A new classification system for bacterial Rieske non-heme iron aromatic ring-hydroxylating oxygenases

Background  

Rieske non-heme iron aromatic ring-hydroxylating oxygenases (RHOs) are multi-component enzyme systems that are remarkably diverse in bacteria isolated from diverse habitats. Since the first classification in 1990, there has been a need to devise a new classification scheme for these enzymes because many RHOs have been discovered, which do not belong to any group in the previous classification. Here, we present a scheme for classification of RHOs reflecting new sequence information and interactions between RHO enzyme components.     

Stereoselective α-galactofuranosylation and synthesis of di- and tetrasaccharide subunits of cell wall polysaccharides of Talaromyces flavus

Stereoselective α-galactofuranosylation employing 2′-carboxybenzyl glycosides as galactosyl donors has been established. The tetrabenzyl-protective group on the galactosyl donor was essential for the α-galactosylation of secondary alcohol acceptors. The present method was successfully applied to the synthesis of di- and tetrasaccharide subunits of cell wall polysaccharides of Talaromyces flavus.     

Identification of rat urinary glycoproteome captured by three lectins using gel and LC-based proteomics

Many different types of urine proteome studies have been done, but urine glycoprotein studies are insufficient. Therefore, we studied the glycoproteins from rat urine, which could be used to identify biomarkers in an animal model. First, urinary proteins were prepared by using the dialysis and lyophilizing methods from rat urine. Glycoproteins enriched with lectin affinity purification, concanavalin A, jacalin and wheat germ agglutinin from the urinary proteins were separated by means of reverse-phase fast protein LC (FPLC) or 1-D PAGE. Each FPLC fraction and 1-D PAGE gel band were trypsin-digested and analyzed by means of nanoLC-MS/MS. LC-MS/MS analyses were carried out by using linear ion trap MS. A total of 318 rat urinary glycoproteins were identified from the FPLC fractions and gel bands; approximately 90% of identified proteins were confirmed as glycoproteins in Swiss-Prot. Many glycoproteins, known as biomarkers, including C-reactive protein, uromodulin, amyloid beta A4 protein, alpha-1-inhibitor 3, vitamin D-binding protein, kallikrein 3 and fetuin-A were identified in this study. By studying urinary glycoproteins collected from rat, these results may help to assist in identifying urinary biomarkers regarding various types of disease models.     

Superprotonic Conductivity of MOFs Confining Zwitterionic Sulfamic Acid as Proton Source and Conducting Medium

A few metal–organic frameworks (MOFs), which typically use strong acids as proton sources, display superprotonic conductivity (≈10⁻¹ S cm⁻¹); however, they are rare due to the instability of MOFs in highly acidic conditions. For the first time, we report superprotonic conductivity using a moderately acidic guest, zwitterionic sulfamic acid (HSA), which is encapsulated in MOF-808 and MIL-101. HSA acts not only as a proton source but also as a proton-conducting medium due to its extensive hydrogen bonding ability and zwitterion effect. A new sustained concentration gradient method results in higher HSA encapsulation compared to conventional methods, producing 10HSA@MOF-808-(bSA)₂ and 8HSA@MIL-101. These MOFs show impressive superprotonic conductivity of 2.47×10⁻¹ and 3.06×10⁻¹ S cm⁻¹, respectively, at 85 °C and 98 % relative humidity, and maintain stability for 7 days.     

Hexaazatriphenylene-Based Two-Dimensional Conductive Covalent Organic Framework with Anisotropic Charge Transfer

The development of covalent organic frameworks (COFs) with efficient charge transport is of immense interest for applications in optoelectronic devices. To enhance COF charge transport properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor-made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD-COF. With the support of theoretical calculations, we found that the HAT units in the HD-COF induce strong, eclipsed π–π stacking. The unique stacking of HAT units and the weak in-plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD-COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD-COF films showed an electrical conductivity as high as 1.25 S cm⁻¹ after doping with tris(4-bromophenyl)ammoniumyl hexachloroantimonate.     

