Surface acidity and basicity of functionalized silica particles

Tetraethoxysilane has been co-hydrolyzed with functionalized organosilanes in a modified Stöber process to produce silica particles with amino, carboxylate or dihydroimidazole groups on the surface. The effects of reaction conditions and the loading of the functionalized organosilane on particle size was examined by TEM. Fluorescence spectroscopy of the surface amino groups covalently modified with fluorescamine, and the surface carboxylate groups with 4-bromomethyl-6,7-dimethoxycoumarin, demonstrated that these functional groups were accessible for further reaction. Changes in surface acidity and basicity caused by the presence of functional groups (amine, dihydroimidazole, carboxylate) on the particle surface were determined using an indicator titration technique. Particles with surface imidazole and amine groups and particles with surface carboxylate groups have enhanced basicity and acidity, respectively. Dihydroimidazole-modified silica had greater surface basicity than the amine-modified silica. The effect on basicity and acidity increases as the amount of added functionalized silane increases. However, this increase is nonlinear with respect to the increase in added functionalized silane. Particles with both surface dihydroimidazole and carboxylate groups demonstrated reduced surface basicity and acidity.     

Thiophenylhydrazonoacetates in heterocyclic synthesis

Benzo[b]thiophen-2-yl-hydrazonoesters 4 were synthesized by coupling of 2-diazo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide ( 1 ) with either ethyl cyanoacetate or ethyl acetoacetate. The reactivity of 4 toward a variety of nitrogen nucleophiles was investigated to yield pyrazole, isoxazole, pyrimidine, triazine, pyrazolopyridine, and pyrazolopyrimidine derivatives. © 2003 Wiley Periodicals, Inc. 15:15–20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10205     

In situ growth of polymer electrolytes on lithium ion electrode surfaces

Polyacrylonitrile (PAN) films were grown on glassy carbon, nickel foam and MnO₂ substrates by cathodic electropolymerisation of acrylonitrile in acetonitrile with tetrabutylammonium perchlorate (TBAP) as the supporting electrolyte. The electronic barrier properties of the films were confirmed by impedance spectroscopy of carbon |PAN| Hg cells while the ionic resistance of the films varied from 200 kΩ cm² in the dry state to 1.4 Ω cm² when plasticised with 1 M LiPF₆ in propylene carbonate. A galvanic cell was prepared by successive electrodepositions of MnO₂ and PAN on a carbon substrate, using liquid lithium amalgam as the top contact. The cell showed a stable open circuit potential and behaved normally under the galvanostatic intermittent titration technique (GITT).     

Forward ion-exchange kinetics of heavy metal ions on the surface of carboxymethyl cellulose Sn(IV) phosphate composite nano-rod-like cation exchanger

The Nernst?CPlanck equations with some additional assumptions was used in this study to investigate the forward kinetics and ion-exchange mechanism of heavy metal ions viz. Ni²⁺?CH⁺, Cu²⁺?CH⁺, Mn²⁺?CH⁺ and Zn²⁺?CH⁺ on the surface of carboxymethyl cellulose Sn(IV) phosphate composite nano-rod-like cation-exchanger. It was observed that heavy metals' exchange processes were imparted by the particle diffusion-controlled phenomenon. Some physical parameters i.e., fractional attainment of equilibrium U(??), self-diffusion coefficients (D _o), energy of activation (E _a), and entropy of activation (??S*) were estimated. These investigations revealed that the equilibrium is attained faster at higher temperature probably because of availability of thermally enlarged matrix of carboxymethyl cellulose Sn(IV) phosphate composite nano-rod-like cation-exchange material. The physical parameters observed for this composite cation exchanger were also compared with other composite ion exchangers. The results showed that the ion-exchange phenomenon is more feasible on the surface of this composite cation exchanger as compared with the other ion exchangers which indicated the usefulness of this composite ion exchanger in various applications.     

High-Sensitivity Immunofluorescence Staining: A Comparison of the Liposome Procedure and the FASER Technique on mGR Detection

Flow cytometry has become a widely-used and powerful tool for the characterization of cells according to their expression of specific proteins. However, sensitivity of this method is still limited since conventionally labeled antibodies can be conjugated with at maximum 1–10 dye molecules. This fact resulted in the need to develop new techniques in order to identify molecules which are expressed in very low but functionally relevant amounts. In the past, we have successfully used a liposome-based high-sensitivity immunofluorescence technique to measure the expression of low abundant membrane bound glucocorticoid receptors (mGR) on different cell types. The use of this technique allows the detection of as few as 50–100 antigen molecules per cell which is due to a 100-fold to 1000-fold increase in fluorescence signal intensity compared with conventional methods. The higher sensitivity is achieved since thousands of dye molecules can be enclosed in liposomes. Another modern high-sensitivity immunofluorescence staining method is the purchasable Fluorescence Amplification by Sequential Employment of Reagents (FASER) procedure. Here, we aimed at comparing sensitivity and specificity of these two techniques for the detection of the mGR. Our data demonstrate the FASER technique to be more sensitive and also more specific for the detection of mGR as compared to the liposome technique. However, both methods have advantages and disadvantages which are discussed in detail.     

