Silica–zirconia membranes for nanofiltration

Inorganic nanofiltration membranes were fabricated from silica–zirconia composite colloidal sol (molar ratio Si/Zr=9/1) using a sol–gel process. Molecular weight cut-off (MWCO) was successfully controlled between 200 and 1000 Da by regulating the colloidal diameters of sol solutions in the final coating stage. The pure water permeabilities ranged from 0.15×10⁻¹¹ to 1.5×10⁻¹¹ m³ m⁻² s⁻¹ Pa⁻¹. Pore size and pore size distribution were estimated based on the dynamic method of humid air permeation, and found to be from 1.0 to 2.9 nm. The MWCO obtained from NF experiments using neutral organic solutes corresponds well with the pore diameters estimated from the dynamic permeation method. Silica–zirconia membranes were found to be stable in aqueous solution for periods in excess of four months.     

Cyclometalated Ir–Sn Construct for Cyanosilylation

Two cyclometalated compounds [Ir^IIICl{(2-biphenylene-1,8-naphthyridine-??C,N}(?? ⁵-pentamethylcyclopentadienyl)] (1) and [Ir^IIICl{(2-(2-N-Methyl-pyrrolyl-1,8-naphthyridine-??C,N}(?? ⁵-pentamethylcyclopentadienyl)] (2) containing naphthyridine based ligands have been synthesized in high yield. Insertion of SnCl₂ to a terminal Ir?CCl bond of 1 affords the mixed Ir?CSnCl₃ compound [Ir^IIISnCl₃{(2-biphenylene-1,8-naphthyridine-??C,N}(?? ⁵-pentamethylcyclopentadienyl)] (3). The heterobimetallic compound 3 is shown to be an excellent catalyst for a variety of cyanosilylation reactions. A cooperative mechanism has been proposed which involves the simultaneous activation of aldehyde and cyanide precursor by Sn and unbound naphthyridine nitrogen.     

HPLC assay for methylmalonyl–CoA epimerase

Methylmalonyl-CoA epimerase (MCE) is broadly distributed in nature and has diverse cellular roles. Many MCE homologues are represented in public databases, but the biochemical function and physiological roles of the majority of these putative proteins have not been investigated. Here, a simplified assay for MCE is described. In this assay, MCE converted (2S)-methylmalonyl-CoA to (2R)-methylmalonyl-CoA which in turn was converted to succinyl-CoA by methylmalonyl-CoA mutase, an enzyme specific for the 2 R isomer. MCE activity was quantified by measuring the disappearance of methylmalonyl-CoA by HPLC. To obtain the methylmalonyl-CoA mutase which was required as a reagent for the assay, an Escherichia coli strain was constructed that expressed high levels of this enzyme as a fusion protein with an 8x histidine tag. This allowed purification of the mutase in a single affinity chromatography step. Previously reported MCE assays required radioactive substrates and/or multiple reagent enzymes that were difficult to obtain. The assay reported here overcomes these difficulties and hence will facilitate studies of MCEs. Such enzymes play important roles in the metabolism of both prokaryotes and higher eukaryotes including humans.     

Polymer–protein-enhanced fluoroimmunoassay for prostate-specific antigen

Prostate-specific antigen (PSA) is a serum glycoprotein overproduced in prostate cancer, the total of which is comprised of two major forms, free and complexed. The common method for measuring of PSA is an Enzyme-linked immunosorbent assay (ELISA). Limits of detection using commercial PSA ELISA kits for free and total PSA were determined in our laboratory to be 1 and 10 ng/mL, respectively. A value of 0.10 was obtained for the free to total PSA ratio, a ratio of 0.25 being indicative of prostate cancer. A possible improvement in the sensitivity and detection limits of free and total PSA may be achieved by the ALYGNSA system (Clarizia et al., Anal Bioanal Chem 393:1531–1538, 2009). This fluorescent assay system employed a selective polymer biolinker system proven to enhance primary antibody orientation. Using this system, free and total PSA detection limits of 0.13 and 0.63 ng/mL, respectively, were realized. This amounted to an 8- and 15-fold improvement in detection limits for free and total PSA, respectively. A free to total PSA ratio of 0.20 was maintained in this study and may be useful for definitive diagnosis of prostate, as well as, other cancers.     

