Determination of lanthanum and rare earth elements in bovine whole blood reference material by ICP-MS after coprecipitation preconcentration with heme-iron as coprecipitant

An analytical method for the determination of lanthanide elements in the bovine whole blood reference material (IAEA A-13) has been investigated by inductively coupled plasma mass spectrometry (ICP-MS). The bovine whole blood reference material was digested with HNO₃ and HClO₄, and then the pH of the digested solution was adjusted to 12 with 3 M sodium hydroxide aqueous solution. In this experimental procedure, lanthanide elements in the blood sample were coprecipitated with iron mainly derived from heme-iron in blood itself. In order to minimize matrix effects due to iron, excess iron in the analysis solution was removed by solvent extraction using methyl isobutyl ketone (MIBK) prior to the determination of lanthanide elements by ICP-MS. The recoveries of all lanthanide elements were almost quantitative in the recovery test. In consequence, it has been found that all lanthanide elements in bovine whole blood reference material are at the wide concentration range of 0.90 pg/g for Tm ∼1880 pg/g for Ce. Received: 2 May 1998 / Revised: 27 July 1998 / Accepted: 30 July 1998     

NMR studies of chiral discrimination by phenylcarbamate derivatives of cellulose

Chiral recognition mechanism of tris(4-trimethylsilylphenylcarbamate) ( 1) and tris(5-fluoro-2-methylphenylcarbamate) ( 2 ) of cellulose which are effective chiral stationary phases for HPLC were investigated using NMR spectroscopy. The phenylcarbamate derivatives are soluble in chloroform and exhibited chiral discrimination for several enantiomers in NMR as well as in HPLC. Especially, enantiomers of 2,2'-dihydroxy-1,1'-binaphthyl ( 4 ) were distinctly discriminated by 2 in ¹H and ¹³C NMR spectroscopies. The binding geometry and dynamics between 2 and the enantiomers of ⁴ were investigated on the basis of spin-lattice relaxation time, ¹H NMR titrations, and intermolecular NOEs in the presence of ². These NMR data were fully consistent with the chromatographic elution order. On the basis of these results, combined with molecular modeling, the chiral discrimination mechanism is proposed.     

trans-[RuCl2(phosphane)2(1,2-diamine)] and Chiral trans-[RuCl2(diphosphane)(1,2-diamine)]: Shelf-Stable Precatalysts for the Rapid,Productive, and Stereoselective Hydrogenation of Ketones

A turnover number (TON) of 2 400 000 and a turnover frequency (TOF) of 63 s⁻¹ are achieved with the chiral Ru^II complex 1 (R=p-CH₃C₆H₄) in the asymmetric hydrogenation of acetophenone. Carbonyl-selective asymmetric hydrogenation of α,β-unsaturated ketones proceeds in the presence of these Ru^II catalysts, and 4-substituted cyclohexanones are selectively converted into cis alcohols.     

Biodegradable Poly(3-hydroxybutyrate) Nanocomposite

This work seeks bringing a technological and social contribution by searching blends and composites of poly(3-hydroxybutyrate) (PHB) and polyethylene widely used in packaging films, and colloidal silica. The mixtures were prepared by extrusion using a single-screw extruder and were analyzed regarding their thermal and mechanical properties and morphology. The results have shown PHB toughness in the studied compositions, which elongation at break was in the range 5–80% compared to 2% for neat PHB. The small amount (0.2 to 0.4%) of added silica seemed to increase in 20% the tensile strength. The thermal degradation by thermogravimetry from room temperature to 800 °C revealed a mixed behavior for the composites between PHB and polyethylene.     

Solid polymer electrolytes based on polystyrene‐polyether block copolymers having branched ether structure

To obtain solid polymer electrolytes (SPEs) having high ionic conductivity together with mechanical integrity, we have synthesized polystyrene (PSt)‐polyether (PE) diblock copolymers via one‐pot anionic polymerization. The PSt block is expected to aggregate to act as hard fillers in the SPE to enhance the mechanical property. The PE block consists of random copolymer (P(EO‐r‐MEEGE)) of ethylene oxide (EO) and 2‐(2‐methoxyethoxy) ethyl glycidyl ether (MEEGE) in different molar ratios ([EO]/[MEEGE] = 100/0, 86/14, 75/25, 68/32, and 41/59). The introduction of the MEEGE moiety in PEO reduced the crystallinity of PEO, and the fast motion of the MEEGE side chain caused plasticization of the PE block, thereby contributing to the fast ion transport. SPEs were fabricated by mixing the obtained diblock copolymer (PSE_x) and lithium bis(trifluoromethanesulfonyl) amide (LiTFSA) with [Li]/[O] = 0.05. Ionic conductivity of the obtained SPEs was dependent on the molar ratio of EO in the PE block (x) as well as the weight fraction of PE block (f_PE) in the block copolymer. PSE_0.86 (f_PE = 0.65) exhibited high ionic conductivity (3.3 × 10^?5 S cm^?1 at 30°C; 1.1 × 10^?4 S cm^?1 at 60°C) comparable with that of P(EO‐r‐MEEGE) (PE_0.85; f_PE = 1.00) (9.8 × 10^?5 S cm^?1 at 30°C; 4.0 × 10^?4 S cm^?1 at 60°C).     

