Search results for "Crystallization"
showing 10 items of 774 documents
Analysis of particles size distributions in Mg(OH)2 precipitation from highly concentrated MgCl2 solutions
2022
Magnesium is a raw material of great importance, which attracted increasing interest in the last years. A promising route is to recover magnesium in the form of Magnesium Hydroxide via precipitation from highly concentrated Mg2+ resources, e.g. industrial or natural brines and bitterns. Several production methods and characterization procedures have been presented in the literature reporting a broad variety of Mg(OH)2 particle sizes. In the present work, a detailed experimental investigation is aiming to shed light on the characteristics of produced Mg(OH)2 particles and their dependence upon the reacting conditions. To this purpose, two T-shaped mixers were employed to tune and control the…
Transmission Electron Microscopy of GroEL, GroES, and the Symmetrical GroEL/ES Complex
1994
Two new 2-D crystal forms of the Escherichia coli chaperone GroEL (cpn60) 2 x 7-mer have been produced using the negative staining-carbon film (NS-CF) technique. These 2-D crystals, which contain the cylindrical GroEL in side-on and end-on orientations, both possess p21 symmetry, with two molecules in the respective unit cells. The crystallographically averaged images correlate well with those obtained by other authors from single particle analysis of GroEL and our own previous crystallographic analysis. 2-D crystallization of the smaller chaperone GroES (cpn10) 7-mer has also been achieved using the NS-CF technique. Crystallographically averaged images of GroES single particle images indic…
Production, crystallization and preliminary X-ray analysis of the human integrin alpha1 I domain.
1999
Integrin α1β1 is one of the main collagen receptors in many cell types. A fast large-scale production, purification and crystallization method for the integrin α1 I domain is reported here. The α1 I domain was crystallized using the vapour-diffusion method with a reservoir solution containing a mixture of PEG 4000, sodium acetate, glycerol and Tris–HCl buffer. The crystals beong to the C2 space group, with unit-cell parameters a = 74.5, b = 81.9, c = 37.3 Å, α = γ = 90.0, β = 90.8°. The crystals diffract to 2.0 Å and a 94.2% complete data set to 2.2 Å has been collected from a single crystal with an R merge of 5.8%.
Effects of ultrasound and high pressure on physicochemical properties and HMF formation in Turkish honey types
2018
Abstract In industrial production, thermal processing of honey at 50 °C commonly induces liquefaction, i.e. it reduces the crystal count and viscosity and delays any subsequent crystallization. Unfortunately, thermal treatment can generate toxic 5-hydroxymethylfurfural (HMF), thereby resulting in quality reduction. Considering this, the present work aims at evaluating the influence of (two) processing technologies as alternatives to thermal processing of honey, namely high hydrostatic pressure (HHP; P = 220–330 MPa, T = 50/60 °C, t = 23/106 min), and ultrasound processing (US; at 24 kHz). The quality parameters evaluated for honey included liquefaction time, HMF content, diastase number, co…
Influence of M23C6 carbides on the heterogeneous strain development in annealed 420 stainless steel
2020
Understanding the local strain enhancement and lattice distortion resulting from different microstructure features in metal alloys is crucial in many engineering processes. The development of heterogeneous strain not only plays an important role in the work hardening of the material but also in other processes such as recrystallization and damage inheritance and fracture. Isolating the contribution of precipitates to the development of heterogeneous strain can be challenging due to the presence of grain boundaries or other microstructure features that might cause ambiguous interpretation. In this work a statistical analysis of local strains measured by electron back scatter diffraction and …
Formation and Transformations of Organic Salt Hydrates: Four Encenicline Hydrochloride Monohydrates and Respective Isostructural Desolvates
2018
Encenicline hydrochloride (Enc-HCl) crystallizes in four different monohydrate phases, but at the same time crystallization in a nonsolvated phase is not observed, indicating that water plays a crucial role in guiding the crystallization process and ensuring structure stability. All monohydrate phases show exceptionally high stability, and the main structural motif stays intact even after dehydration, leading to isostructural (for I and II) or isomorphic (for III) desolvates. Three monohydrate phases with determined crystal structure information consists of Enc-HCl-water hexamers that are stacked into similar slabs, that are further packed identically in monohydrates I, II, and III. The fea…
Anion-Assisted Crystallization of a Novel Type of Rhenium(IV)-Based Salt
2016
A novel rhenium(IV)–manganese(II) double salt of formula (NBu4)10[{ReCl4(ox)}3Mn]2[ReCl6] (1) (NBu4+ = tetra-n-butylammonium cation and ox2– = oxalate dianion) has been prepared through the simultaneous use of two different anionic ReIV complexes, namely, [ReCl4(ox)]2– and [ReCl6]2–, in the presence of MnII ion, the [ReCl6]2– anion playing a key role in the crystallization process. 1 has been magnetically characterized and its crystal structure determined by single-crystal X-ray diffraction. The study of the magnetic properties reveals the occurrence of intramolecular antiferromagnetic exchange between ReIV and MnII ions. Remarkably, 1 is the first reported example of ReIV salt based on two…
Enantioselective Synthesis of α-Quaternary Amino Acids by Alkylation of Deprotonated α-Aminonitriles.
2015
A series of α-quaternary arylglycines were prepared in high optical purity (up to 98% ee) by α-alkylation of deprotonated α-aminonitriles derived by the Strecker reaction from (4S,5S)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane. The procedure includes only chromatographic purification of the final products and is devoid of chromatography or crystallization operations on intermediates to raise the optical purity.
Synthesis of bi- and tricyclic β-lactam libraries in aqueous medium
2007
Water as a solvent is not only inexpensive and environmentally benign, but may allow good reactivity. The present work focuses on the application of a modified Ugi reaction, i.e. the Ugi four-centre three-component reaction (U-4C-3CR), in aqueous medium to construct β-lactam libraries. All the attempted reactions could be successfully performed in water. The reaction conditions under which the precipitation process was effective were investigated; no further work-up or purification was necessary. In several cases when less water-soluble β-amino acids were used, the precipitated products were isolated easily by simple filtration. In other cases, evaporation of the solvent was appropriate for…
High oxidation state aqueous organometallics. Formation and structure of an oxo-centred Cp*MoV trinuclear cation by chemical reduction of Cp*2Mo2O5
2002
International audience; Reduction of Cp*2Mo2O5 by zinc/CF3CO2H in MeOH–H2O yields a salt which is composed of [Cp*3Mo3O4(O2CCF3)3]+ and [Zn2(O2CCF3)6]2− ions after crystallisation from THF–Et2O.