Search

Researchers expect carbon nanotube (CNT) yarns as an alternative to metallic wiring. However, the electrical properties of CNT yarns remain relatively low, necessitating further improvement. In this study, we fabricated CNT yarns by dry-spinning and performed several post-synthesis treatments to enhance the electrical properties. Polymer solution impregnation increased the electrical conductivity 1.82 × and the current capacity 1.58 × , attributable to densification of the CNT yarn bundles. Graphitization (GT) increased the electrical conductivity 2.58 × and the current capacity 1.83 × , attributable to purification of the crystalline structure. Iodinemonochloride/dichloromethane (ICl/DCM) doping increased the electrical conductivity 1.79 × and the current capacity 1.31 × , attributable to the increased electron carrier density. We achieved further enhancement by a two-step treatment—GT and ICl/DCM doping—resulting in a 4.88 × increase in conductivity and reaches a maximum of 5.12 × 105 S/m. We observed greater doping effects after GT, which increased the electrical conductivity 1.89 × , whereas doping for pristine CNT yarn only increased the electrical conductivity 1.79 ×. The X-ray photoelectron spectra of CNT yarn in each step indicated a positive relationship between the peak area of the π–π∗ transition component and the electrical conductivity. Therefore, we hypothesize that purification of the crystalline structure increases the electron carrier density by doping. [Display omitted] • Electrical properties of CNT yarns are affected by the post-synthesis treatment. • Single treatment is the mostly performed in enhancing the electrical properties. • Combination of treatments exhibit even more remarkable enhancement effect. • New density states may be produced by the combination of treatments. [ABSTRACT FROM AUTHOR]

Some molecular probes that can detect reactive oxygen species (ROS) with deep-red fluorescence (FL) were designed and synthesized through modification of di(acenaphtho)BODIPY (DAB), which has a sharp absorption band around 680 nm. In order to detect ROS, anthracene or maleimide moiety was substituted at α - or meso -position of DAB, which would work as an FL switch. The obtained DAB having an anthracene moiety at the α -position showed suppressed FL and potential usefulness as a probe for detecting 1O 2 and the 2-cyano-2-propyl radical (•CP) in acetonitrile. On the other hand, although DAB having an N -phenylmaleimide moiety at the meso -position showed suppressed FL, it could detect neither the hydroxyl radical nor •CP. DAB having a hydroxylamine moiety, which was accidently obtained as an intermediate in synthesis, worked as a •CP probe in ethanol and in acetonitrile. These DAB probes are promising tools for studying objects of interest related to ROS such as behaviors caused by oxidative stresses, antioxidation processes in living bodies, medicinal substances, food factors, and so on. [Display omitted] • Modified di(acenaphtho)BODIPYs as ROS detection probes having deep red fluorescence. • α -Anthracenyl substituent acts as a switch for fluorescence by trapping singlet oxygen. • meso -Phenyl-hydroxylamine moiety works for detection of free radicals. [ABSTRACT FROM AUTHOR]

Thermocapillary-driven convection in a hanging droplet is experimentally investigated under normal- and micro-gravity conditions. A droplet is hung on a heated cylindrical rod facing downward, and another rod cooled is placed just beneath the droplet to create the designated temperature difference between both ends of the droplet. A transition of the flow field from a two-dimensional axisymmetric ‘steady’ flow to three-dimensional time-dependent ‘oscillatory’ ones by increasing temperature difference is realized. The oscillatory flow is accompanied with thermal waves due to so-called hydrothermal wave (HTW) instability, which propagates over the free surface at a constant frequency. The present study aims to understand the transition conditions of the flow from the steady to the oscillatory ones, and to characterize the convective field inside the droplet with the HTW by imposing a range of temperature differences. We discuss the transition condition and the flow fields in the oscillatory regimes after the transition obtained in the terrestrial and on-orbit experiments in ‘Kibo,’ the Japanese Experiment Module aboard the International Space Station. [ABSTRACT FROM AUTHOR]

