Immobilization and direct electrochemistry of cytochrome <Emphasis Type="BoldItalic">c</Emphasis> at a single-walled carbon nanotube-modified electrode

A single-walled carbon nanotube (SWNT)-modified electrode was fabricated and characterized by SEM and ac impedance techniques. The direct electrochemistry of cytochrome c (Cyt c), which was adsorbed on the surface of the SWNT, was studied by cyclic voltammetry. The results from cyclic voltammetry and infrared spectroscopy indicated that Cyt c remained in its original structure and did not undergo structural change after its immobilization on the SWNT. Further results demonstrated that the SWNT had promotional effects on the direct electron transfer of Cyt c and also indicated that the immobilized Cyt c retained its electrocatalytic activity to the reduction of H₂O₂. This modified electrode might be used in development of new biosensors and the biofuel cells.     

Biocompatible hydrogels based on chitosan,cellulose/starch,PVA and PEDOT:PSS with high flexibility and high mechanical strength

Fabricating mechanically strong hydrogels that can withstand the conditions in internal tissues is a challenging task. We have designed hydrogels based on multicomponent systems by combining chitosan, starch/cellulose, PVA, and PEDOT:PSS via one-pot synthesis. The starch-based hydrogels were homogeneous, while the cellulose-based hydrogels showed the presence of cellulose micro- and nanofibers. The cellulose-based hydrogels demonstrated a swelling ratio between 121 and 156%, while the starch-based hydrogels showed higher values, from 234 to 280%. Tensile tests indicated that the presence of starch in the hydrogels provided high flexibility (strain at break?>?300%), while combination with cellulose led to the formation of stiffer hydrogels (elastic moduli 3.9–6.6 MPa). The ultimate tensile strength for both types of hydrogels was similar (2.8–3.9 MPa). The adhesion and growth of human osteoblast-like SAOS-2 cells was higher on hydrogels with cellulose than on hydrogels with starch, and was higher on hydrogels with PEDOT:PSS than on hydrogels without this polymer. The metabolic activity of cells cultivated for 3 days in the hydrogel infusions indicated that no acutely toxic compounds were released. This is promising for further possible applications of these hydrogels in tissue engineering or in wound dressings.

Graphical abstract

     

Chemie der Seltenerdmetalle, 15. Mitt.: Chlortartratkomplexe der Seltenerdmetalle des Typs LnH2TCl·xH2O

Zusammenfassung Es wurden Komplexe des Typs YH₂ TCl·2H₂O, LaH₂ TCl·3H₂O und CeH₂ TCl·3H₂O isoliert. Die Individualität der Verbindungen wurde mit Hilfe der Thermoanalyse, IR-Absorptionsspektren und Röntgenstreuung geklärt.Complexes of the types YH₂ TCl·2H₂O, LaH₂ TCl·3H₂O and CeH₂ TCl·3H₂O were isolated, and the compounds characterized by thermogravimetric analysis, I. R. spectroscopy and X-ray diffraction.Mit 3 Abbildungen Ln=Y, La, Ce; H₄ T=C₄H₆O₆.     

Chemie der Seltenerdmetalle, 19. Mitt.: Dissoziation des Ce(III)-succinats im sauren Gebiet

Zusammenfassung Die Dissoziation von Ce₂ Suc ₃·3 H₂O^** in Perchlorsäure-Lösungen wurde verfolgt und die Dissoziationskonstanten der Succinationen: (CeSuc)⁺ und (CeSuc ₂)^– unter Benützung einer Löslichkeitsmethode in 1m-NH₄ClO₄-Lösung bei 25°C bestimmt. Die Löslichkeitsprodukte von Ce₂ Suc ₃: [Ce³⁺]²[Suc ^2–]³, [CeSuc ⁺]²[Suc ^2–], [CeSuc ⁺][CeSuc ₂ ^–] wurden bestimmt.

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The dissociation of Ce₂ Suc ₃·3H₂O in perchloric acid solutions was investigated. The dissociation constants of the succinate ions (CeSuc)⁺ and (CeSuc ₂)^– were determined inM-NH₄ClO₄ at 25° using a solubility method and the solubility products of Ce₂ Suc ₃, i. e. [Ce³⁺]²[Suc ^2–]³, [CeSuc ⁺]²[Suc ^2–], [CeSuc ⁺][CeSuc ₂ ^–] measured.

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18. Mitt.:R. Pastorek, Lanthantartrate im neutralen und alkal. Bereich. Mh. Chem.99, 676 (1968).     

Inorganic-Organic Hybrid Polymers from the Polymerisation of Methacrylate-Substituted Oxotantalum Clusters with Methylmethacrylate: A Thermomechanical and Spectroscopic Study

New inorganic-organic hybrid materials were prepared by free-radical polymerization of methyl methacrylate (MMA) with methacrylate-substituted oxotantalum cluster [Ta₄O₄(OEt)₈(OMc)₄] and their properties evaluated. The cluster was prepared by the reaction of the parent alkoxide with methacrylic acid. Samples of the hybrid materials were produced with Ta-cluster to methyl methacrylate in the ratios of 1:50 and 1:100 and were characterized by thermal and spectroscopic techniques. The glass transition temperatures of the hybrid materials are shifted to higher temperatures than pure PMMA as a result of cross-linking of the polymer by the oxotantalum clusters. The increase in T_g is also observed from the dynamic mechanical analysis (DMA). Evidence of crosslinking between the Ta-cluster and PMMA is obtained from infrared spectroscopic study. Surface studies performed by X-ray photoelectron spectroscopy (XPS) provide information about the atomic concentrations of the surface and indicate tantalum bonded to oxygen.     

