Application of Functionalized Ag Nanoparticles for the Determination of Proteins at Nanogram Levels Using the Resonance Light Scattering Method

A novel method for the determination of proteins in aqueous solutions has been developed based on the enhancement of resonance light scattering (RLS) of Ag nanoparticles in the presence of proteins. Factors including acidity of the media, concentration of Ag hydrosol, reaction time, temperature, and interference of non-protein substances were investigated. Under the optimal conditions, with the enhanced RLS signals at 452nm, the linear ranges of calibration curves were 0–0.8µgmL^–1 for bovine serum albumin (BSA), 0–1.2µgmL^–1 for human serum albumin (HSA), and 0–2.5µgmL^–1 for human -IgG (-IgG), respectively. The detection limits were 1.3ngmL^–1 for BSA, 10ngmL^–1 for HAS, and 5.7ngmL^–1 for -IgG.This method has been applied to the analysis of synthetic samples and real human serum samples, and the results were in good agreement with those reported by the hospital, indicating that the method presented here is not only sensitive and simple, but also reliable and suitable for practical applications.     

The determination of trace amounts of tin by flow-injection hydride generation atomic-absorption spectrometry with on-line ion-exchange separation and preconcentration

A hydride generation atomic-absorption spectrometric (AAS) method with flow-injection (FI), aimed at developing a practical routine assay for the determination of tin in food digests, is described. In order to modify the sample matrix and to achieve optimized and reproducible conditions for the hydride generation reaction, the analyte is initially converted into its chlorostannate-complex thereby allowing it to be separated and preconcentrated on-line on an incorporated micro-column packed with a strongly basic anion exchanger and subsequently to be eluted by diluted nitric acid under strictly controlled conditions. Optimum acidic conditions for the FI hydride generation AAS system was found to be 0.01-0.05M nitric acid. At a consumption of 2.7-ml sample volume, aspirated by time-based injection, the procedure resulted in an enrichment factor of 3.5 and yielded a detection limit of 0.08 microg/l. (3sigma) at a sampling frequency of 72/hr. The precision was 2.5% rsd at the 10 microg/l. level. Potential interferents, such as Ni(II), Co(II), Zn(II) and Fe(III) could, at a Sn level of 10 microg/l., be tolerated at an excess of 1000 times without impairing the assay, while a 100-1000-fold excess of Cu(II) decreased the signal by 10-15%. Recoveries in the range 94-102% were obtained for canned food sample digests spiked with 10 microg/l. Sn.     

Application of the slotted quartz tube in flow-injection flame atomic-absorption spectrometry

The slotted quartz has been applied to flow-injection flame atomic-absorption spectrometry (FI-FAAS) showing several important advantages. The tube life was improved by a factor of 5-6 compared to conventional continuous aspiration. Flow impact systems were found not to be necessary in the applications so that larger enhancement factors may be achieved without sacrifice in precision. For 1.0 mg/l. copper, 1.0 mg/l. lead, 0.1 mg/l. cadmium and 1.0 mg/l. gold sensitivity enhancement factors of 3.1, 5.5, 5.3 and 4.0 were obtained with precisions of 1.3%, 1.1%, 1.6% and 1.7% RSD (n = 11) respectively. Application of the slotted quartz tube FI-FAAS method to the determination of heavy metals in urine has shown improved tolerance to interfering matrices. Recoveries obtained by spiking undiluted urine samples with 0.1 mg/l. copper and lead, and 0.01 mg/l. cadmium were in the range 100-102%.     

