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Aqueous two-phase systems are generated by mixing aqueous solutions of two water-soluble polymers, or a polymer and a salt. These systems offer extremely mild conditions for separation of cells, organelles, proteins and other biomolecules, in biochemical processes. Considerable attention has been directed towards the use of the two-phase systems in several areas of biotechnology. The present paper
Precipitation and recovery of precipitates is one of the unit operations in chemical engineering that can be operated on a large scale. Experiences from the area of biotechnology have clearly shown that there is not enough selectivity in the precipitation methods used to be able to separate, for example, complex mixtures of proteins from cell homogenates. Moreover, methods to precipitate proteins
Purification of a biochemical product from fermentation broths or other complex biological mixtures generally involves a combination of techniques which resolve substances according to differences in their physicochemical properties. These techniques have traditionally been optimized individually rather than as a part of the integrated, continuous process. Moreover, a lot of the development and re
Partitioning in aqueous two-phase system (ATPS) provides a rapid and gentle means of separation of soluble as well as particulate biomaterials, e.g. proteins, nucleic acids, cells, viruses, organelles, and membranes. Partitioning between the two phases is a complex phenomenon, guided mainly by the interaction of the partitioned substance and the phase components, e.g., through hydrogen bonds, van
Conventional aqueous two-phase extraction by spontaneous partitioning has often problems with low specificity. The introduction of an affinity ligand into one of the phases has been attempted to enhance the specificity of protein partitioning (1-7; Chapters 29-31). However, this procedure still has some limitations in the effective removal of impurities as well as recovery and reuse of the ligand.
A hydrothermal method was used to prepare three nano-crystalline samples of TiO2 (S1), N-doped TiO2 (S2), and (N, Ta)-codoped TiO2 (S3) with average crystallite sizes (D) of 13-25 nm. X-ray diffraction studies confirmed a single phase of the samples with a tetragonal/anatase structure. A slight increase in the lattice parameters was observed when N and/or Ta dopants were doped into the TiO2 host l
Energy dispersive extended X-ray absorption fine structure (EDE) has been applied to Pd nanoparticle nucleation at a liquid/liquid interface under control over the interfacial potential and thereby the driving force for nucleation. Preliminary analysis focusing on Pd K edge-step height determination shows that under supersaturated conditions the concentration of Pd near the interface fluctuate ove
The interfacial reduction of aqueous [PdCl4]2- at the interface with an organic solution of ferrocene has been characterised by X-ray absorption fine structure (XAFS) spectroscopy. Use of a liquid-liquid interface as a model for homogeneous nucleation permits control of the thermodynamic driving force for nucleation, through variation of the [PdCl4]2- and ferrocene concentrations in the bulk of th
In concentrated solutions of aqueous RbCl, all of the Rb+ and Cl– ions exist as contact ion pairs. This full structural assessment is derived from the refinement of three independent experimental measurements: the Rb and Cl K-edge X-ray absorption fine structure (XAFS) and the X-ray diffraction spectra (XRD). This simultaneous refinement of the XAFS and XRD data provides high accuracy since each m
X-ray diffraction measurements of liquid water are reported at pressures up to 360 MPa corresponding to a density of 0.0373 molecules per Å3. The measurements were conducted at a spatial resolution corresponding to Qmax = 16 Å-1. The method of data analysis and measurement in this study follows the earlier benchmark results reported for water under ambient conditions having a density of 0.0333 mol
For ∼50 years mixtures of cobalt(II) and manganese(II) acetates with sodium bromide or hydrobromic acid in acetic acid have been used as catalysts for the homogeneous aerobic oxidation of alkylaromatic compounds. They are known to be stable mixtures. While characterizing this mixture via EXAFS, it was thus surprising to observe an unexpected change in the color of the reaction mixture from deep bl
The structure and chemical state of supported Pd nanoparticles in contact with H 2 in the aqueous phase have been explored by X-ray absorption spectroscopy to better understand their surface reactivity in polar condensed media. The Pd-Pd distances at substantial H 2 pressures indicate the presence of sorbed hydrogen and point to the presence of Pd hydrides, proving that such nanoparticles are har
We present a new methodology involving the simultaneous refinement of both x-ray absorption and x-ray diffraction spectra (x-ray absorption/diffraction structural refinement, XADSR) to study the hydration and ion pair structure of CaCl2 and RbBr salts in concentrated aqueous solutions. The XADSR method combines the x-ray absorption fine structure (XAFS) spectral analysis of both the cation and ani
Steady-state and picosecond time-resolved X-ray absorption spectroscopy is used to study the ground and lowest triplet states of [ReX(CO) 3 (bpy)] n+ , X = Etpy (n = 1), Cl, or Br (n = 0). We demonstrate that the transient spectra at both the Re L 3 -and Br K-edges show the emergence of a pre-edge feature, absent in the ground-state spectrum, which is associated with the electron hole created in
We use ultrafast x-ray absorption spectroscopy to determine the solvent structure change upon laser abstraction of the electron from I. The transition from hydrophilic to hydrophobic occurs over 4 ps during which a transient I-OH2 species is formed.
