Zn(2+) plays important roles in various biological systems; as a result, the development of tools that can visualize chelatable Zn(2+) has attracted much attention recently. We report here newly synthesized fluorescent sensors for Zn(2+), ZnAF-Rs, whose excitation maximum is shifted by Zn(2+) under physiological conditions. Thus, these sensors enable ratiometric imaging, which is a technique to reduce artifacts by minimizing the influence of extraneous factors on the fluorescence of a probe. Ratiometric measurement can provide precise data, and some probes allow quantitative detection. ZnAF-Rs are the first ratiometric fluorescent sensors for Zn(2+) that enable quantitative analysis under physiological conditions. ZnAF-Rs also possess suitable K(d) for applications, and high selectivity against other biologically relevant cations, especially Ca(2+). Using these probes, changes of intracellular Zn(2+) concentration in cultured cells were monitored successfully. We believe that these probes will be extremely useful in studies on the biological functions of Zn(2+).

V1-ATPases are highly conserved ATP-driven rotary molecular motors found in various membrane systems. We recently reported the crystal structures for the Enterococcus hirae A3B3DF (V1) complex, corresponding to the catalytic dwell state waiting for ATP hydrolysis. Here we present the crystal structures for two other dwell states obtained by soaking nucleotide-free V1 crystals in ADP. In the presence of 20 μM ADP, two ADP molecules bind to two of three binding sites and cooperatively induce conformational changes of the third site to an ATP-binding mode, corresponding to the ATP-binding dwell. In the presence of 2 mM ADP, all nucleotide-binding sites are occupied by ADP to induce conformational changes corresponding to the ADP-release dwell. Based on these and previous findings, we propose a V1-ATPase rotational mechanism model.

Polycrystalline samples of YxAlyB14 (x ∼ 0.57) with different fractional occupancies y (0.41 ≤ y ≤ 0.63) were synthesized and their thermoelectric properties investigated. Electrical conductivities generally followed three-dimensional variable range hopping with a rapid delocalization indicated as electrons were increased. Positive Seebeck coefficients were obtained for the Al-poor sample, y = 0.41, which was shifted in the negative direction with increase of y. Maximum Seebeck coefficient values were approximately 400 μV K−1 at 850 K and −200 μV K−1 at 1000 K, for p-type and n-type, respectively. Excellent control of p-n characteristics was achieved in a system with the same crystal structure and consisting of the same elements.

Disordered layered p-type bismuth telluride was obtained by high pressure (1 GPa) and high strain deformation along the c-axis direction of commercially available single crystals. After initial deformation the p-type bismuth telluride flakes were subsequently fully densified by cold pressing (800 MPa at room temperature). As a result of the severe plastic deformation, the samples showed highly anisotropic electrical and thermal conductivities. In particular, the thermal conductivity measured along the pressing direction was as low as 0.34 W m À1 K À1 , which is one of the lowest values reported for fully dense ptype bismuth telluride. The full set of thermoelectric properties of the disordered bismuth antimony telluride is critically discussed.

The aluminoboride YxAlyB14 (x ∼ 0.57, 0.41 ≤ y ≤ 0.63) has been found to show striking p-n control of the thermoelectric properties through variations of the y occupancy of the Al site. The effect of Al was investigated in further extremes. Polycrystalline samples of Al-free YxB14(x ∼ 0.55; “YB25”) were successfully synthesized in sufficient amounts for bulk spark plasma sintering (SPS) samples and their thermoelectric properties were investigated. Y0.56Al0.57B14 was also prepared in comparison, and further Al was added to the samples through SPS treatment. We observed that Y0.55B14 exhibits large positive Seebeck coefficients, ∼1000 μV K−1, around room temperature and the absolute value of the Seebeck coefficient largely decreases with increase of temperature while that of Y0.56Al0.57B14 is proportional to T−1/2, indicating a strong effect of Al on the electronic structure around the Fermi level. Y0.55B14 was found to be strongly disordered with a relatively low thermal conductivity and short localization length of 0.65 Å which is close to that previously determined for the disordered and thermally glass-like compound YB66. Occupancy of Al could not be increased further for the Al-rich sample, although Al was discovered to act as a sintering aid to enhance density and ZT could be significantly improved by 50%.

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A first clathrate compound with selenium guest atoms, [Ge(46-x)P(x)]Se(8-y)□(y) (x = 15.4(1); y = 0-2.65; □ denotes a vacancy), was synthesized as a single-phase and structurally characterized. It crystallizes in the space group Fm3 with the unit cell parameter a varying from 20.310(2) to 20.406(2) Å and corresponding to a 2 × 2 × 2 supercell of a usual clathrate-I structure. The superstructure is formed due to the symmetrical arrangement of the three-bonded framework atoms appearing as a result of the framework transformation of the parent clathrate-I structure. Selenium guest atoms occupy two types of polyhedral cages inside the positively charged framework; all selenium atoms in the larger cages form a single covalent bond with the framework atoms, relating the title compounds to a scanty family of semiclathrates. According to the measurements of electrical resistivity and Seebeck coefficient, [Ge(46-x)P(x)]Se(8-y)□(y) is an n-type semiconductor with E(g) = 0.41 eV for x = 15.4(1) and y = 0; it demonstrates the maximal thermoelectric power factor of 2.3 × 10(-5) W K(-2) m(-1) at 660 K.

Boron carbide/hafnium diboride composites were prepared by spark plasma sintering of a mixture of hafnium diboride and boron carbide powders. Boron carbide was prepared with a 13.3 at.% composition of carbon, known as the ideal carbon content to maximize the dimensionless figure of merit. The hafnium diboride content was varied between 0 and 20% by weight, and the effect on the thermoelectric properties was studied. Addition of HfB 2 generally yielded an increase in the electrical conductivity and simultaneously a reduction in thermal conductivity, indicating it has potential as an enhancer of thermoelectric properties. However, the increase in electrical conductivity was not as large as observed in some composite systems, since HfB 2 turned out to be a poor sintering additive leading to lower relative densities, and was furthermore offset by a moderate decrease in Seebeck coefficient. For future composite design, the sintering characteristics of the additives can be concluded as an important additional parameter to be taken into account. The optimal hafnium diboride content for relatively dense samples was found to be 10 wt%, resulting in an improvement in the maximum figure of merit, up to ZT = 0.20 at 730°C.