Theoretical investigation of novel silsesquioxane-supported Phillips-type catalyst by density functional theory (DFT) method

In spite of great commercial importance of the Phillips CrO_x/SiO₂ catalyst and long term research efforts, the precise physicochemical nature of active sites and polymerization mechanisms still remains unclear. The difficulties in a clear mechanistic understanding of this catalyst mainly come from the complexity of the surface chemistry of the amorphous silica gel support. In this work, novel silsesquioxane-supported Phillips Cr catalysts are utilized as realistic models of the industrial catalyst for theoretical investigation using the density functional theory (DFT) method in order to elucidate the effects of surface chemistry of silica gel in terms of supporting of chromium compounds and fluorination of the silica surface on the catalytic properties of the Phillips catalyst. Both qualitative and quantitative aspects with respect to various electronic properties and thermodynamic characteristics of the model catalysts were achieved. The future prospects of a state-of-the-art catalyst design and mechanistic approaches for the heterogeneous SiO₂-supported Phillips catalyst has been demonstrated. The text was submitted by the authors in English.     

Self-assembled biotinylated disulfide derivative monolayer on gold electrode for immobilizing enzymes

Based on self-assembled biotinylated disulfide derivative monolayer on gold electrode, the sensors immobilized monolayer or multilayer membranes composed of avidin and biotinlabeled glucose oxidase (B.GOD) or of avidin-B.GOD complex (ABC) and B.COD were prepared. The present technique may be useful for controlling the enzyme content of the sensors in molecular level by repeating the deposition of enzyme layers. The sensors have the characteristics of shorter response time, higher sensitivity. The linear range is from 6.0 x 10(-6) - 5.0 x 10(-3) M. The sensor can be used for more than 1 month and can be reactivated. The sensor was used to determine glucose in human blood serum, and the results are satisfactory.     

Solvent effects on infrared spectra of methyl 4-hydroxybenzoate in pure organic solvents and in ethanol/CCl4 binary solvents

Infrared spectroscopy studies of methyl 4-hydroxybenzoate (MHB) in 17 different organic solvents and in ethanol/CCl4 binary solvent were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration nu(C=O) of MHB in single solvents were correlated with the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The assignments of the two bands of nu(C=O) of MHB in alcohols and the single one of that in non-alcoholic solvents were discussed. The shifts of nu(C=O) of MHB in ethanol/CCl4 binary solvents showed that several kinds of solute-solvent hydrogen bonding interactions coexisted in the mixture solvents, with a change in the mole fraction of ethanol in the binary solvents.     

The determination of trace amounts of heavy metals in waters by a flow-injection system including ion-exchange preconcentration and flame atomic absorption spectrometric detection

The flow-injection system combines on-line ion-exchange preconcentration with atomic absorption spectrometry (a.a.s.) for the determination of traces (μg l^?1) of heavy metals in water samples. Miniature columns packed with 60–100 mesh chelating resin (122) with a salicylic acid functional group are used for preconcentration. A multifunctional rotary sampling valve which incorporated two parallel sampling columns allows sampling, exchange, elution and a.a.s. to be achieved sequentially. The increases in sensitivity for nickel, copper, lead and cadmium were 20–28-fold at a sampling rate of 40 h^?1 with 5-ml samples. Relative standard deviations were 1.5–4.1%. The recoveries of these four metals added to tap, sea and polluted waters were generally satisfactory, except for cadmium in polluted water. The effects of column diameter and elution flow rates on sensitivity are discussed. Possible interferences are described.     

Synthesis and characterization of chitosan-graft-polycaprolactone copolymers

The graft copolymers of chitosan with polycaprolactone (PCL) were prepared through a protection-graft-deprotection route using phthaloylchitosan as intermediate. PCL macromonomers terminated with isocyanate groups reacted with hydroxyl groups of phthaloyl-protected chitosan regioselectively, and then phthaloyl groups were deprotected to give the free amino groups. The graft reaction was carried out in homogeneous system and yielded copolymers with high grafting content due to solubilization. FTIR, NMR and XRD were detected to characterize the resultant chitosan-graft-PCL copolymers.     

Palladium salicylaldimine complexes containing boronate esters

Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na₂PdCl₄ afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC₆H₄C(O)H) with H₂NC₆H₄Bpin (pin=1,2-O₂C₂Me₄) afforded the boron-containing Schiff bases, 2-HOC₆H₄C(H)=NC₆H₄Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na₂PdCl₄ afforded complexes of the type PdL₂ (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.     

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.