Circulation microchannel for liquid–liquid microextraction

A new method has been developed for liquid–liquid microextraction utilizing a circulation microchannel. A glass microchemical chip having a circular shallow microchannel in contact with a surrounding deeper microchannel was fabricated by a two-step photolithographic wet-etching technique. Surface modification reagent was selectively introduced to the shallow channel by utilizing capillary force, and the surface of the shallow channel was selectively made hydrophobic. With the aid of the hydrophobic/hydrophilic surface patterning, it was possible to keep organic solvent in the circular channel while the aqueous sample solution was continuously flowing in the deep channel. As a result, concentration extraction from sample solution to stationary extractant with a nanoliter scale volume became possible. Concentration extraction has been difficult in a multiphase continuous flow. Function of the newly developed microextraction system was verified with methyl red as a test sample, and concentration extraction to reach equilibrium was successfully carried out. A novel surface modification method utilizing frozen liquid as a masking material was also developed as a reverse process to make the shallow channel hydrophilic and the deep channel hydrophobic. Visualization of circulation motion inside the circular shallow channel induced by flow in the deep channel was observed with a particle tracing method.     

2,1,3-Benzothiadiazole-containing donor–acceptor–acceptor dyes for dye-sensitized solar cells

A series of organic dyes with a donor–acceptor–acceptor (D–A–A) configuration, in which various diarylthienylamine donors and a cyanoacrylic acid acceptor are bridged by a low-band-gap 2,1,3-benzothiadiazole acceptor, have been synthesized, characterized, and employed as photosensitizers for dye-sensitized solar cells (DSSCs). The adoption of 2,1,3-benzothiadiazole as the bridging acceptor endowed these tailor-made dyes with superior light-harvesting capabilities in comparison to their previously reported pyrimidine-based analogs. After fine-tuning the fabrication conditions, DSSCs based on these dyes showed solar spectral responses extending to the near-IR region and achieved power conversion efficiencies (PCEs) of up to 3.16% (OHexDPTB) under simulated AM 1.5G irradiation (100 mW cm^?2).     

HPTLC–densitometric and HPTLC–MS methods for analysis of flavonoids

HPTLC silica gel plates without and with fluorescence indicator F₂₅₄ in combination with n-hexane–ethyl acetate–formic acid (20:19:1, v/v/v) as a developing solvent were explored for the HPTLC–densitometric and HPTLC–MS/(MSⁿ) analyses of flavonoids. Pre-development of the plates with chloroform–methanol (1:1, v/v) was needed for reliable HPTLC–densitometric analyses of flavonoid aglycones in the whole R_F range, while 2-step pre-development (1^st methanol–formic acid (10:1, v/v), 2^nd methanol), that decreased background signals of formic acid adducts, was required for HPTLC–MS analyses. Optimization with conditioning of the adsorbent layer with water before development and saturation of the twin trough chamber resulted in required decrease of the R_F values of studied flavonoids (flavone, apigenin, luteolin, chrysin, quercetin dihydrate, myricetin, kaempferide, kaempferol, naringenin, pinocembrin).

Detection was performed based on fluorescence quenching (on the plates with F₂₅₄), natural fluorescence and after post-chromatographic derivatization with natural product reagent without or with further enhancement and stabilization of fluorescent zones with polyethylene glycol (PEG 400 or PEG 4000) or paraffin–n-hexane reagents. For all three reagents, drying temperature and time passed after drying influenced the intensity, which was increasing the first 20?min, and the stability (less than 2?h for PEGs and at least 24?h for paraffin–n-hexane) of the standards’ zones.

Optimal wavelengths for densitometric evaluation were selected based on in-situ absorption spectra scanned before and after derivatization and after stabilization. The developed method was tested via analyses of propolis, roasted coffee, rose hip, hibiscus, rosemary and sage crude extracts. To further increase the reliability of the obtained densitometric results HPTLC–MS/(MSⁿ) analyses of all crude extracts were performed. Several phenolic and non-phenolic compounds were tentatively identified.

Some possible interferences with phenolic acids (chlorogenic acid, rosmarinic acid, protocatechuic acid, gallic acid, syringic acid, ellagic acid, trans-cinnamic acid, o-coumaric acid, m-coumaric acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid) that are often present in the extracts together with flavonoids were also examined.     

