Solid-phase System Research Articles

Tetrabutylammonium phosphomolybdate on fluorapatite: an efficient solid catalyst for solvent-free selective oxidation of sulfides

A new synthetic method of sulfoxides and sulfones using solvent-free oxidations of sulfides with urea–hydrogen peroxide complex (urea–H 2O 2) and tetrabutylammonium phosphomolybdate catalyst on fluorapatite ((Bu 4N) 3[PMo 12O 40]/FAp). In the solid-phase system the oxidations of aromatic and alkyl sulfides proceeded at 4–25 °C and the corresponding sulfoxides or sulfones were selectively obtained in good yields by controlling the amount of urea–H 2O 2.

Detection and specification of noncomplement binding anti-HLA alloantibodies

The aim of the study was to investigate the distribution of human leukocyte antigen (HLA) -specific immunoglobulin (Ig) isotypes/subclasses in alloimmunized patients awaiting a kidney retransplant. Sera from 102 patients were analyzed for the presence of anti-HLA-A, anti-HLA-B alloantibodies by complement-dependent cytotoxicity test with the addition of dithiothreitol (CDC+DTT). Furthermore, anti-HLA class I and class II alloantibodies were determined using a commercial solid-phase (enzyme-linked immunosorbent assay [ELISA]) system. The respective isotypes/subclasses were defined by replacing the IgG 1–4 secondary antibody with IgG 1-, IgG 2-, IgG 3-, IgG 4-, IgA 1-, IgA 2-, and IgM-specific antibodies. The HLA specificities of the noncomplement-binding IgG 2 and IgG 4 antibodies were determined and compared with the mismatches from the failed transplants. Thirty-eight of 102 (37%) sera were positive in the class I CDC+DTT, in contrast to 41 of 102 (40%) detected by class I ELISA and 47 of 102 (46%) by class II ELISA. Seventeen of 102 (17%) positive reaction were observed for the IgM-isotype, whereas none were detected for the IgA-isotype. Twenty-five of 102 (25 %) sera contained noncomplement-binding IgG 2 and/or IgG 4 antibodies; in the majority of the cases, 22 of 25 (88%) were directed against the organ donor antigen. These data show that donor-specific, noncomplement-binding IgG 2 and IgG 4 alloantibodies exist with high prevalence in HLA-immunized retransplant candidates. Therefore, a thorough antibody screening workup, including CDC with or without DTT and ELISA screening should be performed for patients before they reenter the waiting list. Defining the Ig isotypes and subclasses can be helpful to explain inconsistent results.

Kinetics of the Formation of Zinc Ferrite in an Ultrasonic Field

wasstudied in a temperature range of 600–800°e . It wasshown that ultrasound action leads to a considerableincrease in conversion at the initial stage of interactionand changes the mechanism of the solid-phase reactionat the main stage over the entire temperature range.The overwhelming majority of studies in the field ofsonochemistry deal with investigation of ultrasoundaction on the reactions of decomposition of metal com-plexes and salts in liquid media [1, 2]. Specific featuresof the ultrasound action in solid-state systems werestudied in most detail for metals and alloys [3], as wellas alkali-metal halide and semiconductor single crys-tals [4]. Ultrasonic treatment of solids was shown toresult in a noticeable change in the dislocation density,increasing it by one or two orders of magnitude. In thisprocess, both the parameters of acoustic oscillations(frequency and power) and the treatment temperaturehave a significant effect on the dislocation structureformed under the action of ultrasound.Information on the specific features of ultrasonicaction on solid-phase oxide systems is based on frag-mentary data. Most works heretofore have beenfocused on studying separate one- and two-componentmodel systems [5–7]. It has been shown that ultrasonicaction may significantly affect the diffusion rate of ionsin both the initial oxide and reaction product. At thesame time, systematic studies aimed, first of all, atextending the range of objects of interest are requiredfor obtaining comprehensive information on the mech-anism of solid-phase sonochemical reactions in oxidesystems.In this connection, in the present work we studiedthe mechanism and kinetics of the solid-phase interac-tion between iron(III) and zinc oxides in an ultrasonicfield:ZnO + Fe

