Synthesis and Characterization of Cyclotri- and Tetrasiloxanes with Pyrenyl Groups.

Cyclosiloxanes directly bearing polyaromatic groups on silicon atoms have scarcely been reported. Herein, hexa(1-pyrenyl)cyclotrisiloxane (2) and octa(1-pyrenyl)cyclotetrasiloxane (3) were successfully prepared from di(1-pyrenyl)silanediol (1) in the presence of a weak base such as tetraethylammonium acetate and triethylamine in MeCN. The structure of the cyclosiloxanes bearing multiple pyrenyl groups in the solid and solution states was evaluated by NMR, X-ray crystallography, and density functional theory (DFT) calculations. All pyrenyl groups of 2 were oriented outward, and no π-π stacking of adjacent pyrenyl groups was observed. However, all pairs of adjacent pyrenyl groups at 1- and 3-positions in 3 are oriented in the same direction and were π-π stacked with respect to each other. The UV-vis spectra of 2 and 3 in organic solvents showed a slight broadening of the peaks, as observed for typical pyrene derivatives. Interestingly, the fluorescence spectra of 2 showed small monomer and strong excimer emissions; however, those of 3 showed only a strong excimer emission in all solvents. Partially pyrenylated cyclotri- and tetrasiloxanes (compounds 4 and 5) showed solvent-dependent monomer and excimer spectra as observed for di(1-pyrenyl)silane derivatives, implying that the excimer emissions of 2 and 3 arise from mainly geminal and vicinal pyrenyl groups, respectively.

Effect of the conformer distribution on the properties of amorphous organic semiconductor films for organic light-emitting diodes.

With the remarkable improvement in the electrical and optical properties of organic light-emitting diodes (OLEDs) in recent years, the details of the higher-order structure of vacuum-deposited amorphous organic films and its formation mechanism need to be understood. In particular, to clarify the effect of the higher-order structure on the film properties, it is necessary to analyze the molecular aggregation states in the vacuum-deposited amorphous films. Toward their deep understanding, the higher-order structure and film properties have often been discussed with relation to the surface diffusion and structural relaxation of the molecules immediately after deposition on the film surface. However, the effect of the variety of conformers, which is specific to amorphous organic materials, on the thermal and electrical properties of the films has not been deeply discussed. In this study, we focused on three structural isomers of OLED materials and discuss the effect of the conformer distribution on the molecular aggregation states and thermal and electrical properties of the vacuum-deposited films. From their comparison, we found that the properties of the film composed of a relatively small number of stable conformers are superior to those of the other two films composed of relatively large numbers of stable conformers. This superiority originates from formation of aggregates of the same conformer, which become the starting points for crystallization when the film is heated. Our detailed comparison and discussion focusing on the variety of conformers will lead to a deeper understanding of the molecular aggregation states and physical properties of amorphous organic films.

Asymmetric synthesis of (S)-3-methyleneglutamic acid and its N-Fmoc derivative via Michael addition-elimination reaction of chiral glycine Ni (II) complex with enol tosylates.

The use of chiral Ni (II)-complexes of glycine Schiff bases has recently emerged as a leading methodology for asymmetric synthesis of structurally diverse Tailor-Made Amino Acids™, playing a key role in the design of modern pharmaceuticals. Here, we report first example of enantioselective preparation of (S)-3-methyleneglutamic acid and its N-Fmoc derivative via a new type of Michael addition-elimination reaction between chiral nucleophilic glycine equivalent and enol tosylates. This reaction was found to proceed with excellent yield (91%) and diastereoselectivity (>99/1 de) allowing straightforward asymmetric synthesis of (S)-3-methyleneglutamic acid derivatives and analogues. The observed results bode well for general application of this Ni (II) complex approach for preparation and biological studies of this previously unknown type of Tailor-Made Amino Acids™.

Columnar Stacking of Partially Fluorinated [4]Helicenes: C-H⋠⋠⋠F Interactions Change the Stacking Orientation.