Novel Soluble Fluorene–Thienothiadiazole and Fluorene–Carbazole Copolymers for Optoelectronics

Summary: Optical, photophysical, electrochemical and photoelectrical properties of novel soluble low-bandgap fluorene – thienothiadiazole based copolymers ( CHTF and CDTF ) and luminescent fluorene – carbazole copolymers, ( CFCzE and CFCZA ) were studied. Fluorene – thienothiadiazole copolymers exhibit in thin films long-wavelength absorption with maxima at 750 – 785 nm and possess low bandgap, high electron affinity and exhibit reversible electrochromic behaviour. Therefore they are of interest for electrochromic and photovoltaic applications. Spectroelectrochemical study was performed and optical switching was demonstrated. Photovoltaic devices with bulk heterojunction made of blends of copolymers and fullerene derivative [60]PCBM were prepared. The power conversion efficiency was 2–3%. On the other hand, the fluorene-carbazole copolymers exhibit blue photoluminescence with high quantum efficiency in solution and also in thin films. Light-emitting devices with intensive broad bluish-green-white emission were fabricated.     

Surface-Regulated Rhodium–Antimony Nanorods for Nitrogen Fixation

Surface regulation is an effective strategy to improve the performance of catalysts, but it has been rarely demonstrated for nitrogen reduction reaction (NRR) to date. Now, surface-rough Rh₂Sb nanorod (RNR) and surface-smooth Rh₂Sb NR (SNR) were selectively created, and their performance for NRR was investigated. The high-index-facet bounded Rh₂Sb RNRs/C exhibit a high NH₃ yield rate of 228.85±12.96 μg h⁻¹ mg⁻¹_Rh at −0.45 V versus reversible hydrogen electrode (RHE), outperforming the Rh₂Sb SNRs/C (63.07±4.45 μg h⁻¹ mg⁻¹_Rh) and Rh nanoparticles/C (22.82±1.49 μg h⁻¹ mg⁻¹_Rh), owing to the enhanced adsorption and activation of N₂ on high-index facets. Rh₂Sb RNRs/C also show durable stability with negligible activity decay after 10 h of successive electrolysis. The present work demonstrates that surface regulation plays an important role in promoting NRR activity and provides a new strategy for creating efficient NRR electrocatalysts.     

Liposomal glyco-microarray for studying glycolipid–protein interactions

A microarray enables high-throughput interaction screening of numerous biomolecules; however, fabrication of a microarray composed of cellular membrane components has proven difficult. We report fabrication of a liposomal glyco-microarray by using an azide-reactive liposome that carries synthetic and natural glycolipids via chemically selective and biocompatible liposome immobilization chemistry. Briefly, liposomes carrying anchor lipid dipalmitoylphosphatidylethanolamine (DPPE)-PEG(2000)-triphenylphosphine and ganglioside (GM1 or GM3) were prepared first and were then printed onto an azide-modified glass slide so as to afford a liposomal glyco-microarray via Staudinger ligation. Fluorescent dye release kinetics and fluorescence imaging confirmed successful liposome immobilization and specific protein binding to the intact arrayed glycoliposomes. The liposomal glyco-microarray with different gangliosides showed their specific lectin and toxin binding with different binding affinity. The azide-reactive liposome provides a facile strategy for fabrication of either a natural or a synthetic glycolipid-based membrane-mimetic glycoarray. This liposomal glyco-microarray is simple and broadly applicable and thus will find important biomedical applications, such as studying glycolipid-protein interactions and toxin screening applications.     

2005 Bunsen–Kirchhoff Award for Analytical Spectroscopy

Announcement

2005 Bunsen–Kirchhoff Award for Analytical SpectroscopyDASp Deutscher Arbeitskreis für angewandte Spektroskopie     

An improved version of Junmeng–Fang–Weiming–Fusheng approximation for the temperature integral

An improved version of Junmeng–Fang–Weiming–Fusheng approximation for the temperature integral has been developed. The accuracy of the improved approximation for the temperature integral has been tested by some numerical analyses. The systematic analysis of the relative errors involved in the kinetic parameters obtained from Junmeng–Fang–Weiming–Fusheng integral method and its improved version has been also carried out. The results have shown that the improved approximation is more accurate than Junmeng–Fang–Weiming–Fusheng approximation as the solution of the temperature integral, and that more accurate kinetic parameters can be determined from the integral method based on the improved temperature integral approximation.     