Growth and characterization of YP0.1V0.9O4 crystal

Tetragonal zircon-type YP0.1V0.9O4 single crystal has been pulled using the Czochraski method from YVO4–YPO4 solid-phase system with pulling rate in the 1.5–1.8mm/h range and the rotation rate at 10–15r/min. The analytic result for the concentration of P element indicates that YP0.1V0.9O4 single crystal can be grown with stoichiometric compositions. The refractive index and the crystal lattice parameters were tested. The optical quality of YP0.1V0.9O4 crystal including the optical uniformity and the optical damage threshold was tested and identified.

MOLCAS: a program package for computational chemistry

The program system MOLCAS is a package for calculations of electronic and structural properties of molecular systems in gas, liquid, or solid phase. It contains a number of modern quantum chemical methods for studies of the electronic structure in ground and excited electronic states. A macromolecular environment can be modeled by a combination of quantum chemistry and molecular mechanics. It is further possible to describe a crystalline material using model potentials. Solvent effects can be treated using continuum models or by combining quantum chemical calculations with molecular dynamics or Monte-Carlo simulations. MOLCAS is especially adapted to treat systems with a complex electronic structure, where the simplest quantum chemical models do not work. These features together with the inclusion of relativistic effects makes it possible to treat with good accuracy systems including atoms from the entire periodic system. MOLCAS has effective methods for geometry optimization of equilibria, transition states, conical intersections, etc. This facilitates studies of excited state energy surfaces, spectroscopy, and photochemical processes.

Rat C-reactive protein activates the autologous complement system.

Activation of complement is a biological function of human C-reactive protein (hCRP), whereas rat CRP (rCRP) has been claimed to be unable to activate complement. As important biological functions of proteins are probably conserved among species, we re-evaluated, using various ligands, the capability of rCRP to activate complement. The activation of complement by hCRP and rCRP was investigated in solid- and fluid-phase systems. In the solid-phase system, purified CRP was fixed to enzyme-linked immunosorbent assay (ELISA) plates and incubated with human or rat recalcified plasma. Dose-dependent binding of human and rat C3 and C4 was observed to human and rat CRP, respectively. In the fluid-phase system, recalcified rat plasma, which contains about 500 mg/l of CRP, or human plasma supplemented with hCRP, were incubated with lyso-phosphatidylcholine. A dose-dependent activation of complement was observed upon incubation with this ligand, as reflected by the generation of activated C4 as well as of CRP-complement complexes. This activation was, in both cases, inhibited by preincubation of plasma with p-aminophosphorylcholine, a specific inhibitor of the interaction of CRP with its ligands, or by chelation of calcium ions. We conclude that rat CRP, similarly to human CRP, can activate autologous complement. These results support the notion that opsonization of ligands with complement is an important biological function of CRP.

Keggin‐Type Polyacid Clusters on Apatite: Characteristic Catalytic Activities in Solvent‐Free Oxidation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Cetylpyridinium dodecatungstate on fluorapatite: efficient and reusable solid catalyst for solvent-free epoxidation

We have developed a new catalytic solid phase system for epoxidations using urea–hydrogen peroxide complex (urea–H2O2) and cetylpyridinium dodecatungstate ((CetylPy)10 [H2W12O42]) catalyst on fluorapatite. In the solid phase system epoxidations of cyclic alkenes and allylic alcohols proceeded without solvent at room temperature to afford the corresponding epoxides in good yields. The recovered solid catalyst phase was reusable for the reaction.

Keggin-type polyacid clusters on apatite: characteristic catalytic activities in solvent-free oxidation

We found that Keggin-type phosphometalates are effective catalysts for solvent-free oxidation with urea–H 2O 2 by dispersing on fluorapatite solid phase. In the solid phase system the phosphomolybdate (NH 4) 3PMo 12O 40 was more effective than the phosphotungstate (NH 4) 3PW 12O 40, whereas the latter was much superior to the former in the liquid-phase reaction with aqueous H 2O 2. In situ formation of novel peroxo-type species from (NH 4) 3PMo 12O 40/FAp and urea–H 2O 2, which may lead to the high catalytic activity in the solid phase system, was observed by 31P solid-state NMR.

