QM/MM investigation of the degradation mechanism of the electron-transporting layer

The mechanism of charge transfer among tris(8-hydroxyquinolinate)aluminum (Alq₃) molecules in the electron-transporting layer (ETL) under amorphous conditions was theoretically investigated using both quantum mechanical/molecular mechanical (QM/MM) calculations and molecular dynamics (MD) simulations. The rate constant of the electron transfer was estimated for the equilibrated structure taken from the QM/MM MD simulations, based on the hopping model and Marcus theory. It was found that the coordination of a (LiF)₄ cluster in ETL drastically lowers the energy of the lowest unoccupied molecular orbital in the Alq₃ molecule. The small rate constant, namely the slow charge mobility, in ETL is believed to be causally related to the low-lying delocalized unoccupied molecular orbital of Alq₃ coordinated by the (LiF)₄ cluster. The results suggest that their interaction has a considerable influence on efficiency and is attributed in part to ETL degradation in organic light-emitting diodes.     

Chiral Brønsted acid catalyzed stereoselective addition of azlactones to 3-vinylindoles for facile access to enantioenriched tryptophan derivatives

Syn-gled out: The syn diastereo- and enantioselective addition of azlactones to 3-vinylindoles was accomplished by using a chiral, binapthol-derived, Br?nsted acid catalyst (see scheme). This method enables facile access to tryptophan derivatives with adjacent quaternary and tertiary stereogenic centers, which are potentially useful for the synthesis of peptidomimetics.     

Scanning near-field IR microscopy of proteins in lipid bilayers

We use infrared near-field microscopy to chemically map the morphology of biological matrices. The investigated sample is built up from surface-tethered membrane proteins (cytochrome c oxidase) reconstituted in a lipid bilayer. We have carried out infrared near-field measurements in the frequency range between 1600 and 1800 cm(-1). By simultaneously recording the topography and chemical fingerprint of the protein-tethered lipid bilayer with a lateral resolution of 80 nm × 80 nm, we were able to probe locally the chemical signature of this membrane and to provide a local map of its surface morphology.     

Analysis of the photomagnetic properties of cyano-bridged heterobimetallic complexes by X-ray diffraction

Single crystal synchrotron X-ray diffraction measurements have been carried out on [Nd(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O (DMF = dimethyl-formamide), 1; [Y(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 2; [Ce(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 3; [Sm(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 4; [Tb(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 5; [Yb(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 6; and [Nd(DMF)(4)(H(2)O)(3)(μ-CN)Co(CN)(5)]·H(2)O, 7, at 15(2) K with and without UV illumination of the crystals. Significant changes in unit cell parameters are observed for all of the iron-containing complexes, while compound 7 shows no response to UV illumination. These results are consistent with previous results and are furthermore reproduced by powder synchrotron X-ray diffraction for compounds 1 and 7. Photoexcited crystal structures have been determined for 1-6 from refinements of two-conformer models, and excited state occupancies in the range 80-94% are found. Significant bond length changes are observed for the Fe-ligand bonds (up to 0.06 ?), the cyano bonds (up to 0.02 ?), and the lanthanide-ligand bonds (up to 0.1 ?). On the contrary, powder X-ray diffraction on the simple compound K(3)Fe(CN)(6), 8, upon UV illumination does not show any structural changes, suggesting that the photomagnetic effect requires the presence of both the transition metal and the lanthanide ion. Photomagnetic measurements show an increase in magnetization of the excited state of 1 of up to 3%, which is much diminished compared with previously published values of 45%. Furthermore, they show that the isostructural complex [La(DMF)(4)(H(2)O)(3)(μ-CN)Fe(CN)(5)]·H(2)O, 9, exhibits identical magnetic responses in the UV-induced excited crystal structure.     