c-Src tyrosine kinase plays roles in a wide range of signaling events and its increased activity is frequently observed in a variety of epithelial and non-epithelial cancers. v-Src, an oncogene first identified in the Rous sarcoma virus, is an oncogenic version of c-Src and has constitutively active tyrosine kinase activity. We previously showed that v-Src induces Aurora B delocalization, resulting in cytokinesis failure and binucleated cell formation. In the present study, we explored the mechanism underlying v-Src-induced Aurora B delocalization. Treatment with the Eg5 inhibitor (+)-S-trityl-L-cysteine (STLC) arrested cells in a prometaphase-like state with a monopolar spindle; upon further inhibition of cyclin-dependent kinase (CDK1) by RO-3306, cells underwent monopolar cytokinesis with bleb-like protrusions. Aurora B was localized to the protruding furrow region or the polarized plasma membrane 30 min after RO-3306 addition, whereas inducible v-Src expression caused Aurora B delocalization in cells undergoing monopolar cytokinesis. Delocalization was similarly observed in monopolar cytokinesis induced by inhibiting Mps1, instead of CDK1, in the STLC-arrested mitotic cells. Importantly, western blotting analysis and in vitro kinase assay revealed that v-Src decreased the levels of Aurora B autophosphorylation and its kinase activity. Furthermore, like v-Src, treatment with the Aurora B inhibitor ZM447439 also caused Aurora B delocalization at concentrations that partially inhibited Aurora B autophosphorylation. Given that phosphorylation of Aurora B by v-Src was not observed, these results suggest that v-Src causes Aurora B delocalization by indirectly suppressing Aurora B kinase activity. • CDK1 inhibition of STLC-arrested cells induces monopolar cytokinesis. • Aurora B localization can be analyzed in monopolar cytokinesis cells. • MPS1 inhibition instead of CDK1 inhibition causes monopolar cytokinesis in STLC-arrested cells. • v-Src reduces Aurora B kinase activity, causing the Aurora B delocalization. • LATS kinases inhibition causes the Aurora B delocalization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solvent effects on the S 1 ← S 0 absorption spectra are investigated for aniline. • MD simulations and TD-DFT calculations reproduce the experimental spectra. • A solvent molecule bound to the nitrogen atom of aniline causes a blue shift. • Methanol is bound to the nitrogen atom less frequently than water in solution. • The absorption band in methanol is thus less-blue shifted than the band in water. Solvent effects on the absorption spectra of aniline (C 6 H 5 NH 2) are investigated. DFT and TD-DFT calculations for 1:1 aniline–water and aniline–methanol complexes predict that an N-bound isomer with an OH···N bond is the global minimum in the S 0 state, while an H-bound isomer with an NH···O bond becomes lower in the S 1 state. The N-bound and H-bound solvents cause blue and red shifts, respectively. MD simulations are used to allocate solvent molecules around aniline for constructing model structures with a complete solvation shell. TD-DFT calculations for the model structures are successful in reproducing the experimental observation that the absorption band in methanol is less blue-shifted than that in the water. At least one water molecule is incessantly bound to the nitrogen atom and causes the significant blue shift. In contrast, methanol molecules are less frequently bound to the nitrogen atom and therefore the blue-shifting effect is less significant. [ABSTRACT FROM AUTHOR]

Abstract: Five human 2,3-oxidosqualnene cyclase (OSC) inhibitors were discovered using the combination of a virtual screening based on a docking study and an isotope-free assay system. All of these inhibitors were revealed to have activities comparable or superior to that of LDAO, a known OSC inhibitor. The computational study of the newly identified inhibitors suggested that CH/π interactions with F444 and W581 contribute to the binding, and these interactions are candidates for additional structural filters in the next generation of virtual screening. [Copyright &y& Elsevier]