Mo/V-Mixed-Oxides – A New Catalyst-System for the Formation of Methacrolein by Oxidative Dehydrogenation of Isobutyraldehyde?

Investigations with acrolien and methacrolein at Mo/V-mixed oxides revealed that this solid-phase system is very suitable for the partial oxidation of both educts to the corresponding carboxylic acids. This work studies the applicability of Mo/V-mixed oxides for the partial oxidation of isobutyraldehyde to methacrolein and compares the results with the catalytic performance of a heteropolyacid-catalyst.

Tubulin, actin, and tau protein interactions and the study of their macromolecular assemblies.

The intracellular polymerization of cytoskeletal proteins into their supramolecular assemblies raises many questions regarding the regulatory patterns that control this process. Binding experiments using the ELISA solid phase system, together with protein assembly assays and electron microscopical studies provided clues on the protein-protein associations in the polymerization of tubulin and actin networks. In vitro reconstitution experiments of these cytoskeletal filaments using purified tau, tubulin, and actin proteins were carried out. Tau protein association with tubulin immobilized in a solid phase support system was inhibited by actin monomer, and a higher inhibition was attained in the presence of preassembled actin filaments. Conversely, tubulin and assembled microtubules strongly inhibited tau interaction with actin in the solid phase system. Actin filaments decreased the extent of in vitro tau-induced tubulin assembly. Studies on the morphological aspects of microtubules and actin filaments coexisting in vitro, revealed the association between both cytoskeletal filaments, and in some cases, the presence of fine filamentous structures bridging these polymers. Immunogold studies showed the association of tau along polymerized microtubules and actin filaments, even though a preferential localization of labeled tau with microtubules was revealed. The studies provide further evidence for the involvement of tau protein in modulating the interactions of microtubules and actin polymers in the organization of the cytsokeletal network.

Selective Preparation of Key Intermediates for the Synthesis of Gemini Surfactants by Phase-Transfer Catalysis

A comparison of liquid-liquid and solid-liquid PTC for the selective synthesis of diglycidyl ether from protected pentaerythritol and epichlorohydrin is presented. Solid-liquid PTC was found to be more useful than liquid-liquid PTC because the use of water or other solvents can be avoided and higher yields and selectivity are achieved. It was proved that etherification takes place in the solid phase-organic phase system even in the absence of the phase-transfer catalyst. However, the use of tetrabutylammonium bisulfate as catalyst is essential due to its crucial effect on the enhancement of the rate of etherification and on the improvement of the selectivity to diglycidyl ether, which is higher than 98%.

Electronic excitation energy transfer in solid solution of 7-diethylamino-3,4-benzophenoxazine-2-one (Nile Red dye) in bis[N-2-(oxybenzylidene)-4-tert-butylaniline]zinc

Transfer of electronic excitation energy from the host material to guest molecules was studied taking the solid-phase system bis[N-(2-oxybenzylidene)-4-tert-butylaniline]zinc + 7-diethylamino-3,4-benzophenoxazine-2-one (the guest compound) as an example. The luminescence excitation spectra and the concentration quenching of green fluorescence of the host compound and the excitation of sensitized red fluorescence of the guest molecules were studied. Among the exciton mechanism of energy migration and Forster"s long-range, single-jump mechanism, the former dominates. The number of jumps (m) and the mean diffusion length of the singlet exciton (l), calculated in the framework of the model of partially delocalized, randomly hopping exciton, were estimated at ≈1.5·103 and ≈450 A, respectively.

