The technology of the selective precipitation of arsenic from solutions for its detection and isolation

This is a technology of the selective precipitation of (AsO4)3− from solutions as the Fe3+ hydroxoarsenate using the FeCl3, NaHCO3 and CH3CO2H. This can be used as a qualitative reaction for arsenic. The dissolving of the Fe3+ and Ag+ arsenates in CH3CO2H in the presence of the CH3CO2Na is discovered. The Fe3+ acetate is stable in water solution without other reagents (it was discovered); and it is stable in CH3CO2H solutions. The arsenic can be isolated using the reactions: Fe3+ hydroxoarsenate + reducing agents, example: Ca(H2PO2)2, as the dark amorphous precipitate (like soot). Then it can be sublimated. This is a safe easy reliable highly sensitive alternative to the Marsh test.

Choosing the Method of Crystallization to Obtain Optimal Results

Anyone who has ever attempted to crystallise a protein or other biological macromolecule has encountered at least one, if not all of the following scenarios: No crystals at all, tiny low quality crystals; phase separation; amorphous precipitate and the most frustrating; large, beautiful crystals that do not diffract at all. In this paper we review a number of simple ways to overcome such problems, which have worked well in our hands and in other laboratories. It brings together information that has been dispersed in various publications and lectures over the years and includes further information that has not been previously published.

Latest methods of fluorescence-based protein crystal identification

Successful protein crystallization screening experiments are dependent upon the experimenter being able to identify positive outcomes. The introduction of fluorescence techniques has brought a powerful and versatile tool to the aid of the crystal grower. Trace fluorescent labeling, in which a fluorescent probe is covalently bound to a subpopulation (<0.5%) of the protein, enables the use of visible fluorescence. Alternatively, one can avoid covalent modification and use UV fluorescence, exploiting the intrinsic fluorescent amino acids present in most proteins. By the use of these techniques, crystals that had previously been obscured in the crystallization drop can readily be identified and distinguished from amorphous precipitate or salt crystals. Additionally, lead conditions that may not have been obvious as such under white-light illumination can be identified. In all cases review of the screening plate is considerably accelerated, as the eye can quickly note objects of increased intensity.

Preparation and Characterization of Magnesium Hydroxide Nanoparticles from Dolomite-Talc Ore

Pure magnesium hydroxide (Mg(OH)2) nanoparticles were synthesized successfully from dolomite-talc ore via chemical precipitation. Carbonate minerals in dolomite-talc ore were dissolved with hydrochloric acid, and Fe2+ was oxidized to Fe3+, then Fe3+ and Al3+ were removed by adding ammonia to adjust pH to reach 6. Magnesium hydroxide (Mg(OH)2) nanoparticles with about 20nm thickness and lamella shape were obtained successfully when pH>10 in the presence of a nonionic surfactant polyethyleneglycol (PEG) with 3wt %, which reached by adding more ammonia. The XRD results show that the amorphous precipitate with 87% Fe2O3 generates at pH=6. However, CaMg2Cl6 (H2O)12 generates when pH = 7, then disappears with the increasing of pH. Mg(OH)2 appears at pH= 9 and pure Mg(OH)2 particle is obtained at pH > 10. Meanwhile, PEG plays an important role in the growth of Mg(OH)2 nanoparticles.

Agarose gel facilitates enzyme crystal soaking with a ligand analog

Orthorhombic crystals of the enzyme aspartyl-tRNA synthetase (AspRS) were prepared in agarose gel, a chemical alternative to microgravity or nano-volume drops. Besides providing a convection-free medium, the network of the polysaccharide improved the stability of the crystalline lattice during soaking with L-aspartol adenylate, a synthetic and non-hydrolysable analog of the catalytic intermediate aspartyl adenylate. When crystals were embedded in the polysaccharide matrix the ligand reached their surfaces more uniformly. Gel-grown crystals exhibited well defined reflections even at high resolution and low mosaicity values, despite their fairly high solvent content and the relatively harsh flash cooling procedure. By contrast, soaked AspRS crystals prepared in solution broke apart within 10–30 s after the ligand was introduced into the mother liquor, and subsequently these fragments became an amorphous precipitate. A general objection to the use of gels in protein crystallization is that chemical interactions may occur between the polysaccharide matrix and proteins or ligands. The example of AspRS shows that this is not a major concern. This method may be generally applicable to crystal soaking with other small molecules or heavy atoms.

Metastabilization of Tetragonal Zirconia by Doping with Low Amounts of Silica

Nanocrystalline tetragonal zirconia was obtained from ZrOCl2 via the modified forced hydrolysis method combined with aging of the hydrous amorphous precipitate in the mother liquor at 100 °C for 48 h (pH = 9.3). The role of the precipitation and aging temperatures in the metastabilization of the tetragonal ZrO2 polymorph is discussed in terms of the structural and textural data of the resultant oxide. The influence of low concentrations of silica (0.01 – 0.35 wt. % Si), spontaneously leached from the glass vessel or intentionally introduced to the parent solution, was shown to be a vital factor, controlling the phase composition of the final prepared zirconia. Using the concepts of zirconium aquatic chemistry, this effect was explained by incorporation of silicates into hydrous zirconia protostructures.