The partial fluorination of polycyclic aromatic hydrocarbons often produces a layered crystal packing, where fluorinated aromatic surfaces are stacked over nonfluorinated aromatic surfaces. Herein, we report the synthesis and crystal packing of partially fluorinated [4]helicenes with steric congestion resulting from H and F atoms in the fjord region. F6 -[4]Helicene forms head-to-tail columnar stacks consisting of an alternate arrangement of perfluorinated and nonfluorinated naphthalene moieties. With decreasing fluorine content, aromatic stacking switched from arene-fluoroarene (ArH -ArF ) hetero-stacking to ArH -ArH /ArF -ArF homo-stacking with the help of intermolecular C-H⋅⋅⋅F contacts in the fjord region. As a result, head-to-head columnar stacks appear. Therefore, the conventional ArH -ArF stacking motif is not always applicable to Fn -[4]helicenes with twisted π-surfaces.

Room-Temperature Phosphorescence from a Series of 3-Pyridylcarbazole Derivatives.

Exploration of pure metal-free organic molecules that exhibit strong room-temperature phosphorescence (RTP) is an emerging research topic. In this regard, unveiling the design principles for an efficient RTP molecule is an essential, but challenging, task. A small molecule is an ideal platform to precisely understand the fundamental role of each functional component because the parent molecule can be easily derivatized. Here, the RTP behaviors of a series of 3-pyridylcarbazole derivatives are presented. Experimental studies in combination with theoretical calculations reveal the crucial role of the n orbital on the central pyridine ring in the dramatic enhancement of the intersystem crossing between the charge-transfer-excited singlet state and the locally excited triplet states. Single-crystal X-ray crystallographic studies apparently indicate that both the pyridine ring and fluorine atom contribute to the enhancement of the RTP because of the restricted motion owing to weak C-H⋅⋅⋅N and H⋅⋅⋅F hydrogen-bonding interactions. The single crystal of the fluorine-substituted derivative shows an ultra-long phosphorescent lifetime (τP ) of 1.1 s and a phosphorescence quantum yield (ΦP ) of 1.2 %, whereas the bromine-substituted derivative exhibits τP of 0.15 s with a ΦP of 7.9 %. We believe that this work provides a fundamental and universal guideline for the generation of pure organic molecules exhibiting strong RTP.

Domain-Swapping Design by Polyproline Rod Insertion.

During domain swapping, proteins mutually interconvert structural elements to form a di-/oligomer. Engineering this process by design is important for creating a higher order protein assembly with minimal modification. Herein, a simple design strategy is shown for domain-swapping formation by loop deletion and insertion of a polyproline rod. Crystal structures revealed the formation of the domain-swapped dimers and polyproline portion formed a polyproline II (PPII) structure. Small-angle X-ray scattering demonstrated that an extended orientation of domain-swapped dimer was retained in solution. It is found that a multiple of three of inserting proline residue is favored for domain swapping because of the helical nature of PPII. The rigid nature of the polyproline rod enables precise control of the interdomain distance and orientation.

Grafting a short chameleon sequence from αB crystallin into a ß-sheet scaffold protein.

Many protein and peptide sequences are self-assembled into ß-sheet-rich fibrous structures called amyloids. Their atomic details provide insights into fundamental knowledge related to amyloid diseases. To study the detailed structure of the amyloid, we have developed a model system that mimics the self-assembling process of the amyloid within a water-soluble protein, termed peptide self-assembly mimic (PSAM). PSAM enables capturing of a peptide sequence within a water-soluble protein, thus making structural and energetics-related studies possible. In this work, we extend our PSAM approach to a naturally occurring chameleon sequence from αB crystallin. We chose "Val-Leu-Gly-Asp-Val (VLGDV)", a five amino-acid sequence, which forms a ß-turn in the native structure and a ß-barrel in the amyloid oligomer cylindrin, as a grafting sequence to the PSAM scaffold. The crystal structure revealed that the sequence grafting induced ß-sheet bending at the grafted site. We further investigated the role of the central glycine residue and found that its role in the ß-sheet bending is dependent on the neighboring residues. The ability of PSAM to observe the structural alterations induced by the grafted sequence provides an opportunity to evaluate the structural impact of a sequence from the peptide self-assembly.