Determination of triamterene by transitory retention in a continuous flow solid phase system with fluorimetric transduction

A rapid and simple flow-through solid phase espectrofluorimetric system (sensor) is described in this paper for the determination of the diuretic triamterene at ng ml −1 level in physiological fluids and in pharmaceuticals. This sensor is based on the transitory retention of the analyte on the cationic ion-exchanger gel Sephadex SP C-25 placed into a quartz flow-cell in the detection zone itself of a spectrofluorimeter and the continuous monitorization of its intrinsic fluorescence. The spectrofluorimeter was tuned at 240 (excitation) and 440 nm (emission). A transitory signal was obtained because the carrier solution used also eluted the analyte from the sensing zone and no derivatization reactions were needed. Triamterene could be determined in the concentration ranges of 10–400 and 2.5–80 ng ml −1 with detection limits of 0.95 and 0.17 ng ml −1 for 300 and 1000 μl of sample volume, respectively. The relative standard deviations (RSD) for ten independent determinations and at three concentration levels of standards solutions were lower than 0.90 for 300 μl and 0.45 for 1000 μl. The RSDs for the determination of triamterene in serum samples and pharmaceuticals were lower than 3.3 and 2.6%, respectively. The method was satisfactorily applied to the determination of triamterene in human serum and pharmaceuticals.

Regioselective lipase-catalyzed synthesis of glucose ester on a preparative scale

Glucose fatty acid monoesters were produced in a stirred-tank reactor in combination with a membrane-pervaporation separation unit for the regeneration of the solvent ethyl methylketone (EMK) on a preparative scale. Yields up to 79% (169 g product) were achieved in the synthesis of 6-O-stearoyl-D-glucose in a mainly solid phase system in the presence of a small amount of EMK maintaining a catalytic liquid phase as well as forming a suitable azeotropic mixture with the reaction water. High residual activity was found using lipase B from Candida antarctica under reduced pressure at 60 °C. EMK could be easily removed from the reaction mixture and is regarded as biocompatible in the preparation of food additives.

Model for simulation of freezing and thawing processes in building materials

This paper presents a mathematical model for simultaneous heat and moisture transfer under freezing–thawing in porous hygroscopic material. Even below 0°C, unfrozen liquid water exists in the material which plays an important role in the processes. The model takes into account the existence of unfrozen liquid water. The system is treated as a three-(gas, liquid and solid) phase system of water. Moisture chemical potential is used as a moisture potential. Under freezing, moisture chemical potential is a unique function of local temperature. So, during freezing, two unknown variables to be solved are solid water content and moisture potential or temperature. A simple example of simulation for freezing processes is shown.

A survey of extraction techniques for drugs of abuse in urine

Sixty nine participants in the United Kingdom national external quality assessment scheme for drugs of abuse in urine reported details of their sample extraction technique by questionnaire. Laboratories were categorised by differences in technique and their analytical test results compared for samples containing d-amfetamine 0.4 (4) and 0.8 (3) mg/l, morphine 0.4 (4) and 0.8 (4) mg/l, and benzoylecgonine 0.15/0.2 (2) and 0.45/0.5 (4) mg/l. Values in parentheses are numbers of samples. For amfetamine, there was no significant difference in the frequency of true positive results between liquid–liquid or solid phase extraction and the Toxi-Lab A system at 0.8 mg/l. Toxi-Lab A gave significantly fewer positives when operating below its specified threshold at 0.4 mg/l. Paradoxically, laboratories using >5 ml urine volume performed less well. Acidification of the extract before volume reduction gave significantly more true positives. For extraction of morphine, solid phase systems significantly outperformed both liquid–liquid and the Toxi-Lab A system at both 0.8 and 0.4 mg/l. No significant differences between extraction techniques were demonstrated for analysis of benzoylecgonine.

Oxygen diffusion in the superconductors of the YBaCuO family: isotope exchange measurements and models