Abstract: A synthetic route to paleic acid 1, antimicrobial agent effective against Mannheimia haemolytica and Pasteurella multocida, has been established. The absolute configuration of the secondary hydroxyl group was controlled by a catalytic asymmetric alkylation of an aldehyde using a chiral titanium sulfonamide complex and the cis double bond was installed using a Wittig reaction. This synthetic route was also applied to the preparation of structurally related analogs, which were used in structure–activity relationship studies for antibacterial activity. [Copyright &y& Elsevier]

Abstract: The structure–activity relationship of the boronic acid derivatives of tyropeptin, a proteasome inhibitor, was studied. Based on the structure of a previously reported boronate analog of tyropeptin (2), 41 derivatives, which have varying substructure at the N-terminal acyl moiety and P2 position, were synthesized. Among them, 3-phenoxyphenylacetamide 6 and 3-fluoro picolinamide 22 displayed the most potent inhibitory activity toward chymotryptic activity of proteasome and cytotoxicity, respectively. The replacement of the isopropyl group in the P2 side chain to H or Me had negligible effects on the biological activities examined in this study. [Copyright &y& Elsevier]

Abstract: Pyrrole- and 1,2,3-triazole-based 2,3-oxidosqualene cyclase (OSC) inhibitors 3 and 4 were discovered by conducting a virtual screening, a docking study based on the crystallographic structure of OSC, and biological assays. The hit rate of the assays was increased by establishing appropriate substructural filters in the virtual screening stage. Amide derivatives of 8 and 12 preserved the inhibitory activity of parent compound 3, which provided a reasonable starting point for further structure–activity-relationship (SAR) studies on related compounds. [Copyright &y& Elsevier]

We achieved a formal total synthesis of scytophycin C. The synthesis demonstrates the utility of the catalytic asymmetric direct thioamide-aldol reaction for the preparation of polyketide structures, and was accomplished via diastereoselective allylation, and allylative cyclization as other key transformations. The reported process accesses Miyashita’s key fragment corresponding to the C7–C18 framework in fewer steps (14 steps) than in previously reported syntheses. [ABSTRACT FROM AUTHOR]

Abstract: Boronic acid derivatives of tyropeptin were synthesized with TP-110 as the lead compound. Due to the lability of the aminoboronic acid moiety, careful design of the deprotection and coupling sequence was required. Liquid–liquid partition chromatography was found to be a powerful tool for purification of compounds of this class. The obtained derivatives showed potent inhibitory activities against the human 20S proteasome in vitro. [Copyright &y& Elsevier]

A catalytic asymmetric total synthesis of CPZEN-45 ( 1 ), anti-XDR-TB agent, was accomplished using a direct aldol reaction of a glycine Schiff base ( 3 ) and uridine-derived aldehyde ( 4 ) catalyzed by Zn(II)–( R , R )-linked-BINOL complex to give the desired stereoisomer selectively. The diazepinone ring system, another key structural element, was successfully constructed by vinyl halide–amide coupling promoted by Cu(I) salt. [ABSTRACT FROM AUTHOR]

Column chromatography-free stereoselective synthesis of Corey's intermediate for Tamiflu (oseltamivir phosphate) was achieved, starting from l -glutamic acid γ-ethyl ester. The reagents and solvents used in the reaction scheme are industrially tractable, rendering the synthesis a potential starting point for process research. [ABSTRACT FROM AUTHOR]

