Large positive magnetoresistance of insulating organic crystals in the non-ohmic region

We report a large positive magnetoresistance ratio in insulating organic crystals theta-(ET)(2)CsZn(SCN)(4) at low temperatures at which they exhibit highly nonlinear current-voltage characteristics. Despite the nonlinearity, the magnetoresistance ratio is independent of the applied voltage. The magnetoresistance ratio depends little on the magnetic field direction and is described by a simple universal function of mu(B)B/k(B)T, where mu(B) is the Bohr magneton. The positive magnetoresistance may be caused by magnetic-field-induced parallel alignment of spins of mobile and localized electrons, and a resulting blockade of electrical conduction due to the Pauli exclusion principle.     

Triacylglycerol/phospholipid molecular species profiling of fatty livers and regenerated non-fatty livers in cystathionine beta-synthase-deficient mice, an animal model for homocysteinemia/homocystinuria

Fatty liver is one of the typical manifestations in homocysteinemia/homocystinuria patients and their genetic animal model, mice lacking cystathionine ??-synthase (Cbs ^?/?). The vast majority of Cbs ^?/? die within 4?weeks after birth via yet unknown mechanisms, whereas a small portion survive to adulthood, escaping fatty degeneration of the liver during lactation periods, through regeneration. To investigate the molecular basis of such fatty changes, we analyzed lipid components in fatty livers of 2-week-old Cbs ^?/? and regenerated non-fatty livers of 8-week-old Cbs ^?/? survivors using a chip-based nanoESI (electrospray ionization)-MS system, which allows quantitative detection of triacylglycerol/phospholipid molecular species. Hepatic levels of all major triacylglycerol species were much higher in Cbs ^?/? than in wild-type mice at 2?weeks, although not at 8?weeks. Levels of some phospholipid species were either up- or downregulated in 2-week-old Cbs ^?/?; e.g. saturated (16:0 and 18:0) or mono-unsaturated (16:1 and 18:1) fatty acids-containing phosphatidylcholine/phosphatidylethanolamine species were upregulated, while poly-unsaturated fatty acids-containing phosphatidylcholine (18:2?C18:2 and 18:2?C20:5), phosphatidylethanolamine (18:1?C20:4), and phosphatidylinositol (18:0?C20:4) were downregulated. Capillary electrophoresis-MS analysis identified high-level accumulation of S-adenosylmethionine and S-adenosylhomocysteine in fatty livers of 2-week-old Cbs ^?/? but much less in non-fatty livers of 8-week-old Cbs ^?/?. Although hepatic S-adenosylmethionine/S-adenosylhomocysteine ratios were comparable between 2-week-old Cbs ^?/? and wild-type, global protein arginine methylation was disturbed in fatty livers of Cbs ^?/?. Our results suggest that cellular signaling mediated by altered phospholipid contents might be involved in pathogenesis of fatty liver in Cbs ^?/?C.     

Evaluation of ferritin-overexpressing brain in newly developed transgenic mice

Aberrant expression of ferritin, a major iron-binding protein, has shown to be involved in neurodegenerative diseases. In this study, we generated transgenic (Tg) mice of human ferritin heavy chain (FTH) gene and investigated the effects of ferritin overexpression in FTH-Tg brain by ¹H-MRI and ¹H-MRS. The mice displayed no apparent neurological symptoms, and no specific morphological and T₂ alterations were found in the brain by MRI, and not even by histological studies. ¹H-MRS, however, revealed that some metabolic markers were significantly altered in FTH-Tg brains compared to wild-type control brains, such as decreases in myo-inositol and glutamine, and an increase in lactate. Our present studies suggested that despite the absence of neurological, morphological, T₂, and histological signatures, brain metabolisms were significantly affected in FTH-Tg mice. This study also highlights the usefulness of ¹H-MRS in the analysis of transgenic mouse models.     

Temperature Dependence of Raman Spectrum in Solid Carbon Tetrabromide

Laser Raman spectra of carbon tetrabromide have been observed for the lattice and intramolecular vibrational regions over a temperature range of 80–370 K. Many bands were observed in the lattice region and the spectrum at the lower temperature in the monoclinic phase is similar to that of γ-Si(CH₃)₄. The temperature dependence of each band has been studied. The v₃ fundamental indicates a distinct variation corresponding to the phase transition.     

Parabolicity and stochastic completeness of manifolds in terms of the Green formula

We present and prove new characterizations of parabolicity and stochastic completeness for a general weighted manifold M as well as the uniqueness of the Markov extensions of the Laplacian in terms of Green?s formula. Moreover, we study the relationship between those properties and the singularity of M in terms of a fractal dimension and capacity.     

Size-dependent partitioning of nano/microparticles mediated by membrane lateral heterogeneity

It is important that we understand the physical, chemical, and biological mechanisms that govern the interaction between nanoparticles (NPs) and heterogeneous cellular surfaces because of the possible cytotoxicity of engineered nanomaterials. In this study, we investigated the lateral localization of nano/microparticles within a biomimetic heterogeneous membrane interface using cell-sized two-phase liposomes. We found that lateral heterogeneity in the membrane mediates the partitioning of nano/microparticles in a size-dependent manner: small particles with a diameter of ≤200 nm were localized in an ordered phase, whereas large particles preferred a fluidic disordered phase. This partitioning behavior was verified by temperature-controlled membrane miscibility transition and laser-trapping of associated particles. In terms of the membrane elastic energy, we present a physical model that explains this localization preference of nano/microparticles. The calculated threshold diameter of particles that separates the particle-partitioning phase was 260 nm, which is in close agreement with our observation (200 nm). These findings may lead to a better understanding of the basic mechanisms that underlie the association of nanomaterials within a cell surface.     