Abstract The thermodynamic and kinetic aspects of the oxygen exchange in the solid oxide-oxygen phase system are discussed for the YBaCuO compounds. For both YBa 2 Cu 3 O 7− x (Y123) and Y 2 Ba 4 Cu 7 O 15− x (Y247) a vacancy model can successfully be used to describe the phase equilibrium. The dependence of some properties (lattice constants, Raman scattering, magnetic properties, and local structure EXAFS) of the nearly-equilibrium Y123 samples on the oxygen-stoichiometry is briefly presented. Studies of the carbon dioxide content in the YBaCuO family compounds show that apart of YBa 2 Cu 4 O 8 (Y124), a complete removal of the carbon without decomposition of the compounds is not possible. In the case of Y247 the influence of the CO 2 content on T C was found to be large. The oxygen-isotope exchange kinetics (tracer diffusion) for all three YBaCuO compounds is discussed in detail. In the structure of Y123 and Y247 the CuO chains are the ‘fastest paths’ for the 18 O diffusion, from which further exchange with the apex and planar sites takes place. A three-dimensional diffusion model for the oxygen exchange is presented. The model and the experimentally determined values of the diffusion coefficients allow the calculation of the isotope distribution for all three oxygen sites as a function of temperature, time and grain size. The kinetics of the low temperature ( 2 Cu 3 O 7− x and Y 0.7 Pr 0.3 Ba 2 Cu 3 O 6.98 . The total OIE in underdoped oxygen depleted Y123 increases with decreasing T C . It has been shown that the OIE in site-selectively substituted samples is mainly due to the oxygen in CuO 2 sites.

Improvement of Staphylococcus aureus-V8-protease hydrolysis of bovine haemoglobin by its adsorption on to a solid phase in the presence of SDS: peptide mapping and obtention of two haemopoietic peptides.

Hydrolysis of bovine haemoglobin by the V8 protease from Staphylococcus aureus (EC 3.4.21.19) was studied in the presence of SDS in a homogeneous-phase and in a solid-phase system. In both cases, hydrolyses were performed at 37 degrees C, in 50 mM phosphate buffer, pH 6.0, containing 0.1% SDS. Solid-phase hydrolyses were carried out with haemoglobin adsorbed on a negatively charged hydrophobic support, namely Amberlyst 15Wet (Rohm and Haas). The peptides were isolated from the hydrolysates by reverse-phase HPLC and analysed for their amino acid composition on a Waters Pico-Tag column, confirmed by second-order derivative spectrometry or by MS. A peptide map of the hydrolysates was drawn up, and numerous new cleavages in haemoglobin chains were observed, especially after Asp. This study showed that SDS permitted a dramatic improvement in the hydrolysis of whole haemoglobin by V8 protease in both homogeneous-phase and solid phase systems after adsorption of haemoglobin on to an anionic support. Moreover, in the heterogeneous phase, all the theoretical cleavage sites of V8 protease, Asp as well as Glu bonds, were hydrolysed, except for four sites which were resistant owing to strong interactions with the support. These results led to us obtain two haemopoietic peptides, namely peptide alpha (Leu(76)-Pro-Gly-Ala-Leu-Ser-Glu(82)) and peptide beta (Lys(94)-Leu-His-Val-Asp-Pro-Glu(100)). These active peptides have never before been prepared from bovine haemoglobin, and they may have great potentialities in biotechnology.

Pesquisa de anticorpos antiplaquetários. As primeiras cem amostras estudadas.

Two types of platelet alloantigens are considered: type I, which refers to platelet alloantigens shared by platelets and other cells; and type II, which comprises the platelet-specific alloantigens. The Human Platelet Alloantigens (HPA) System consists of five diallelic alloantigens and eleven low frequency antigens. According to serological antigen capture assays, immunochemical methods and studies of Molecular Genetics, the glycoproteins (GP) of platelet membrane that are most frequently associated with antibodies are GPIIb-IIIa, GPIb-IX and GPIa-IIa. It is possible to detect platelet antibodies using different laboratory methods. Our experience was restricted to a solid phase system. In this method we used the indirect technique for the screening of alloantibodies and the direct technique for the detection of autoantibodies. The procedure with chloroquine solution was performed in order to differentiate between the presence of HLA and non-HLA platelet specific antibodies. Our comments are based on results obtained in a hundred samples tested throughout a period of eleven months and we briefly review the clinical features related to the diagnosis of autoimmune and alloimmune thrombocytopenia, drug-induced thrombocytopenia and other different factors of platelet destruction. The concepts of transfusional practice applied to emergency situations, platelet refractoriness strategy and the comprehensive management of patients are approached in this work.