Interaction of Polymethine Dyes with Detonation Nanodiamonds

Among cationic, anionic, and merocyanine polymethine dyes, the binding to detonation nanodiamond (DND) colloid particles in hydrosol occurs only for negatively charged dye species. This, in view of the positive ζ-potential of the DND used in this study, suggests the predominance of electrostatic interactions over other intermolecular forces in such systems. Indeed, after decorating the merocyanine and the cationic dye by one and two negatively charged sulfopropyl groups, respectively, so that the net charge of their colored species becomes negative, the compounds also demonstrate affinity to the DND particles. In all cases, the binding of dyes to DND is accompanied by a decrease in fluorescence intensity and a bathochromic shift of their absorption and fluorescence bands. A quantitative study of the dyes adsorption on the DND nanoparticles as performed using the Küster-Freundlich and Langmuir equations reveals some peculiarities of their attaching to the DND aggregates and allows estimating the specific area of the DND particles at a concentration of 0.0212 wt/vol %.     

Stroke-Based Surface Reconstruction

In this paper, we present a surface reconstruction via 2D strokes and a vector field on the strokes based on a two-step method. In the first step, from sparse strokes drawn by artists and a given vector field on the strokes, we propose a nonlinear vector interpolation combining total variation (TV) and $H^1$ regularization with a curl-free constraint for obtaining a dense vector field. In the second step, a height map is obtained by integrating the dense vector field in the first step. Jump discontinuities in surface and discontinuities of surface gradients can be well reconstructed without any surface distortion. We also provide a fast and efficient algorithm for solving the proposed functionals. Since vectors on the strokes are interpreted as a projection of surface gradients onto the plane, different types of strokes are easily devised to generate geometrically crucial structures such as ridge, valley, jump, bump, and dip on the surface. The stroke types help users to create a surface which they intuitively imagine from 2D strokes. We compare our results with conventional methods via many examples.     

Computational studies on nonenzymatic pyroglutamylation mechanism of N-terminal glutamic acid residues in aqueous conditions*

Spontaneous cyclisation of glutamic acid (Glu) residues located at N-termini in peptides and proteins is called ‘pyroglutamylation’ and is assumed to be involved in several neurodegenerative diseases. Although it has long been believed that N-terminal Glu residues undergo pyroglutamylation enzymatically, it has recently been experimentally confirmed that nonenzymatic pyroglutamylation can proceed in some types of aqueous buffer. However, the detailed mechanism has not been proposed or investigated, and even whether some small-molecule catalysts are required for pyroglutamylation has not been clarified. Therefore, we investigated three types of pyroglutamylation mechanism of N-terminal Glu residues using quantum chemical calculations: in the absence of any catalysts, catalysed by one water molecule, and catalysed by two water molecules. All calculations were performed using N-terminal Glu residues capped with a methylamino group on the C-terminal as a model compound. Optimised energy minima and transition state geometries were obtained using the B3LYP density functional method. The pyroglutamylation mechanism is roughly divided into two steps: cyclisation and dehydration, and the calculated activation barrier was 108 and 107?kJ mol^?1 in the two- and three-water-assisted pathways, respectively. The results of computational analysis suggest that water molecules can act as catalysts for pyroglutamylation.

The calculated activation barrier of two-water-assisted pyroglutamylation was 108?kJ mol^?1, and the results of computational analysis indicate that water molecules can act as catalysts for pyroglutamylation.     

Stimuli-Responsible SNARF Derivatives as a Latent Ratiometric Fluorescent Probe

Fluorescence imaging is a powerful technique for continuous observation of dynamic intracellular processes of living cells. Fluorescent probes bearing a fluorescence switching property associated with a specific recognition or reaction of target biomolecule, that is, stimuli-responsibility, are important for fluorescence imaging. Thus, fluorescent probes continue to be developed to support approaches with different design strategies. When compared with simple intensity-changing fluorescent probes, ratiometric fluorescent probes typically offer the advantage of less sensitivity to errors associated with probe concentration, photobleaching, and environmental effects. For intracellular usage, ratiometric fluorescent probes based on small molecules must be loaded into the cells. Thus, probes having intrinsic fluorescence may obscure a change in intracellular signal if the background fluorescence of the remaining extracellular probes is high. To overcome such disadvantages, it is necessary to minimize the extracellular background fluorescence of fluorescent probes. Here, the design strategy of the latent ratiometric fluorescent probe for wash-free ratiometric imaging using a xanthene dye seminapthorhodafluor (SNARF) as the scaffold of fluorophore is discussed.