Zinc-phosphate nanoparticles with reversibly attached TNF-α analogs: an interesting concept for potential use in active immunotherapy

The authors’ intention was to prepare nanometer-sized zinc-phosphate nanoparticles that would be capable of binding histidine-rich TNF-α analogs onto their surface via a coordinative bond. Zinc-phosphate nanoparticles with a size of around 60 nm were prepared by a wet precipitation method and characterized using SEM, EDX, XRD, and DLS. First, BSA was bound as a testing protein, afterward two TNF-α analogs with decreased activity were bound to the described nanoparticles. The efficiency of binding and the existence of coordinative bond were confirmed with SDS-PAGE analysis. During binding, particle storage, and release experiments, the prepared TNF-α analogs retained their biological activity—hence the epitopes necessary for formation of antibodies stayed intact. The particle size did not change within a period of 2 weeks. No significant agglomeration was observed, the particles could be quickly dispersed in ultrasound. The present nanoparticles and the general approach of coordinative binding are widely applicable for natural and engineered histidine-rich proteins. The nanoparticles bearing appropriate TNF-α analogs could also be potentially used for active immunotherapy to tackle the chronic inflammatory diseases associated with pathogenically elevated levels of TNF-α.     

Thermal Raman shift of the C60 tangentialA g mode

Fullerence C₆₀ exhibits a continuous and reversibleA _g (2) mode softening from 1469 to 1459 cm^–1, which is linear with laser power up to 21.9 kW/cm² for C₆₀ crystals under vacuum. Model calculations taking into account the temperature distribution that is induced by the Gaussian intensity profile of the laser beam reproduce the measured frequency shifts. A thermal conductivity of microcrystalline fullerene of 0.27(±0.03) W/mK is derived from this numerical analysis.     

Biochemical analysis with microfluidic systems

Microfluidic systems are capillary networks of varying complexity fabricated originally in silicon, but nowadays in glass and polymeric substrates. Flow of liquid is mainly controlled by use of electroosmotic effects, i.e. application of electric fields, in addition to pressurized flow, i.e. application of pressure or vacuum. Because electroosmotic flow rates depend on the charge densities on the walls of capillaries, they are influenced by substrate material, fabrication processes, surface pretreatment procedures, and buffer additives. Microfluidic systems combine the properties of capillary electrophoretic systems and flow-through analytical systems, and thus biochemical analytical assays have been developed utilizing and integrating both aspects. Proteins, peptides, and nucleic acids can be separated because of their different electrophoretic mobility; detection is achieved with fluorescence detectors. For protein analysis, in particular, interfaces between microfluidic chips and mass spectrometers were developed. Further levels of integration of required sample-treatment steps were achieved by integration of protein digestion by immobilized trypsin and amplification of nucleic acids by the polymerase chain reaction. Kinetic constants of enzyme reactions were determined by adjusting different degrees of dilution of enzyme substrates or inhibitors within a single chip utilizing mainly the properties of controlled dosing and mixing liquids within a chip. For analysis of kinase reactions, however, a combination of a reaction step (enzyme with substrate and inhibitor) and a separation step (enzyme substrate and reaction product) was required. Microfluidic chips also enable separation of analytes from sample matrix constituents, which can interfere with quantitative determination, if they have different electrophoretic mobilities. In addition to analysis of nucleic acids and enzymes, immunoassays are the third group of analytical assays performed in microfluidic chips. They utilize either affinity capillary electrophoresis as a homogeneous assay format, or immobilized antigens or antibodies in heterogeneous assays with serial supply of reagents and washing solutions.     

Synthesis of acetylenic β-diketones and their conversion into 4H-pyran-4-ones,pyrazoles, and 1-hydroxy-4-pyridones

A simple method for the synthesis of acetylenic β-diketones is described. They can be cyclized to the corresponding 4H-pyran-4-ones with acids. Their reaction with hydrazine hydrate gave pyrazole derivatives isomeric with those obtained from 4H-pyran-4-ones. With hydroxyl-amine hydrochloride in ethanol, 1-hydroxy-4-pyridones are formed.     

Studies on enaminonitriles: A new synthesis of 1,3‐substituted pyrazole‐4‐carbonitrile

3‐Diethylaminoacrylonitrile ( 1 ) reacts with hydrazonyl halides ( 2a‐d ) to yield 1,3‐disubstituted pyrazole‐4‐carbonitriles 5a‐d. The acetyl 1‐p‐chlorophenylpyrazole‐4‐carbonitrile ( 5a ) condensed with hydrazine hydrate to yield the bishydrazone 10 and with dimethylformamide dimethylacetal to yield 1‐aryl‐3‐(3‐dimethylamino)acryloyl pyrazole‐4‐carbonitrile ( 11 ). This enamine reacts with hydrazine hydrate to yield the pyrazolylpyrazole ( 12 ) and with naphthoquinone to yield the 3‐naphthofuranoyl pyrazole 13. The pyra‐zolyl pyridine derivative 14 was obtained upon treatment of 11 with acetylacetone in the presence of ammonium acetate. Compound 11 was coupled with p‐chlorobenzene diazonium chloride to yield the hydrazone 16 that was coupled further with p‐chlorobenzenediazonium chloride to yield the formazane 18.