Additive character of electron donation by methyl substituents within a complete series of polymethylated [1-(η6-Me9n)C6H(6-n))-closo-1,2,3-FeC2B9H11] complexes. Linear correlations of the NMR parameters and Fe(II/III) redox potentials with the number of arene methyls

A systematic method for the incorporation of the {(η(6)-Me(n)C(6)H(6-n))Fe} fragment into the dicarbollide cage was developed based on reactions between [(η(6)-Me(n)C(6)H(6-n))(2)Fe][PF(6)](2) salts (1) and Tl(2)[nido-7,8-C(2)B(9)H(11)]. These reactions proceed with elimination of one arene ligand to generate a complete series of the neutral [1-(η(6)-Me(n)C(6)H(6-n))-closo-1,2,3-FeC(2)B(9)H(11)] (2) complexes with n = 1-6 in yields ranging 15-70% depending on the arene. The structures of mesitylene and pentamethylbenzene complexes were established by X-ray diffraction analyses. All compounds were characterized by (11)B and (1)H NMR measurements, mass spectra, melting points and elemental analyses. Correlations between selected (1)H and (11)B NMR parameters and the Fe(II/III) redox potentials and the number of arene methyls for complexes 2 are linear. These facts establish direct evidence for a strictly additive character of electron donation by the methyl substituents to the arene ring and further to the Fe center and the second (dicarbollide) ligand.Correlations between the number of arene methyls (n) and selected (1)H and (11)B NMR parameters or the Fe(II/III) redox potentials for complexes [1-(η(6)-MenC(6)H(6-n))-closo-1,2,3-FeC(2)B(9)H(11)] are of strictly linear character.     

Immobilized endoproteinase Glu‐C to magnetic bead cellulose as a tool in proteomic analysis

Magnetic bead cellulose activated with divinyl sulfone was used for the immobilization of Staphylococcus aureus endoproteinase Glu‐C (EC 3.4.21.19). The immobilized proteinase was characterized by increased thermostability, by decreased self‐cleavage activity, and a possibility of repeated use. The prepared immobilized enzyme was applied for the proteolytic cleavage of α‐casein and BSA under different conditions (different composition of buffers, different pH, and different time of digestion). The possibilities of the direct use of enzyme reaction products for MALDI TOF MS analysis were shown.     

Speciation analysis to unravel the soil-to-plant transfer in highly arsenic-contaminated areas in Cornwall (UK)

Two areas near derelict calciners in Cornwall (UK) were chosen to study the uptake of arsenic from arsenic-contaminated soil into indigenous plants (heather, Calluna vulgaris; blackberry, Rubus ulmifulmus; gorse, Ulex europaeus). With total arsenic concentrations in soil ranging from 1240 to 2860 mg kg^?1 at Site 1 (Tuckingmill), no adverse effects on the growth of the plants studied were observed. Very low soil-to-plant transfer factors (0.01 to 0.03) were found although they were much higher when the extractable soil arsenic concentrations were taken into account (0.1 to 1.1). In the central dump area at Site 2 (Bissoe, 9.78% [w/w] arsenic in soil), the only plant to grow was heather, although it was severely impaired. However, heather was thriving at the edge of the dump where higher soil arsenic concentrations were found (10.32% [w/w]), indicating that arsenic is not a growth-limiting factor in itself. Soil-to-plant transfer factors in the range 2 × 10^?5–9 × 10^?4 confirm that arsenic is indeed effectively excluded from uptake, even taking into account extractable soil arsenic concentrations (9 × 10^?4–1.2 × 10^?2).

Extraction of bioavailable arsenic from soil using 0.05 mol L^?1 ammonium sulphate yielded recoveries from 1.18 to 3.34% of the total arsenic, predominantly in the form of arsenate. Extraction of arsenic and its metabolites from plants was achieved with water or a water/methanol mixture yielding recoveries up to 22.4% of the total arsenic, with arsenite and arsenate the predominant arsenic species and a minor fraction consisting of methylarsonic acid, dimethylarsinic acid and trimethylarsine oxide. The identity of the remainder of the non-extractable arsenic species still has to be revealed. Although the data suggest that higher plants synthesise organoarsenic compounds it cannot be excluded that symbiotic organisms have synthesised these compounds.     