Stereoselective direct glycosylation with anomeric hydroxy sugars by activation with phthalic anhydride and trifluoromethanesulfonic anhydride involving glycosyl phthalate intermediates

An efficient direct one-pot glycosylation method with anomeric hydroxy sugars as glycosyl donors employing phthalic anhydride and triflic anhydride as activating agents has been developed. Thus, highly stereoselective beta-mannopyranosylations were achieved by the reaction of 2,3-di-O-benzyl-4,6-O-benzylidene-D-mannopyranose (2) with phthalic anhydride in the presence of DBU at room temperature followed by sequential addition of DTBMP and Tf2O and glycosyl acceptors to the reaction mixture at -78 degrees C in one-pot. Stereoselective alpha-glucopyranosylations with 2,3-di-O-benzyl-4,6-O-benzylidene-D-glucopyranose (25) and other glycosylations with glucopyranoses and mannopyranoses having tetra-O-benzyl- and tetra-O-benzoyl protecting groups were also possible by utilizing the present one-pot glycosylation protocol. The possible mechanism for the beta-mannosylation with 2 was proposed based on the NMR study, in which alpha-mannosyl phthalate 55alpha and alpha-mannosyl triflate 59 were detected as intermediates. The versatility and efficiency of the present glycosylation methodology, especially those of the beta-mannopyranosylation protocol, were readily demonstrated by the efficient synthesis of protected beta-(1-->4)-D-mannotriose 62 and beta-(1-->4)-D-mannotetraose 67 with perfect beta-stereoselectivity.     

A cytotoxic and apoptosis-inducing sesquiterpenoid isolated from the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk)

Repeated silica gel and octadecyl silica gel (ODS) column chromatography of the aerial parts of Artemisia princeps PAMPANINI (Sajabalssuk) led to the isolation of a new sesquiterpenoid, 3-((S)-2-methylbutyryloxy)-costu-1(10),4(5)-dien-12,6 alpha-olide (2), along with two previously reported sesquiterpenoids: 8 alpha-angeloyloxy-3beta,4 beta-epoxy-6 beta H,7 alpha H,8 beta H-guaia-1(10),11(13)-dien-12,6 alpha-olide (1, carlaolide B) and 3beta,4 beta-epoxy-8 alpha-isobutyryloxy-6 beta H,7 alpha H,8 beta H-guaia-1(10),11(13)-dien-12,6 alpha-olide (3, carlaolide A). The structure of compound 2 was elucidated by spectroscopic data analysis, including one dimensional (1D) and two dimensional (2D) nuclear magnetic resonance (NMR) experiments. Of the isolates, compound 2 exhibited potent cytotoxicity against human cervix adenocarcinoma cells and induced apoptosis.     

Effect of electrode spacing on image flicker in fringe-field-switching liquid crystal display

Low-frequency driving of a liquid crystal display (LCD) panel to minimise power consumption has drawn much attention recently. In case an LCD panel is driven by a low-frequency fringe field, image flickering phenomenon is detected by the naked human eye when the sign of the applied electric field is reversed. We investigated the effect of electrode spacing on the image flickering phenomenon induced by the flexoelectric effect in a fringe-field-switching (FFS) liquid crystal cell. We found that the image flicker in an FFS cell under low-frequency driving can be eliminated in a simple manner by changing the electrode spacing.     

Metal Oxide/Graphene Composites for Supercapacitive Electrode Materials

Graphene composites with metal or metal oxide nanoparticles have been extensively investigated owing to their potential applications in the fields of fuel cells, batteries, sensing, solar cells, and catalysis. Among them, much research has focused on supercapacitor applications and have come close to realization. Composites include monometal oxides of cobalt, nickel, manganese, and iron, as well as their binary and ternary oxides. In addition, their morphological control and hybrid systems of carbon nanotubes have also been investigated. This review presents the current trends in research on metal oxide/graphene composites for supercapacitors. Furthermore, methods are suggested to improve the properties of electrochemical capacitor electrodes.     

Dynamical characteristics of bacteria clustering by self-generated attractants

Motivated by the recent work on Escherichia coli bacteria clustering [Park, S., Wolanin, P.M., Yuzbashyan, E.A., Lin, H., Darnton, N.C., Stock, J.B., Silberzan, P., Austin, R., 2003. Proc. Natl. Acad. Sci. U.S.A. 100 (24), 13910], we have conducted a computer simulation of E. coli chemotaxis induced by a self-excreted attractant and investigated how bacteria clusters interact through a self-excreted attractant. By modeling the variation of tumbling frequency in the context of phosphorylation rate change, we have investigated the dependency of clustering behavior on the sensitivity of cells to the attractant. We have found that there exists an optimal sensitivity leading to bigger clusters and that the geometry surrounding the cells also plays an important role in localizing the cluster formation. This result suggests that bacterial cluster formation can be reduced by making bacteria more sensitive to attractants, which is opposite to an instinctive way (making them retarded to attractants). In addition, we have studied the effect of an initial cell distribution on clustering.