Runt-related transcription factor-2 (Runx2) is the master regulator of osteoblastogenesis with an ability to promote differentiation of mesenchymal stem cells into the osteoblastic lineage. We have previously shown constitutive and functional expression of Runx2 by astroglial cells. In this study, we investigated the possible expression of Runx2 by both murine microglia and microglial cell line BV-2 cells. Runx2 expression was seen in cultured microglia and BV-2 cells, while sustained exposure to 1mM ATP led to a significant but transient increase in mRNA and corresponding protein expression of Runx2 within 24h. The increase in Runx2 expression was invariably prevented by several chemicals with antagonistic properties for P2X7 purinergic receptor, calmodulin and calcineurin in BV-2 cells, with a P2X7 receptor agonist more than quadrupling Runx2 expression. A significant increase in Runx2 expression was seen in osteoclastic cells, but not in osteoblastic or chondrocytic cells, when exposed to a high concentration of ATP. In BV2-cells with control siRNA, a significant decrease was found in the number of cells with at least one process within 3h after the exposure to 1mM ATP, followed by an increase up to 24h. However, Runx2 siRNA significantly deteriorated the property to induce delayed process extension during 6-24h after exposure to ATP along with drastically decreased Runx2 protein levels. These results suggest that Runx2 is constitutively and functionally expressed by microglial cells with responsiveness to ATP for upregulation in the murine brain. [ABSTRACT FROM AUTHOR]

The anionic polymerizations of 2-chloroethyl methacrylate (1), 2-bromoethyl methacrylate (2), and 2-iodoethyl methacrylate (3) were carried out in THF at −78 °C with 1,1-diphenyl-3-methylpentyllithium in the presence of LiCl. The polymerizations proceeded in a controlled manner to quantitatively afford polymers with predictable molecular weights and narrow molecular weight distributions. Under similar conditions, the anionic block copolymerizations by the sequential addition of methyl methacrylate (MMA) followed by 1, 2, and 3 generated the corresponding diblock copolymers with well-defined structures. On the other hand, in the block copolymerization by the reverse addition of monomer, a well-defined diblock copolymer, poly(1)-block-PMMA, could be synthesized only by the sequential addition of 1 followed by MMA, whereas the block copolymerizations using 2 and 3 were not successful because of instabilities of the propagating chain-end anions derived from 2 and 3. The side reactions which occurred during the polymerization were discussed. [Copyright &y& Elsevier]

Protein-tyrosine kinase (PTKase) and protein-tyrosine phosphatase (PTPase) regulate the intracellular signal transduction in various biological processes. PTPase often negatively regulates the intracellular protein-tyrosine phosphorylation. PTPases are considered to be involved in the etiology of diabetes mellitus and neural diseases, such as Alzheimer''s disease and Parkinson''s disease. Therefore, PTPase inhibitors should be useful tools to study the role of PTPases in these diseases and other biological phenomena, and they hopefully may be developed into chemotherapeutic agents. We first discovered a naturally occurring PTPase inhibitor, dephostatin, in 1993. Later, we developed stable and safe dephostatin analogues by a molecular design approach employing the concept of CH/π interaction. We prepared Et-3,4-dephostatin as a stable analogue and found it to inhibit PTP-1B and SHPTP-1 PTPases selectively. Et-3,4-dephostatin increased the tyrosine phosphorylation of the insulin receptor and insulin receptor substrate-1 (IRS-1), with or without insulin, in differentiated 3T3-L1 mouse adipocytes. It also increased the phosphorylation and activation of Akt. The analogue also enhanced translocation of glucose transporter 4 (GLUT4) from the cytoplasm to the membrane and 2-deoxyglucose transport. It also showed an in vivo antidiabetic effect in terms of reducing the high blood glucose level in KK-Ay mice after oral administration. Since Et-3,4-dephostatin contains a nitrosamine moiety, we designed nitrosamine-free dephostatin analogues employing the concept of CH/π interaction. Then, we synthesized methoxime- and hexyl-methoxime-3,4-dephostatin as nitrosamine-free analogues. These analogues also showed antidiabetic activity in vivo and illustrate the utility of the CH/π interaction molecular design approach. [Copyright &y& Elsevier]

