Synthesis and Photophysical Properties of Hetero‐Bischelated Complexes of Rhodium(III) Containing Phenyl‐Pyridin‐2‐Ylmethylene‐Amine

Three new hetero‐bischelated rhodium (III) complexes of cis‐[Rh(PA)(L)Cl₂]Cl (where PA = phenylpyridin‐2‐ylmethylene‐amine; L = 2,2′‐bipyridine, 2,2′‐dipyridylamine and 1,10‐phenanthroline) have been successfully prepared and characterized. Each complex shows high intensity bands in the UV region, and these are assigned to spin‐allowed π‐π* transitions. The medium‐intensity absorption band profile in the lower energy region can be explained by convolution of spin‐allowed CT and d‐d* transitions. The emission spectra at low temperature (77 K) of these complexes in EtOH/MeOH (4:1 v/v) are virtually identical. They all exhibit a broad, symmetric, and structureless red emission with a microsecond lifetime and hence are assigned as the d‐d* phosphorescence.     

Preparation of TiO2 Sol Using TiCl4 as a Precursor

A titanium dioxide sol with narrow particle size distribution was synthesized using TiCl₄ as the starting material. The sol was prepared by a process where HCl was added to a gel of hydrated titanium oxide to dissolve it. The resulting aqueous titanic acid solution was heated to form titanium dioxide sol. The effects of preparation parameters were investigated. TiCl₄ was slowly added to distilled water at 5°C. Aqueous solution of sodium hydroxide was added to adjust the pH of the system to 8–12. After aging for a period of time, the peptized sol was filtered and sufficiently washed. The filtered cake was repulped in water. Hydrochloric acid was slowly added to the solution with stirring. After condensation reaction and crystallization, a transparent sol with suspended TiO₂ was formed. XRD results show that the crystalline phase was anatase. The suspended TiO₂ particles were rhombus primary particles with the major axis ca. 20 nm and the minor axis ca. 5 nm. The TiO₂ particles prepared at pH 8 had the largest surface area of 141 cm³/g and it was microporous. The compositions of the solution which yielded the smallest suspended TiO₂ particles were TiO₂:HCl (35% HCl) = 1:1 (molar ratio), concentration of TiO₂ = 10%. Hydroxypropyl cellulose with viscosity of 150–400 cps was added as a dispersant. The sol was excellent in dispersibility and long-term stability. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The dip-coating on glass can be less than three times to have one monolayer TiO₂. The transparent TiO₂ thin film had strong hydrophilicity after being illuminated by UV light.     

Monolayers as models for supported catalysts: zirconium phosphonate films containing manganese(III) porphyrins

Organized monolayer films of a manganese tetraphenylporphyrin have been prepared and used as supported oxidation catalysts. Manganese 5,10,15,20-tetrakis(tetrafluorophenyl-4'-octadecyloxyphosphonic acid) porphyrin (1) has been immobilized as a monolayer film by a combination of Langmuir-Blodgett (LB) and self-assembled monolayer techniques that use zirconium phosphonate linkages to bind the molecule to the surface. Analysis by FTIR, XPS, UV-vis and polarized optical spectroscopy show that the films consist of noninteracting molecules effectively anchored and oriented nearly parallel to the surface. The monolayer films are stable to the solvent and temperature conditions needed to explore organic oxidations. The activity of films of 1 toward the epoxidation of cyclooctene using iodosylbenzene as the oxidant was compared to that of Manganese 5,10,15,20-tetrakis(pentafluorophenyl) porphyrin (2) and 1 under equivalent homogeneous conditions. The immobilized porphyrin 1 shows an enhanced activity relative to either homogeneous reaction. The main difference between 1 and 2 is the four alkyl phosphonate arms in 1 designed to incorporate the porphyrin within the films. The increased activity of immobilized 1 is a combination of the porphyrin structure, which prohibits the formation of mu-oxo dimers even in solution, and a change in conformation when anchored to the surface. The study demonstrates that careful monolayer studies can provide useful models for the design and study of supported molecular catalyst systems.     

On-membrane digestion of beta-casein for determination of phosphorylation sites by matrix-assisted laser desorption/ionization quadrupole/time-of-flight mass spectrometry

This article discusses the features of a newly developed matrix-assisted laser desorption/ionization quadrupole/time-of-flight (MALDI-QqTOF) mass spectrometer that is useful in the analysis of phosphorylated peptides. Aliquots of beta-casein, a commonly used phosphorylated protein standard, were digested with trypsin directly on a non-porous polyurethane membrane used as sample support in MALDI-QqTOF mass spectrometry (MS) experiments. Although a complete peptide map was obtained, it was difficult to obtain sequence information for some of the tryptic fragments, in particular T1-2, which bears four phosphate groups and is thus difficult to ionize in positive mode. This article focuses on the sequencing of this particular fragment by comparing MS/MS spectra obtained using different precursor ions. These precursors associated with T1-2 were [M + H](+), [M + H](2+), and [M + H - nH(3)PO(4)](+) ions. Typically, phosphorylated ions showed facile unimolecular losses of phosphoric acid moieties, and produced limited backbone fragmentation. The abundance of [M + H](2+) ions of T1-2 in the full mass spectrum was low relative to that of [M + H](+). [M + H - 4H(3)PO(4)](+) ions as MS/MS precursors underwent backbone fragmentations, with phosphoserine residues transformed into dehydroalanines or serines. Unusual b + 18 u fragments were observed, although only for segments with previously phosphorylated serines. These partly interfered with c-ions, and were noticeable due to overlapping isotopic envelopes. It was possible to establish the sequence of phosphorylated tryptic fragment T1-2 and the location of phosphate groups using the mass of dehydroalanine residues (69 Da) and b + 18 u fragments as markers. All MS and MS/MS spectra obtained with fully phosphorylated beta-casein were compared with spectra acquired with dephosphorylated beta-casein obtained commercially. These comparisons helped assess the spectral differences caused by the presence of phosphate groups. Also, they highlighted the potential usefulness of conducting dephosphorylation directly on the probe prior to MALDI analysis in future studies.     

