On the Phononic Bandgap of Carbon Nanotubes

On the phononic bandgap of carbon nanotubes (CNTs), we show in what chirality CNTs have phononic bandgaps and its dependence on the diameters of CNTs. We find that, though the rule where CNTs have phononic bandgaps is the same as in the electronic structure case, the diameter dependence is different. The phononic bandgaps of the zigzag-CNTs reveal “three” kinds of diameter dependence due to the anisotropy of graphene phonon band around the K point in k-space. We also show the crossover from one- to two-dimensional characteristics in phononic bandgaps

Diarylethene Self-Assembled Monolayers: Cocrystallization and Mixing-Induced Cooperativity Highlighted by Scanning Tunneling Microscopy at the Liquid/Solid Interface

International audienceThe control over 2-D multi-component molecular orderings on surfaces is a key technology to realize advanced materials with stimuli-responsive properties. The fractional coverage (θ) at a given concentration can be determined from two parameters: the equilibrium constant (Ke) and the degree of cooperativity (σ). The parameters for the formation of self-assembled monolayer of pure diarylethene isomers were obtained by STM measurements on HOPG. These mono-component parameters were used as references to highlight a cocrystallization process between the open-and closed-ring isomers. Moreover it was observed that the presence of the closed-ring isomer induces cooperativity in the formation of the molecular ordering of the open-ring isomer. The quantitative analysis of the ordering formation process by using a model simulation presented in this work provides a better understanding of mixing of components in a molecular ordering and photoinduced interchanges at the liquid/solid interface

Cooperativity Analysis of the Open-, Closed-and Annulated-Isomers of Diarylethene that form 2-D Ordering at the Liquid/Solid Interface and their Photochemical Interchanges

International audienc

Diarylethene Self-Assembled Monolayers: Cocrystallization and Mixing-Induced Cooperativity Highlighted by Scanning Tunneling Microscopy at the Liquid/Solid Interface

International audienceThe control over 2-D multi-component molecular orderings on surfaces is a key technology to realize advanced materials with stimuli-responsive properties. The fractional coverage (θ) at a given concentration can be determined from two parameters: the equilibrium constant (Ke) and the degree of cooperativity (σ). The parameters for the formation of self-assembled monolayer of pure diarylethene isomers were obtained by STM measurements on HOPG. These mono-component parameters were used as references to highlight a cocrystallization process between the open-and closed-ring isomers. Moreover it was observed that the presence of the closed-ring isomer induces cooperativity in the formation of the molecular ordering of the open-ring isomer. The quantitative analysis of the ordering formation process by using a model simulation presented in this work provides a better understanding of mixing of components in a molecular ordering and photoinduced interchanges at the liquid/solid interface. (1) Sakano, T.; Imaizumi, Y.; Hirose, T.; Matsuda, K. Chem. Lett. 2013, 42, 1537. (2) Yokoyama, S.; Hirose, T.; Matsuda, K. Chem. Commun. 2014, 50, 5964. (3) Frath, D.; Sakano, T.; Imaizumi, Y.; Yokoyama, S.; Hirose, T.; Matsuda, K. Chem. Eur. J. 2015, 21, 11350

Catabolic regulation analysis of Escherichia coli and its crp, mlc, mgsA, pgi and ptsG mutants

<p>Abstract</p> <p>Background</p> <p>Most bacteria can use various compounds as carbon sources. These carbon sources can be either co-metabolized or sequentially metabolized, where the latter phenomenon typically occurs as catabolite repression. From the practical application point of view of utilizing lignocellulose for the production of biofuels etc., it is strongly desirable to ferment all sugars obtained by hydrolysis from lignocellulosic materials, where simultaneous consumption of sugars would benefit the formation of bioproducts. However, most organisms consume glucose prior to consumption of other carbon sources, and exhibit diauxic growth. It has been shown by fermentation experiments that simultaneous consumption of sugars can be attained by <it>ptsG, mgsA </it>mutants etc., but its mechanism has not been well understood. It is strongly desirable to understand the mechanism of metabolic regulation for catabolite regulation to improve the performance of fermentation.</p> <p>Results</p> <p>In order to make clear the catabolic regulation mechanism, several continuous cultures were conducted at different dilution rates of 0.2, 0.4, 0.6 and 0.7 h^-1using wild type <it>Escherichia coli</it>. The result indicates that the transcript levels of global regulators such as <it>crp, cra, mlc </it>and <it>rpoS </it>decreased, while those of <it>fadR, iclR, soxR/S </it>increased as the dilution rate increased. These affected the metabolic pathway genes, which in turn affected fermentation result where the specific glucose uptake rate, the specific acetate formation rate, and the specific CO₂evolution rate (CER) were increased as the dilution rate was increased. This was confirmed by the ¹³C-flux analysis. In order to make clear the catabolite regulation, the effect of <it>crp </it>gene knockout (Δ<it>crp</it>) and crp enhancement (<it>crp⁺</it>) as well as <it>mlc, mgsA, pgi </it>and <it>ptsG </it>gene knockout on the metabolism was then investigated by the continuous culture at the dilution rate of 0.2 h^-1and by some batch cultures. In the case of Δ<it>crp </it>(and also Δ<it>mlc</it>) mutant, TCA cycle and glyoxylate were repressed, which caused acetate accumulation. In the case of <it>crp⁺</it>mutant, glycolysis, TCA cycle, and gluconeogenesis were activated, and simultaneous consumption of multiple carbon sources can be attained, but the glucose consumption rate became less due to repression of <it>ptsG </it>and <it>ptsH </it>by the activation of Mlc. Simultaneous consumption of multiple carbon sources could be attained by <it>mgsA, pgi</it>, and <it>ptsG </it>mutants due to increase in <it>crp </it>as well as <it>cyaA</it>, while glucose consumption rate became lower.</p> <p>Conclusions</p> <p>The transcriptional catabolite regulation mechanism was made clear for the wild type <it>E. coli</it>, and its <it>crp, mlc, ptsG, pgi, and mgsA </it>gene knockout mutants. The results indicate that catabolite repression can be relaxed and <it>crp </it>as well as <it>cyaA </it>can be increased by <it>crp⁺, mgsA, pgi</it>, and <it>ptsG </it>mutants, and thus simultaneous consumption of multiple carbon sources including glucose can be made, whereas the glucose uptake rate became lower as compared to wild type due to inactivation of <it>ptsG </it>in all the mutants considered.</p

Spindle checkpoint activation at meiosis I advances anaphase II onset via meiosis-specific APC/C regulation

During mitosis, the spindle assembly checkpoint (SAC) inhibits the Cdc20-activated anaphase-promoting complex/cyclosome (APC/CCdc20), which promotes protein degradation, and delays anaphase onset to ensure accurate chromosome segregation. However, the SAC function in meiotic anaphase regulation is poorly understood. Here, we examined the SAC function in fission yeast meiosis. As in mitosis, a SAC factor, Mad2, delayed anaphase onset via Slp1 (fission yeast Cdc20) when chromosomes attach to the spindle improperly. However, when the SAC delayed anaphase I, the interval between meiosis I and II shortened. Furthermore, anaphase onset was advanced and the SAC effect was reduced at meiosis II. The advancement of anaphase onset depended on a meiosis-specific, Cdc20-related factor, Fzr1/Mfr1, which contributed to anaphase cyclin decline and anaphase onset and was inefficiently inhibited by the SAC. Our findings show that impacts of SAC activation are not confined to a single division at meiosis due to meiosis-specific APC/C regulation, which has probably been evolved for execution of two meiotic divisions