Here we describe the synthesis and electrochemical testing of a heteroleptic bis(tridentate) ruthenium(II) complex [RuII(LR)(L)] (LR =2,6-bis(1-(2-octyldodecan)benzimidazol-2-yl)pyridine, L = 2,6-bis(benzimidazolate)pyridine). It is a neutral complex which undergoes a quasireversible oxidation and reduction at relatively low potential. The newly synthesised compound was used for studies of ion-transfer at the three-phase junction because of the sensitivity of this method to cation expulsion. The [RuII(LR)(L)] shows exceptional stability during cycling and is sufficiently lipophilic even after oxidation to persist in the organic phase also using very hydrophilic anions such as Cl−. We believe that this, in combination with a comparably low redox potential, will make [RuII(LR)(L)] useful as electron-donor in phase-separated catalysis and voltammetric ion-selective membranes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Structure-activity relationship study of leucinostatin A, a natural nonapeptide, was performed to gain insight into the structural requirements for leucinostatin A to exhibit antiproliferative activity against DU-145 prostate cancer cells under cocultured conditions with the corresponding stromal cells. Twenty truncated peptide analogs of leucinostatin A revealed that the nonapeptide structure as a whole is essential for the biological activity. Alanine scanning demonstrated the importance of some of the amino acid components, including hydroxyleucine and the second leucine from the N-terminus. Two of the three aminoisobutyric acids could be substituted with one of the enantiomers of alanine, clearly demonstrating that each methyl group in these portions has a distinct influence on the growth-inhibitory activity. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Caprazamycin B was successfully synthesized via caprazol. In the present synthesis, the choices of the segment coupling conditions and protecting groups were unexpectedly narrow. Only Shiina’s protocol provided the ester linkage between the unreactive secondary hydroxyl group on the diazepanone ring system and the side chain moiety (western zone). Upon final global deprotection, hydrogenolysis conditions were compatible with substructures that are unstable under acidic and basic environments. [ABSTRACT FROM AUTHOR]

Abstract: Intervenolin is a natural antitumor quinolone that inhibits the growth of MKN-74 gastric tumor cells cocultured with Hs738 gastric stromal cells, and exhibits selective anti-Helicobacter pylori activities. In this report, a structure–activity relationship study of intervenolin is presented. Suitable substituents on the nitrogen, including iminodithiocarbonate moiety, alleviated acute toxicity, and four derivatives displayed specific anti-H. pylori activity. One intervenolin analog with quinoline scaffold also exhibited selective growth inhibition toward cocultured MKN-74, and in vivo antitumor effect. [Copyright &y& Elsevier]

Abstract: A series of thermo-responsive and water-soluble 4- and 8-arm star-branched poly(2-(2′-methoxyethoxy)ethyl methacrylate) (poly(1)) with well-defined structures were synthesized by living anionic polymerization of 1, followed by a linking reaction with a core compound substituted with either four or eight benzyl bromide moieties. Furthermore, two kinds of sequentially different 4-arm star block copolymers composed of poly(1)-block-poly ((2,2-dimethyl-1,3-dioxolan-4-yl)methyl methacrylate) (poly(4)) were also synthesized by the same linking reaction of the corresponding AB or BA diblock copolymer anion with a core compound substituted with four benzyl bromide moieties. Thus, both well-defined 4-arm (AB)4 and (BA)4 star-block copolymers, whose A and B are poly(1) and poly(4) segments, were successfully synthesized. These star-block copolymers were quantitatively converted to the corresponding 4-arm (AC)4 and (CA)4 star-block copolymers with the same compositions by hydrolytic acetal cleavage of the poly(4) segment to poly(2,3-dihydroxypropyl methacrylate) (C segment). Poly(1) segments have LCST values and, on the other hand, both water-insoluble poly(4)s and water-soluble poly(2,3-dihydroxypropyl methacrylate)s are non-thermo-responsive segments. The thermo-responsive behavior of the resulting 4- and 8-arm star-branched poly(1) as well as the 4-arm (AB)4, (BA)4, (AC)4, and (CA)4 star-branched block copolymers has been extensively studied in terms of molecular weight, arm number, composition, and block sequence. As expected, such variables were observed to affect their LCST values. Interestingly, the thermo-responsive behavior of the 4-arm (AC)4 and (CA)4 stars was different from that of the block copolymers used as arm segments. [Copyright &y& Elsevier]