Phase Diagram for the RbBr–CuBr System

The phase diagram for the RbBr–CuBr system has been determined. In the system two intermediate compounds are formed: RbCu₂Br₃, melting congruently at 537 K and Rb₃CuBr₄, melting incongruently at 544 K. The coordinates of the two eutectic points are: 501 K, 54 mole% CuBr and 522 K, 74 mole% CuBr. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Hellmann–Feynman theorem for statistical averages

We discuss the Hellmann–Feynman theorem for degenerate states and its application to the calculation of the derivatives of statistical averages with respect to external parameters.     

Microwave-assisted sol–gel synthesis for molecular imprinting

Molecularly imprinted polymers have been the subject of intense research for several decades in both academic and industrial settings. In this paper, we introduce a novel microwave-assisted sol–gel method for molecular imprinting of silica microspheres. The microspheres were characterized, and their adsorption of imprint and non-imprint molecules was investigated. The dye molecules methyl orange and ethyl orange were used as templates. Good molecular imprinting was observed as evaluated by the re-adsorption of dye into the silica matrix followed by the removal of dye from the supernatant solution.     

Characterization of Deep Eutectic Solvents for Dispersive Liquid–Liquid Microextraction for Phenolics

Dispersive liquid–liquid microextraction using deep eutectic solvents, as novel extraction solvents, was developed for the separation, preconcentration, and determination of chlorophenol, 2,3-dihydroxybenzoic acid, p-cresol, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol in vegetable oil. Seven deep eutectic solvents composed of choline chloride and different hydrogen bond donors (ethyl glycol, glycerol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol, urea, and acetic acid) were characterized. The deep eutectic solvents formed by choline chloride-1,6-hexanediol in a 1:2 molar ratio provided the highest extraction efficiency. The sonication time, deep eutectic solvent volume, and disperser solvent were optimized. Under the optimal conditions of a sonication time of 11?min, a deep eutectic solvent volume of 90?µL, and acetone as the disperser solvent, extraction recoveries from 76.1 to 88.3% were obtained with 8.46 to 9.46 enrichment factors and the limits of detection exceeding 0.1?µg/mL with the relative standard deviations from 1.0 to 3.5%. This method using dispersive liquid–liquid microextraction with deep eutectic solvents is simple and provides high enrichment.     

Combinatorial screening of ternary Pt–Ni–Cr catalysts for methanol electro-oxidation

Methanol electro-oxidation activity of ternary Pt–Ni–Cr system was studied by using a combinatorial screening method. A Pt–Ni–Cr thin-film library was prepared by sputtering and quickly characterized by a multichannel multielectrode analyzer. Among the 63 different composition thin-film catalysts, Pt₂₈Ni₃₆Cr₃₆ showed the highest methanol electro-oxidation activity and good stability. This new composition was also studied in its powder form by synthesizing and characterizing Pt₂₈Ni₃₆Cr₃₆/C catalyst. In chronoamperometry testing, the Pt₂₈Ni₃₆Cr₃₆/C catalyst exhibited “decay-free” behavior during 600 s operation by keeping its current density up to 97.1% of its peak current density, while the current densities of Pt/C and Pt₅₀Ru₅₀/C catalysts decreased to 14.0% and 60.3% of their peak current densities, respectively. At 600 s operation, current density of the Pt₂₈Ni₃₆Cr₃₆/C catalyst was 23.8 A g_{noble metal}⁻¹, while that of those of the Pt/C and Pt₅₀Ru₅₀/C catalysts were 2.74 and 18.8 A g_{noble metal}⁻¹, respectively.     

Liquid–liquid equilibrium calculations for methanol–gasoline blends using continuous thermodynamics

This work presents the application of continuous thermodynamics to investigate the limited miscibility of methanol–gasoline blends. To predict the liquid–liquid equilibrium of these systems, the Gaussian distribution function was used to represent the composition of paraffins in the gasoline. The naphthenes and aromatics were represented by model compounds. A model has been developed using three different continuous versions of the UNIFAC model. Methanol is an associating component, and association affects phase equilibria. Therefore, the CONTAS (continuous thermodynamics of associating systems) model based on the Flory–Huggins equation, for multicomponent methanol–gasoline blends has also been investigated. The predicted results including the cloud point curve, shadow curve and phase separation data have been compared with experimental data and good agreement was found for the two UNIFAC and CONTAS models.