Critical behavior of megabase-size DNA toward the transition into a compact state

We studied the changes in the higher-order structure of a megabase-size DNA (S120-1 DNA) under different spermidine (SPD) concentrations through single-molecule observations using fluorescence microscopy (FM) and atomic force microscopy (AFM). We examined the difference between the folding transitions in S120-1 DNA and sub-megabase-size DNA, T4 DNA (166 kbp). From FM observations, it is found that S120-1 DNA exhibits intra-chain segregation as the intermediate state of transition, in contrast to the all-or-none nature of the transition on T4 DNA. Large S120-1 DNA exhibits a folding transition at lower concentrations of SPD than T4 DNA. AFM observations showed that DNA segments become aligned in parallel on a two-dimensional surface as the SPD concentration increases and that highly intense parallel alignment is achieved just before the compaction. S120-1 DNA requires one-tenth the SPD concentration as that required by T4 DNA to achieve the same degree of parallel ordering. We theoretically discuss the cause of the parallel ordering near the transition into a fully compact state on a two-dimensional surface, and argue that such parallel ordering disappears in bulk solution.     

Solid phase total synthesis of callipeltin E isolated from marine sponge Latrunculia sp.

Solid phase total synthesis of callipeltin E (1), truncated linear peptide isolated from marine sponge, Latrunculia sp. was achieved. Our strategy based on traditional Fmoc-SPPS was in common use TFA-treatment final deprotection to reach callipeltin E (1) contained acid-sensitive βMeOTyr.     

Preparation of an Electrode Modified with an Electropolymerized Film as a Mediator of NADH Oxidation and Its Application in an Ethanol/O2 Biofuel Cell

This paper reports a novel mediator for the oxidation of β‐nicotinamide adenine dinucleotide (NAD⁺/NADH), an electropolymeric film (pAPRu) of [Ru(NH₂‐phen)₃]²⁺. A pAPRu‐modified electrode was prepared via electropolymerization and exhibited catalytic activity toward the electrochemical oxidation of NADH due to the imine moieties of pAPRu. The electrochemical oxidation of ethanol was observed using an alcohol dehydrogenase (ADH)‐immobilized electrode. A compartmentless ethanol/O₂ biofuel cell composed of an ADH anode and a bilirubin oxidase cathode was constructed. The maximum current density and the maximum power density of the biofuel cell were 190 µA cm^?2 and 31 µW cm^?2 (at 0.29 V), respectively.     

Analysis of adsorption and binding behaviors of silver nanoparticles onto a pyridyl-terminated surface using XPS and AFM

In this study, we analyzed adsorption and binding behaviors of citrate-capped silver nanoparticles (AgNPs) on a pyridyl-terminated surface using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Adsorption of the AgNPs onto the pyridyl-terminated silicon wafer surface was completed through pH-controlled sol immersion. The adsorption occurred predominantly at a pH less than the pK(b) value of the pyridyl group and more than the pK(a1) of citric acid, indicating that the driving force behind adsorption was electrostatic interaction. Adsorption of citrate onto the pyridyl group also occurred at pK(a1) < pH < pK(b) without AgNPs. According to XPS in the N1s region, larger deprotonation from the pyridinium-formed pyridyl groups was demonstrated subsequent to adsorption of the AgNPs. The deprotonation from the pyridinium indicates the formation of the neutral pyridyl group as the counterpart of hydrogen bonding with the carboxyl group of citrate. The binding state between the pyridyl group and citrate surrounding AgNPs is expected to be kept stable through hydrogen bonding and van der Waals force derived from the AgNPs approach to the pyridyl surface.     

Preparation and evaluation of a chrysotile asbestos-containing standard material for validating x-ray diffractometric quantitation

A standard material containing chrysotile asbestos for the validation of x-ray diffractometric quantitation was developed using an asbestos-containing building material i.e., perlite board. The board as the base material was crushed, pulverized, and homogenized. The homogeneity of the powder of perlite board was estimated by analysis of variance. The diffraction intensity values of the crystalline phases and the concentrations of elements determined by x-ray diffractometry and x-ray fluorescence analysis were used for analysis of variance. There is no significant difference between the within-bottle variance and the between-bottle variance, indicating that the powdered perlite board was sufficiently homogenous. The concentration of chrysotile in the material was determined using two methods: an internal standard/x-ray diffractometry method and the x-ray diffractometry/Rietveld refinement. The concentration of chrysotile in the material was determined by an internal standard/x-ray diffractometry method and the material had a chrysotile concentration of 24.1 ± 0.2 mass%.