Temperature-dependent mechanistic transition for photoinduced electron transfer modulated by excited-state vibrational relaxation dynamics

The electron transfer (ET) dynamics of an unusually rigid pi-stacked (porphinato)zinc(II)-spacer-quinone (PZn-Q) system, [5-[8'-(4' '-[8' '-(2' ' ',5' ' '-benzoquinonyl)-1' '-naphthyl]-1' '-phenyl)-1'-naphthyl]-10,20-diphenylporphinato]zinc(II) (2a-Zn), in which sub-van der Waals interplanar distances separate juxtaposed porphyryl, aromatic bridge, and quinonyl components of this assembly, have been measured by ultrafast pump-probe transient absorption spectroscopy over a 80-320 K temperature range in 2-methyl tetrahydrofuran (2-MTHF) solvent. Analyses of the photoinduced charge-separation (CS) rate data are presented within the context of several different theoretical frameworks. Experiments show that at higher temperatures the initially prepared 2a-Zn vibronically excited S1 state relaxes on an ultrafast time scale, and ET is observed exclusively from the equilibrated lowest-energy S1 state (CS1). As the temperature decreases, production of the photoinduced charge-separated state directly from the vibrationally unrelaxed S1 state (CS2) becomes competitive with the vibrational relaxation time scale. At the lowest experimentally interrogated temperature ( approximately 80 K), CS2 defines the dominant ET pathway. ET from the vibrationally unrelaxed S1 state is temperature-independent and manifests a subpicosecond time constant; in contrast, the CS1 rate constant is temperature-dependent, exhibiting time constants ranging from 4x10(10) s(-1) to 4x10(11) s(-1) and is correlated strongly with the temperature-dependent solvent dielectric relaxation time scale over a significant temperature domain. Respective electronic coupling matrix elements for each of these photoinduced CS1 and CS2 pathways were determined to be approximately 50 and approximately 100 cm-1. This work not only documents a rare, if not unique, example of a system where temperature-dependent photoinduced charge-separation (CS) dynamics from vibrationally relaxed and unrelaxed S1 states can be differentiated, but also demonstrates a temperature-dependent mechanistic transition of photoinduced CS from the nonadiabatic to the solvent-controlled adiabatic regime, followed by a second temperature-dependent mechanistic evolution where CS becomes decoupled from solvent dynamics and is determined by the extent to which the vibrationally unrelaxed S1 state is populated.     

TNF-alpha upregulates PTEN via NF-kappaB signaling pathways in human leukemic cells

TNF-alpha plays a variety of biological functions such as apoptosis, inflammation and immunity. PTEN also has various cellular function including cell growth, proliferation, migration and differentiation. Thus, possible relationships between the two molecules are suggested. TNF-alpha has been known to downregulate PTEN via NF-kappaB pathway in the human colon cell line, HT-29. However, here we show the opposite finding that TNF-alpha upregulates PTEN via activation of NF-kappaB in human leukemic cells. TNF-alpha increased PTEN expression at HL-60 cells in a time- and dose-dependent manner, but the response was abolished by disruption of NF-kappaB with p65 antisense phosphorothioate oligonucleotide or pyrrolidine dithiocarbamate. We found that TNF-alpha activated the NF-kappaB pathways, evidenced by the translocation of p65 to the nucleus in TNF-alpha-treated cells. We conclude that TNF-alpha induces upregulation of PTEN expression through NF-kappaB activation in human leukemic cells.     

A simple fabrication route to a highly transparent super-hydrophobic surface with a poly(dimethylsiloxane) coated flexible mold

A super-hydrophobic and highly transparent nanostructured film was fabricated via imprinting and conformally uniform chemical anchoring of poly(dimethylsiloxane) on a controlled nanoscopic dimension.     

Preparation of a nanoporous CaCO3-coated TiO2 electrode and its application to a dye-sensitized solar cell

A nanoporous CaCO3 overlayer-coated TiO2 thick film was prepared by the topotactic thermal decomposition of Ca(OH)2, and its performance as an electrode of a dye-sensitized solar cell was investigated. As compared to bare TiO2, nanoporous CaCO3-coated TiO2 provided higher specific surface area and, subsequently, a larger amount of dye adsorption; this in turn increased short-circuit current (Jsc). Furthermore, the CaCO3 coating demonstrated increased impedance at the TiO2/dye/electrolyte interface and increased the lifetime of the photoelectrons, indicating the improved retardation of the back electron transfer, which increases Jsc, open-circuit voltage (Voc), and fill factor (ff). Thereby, the energy conversion efficiency (eta) of the solar cell improved from 7.8 to 9.7% (an improvement of 24.4%) as the nanoporous CaCO3 layer was coated onto TiO2 thick films.     

Three New Phthalide Glycosides from the Rhizomes of Cnidium officinale and Their Recovery Effect on Damaged Otic Hair Cells in Zebrafish

The extract from Cnidium officinale rhizomes was shown in a prior experiment to markedly recover otic hair cells in zebrafish damaged by neomycin. The current study was brought about to identify the principal metabolite. Column chromatography using octadecyl SiO₂ and SiO₂ was performed to isolate the major metabolites from the active fraction. The chemical structures were resolved on the basis of spectroscopic data, including NMR, IR, MS, and circular dichroism (CD) data. The isolated phthalide glycosides were assessed for their recovery effect on damaged otic hair cells in neomycin-treated zebrafish. Three new phthalide glycosides were isolated, and their chemical structures, including stereochemical characteristics, were determined. Two glycosides (0.1 μM) showed a recovery effect (p < 0.01) on otic hair cells in zebrafish affected by neomycin ototoxicity. Repeated column chromatography led to the isolation of three new phthalide glycosides, named ligusticosides C (1), D (2), and E (3). Ligusticoside C and ligusticoside E recovered damaged otic hair cells in zebrafish.     

