Fractionation of hydrogen isotopes between crystalline hydrates and saturated solution of cobalt dichloride

The hydrogen isotopic fractionation factors between the crystal water (CW) in crystalline hydrates and the saturated aqueous solution of cobalt dichloride, alphaCW-st.sol, were experimentally determined in the temperature range from 10 to 55 degrees C under equilibrium condition: alphaCW-st.sol in cobalt dichloride hexahydrate, CoCl2 x 6H2O, from 10 to 43 degrees C, and in cobalt dichloride dihydrate, CoCl2 x 2H2O, at 50 and 55 degrees C. The empirical relationship between ln alphaC.W.-st.sol and (1/T2) on the CW of CoCl2 x 6H2O in the temperature range from 10 to 43 degrees C was obtained as: 10(3)ln alphaCW-st.sol=-2.46(10(6)/T2)+17.6. The CW of dihydrate of cobalt dichloride exhibits larger depletion of deuterium than that of hexahydrate. The values of alphaCW-st.sol in CoCl2 x 2H2O are similar to that of CuCl2 x 2H2O and BaCl2 x 2H2O at 25 degrees C. This fact indicates that the hydrogen fractionation factor between the CW and the saturated aqueous solution of cobalt dichloride strongly depends on the structure of crystalline hydrate rather than the chemical species of cation and/or the crystallized temperature.     

'Information-Based-Acquisition' (IBA) technique with an ion-trap/time-of-flight mass spectrometer for high-throughput and reliable protein profiling

Highly complex protein mixtures can be analyzed after proteolysis using liquid chromatography/mass spectrometry (LC/MS). In an LC/MS run, intense peptide ions originating from high-abundance proteins are preferentially analyzed using tandem mass spectrometry (MS(2)), so obtaining the MS(2) spectra of peptide ions from low-abundance proteins is difficult even if such ions are detected. Furthermore, the MS(2) spectra may produce insufficient information to identify the peptides or proteins. To solve these problems, we have developed a real-time optimization technique for MS(2), called the Information-Based-Acquisition (IBA) system. In a preliminary LC/MS run, a few of the most intense ions detected in every MS spectrum are selected as precursors for MS(2) and their masses, charge states and retention times are automatically registered in an internal database. In the next run, a sample similar to that used in the first run is analyzed using database searching. Then, the ions registered in the database are excluded from the precursor ion selection to avoid duplicate MS(2) analyses. Furthermore, real-time de novo sequencing is performed just after obtaining the MS(2) spectrum, and an MS(3) spectrum is obtained for accurate peptide identification when the number of interpreted amino acids in the MS(2) spectrum is less than five. We applied the IBA system to a yeast cell lysate which is a typical crude sample, using a nanoLC/ion-trap time-of flight (IT/TOF) mass spectrometer, repeating the same LC/MS run five times. The obtained MS(2) and MS(3) spectra were analyzed by applying the Mascot (Matrix Science, Boston, MA, USA) search engine to identify proteins from the sequence database. The total number of identified proteins in five LC/MS runs was three times higher than that in the first run and the ion scores for peptide identification also significantly increased, by about 70%, when the MS(3) spectra were used, combined with the MS(2) spectra, before being subjected to Mascot analysis.     

Current-induced metallic state in an organic (EDT-TSF)2GaCl4 conductor

A newly prepared organic conductor, (EDT-TSF)(2)GaCl(4), shows considerable nonlinear conductance in the insulating state below 20 K, and a metallic state is restored by the application of moderate currents. This conductor has a stacking structure with a quasi-one-dimensional open Fermi surface, similar to the sulfur analogues. Since the interchain interaction is enhanced by the selenium substitution, the static magnetic susceptibility as well as ESR does not show any anomaly around 20 K, and low-temperature X-ray investigation does not show any extra spots. Isostructural (EDT-TSF)(2)FeCl(4) shows similar conducting properties, although the magnetic interaction of the anion is weak. Like this, nonlinear conductance is a versatile tool to restore a metallic state when the metal-insulator transition is almost suppressed.     

Large-aperture focusing of x rays with micropore optics using dry etching of silicon wafers

Large-aperture focusing of Al K(α) 1.49 keV x-ray photons using micropore optics made from a dry-etched 4 in. (100 mm) silicon wafer is demonstrated. Sidewalls of the micropores are smoothed with high-temperature annealing to work as x-ray mirrors. The wafer is bent to a spherical shape to collect parallel x rays into a focus. Our result supports that this new type of optics allows for the manufacturing of ultralight-weight and high-performance x-ray imaging optics with large apertures at low cost.