Zinc, cadmium, and mercury 1,2-benzenedithiolates with intramolecular NH...S hydrogen bonds

Mononuclear Zn, Cd, and Hg 1,2-benzenedithiolates with intramolecular NH...S hydrogen bonds, [M(II){1,2-S2-3,6-(RCONH)2C6H2}2](2-) (R = CH 3, t-Bu; M = Zn, Cd, Hg), were synthesized and characterized by X-ray analysis and spectral measurements. The presence of intramolecular NH...S hydrogen bonds was established by the IR spectra. (199)Hg and (113)Cd nuclear magnetic resonance showed a stabilized four-thiolate coordinated structure and suggested the influence of the NH...S hydrogen bonds to ppi(Hg)-ppi(S) interactions. The NH stretching bands show that the NH...S hydrogen bonds in Cd and Hg complexes are stronger than those in the corresponding Zn complex. These results are supported by theoretical calculations. The experimental and theoretical results suggested that the NH...S hydrogen bond influences the efficient capture of toxic Cd and Hg ions by metallothioneins.     

Single molecular multianalyte (Ca2+, Mg2+) fluorescent probe and applications to bioimaging

Intracellular signal transduction relies on spatial and temporal signal transmitter dynamics. To clarify the correlations of these transmitter molecules, multicolor-imaging has been widely used. However, in the case of applying multiple indicators in a cell, spectral overlap of the indicators prevents accurate quantitative analysis. Moreover, the invasive (toxic) effect, the localization, the metabolism, as well as photobleaching of these indicators complicate the situation. Here, we show that single-molecular multifluorescent probes can overcome these problems. While intracellular calcium plays a critical role as a signal transmitter and magnesium acts as a cofactor in many situations, the correlations between the two cations are now the main issue. We designed and synthesized a Ca2+-Mg2+ responsive multifluorescent probe, KCM-1. KCM-1 shows a spectral blue shift upon complexation to Ca2+ and a red shift to the presence of Mg2+. With data analyzed at different excitation wavelengths, the concentrations of Ca2+ and Mg2+ are simultaneously quantified. Furthermore, by using the AM-ester method, intracellular Ca2+ and Mg2+ concentrations are simultaneously imaged. Such a type of intracellular multiple analyte imaging by a single-molecular multifluorescent probe is successfully demonstrated for the first time.     

Low-temperature synthesis of anatase-brookite composite nanocrystals: the junction effect on photocatalytic activity

Anatase-brookite composite nanocrystals have successfully been synthesized at 50 degrees C using a simple liquid-phase process. The photocatalytic activity of the sample for the gas-phase oxidation of CH3CHO is 5.4 times greater than that of a single-phase anatase sample with comparable crystallite size and surface area. Electron energy loss spectra suggest that this high activity results from junction between anatase and brookite crystals.     

Tetracyanoanthraquinodimethanes with a chiral amide group: preparation, properties, and charge-transfer photochirogenetic reaction with 1,2-dianisylacenaphthene-1,2-diol

[reaction: see text] A series of butterfly-shaped tetracyanoanthraquinodimethanes (TCNAQs) with a chiral amide auxiliary 1a-f were prepared from the corresponding anthraquinones. They are stronger acceptors than the unsubstituted derivative and undergo one-wave two-electron reduction. They form weak electron-donor-acceptor (EDA) complexes with the title pinacol 2. Upon charge-transfer excitation of these complexes, dihydro-TCNAQs 3 and 1,8-dianisoylnaphthalene 4 were efficiently formed, the latter of which is the product of a retropinacol reaction via 2+*. Partial enantiodifferentiation of rac-2 was realized during the photoreactions with 2-[(R)-1-phenylethylcarbamoyl]-TCNAQ 1ain CD3CN. Thus, optically active (S,S)-(+)-pinacol 2 (12.3% ee at 54% conversion; 21.5% ee at 70% conversion) was recovered from the photolyzates. This reaction represents a new and rare example of the pseudokinetic resolution of tert-alcohol accompanied by C-C bond fission. Significant differences in the association constants for the diastereomeric EDA complexes are responsible for the observed enantiodifferentiation.     

Chemistry and biology of moverastins, inhibitors of cancer cell migration, produced by Aspergillus

Cancer cell migration is a required step in cancer metastasis. We screened for inhibitors of cancer cell migration of microbial origin, and obtained moverastin, a member of the cylindrol family, from Aspergillus sp. F7720. However, the results of an NMR spectroscopic analysis raised the possibility that moverastin is a mixture of two diastereomers. Separation of the C-10 epimers of synthetic moverastin and a bioassay revealed that both diastereomers (moverastins A and B) had inhibitory effects on cell migration. Furthermore, we demonstrated that moverastins A and B inhibited FTase in vitro, and they also inhibited both the membrane localization of H-Ras and the activation of the PI3K/Akt pathway in EC17 cells. Thus, moverastins inhibited the migration of tumor cells by inhibiting the farnesylation of H-Ras, and subsequent H-Ras-dependent activation of the PI3K/Akt pathway.     

0.23 eV energy resolution obtained using a cold field-emission gun and a streak imaging technique

We demonstrate that a high energy resolution of 0.23 eV is possible by using a cold field-emission electron gun (CFEG) without a monochromator. We have used a 300 kV transmission electron microscope (Hitachi, HF-3000) equipped with a CFEG and an energy filter (Gatan, GIF2002). Since energy instability is critical for high energy resolution in electron energy-loss spectroscopy, we have applied a high-speed 'streak imaging' acquisition technique, in which a series of time-resolved spectra are acquired as a two-dimensional spectrum. With this technique, we can easily record 1000-20,000 spectra with an exposure time of 0.353 ms per spectrum. Instability of less than 1.4 kHz has been corrected in the time-resolved spectra, allowing the inherent performance of the CFEG to be realized.     

A unique site-selective reaction of ketones with new recyclable hypervalent iodine(III) reagents based on a tetraphenylmethane structure

We have synthesized new recyclable reagents having a tetraphenylmethane backbone and used them in the site-selective alpha-tosyloxylation of ketones.     

Macroscopic quantum tunneling in a d-wave high-TC Bi2Sr2CaCu2O8 + delta superconductor

While Josephson-junction-like structures intrinsic to the layered cuprate high temperature superconductors offer an attractive stage for exploiting possible applications to new quantum technologies, the low energy quasiparticle excitations characteristically present in these d-wave superconductors may easily destroy the coherence required. Here we demonstrate for the first time the feasibility of macroscopic quantum tunneling in the intrinsic Josephson junctions of a high temperature superconductor Bi(2)Sr(2)CaCu(2)O(8 + delta), and find it to be characterized by a high classic-to-quantum crossover temperature and a relatively weak quasiparticle dissipation.     

Measuring the thermal conductivity of a single carbon nanotube

Although the thermal properties of millimeter-sized carbon nanotube mats and packed carbon nanofibers have been readily measured, measurements for a single nanotube are extremely difficult. Here, we report a novel method that can reliably measure the thermal conductivity of a single carbon nanotube using a suspended sample-attached T-type nanosensor. Our experimental results show that the thermal conductivity of a carbon nanotube at room temperature increases as its diameter decreases, and exceeds 2000 W/mK for a diameter of 9.8 nm. The temperature dependence of the thermal conductivity for a carbon nanotube with a diameter of 16.1 nm appears to have an asymptote near 320 K. The present method is, in principle, applicable to any kind of a single nanofiber, nanowire, and even single-walled carbon nanotube.