An increased number of CD4+CD25+ cells induced by an oral administration of Lactobacillus plantarum NRIC0380 are involved in antiallergic activity.

BACKGROUND: Our previous study showed that an oral administration of Lactobacillus plantarum NRIC0380 inhibited immunoglobulin E (IgE) production in a murine model, and that orally administered NRIC0380 induced CD4+CD25+ Foxp3+ T, i.e. regulatory T (Treg), cells in the spleen and Peyer's patch of mice. Although it has been reported that Treg cells might suppress the allergic symptoms, the involvement of the cells in the antiallergic activity of lactic acid bacteria has not been clearly demonstrated. We therefore examined in detail the antiallergic activity of Treg cells obtained from mice that had been fed NRIC0380. METHODS: Treg cells were obtained from mice that had been fed NRIC0380. The T cell-suppressive effect of the cells was analyzed by coculturing the cells with splenocytes of ß-lactoglobulin-immunized mice and ß-lactoglobulin. The effects of the Treg cells on the IgE production and cutaneous anaphylaxis reaction were then analyzed by transferring the cells into another mouse. RESULTS: The Treg cells obtained from the mice that had been fed NRIC0380 showed similar T cell-suppressive activity to those cells obtained from the control mice. The Treg cells obtained from the mice fed NRIC0380 significantly inhibited the IgE production and active cutaneous anaphylaxis reaction when transferred into another mouse that was subsequently immunized with the antigen. Furthermore, the Treg cells also significantly suppressed the passive cutaneous anaphylaxis reaction when cotransferred with the IgE antibody into another mouse. CONCLUSIONS: The induction of Treg cells by the oral administration of NRIC0380 would be involved in the antiallergic activity of NRIC0380.

Induction of ALDH activity in intestinal dendritic cells by Lactobacillus plantarum NRIC0380.

Lactic acid bacteria have been reported to have various immune-regulating activities. We also found in the previous study that the oral administration of heat-killed Lactobacillus plantarum NRIC0380 induced CD4(+)CD25(+)Foxp3(+) cells (Treg cells). We examine in this present study the influence of NRIC0380 on the function of intestinal dendritic cells (DCs) in vitro and in vivo. The aldehyde dehydrogenase (ALDH) activity was significantly induced in DCs obtained from the mesenteric lymph node (MLN) by culturing with NRIC0380. The oral administration of NRIC0380 also significantly increased ALDH-positive DCs in MLN. NRIC0380 significantly enhanced the production of TGF-ß from MLN cells in vitro. These effects were not apparent in cells from the Peyer's patch (PP) and spleen (SPL). NRIC0380 also significantly enhanced the expression of B7-H1 on DCs of all organs in vitro. The effects of NRIC0380 on DCs, especially those located in MLN, might be involved in its function to induce Treg cells.

Improved methane fermentation of chicken manure via ammonia removal by biogas recycle.

This study demonstrates methane fermentation that was carried out along with ammonia striping to avoid ammonia accumulation that significantly inhibited methane production. Ammonia was successfully removed by means of recycling of biogas followed by gas washing in sulfuric acid to capture ammonia, when chicken manure was anaerobically digested for 4 days at 55 degrees C and at an initial pH of 8-9. By using this method, 80% of total nitrogen in chicken manure was converted to ammonia and 82% of the produced ammonia was removed. A bench scale reactor equipped with an ammonia-stripping unit for methane production from chicken manure was developed and operated in repeated batch mode. At an initial pH of 8 and at 55 degrees C, 195 and 157 ml g-VS(-1) of methane was successfully produced from the treated chicken manure and the mixture of treated chicken manure and raw chicken manure in the ratio of 1:1, respectively. In this method, ammonia concentration was maintained at a level lower than 2g-N kg-wet sludge(-1) in the reactor.