Nanocrystalline Skinnerite (Cu3SbS3) Prepared by High-Energy Milling in a Laboratory and an Industrial Mill and Its Optical and Optoelectrical Properties

Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu₃SbS₃) in a laboratory mill and an industrial mill. This synthesis was completed after 30 min of milling in the laboratory mill and 120 min in the industrial mill, as corroborated by X-ray diffraction. XRD analysis confirmed the presence of pure monoclinic skinnerite prepared in the laboratory mill and around 76% monoclinic skinnerite, with the secondary phases famatinite (Cu₃SbS₄; 15%), and tetrahedrite (Cu_11.4Sb₄S₁₃; 8%), synthesized in the industrial mill. The nanocrystals were agglomerated into micrometer-sized grains in both cases. Both samples were nanocrystalline, as was confirmed with HRTEM. The optical band gap of the Cu₃SbS₃ prepared in the laboratory mill was determined to be 1.7 eV with UV–Vis spectroscopy. Photocurrent responses verified with I–V measurements under dark and light illumination and Cu₃SbS₃ nanocrystals showed ~45% enhancement of the photoresponsive current at a forward voltage of 0.6 V. The optical and optoelectrical properties of the skinnerite (Cu₃SbS₃) prepared via laboratory milling are interesting for photovoltaic applications.     

An overview on the application of ultrasound in extraction,separation and purification of plant polysaccharides

In view of the recent emphasis on non-conventional chemistry, application of ultrasound in isolation of plant polysaccharides represents a viable alternative to traditional extraction processes. This review presents an extensive literature survey of ultrasound-assisted extraction of polysaccharides from different plant materials, particularly herbal plants and secondary agricultural plant sources. Targeted, multistep methods were applied with respect to differences in the types of polysaccharides and their location in plant cell walls. The effectiveness of the methods was evaluated according to yield and properties of the isolated polysaccharides in comparison to classical extraction methods. Substantial shortening of extraction time, reduction of reagent consumption and/or extraction temperature are the most important advantages of the ultrasonic treatment. In combination with sequential extraction steps using different solvents, sonication was shown to be effective in separation and/or purification of polysaccharides. The disadvantages of the sonication treatment, such as degradation and compositional changes of the polysaccharide preparations are discussed as well.     

Synthesis of 5-Arylamino-4-pyrone Carboxamides. A Contribution to the Knowledge About the Reaction of Aromatic Amines and 5-Hydroxy-4-pyrones.

The reaction of aromatic amine and 5-hydroxy-4-pyrone carboxylates in glacial acetic acid gave new type of 4-pyrone derivatives, that is 5-arylamino-4-pyrone carboxanilides (3-9).     

Alkylated poly(styrene-divinylbenzene) monolithic columns for mu-HPLC and CEC separation of phenolic acids

Macroporous poly(styrene-divinylbenzene) monolithic columns were prepared in fused silica capillaries of 100 microm id by in-situ copolymerization of styrene with divinylbenzene in the presence of propan-1-ol and formamide as the porogen system. The monoliths were subsequently alkylated with linear alkyl C-18 groups via Friedel-Crafts reaction to improve the retention and chromatographic resolution of strongly polar phenolic acids. A new thermally initiated grafting procedure was developed in order to shorten the time of the alkylation process. The grafting procedure was optimized with respect to the reaction temperature, time, the grafting reactant concentration, and the solvent used. The type of solvent and the grafting temperature are the most significant factors affecting the hydrodynamic properties, porosity, and efficiency of the columns. While the equivalent particle diameter of the grafted column increased, the capillary-like flow-through pore diameter decreased in comparison to non-alkylated monoliths. The hydrodynamic permeability of the monolith decreased, but the monolithic column still permitted fast micro-HPLC separations.     

Immobilized Metal Affinity Chromatography of Phosphorylated Proteins Using High Performance Sorbents

The interactions of two model phosphoproteins (porcine pepsin and ovalbumin) with two different immobilized metal affinity chromatography (IMAC) sorbents containing immobilized Fe³⁺, Ga³⁺, and UO₂ ²⁺ ions have been investigated under various conditions. Both proteins were adsorbed on immobilized uranyl ions under acidic conditions similar to those on immobilized Fe³⁺ and Ga³⁺ ions. The retained proteins could be released either by the presence of phosphate ions in the elution buffer (immobilized Ga³⁺ and Fe³⁺ ions) or by an increased pH (all tested immobilized ions). The IMAC sorbents employed could be used under the conditions of high-performance chromatography and are suitable for the separation and analysis of intact phosphoproteins.