Rapid separation of phenylthiohydantoin amino acids: ambient pressure ion-mobility mass spectrometry (IMMS)

An electrospray ionization (ESI) ambient pressure ion-mobility spectrometer (APIMS) interfaced to an orthogonal reflector time-of-flight mass spectrometer (TOFMS) was evaluated for the first time as a detector for the identification of phenylthiohydantoin (PTH)-derivatized amino acids, the final products in the Edman sequencing process of peptides and proteins. The drift and flight times of the twenty common PTH amino acids were characterized by a well-defined 2-D mobility/mass spectral pattern. The combination of mobility/mass modes of analysis gave rise to a unique trend-line formation for the series of PTH amino acids. In addition, each PTH amino acid had a unique reduced mobility constant K(o), thus enabling the differentiation of all the amino acid derivatives including the PTH-leucine and PTH-isoleucine isomers. More importantly it was shown that it was possible to resolve a complete reference mixture of PTH amino acids in a single experimental run in less than 1 min. Detection limits for the PTH amino acids were found to range from 1.04 to 3.52 ng; indicating that the limits of detection were less than 17.0 pmol for all of the PTH amino acids.     

Influence of inhibitory compounds and minor sugars on xylitol production by <Emphasis Type="Italic">Debaryomyces hansenii</Emphasis>

To obtain in-depth information on the overall metabolic behavior of the new good xylitol producer Debaryomyces hansenii UFV-170, batch bioconversions were carried out using semisynthetic media with compositions simulating those of typical acidic hemicellulose hydrolysates of sugarcane bagasse. For this purpose, we used media containing glucose (4.3–6.5 g/L), xylose (60.1–92.1 g/L), or arabinose (5.9–9.2 g/L), or binary or ternary mixtures of them in either the presence or absence of typical inhibitors of acidic hydrolysates, such as furfural (1.0–5.0 g/L), hydroxymethylfurfural (0.01–0.30 g/L), acetic acid (0.5–3.0 g/L), and vanillin (0.5–3.0 g/L). D. hansenii exhibited a good tolerance to high sugar concentrations as well as to the presence of inhibiting compounds in the fermentation media. It was able to produce xylitol only from xylose, arabitol from arabinose, and no glucitol from glucose. Arabinose metabolization was incomplete, while ethanol was mainly produced from glucose and, to a lesser less extent, from xylose and arabinose. The results suggest potential application of this strain in xyloseto-xylitol bioconversion from complex xylose media from lignocellulosic materials.     

Mixed ligand palladium(II) and platinum(II) complexes of tertiary diphosphines and benz-1,3-imidazoline-2-thione,benz-1,3-oxazoline-2-thione or benz-1,3-thiazoline-2-thione

Palladium(II) and platinum(II) complexes containing the mixed ligands tertiary diphosphines Ph₂P(CH₂) _n PPh₂, (n = 1–4) and benz-1,3-imidazoline-2-thione, benz-1,3-oxazoline-2-thione or benz-1,3-thiazoline-2-thione have been prepared and characterized by elemental analysis, magnetic susceptibility, molar conductance and i.r. spectral data. ³¹P–{¹H}-n.m.r. data have been applied to characterize the produced linkage isomers.     

R7-binding protein targets the G protein β5/R7-regulator of G protein signaling complex to lipid rafts in neuronal cells and brain

Background  

Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), composed of Gα, Gβ, and Gγ subunits, are positioned at the inner face of the plasma membrane and relay signals from activated G protein-coupled cell surface receptors to various signaling pathways. Gβ5 is the most structurally divergent Gβ isoform and forms tight heterodimers with regulator of G protein signalling (RGS) proteins of the R7 subfamily (R7-RGS). The subcellular localization of Gβ 5/R7-RGS protein complexes is regulated by the palmitoylation status of the associated R7-binding protein (R7BP), a recently discovered SNARE-like protein. We investigate here whether R7BP controls the targeting of Gβ5/R7-RGS complexes to lipid rafts, cholesterol-rich membrane microdomains where conventional heterotrimeric G proteins and some effector proteins are concentrated in neurons and brain.     

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Decomposition of dichlorodifluoromethane in thermal plasma was investigated theoretically by computing the equilibrium composition of the gas mixtures involving carbon, chlorine and fluorine in presence of argon (which is assumed to be the main plasma gas) and/or in addition of hydrogen and calcium together with hydrogen. The calculations were carried out for the temperature range between 500 and 6000 K and for the total pressure of the system of 1 bar. Use is made of the fact that a thermal plasma is a plasma in (local) thermal equilibrium, which makes possible the theoretical determination of its equilibrium composition at definite temperature by employing Gibbs free energy data for the compounds present in the system and assuming that the equilibrium of the system corresponds to its minimum energy state. The results of calculations show that toxic molecules and radicals can be, under convenient conditions (appropriate temperature and amount of added substances), converted into stable non-toxic species like CaF₂ and CaCl₂.