Microstructural investigation of morphology and kinetics of methane hydrate in the presence of tetrabutylammonium bromide: Insights for preservation and inhibition.

Developing highly efficient methane (CH4) hydrate storage methods and understanding the hydrate dissociation kinetics can contribute to advancing CH4 gas storage and transport. The effects of tetrabutylammonium bromide (TBAB) (a thermodynamic promoter) addition on the kinetics of CH4 hydrate were evaluated on the microscopic scale using synchrotron x-ray computed tomography (CT) and powder x-ray diffraction. Microscopic observations showed that a 5 wt. % TBAB solution facilitated the nucleation of CH4 hydrate owing to the initial growth of TBAB semi-clathrate hydrate particles. The CH4 hydrate crystals in the CH4 + TBAB hydrate sample were sponge-like with many internal pores and exhibited slightly enhanced self-preservation compared to the pure CH4 hydrate, both in the bulk and after pulverization to a fine powder. This study demonstrates the feasibility of controlling the rate of CH4 hydrate formation and preservation by using aqueous TBAB solutions in CH4 hydrate formation.

Advanced X-ray imaging at beamline 07 of the SAGA Light Source.

The SAGA Light Source provides X-ray imaging resources based on high-intensity synchrotron radiation (SR) emitted from the superconducting wiggler at beamline 07 (BL07). By combining quasi-monochromatic SR obtained by the newly installed water-cooled metal filter and monochromatic SR selected by a Ge double-crystal monochromator (DCM) with high-resolution lens-coupled X-ray imagers, fast and low-dose micro-computed tomography (CT), fast phase-contrast CT using grating-based X-ray interferometry, and 2D micro-X-ray absorption fine structure analysis can be performed. In addition, by combining monochromatic SR obtained by a Si DCM with large-area fiber-coupled X-ray imagers, high-sensitivity phase-contrast CT using crystal-based X-ray interferometry can be performed. Low-temperature CT can be performed using the newly installed cryogenic system, and time-resolved analysis of the crystallinity of semiconductor devices in operation can be performed using a time-resolved topography system. The details of each instrument and imaging method, together with exemplary measurements, are presented.

Fast diffraction-enhanced imaging using continuous sample rotation and analyzer crystal scanning.

Diffraction-enhanced imaging (DEI) has high sensitivity and a wide dynamic range of density and thus can be used for fine imaging of biological and organic samples that include large differences in density. A fast DEI method composed of continuous fast sample rotations and slow analyzer crystal scanning was developed to shorten the measurement period. Fine sectional images of a biological sample were successfully obtained within a half measurement period of the conventional step-scanning method while keeping the same exposure time. In addition, a fine three-dimensional image of a rat tail was obtained with a 375 s measurement period.

Novel Zeff imaging method for deep internal areas using back-scattered X-rays.

Elemental kinds, composition ratios, effective atomic number (Zeff), and spatial distributions are the most basic information on materials and determine the physical and chemical properties of materials. X-ray fluorescence analysis have conventionally been used for elemental mapping, however maps on deep internal areas cannot be obtained because the escape depth of fluorescence X-rays is limited to a few mm from the surface of samples. Herein, we present a novel Zeff imaging method that uses back-scattered X-rays. The intensity ratio of elastic and inelastic back-scattered X-rays depends on the atomic number (Z) of a single-element sample (Zeff for a plural-element sample), and so Zeff maps in deep areas can be obtained by spectrum analysis of the scattered high-energy incident X-rays. We demonstrated the feasibility of observing a phantom covered by an aluminum plate by using synchrotron radiation X-ray. A fine Zeff map that can be used to identify materials was obtained from only front-side observation. The novel method opens up a new way for Zeff mapping of deep areas of thick samples from front-side observation.

A method of cryoprotection for protein crystallography by using a microfluidic chip and its application for in situ X-ray diffraction measurements.

We demonstrate a seamless and contactless method from protein crystallization to X-ray analysis using a microfluidic chip with the aim of obtaining a complete crystallographic data set of a protein crystal under cryogenic conditions. Our microfluidics-based approach did not require direct manipulation of the protein crystal. Therefore, the microfluidic chip approach is suitable for novices of X-ray analysis of protein crystals. We also investigated the effect of stepwise cryoprotection on the quality of protein crystals. Protein crystals with cryoprotection via on-chip manipulation did not show deterioration of crystallographic quality of the protein crystal. The complete diffraction data set of a protein crystal, which is required for determining the 3D structure of the target protein, is obtainable by a simple manipulation.

Structure of a highly acidic ß-lactamase from the moderate halophile Chromohalobacter sp. 560 and the discovery of a Cs(+)-selective binding site.

Environmentally friendly absorbents are needed for Sr(2+) and Cs(+), as the removal of the radioactive Sr(2+) and Cs(+) that has leaked from the Fukushima Nuclear Power Plant is one of the most important problems in Japan. Halophilic proteins are known to have many acidic residues on their surface that can provide specific binding sites for metal ions such as Cs(+) or Sr(2+). The crystal structure of a halophilic ß-lactamase from Chromohalobacter sp. 560 (HaBLA) was determined to resolutions of between 1.8 and 2.9 Šin space group P31 using X-ray crystallography. Moreover, the locations of bound Sr(2+) and Cs(+) ions were identified by anomalous X-ray diffraction. The location of one Cs(+)-specific binding site was identified in HaBLA even in the presence of a ninefold molar excess of Na(+) (90 mM Na(+)/10 mM Cs(+)). From an activity assay using isothermal titration calorimetry, the bound Sr(2+) and Cs(+) ions do not significantly affect the enzymatic function of HaBLA. The observation of a selective and high-affinity Cs(+)-binding site provides important information that is useful for the design of artificial Cs(+)-binding sites that may be useful in the bioremediation of radioactive isotopes.

X-ray diffraction of protein crystal grown in a nano-liter scale droplet in a microchannel and evaluation of its applicability.

We describe the technical aspects of the in-situ X-ray diffraction of a protein crystal prepared by a nanodroplet-based crystallization method. We were able to obtain diffraction patterns from a crystal grown in a capillary without any manipulation. Especially in our experimental approach, the crystals that moved to the nanodroplet interface were fixed strongly enough to carry out X-ray diffraction measurements that could be attributed to the high surface tension of the nanodroplet. The crystal was damaged by an indirect action of the X-rays because our in-situ X-ray diffraction measurement was carried out in the liquid phase without freezing the crystal; however, the obtained several diffraction patterns were of sufficiently fine quality for the crystal structure factors to be generated. We consider the technical examination presented in this paper to represent a seamless coupling of crystallization to X-ray analysis.

Crystallization and preliminary X-ray study of alkaline mannanase from an alkaliphilic Bacillus isolate.

An alkaline mannanase (EC 3.2.1.78) from the alkaliphilic Bacillus sp. strain JAMB-602 was cloned and sequenced. The deduced amino-acid sequence of the enzyme suggested that the enzyme consists of a catalytic and unknown additional domains. The recombinant enzyme expressed by B. subtilis was crystallized using the hanging-drop vapour-diffusion method at 277 K. X-ray diffraction data were collected to 1.65 A. The crystal belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 70.7, b = 79.5, c = 80.4 A. The asymmetric unit contains one protein molecule, with a corresponding VM of 2.26 A3 Da(-1) and a solvent content of 45.6%. Molecular replacement for initial phasing was carried out using the three-dimensional structure of a mannanase from Thermomonospora fusca as a search model, which corresponds to the catalytic domain of the alkaline mannanase. It gave sufficient phases to build the unknown domain.