Topological analysis of some special classes of graphs. II. steps,ladders, cylinders

A general strategy is proposed for generating the eigenvectors and the eigenvalues of some special classes of graphs from the well-known chemical graphs such as lines and cycles which are isomorphic to the hydrogen-suppressed linear and cyclic polyenes. This method is applied to step graphs, ladders, cylinders, etc. Net sign analyses are then performed for all these special classes of graphs.     

Rapid flow-injection sandwich-type immunoassays of proteins using an immobilized antibody reactor and adenosine deaminase-antibody conjugates

A rapid flow-injection sandwich enzyme immunoassay suitable for the direct determination of proteins in biological samples is described. The proposed system utilizes highly active adenosine deaminase—antibody conjugates in conjunction with a flow-through immunoreactor and an ammonium ion-selective potentiometric detector. After appropriate sample/reagent injection steps, the enzyme activity bound to the reactor is measured by diverting a coninuously flowing stream of substrate (adenosine) through the packed immunocolumn and detecting liberated ammonium ions downstream with a tubular ammonium ion-selective electrode. The bound enzyme activity is directly proportional to the concentration of analyte in the original sample. By using non-equilibrium flow-rates of sample and reagent slugs, a single protein assay takes less than 12 min, including regeneration of the reactor. The proposed method is shown to be selective, reproducible and capable of determining accurately the model protein (human IgC) at sub-μg ml^?1 concentrations.     

Theoretical studies on the intramolecular cyclization of alkyl halide anions

The intramolecular cyclization reactions of alkyl fluoride and chloride anions¹ were investigated theoretically using the AM1 method. Formation of five-membered ring was the most reactive and that of three-membered ring was the least reactive process in both series. For the fluoride series the reactivity order of n = 5 > 6 > 7 > 4 > 3 was dictated by the enthalpy (ΔH≠) effect while for the chloride series the entropy (ΔS≠) effect was found to play somewhat greater role due to the much better leaving ability of the chloride anion leading to the reactivity order of n = 5 > 6 > 4 > 7 > 3. For both series, BEP principle held and the degree of bond formation was greater with the fluoride series owing to the poor electron acceptor ability of the cleaving bond.     

Supercritical fluid extraction of the fluoroquinolones norfloxacin and ofloxacin from orally treated-chicken breast muscles

Supercritical fluid extraction (SFE) of the fluoroquinolones norfloxacin and ofloxacin from chicken breast muscles was examined. A liquid chromatography with fluorescence detection was used for the determination of the fluoroquinolones. Extraction conditions of the SFE were optimized by determining the extraction parameters to achieve a sufficiently high recovery of each fluoroquinolone in fortified-muscle samples. Recovery values for the extraction of the fluoroquinolones using the SFE ranged from 70 to 87%. Chickens were treated orally with each fluoroquinolone and their muscles were extracted at set time intervals for time-course determination of the fluoroquinolones in chickens. The SFE combined with liquid chromatographic analysis showed that the concentrations of the fluoroquinolones decreased gradually with time in the chicken muscles after oral treatment, giving a concentration less than 5 ng/ml in 120 h. No further sample cleanup procedures were required after the SFE. These results suggest that SFE method is an extraction method for the determination of norfloxacin and ofloxacin in chicken muscle.     

Zeb1 for RCP-induced oral cancer cell invasion and its suppression by resveratrol

Rab coupling protein (RCP) is upregulated in head and neck squamous cell carcinoma (HNSCC) and is correlated with the progression and survival of patients. However, the role of RCP in one of the aggressive types of HNSCC, oral squamous cell carcinoma (OSCC), remains elusive. In the present study, we identified the important role of Zeb1 in RCP-induced OSCC epithelial-to-mesenchymal transition (EMT) and invasion. RCP induces Zeb1 expression, and silencing Zeb1 expression significantly inhibits RCP-induced OSCC invasion. In addition, Zeb1 upregulates MT1-MMP expression to promote OSCC EMT and invasion. Furthermore, we observed that the β1 integrin/EGFR/β-catenin signaling cascade mediates RCP-induced Zeb1 expression to promote OSCC invasion. Notably, we provide evidence that resveratrol (REV) strongly inhibits RCP-induced Zeb1 expression through blocking β1 integrin endosome recycling and EGFR activation, leading to suppression of RCP-induced OSCC invasion, demonstrating the important role of RCP in OSCC invasion and its reversion by REV. Collectively, the present study provides evidence for the first time that RCP aggravates OSCC invasion through increasing Zeb1 expression and subsequently upregulating MT1-MMP expression and that this process is reversed by REV, providing novel biomarkers and indicating the therapeutic potential of REV in OSCC.Subject terms: Oral cancer, Cell invasion     

Rapid and sensitive silver-lipopolysaccharide staining using PhastSystem in fast horizontal polyacrylamide gel electrophoresis

A rapid and sensitive silver-lipopolysaccharide staining method has been developed by using PhastSystem. The total time of the procedure (including time of Phastgel electrophoresis) is within 2 h. It is at least 10 times faster than the previous reported methods and the sensitivity is also increased.