Isolation, characterization and molecular evolution of a novel pearl shell lectin from a marine bivalve, Pteria penguin

Summary A novel lectin, PPL, was isolated from the mantle of penguin wing oyster (Pteria penguin) by affinity chromatography on mucin-Sepharose 4B and cation exchange chromatography on HiTrap SP. This lectin was estimated to be a 21-kDa monomer by gel filtration, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted time of flight (MALDI-TOF) mass spectrometry. However, dynamic light scattering experiments revealed that a non-covalently linked dimer formed under high salt conditions (500 mM NaCl). Interestingly, PPL showed an increasing hemagglutinating activity with increasing salt concentration. The amino acid sequence of PPL was determined by direct protein sequence analysis and cDNA cloning. The 167-amino acid sequence included 24 lysine residues and had two tandemly repeated homologous domains (residues 20–78 and 107–165) with 44% internal homology. PPL showed sequence homology to L-rhamnose-binding lectins from fish eggs and a D-galactose-binding lectin from sea urchin eggs, with sequence identities in the range 37–48%. PPL agglutinated various animal erythrocytes independently of calcium ions. The minimum concentration of PPL needed to agglutinate rabbit erythrocytes was 0.5 μg/ml, and the most effective saccharides to inhibit the hemagglutination were D-galactose, methyl-D-galactopyranoside and N-acetyl-D-lactosamine. Lactose also inhibited hemagglutination, but L-rhamnose did so only weakly despite the sequence homology with trout egg L-rhamnose-binding lectins. The carbohydrate-binding specificity of PPL was further examined by frontal affinity chromatography using 37 different pyridylaminated oligosaccharides. PPL was found to have strong binding affinity for various oligosaccharides that have Galβ1-4Glu/GlcNAc, Galβ1-3GalNAc/GlcNAc and Galα 1-4Gal moieties in their structure. PPL had a high thermal stability and retained 50% of its hemagglutinating activity after incubation at 70°C for 100 min. It agglutinated some Gram-negative bacteria by recognizing lipopolysaccharides. Together, these results suggest that PPL is a new member of the trout egg lectin family which participates in the self-defense mechanism against bacteria and pathogens with a distinct carbohydrate-binding specificity. We conclude that the trout egg lectin family proteins, in particular their carbohydrate recognition domains, have acquired diverse carbohydrate-binding specificities during molecular evolution.     

Fusaspirols A-D,novel oxaspirol derivatives isolated from Fusarium solani B-18

Four novel compounds with γ-methylidene-spirobutanolide core, fusaspirols A-D, were isolated from the brown rice culture of Fusarium solani B-18. Their structures were established by extensive spectroscopic analyses of 1D/2D-NMR, HRESITOFMS, and chemical derivatization. The absolute configurations of secondary alcohols in fusaspirols A and D were determined using modified Mosher's ester method. Fusaspirol A and 4,9-di-O-acetylfusaspirol A activated a signaling pathway in osteoclastic differentiation of murine macrophage derived RAW264.7?cells.     

Chiral recognition by cyclic oligosaccharides. Enantioselective complexation of binaphthyl derivatives with cyclodextrins

Abstract

Chiral recognition of binaphthyl derivatives, such as 1,1′-bi-2-naphthol (1), 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate (2), and 2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylic acid (3), by cyclodextrins (CDxs) has been studied. The S enantiomers of 1 and 2 are bound to heptakis(2,3,6-tri-O-methyl)-β-CDx (TMe-β-CDx) as well as β-CDx more strongly than the R enantiomers. The molecular mechanics and molecular dynamics calculations for the 1:1 complex of 1 and β-CDx suggest that more effective van der Waals contacts and intermolecular hydrogen bonding stabilize the complex of S-1 compared with that of R-1. Meanwhile the R enantiomer of 3 is the preferable guest for β- and TMe-β-CDxs. Circular dichroism spectroscopy suggests that the complex of S-3 is more unstable than that of R-3 because the dihedral angle of the naphthalene planes of S-3 needs to be reduced for forming the inclusion complex. The enantiomers of the guest binaphthyls are completely separated by means of capillary zone electrophoresis (CZE) when TMe-β-CDx is used as a separating agent. The results of the CZE correspond well with those of the binding constants of the inclusion complexes.     

Isolation of peridinin-related norcarotenoids with cell growth-inhibitory activity from the cultured dinoflagellate of Symbiodinium sp., a symbiont of the Okinawan soft coral Clavularia viridis,and analysis of fatty acids of the dinoflagellate

Two norcarotenoids, 1 and 2, related to peridinin (3) were isolated from the cultured dinoflagellate of the genus Symbiodinium, a symbiont of the Okinawan soft coral Clavularia viridis, which contains in abundance antitumor marine prostanoids such as clavulones. The structures of 1 and 2 were elucidated on the basis of spectroscopic analysis. These compounds showed significant growth-inhibitory activity in vitro toward cancer cells. Analysis of fatty acids of the dinoflagellate was also carried out, suggesting that the marine prostanoids are produced by the host soft coral itself.