarchical superstructures. Mirror‐imaged CD spectra showed a split‐type Cotton effect after the formation of self‐assembled aggregates of BC7R and BC7S, thereby suggesting the formation of intermolecular exciton couplets with opposite optical activities. Both twisted and helical ribbons with preferential helicity that corresponded to the twisting character of the intermolecular exciton couplet were found in the aggregates. The formation of helical ribbons was attributed to the merging of twisted ribbons through an increase in width to improve morphological stability. As a result, control of the helicity of hierarchical superstructures from the self‐assembly of bent‐core molecules could be achieved by taking advantage of the transfer of chiral information from the molecular level onto the hierarchical scale.     

The synthesis of Lewis acid ZrO2 nanoparticles and their applications in phospholipid adsorption from Jatropha oil used for biofuel

ZrO(2) nanoparticles were successfully fabricated via a facile hydrothermal process. The diameter and surface area of the as-prepared ZrO(2) nanoparticles were approximately 5-10 nm and 102 m(2)/g, respectively. For the first time, Zr atoms with partial positive charges in a Lewis acid ZrO(2) nanoparticle adsorbent were used for the adsorption of negatively charged phospholipids from Jatropha oil. The capacity for phospholipid adsorption using the ZrO(2) nanoparticles was better than that of commercial ZrO(2) powder due to the larger surface area of the ZrO(2) nanoparticles. Phospholipid removal makes Jatropha oil a potential oil for biofuel applications.     

Synthesis of high-quality carbon nanodots from hydrophilic compounds: role of functional groups

A simple one-pot hydrothermal approach has been demonstrated for the preparation of highly water soluble and photoluminescent carbon nanodots (C-dots) from low-cost organic compounds. We found that the compounds incorporating amino and carboxylic acid groups are suitable for the preparation of highly photoluminescent and water-soluble C-dots.     

Induction of apoptosis in human breast adenocarcinoma cells MCF-7 by monapurpyridine A, a new azaphilone derivative from Monascus purpureus NTU 568

A new azaphilonidal derivative, monapurpyridine A (MPA), has recently been isolated from the fermented products of Monascus purpureus NTU 568. The structure of MPA was elucidated by nuclear magnetic resonance (1H-NMR, 13C-NMR, COSY, HMQC, and HMBC) and other spectroscopic analyses. Biological evaluation revealed that MPA could induce cell death in human breast adenocarcinoma cells MCF-7, and it has no significant toxicity to normal mammary epithelial cells M10. The MTT assay and flow cytometric analysis were employed to investigate cell viability and cell cycle influenced by MPA. Moreover, we used Western blot and caspase activity assay to demonstrate the activation of caspase-3, -8 and -9 resulted from MPA. All evidence supported that MPA was suitable for developing into a chemotherapeutic or chemopreventive agent against breast cancer.     

Induction of Apoptosis by Ethanolic Extract of <em>Corchorus olitorius </em>Leaf in Human Hepatocellular Carcinoma (HepG2) Cells via a Mitochondria-Dependent Pathway

Corchorus olitorius L., is a culinary and medicinal herb, widely used as a vegetable in several countries in Asia. Many studies have shown that C. olitorius contains several antioxidants and exhibits anti-inflammatory and anti-proliferative activities in various in vitro and in vivo settings. Recently, C. olitorius has been approved for its antitumor activity; however, the underlying molecular mechanisms remain unclear. The goal of this study was to investigate the effects of ethanol extract of C. olitorius (ECO) on the growth of human hepatocellular carcinoma (HepG2) cells and gain some insights into the underlying mechanisms of its action. We found that HepG2 cells, treated with ECO for 24 h at a concentration higher than 12.5 μg/mL, displayed a strong reduction in cell viability, whereas normal FL83B hepatocytes were not affected. DNA fragmentation and nuclear condensation were evidenced by the increased subG1 population of ECO-treated HepG2 cells. ECO triggered the activation of procaspases-3 and -9 and caused the cleavage of downstream substrate, poly ADP-ribose polymerase (PARP), followed by down-regulation of the inhibitor of caspase-activated DNase (ICAD) signaling. Moreover, the increased release of cytochrome c from mitochondria with decreased membrane potential demonstrated the apoptosis induced through the caspases cascade. Our findings indicated that ECO might be effective against hepatocellular carcinoma through induction of apoptosis via mitochondria-dependent pathway.     

Intriguing electrochemical behavior of free base porphyrins: effect of porphyrin-meso-phenyl interaction controlled by position of substituents on meso-phenyls

Electrochemical properties of substituted free base meso-tetraphenylporphyrins (H(2)T(o,o'-X)PP, H(2)T(o-X)PP, and H(2)T(p-X)PP, where X = OCH(3), CH(3), H, F, or Cl on the phenyl rings) are examined by cyclic voltammetry. When a substituent is located only at the para position of the meso-phenyl group, the difference between the first and second oxidation potentials (ΔE(ox), i.e., E(2)(ox) - E(1)(ox)), is generally significantly smaller than those of the H(2)TPPs with bulky o,o'-substituents on the phenyl group. This trend is elucidated with density functional theory calculations and attributed mainly to the sterically controlled π-conjugation of the meso-phenyl groups to the central porphyrin ring, rather than the often discussed deformation of porphyrin.