Bis­[(2,2‐di­methyl‐1,3‐propane­diamine‐κ2N,N′)(piperidine‐2‐car­boxylato‐κ2N,O)­platinum(II)] sulfate

The title compound, [Pt(C₆H₁₀NO₂)(C₅H₁₄N₂)]₂(SO₄), crystallizes with two cations in the asymmetric unit. The two complex cations, which have a square‐planar Pt^II coordination, are chemically identical but differ slightly in the conformations of their amine groups. A neutral complex, viz. (2,2‐di­methyl‐1,3‐propane­di­amine‐κ²N,N′)bis(2‐piperidine­carb­oxyl­ato‐κN)platinum(II), is shown to form in solution and to change rapidly into the title compound.     

Aurones and Flavonols from Coreopsis lanceolata L. Flowers and Their Anti-Oxidant,Pro-Inflammatory Inhibition Effects,and Recovery Effects on Alloxan-Induced Pancreatic Islets in Zebrafish

(1) Background: Many flavonoids have been reported to exhibit pharmacological activity; a preparatory study confirmed that Coreopsis lanceolata flowers (CLFs) contained high flavonoid structure content; (2) Methods: CLFs were extracted in aqueous methanol (MeOH:H₂O = 4:1) and fractionated into acetic ester (EtOAc), normal butanol (n-BuOH), and H₂O fractions. Repeated column chromatographies for two fractions led to the isolation of two aurones and two flavonols; (3) Results: Four flavonoids were identified based on a variety of spectroscopic data analyses to be leptosidin (1), leptosin (2), isoquercetin (3), and astragalin (4), respectively. This is the first report for isolation of 2–4 from CLFs. High-performance liquid chromatography (HPLC) analysis determined the content levels of compounds 1–4 in the MeOH extract to be 2.8 ± 0.3 mg/g (1), 17.9 ± 0.9 mg/g (2), 3.0 ± 0.2 mg/g (3), and 10.9 ± 0.9 mg/g (4), respectively. All isolated compounds showed radical scavenging activities and recovery activities in Caco-2, RAW264.7, PC-12, and HepG2 cells against reactive oxygen species. MeOH extract, EtOAc fraction, and 1–3 suppressed NO formation in LPS-stimulated RAW 264.7 cells and decreased iNOS and COX-2 expression. Furthermore, all compounds recovered the pancreatic islets damaged by alloxan treatment in zebrafish; (4) Conclusions: The outcome proposes 1–4 to serve as components of CLFs in standardizing anti-oxidant, pro-inflammatory inhibition, and potential anti-diabetic agents.     

The effect of branching on the physical properties of 73/27 4‐hydroxybenzoic acid/2‐hydroxy‐6‐naphthoic acid

The 73/27 4‐hydroxybenzoic acid (HBA)/2‐hydroxy‐6‐naphthoic acid (HNA) copolyester was prepared by the inclusion of two crosslinkable oligomers. These systems were synthesized by melt polymerization and characterized using differential scanning calorimetry, thermogravimetric analysis, polarized optical microscope and wide‐angle X‐ray diffraction. The transition from thermoplastic to thermosetting character occurred when 10 wt% or above of oligomer was added to the 73/27 HBA/HNA random mixture. The melt rheology of the HBA/HNA copolyesters containing two oligomers was investigated. The copolyesters displayed an increase in complex viscosity and transition from liquid‐like to solid‐like behavior as the oligomer content increased, and finally there was no melting transition when the oligomer content reached 10 wt%. Shear storage modulus measured by a dielectric mechanical analysis decreased slightly with increasing oligomer content. An adhesive test using an aluminum sheet revealed an increase in the lap shear strength up to 5 wt% of oligomer content without a significant reduction in shear storage modulus. On the other hand, the 73/27 HBA/HNA containing 10 wt% oligomer displayed a dramatic decrease in lap shear strength. Copyright © 1999 John Wiley & Sons, Ltd.     

Characterization of short glass fiber filled polystyrene by fiber orientation and mechanical properties

A quasi-steady state, non-isothermal, compressible, inelastic, and creeping flow of polymer melt into a thin cavity is analyzed to predict fiber orientation states. Modified Cross model and Tait's state equation are adopted to consider shear-thinning behavior and compressibility of the polymer melt. Second order tensors are introduced to describe 3-dimensional fiber orientation. Flow-induced fiber orientation can be predicted by solving the equations of change for the orientation tensor with a suitable closure approximation. The orthotropic closure is applied except for the case of low interaction coefficient. Fiber orientation develops mainly due to shear flow in the skin layer and due to stretching effect in the core layer. It turns out that the compressibility, which induces additional velocity gradients during packing, reduces development of the fiber orientation. Results are dependent upon the magnitude of the interaction coefficient. The larger the interaction coefficient, the smaller the orientation development and the effect of compressibility. To predict orientation dependent mechanical properties, the orientation averaging for an arbitrary orientation is carried out from the properties of a transversely isotropic unit cell. The compressibility reduces the axial modulus and increases the transverse modulus. Opposite trends are observed for thermal expansion coefficients. It is also observed that the consideration of compressibility reduces the overall anisotropy of the molded product. Effects of compressibility on mechanical properties of the parts are reduced as the interaction coefficient becomes larger.