Characterization of the interaction between a new merocyanine dye and bovine serum albumin

A new merocyanine dye was synthesized, and its acidity constant was determined by spectrophotometric and chemometrics methods. The interactions of the new cyanine dye with bovine serum albumin (BSA) have been studied by fluorescence and UV absorption spectroscopy at pH 7.40. A visual color change from red to blue was observed by addition of BSA to aqueous solution of the dye. The quenching constants and binding parameters (binding constants and number of binding sites) were determined at different temperatures. The calculated thermodynamic parameters confirmed that the binding reaction is mainly entropy-driven, whereas electrostatic interaction plays major role in the reaction. The displacement experiment confirmed binding of the dye to the subdomain IIA (site 1) of albumin. Moreover, synchronous fluorescence spectroscopy studies revealed the dye induces some local conformational change in BSA. The binding distance, r, between donor (serum albumin) and acceptor (dye) was obtained according to Förster’s theory.     

Chemical preparation and characterization of fibrous poly(3-methylthiophene) decorated by TiO2 nanoparticles

In this article, we report on the chemical oxidative polymerization of 3-methylthiophene (3MTh) in a concentrated TiO₂/CHCl₃ homogeneous suspension with an oxidant/monomer mole ratio of 3 at room temperature. According to the scanning electron microscopy images, in this condition, poly(3-methylthiophene) (P3MTh) was prepared with fibrous morphology decorated by nano-dimensional TiO₂ particles. P3MTh/TiO₂ was also characterized by Fourier transform infrared spectroscopy and X-ray diffraction techniques. It was found that no aggregation of nanoparticles occurred during the polymerization process. In addition, the thermal stability of P3MTh/TiO₂ nanocomposite was investigated by thermogravimetric analysis and compared with that of an analogously prepared neat P3MTh. The thermal degradation of P3MTh in the temperature range of 300–550°C decreases significantly due to the presence of the TiO₂ nanoparticles in the polymer composite.     

Label-free and sensitive impedimetric nanosensor for the detection of cocaine based on a supramolecular complexation with β-cyclodextrin,immobilized on a nanostructured polymer film

Cocaine, a powerful addictive stimulant drug, has a variety of adverse effects on the body, thus its sensitive detection is very important. Here, we report on a simple, label-free, and sensitive impedimetric sensor for determination of cocaine based on its affinity to form an inclusion complex with β-cyclodextrin (β-CD). First, we prepared nanostructured poly N-acetylaniline film via electropolymerization of its monomer on a glassy carbon electrode (PNAANI/GC), subsequently overoxidized it, and conjugated β-CD to the polymer backbone. The designed and synthesized nanostructured PNAANI film serves a dual function in the sensor: on one hand, it maintains a high effective surface area on a geometrically small electrode that significantly enhances the number of β-CD molecules immobilized on the electrode; on the other hand, it provides an upright-oriented β-CD conjugation to the polymer backbone, thus all the β-CD receptors are actively involved in responding to the target. Sensitivity of the sensor was further enhanced by preconcentration of cocaine on the modified electrode surface. We attributed the changes in the interfacial charge transfer resistance (R _ct) of the electrode to cocaine concentration. Under optimized condition (pH 7.4, 5-min accumulation at an open circuit voltage), the sensor responded to cocaine concentration in the range of 100 nM–1.0 mM with a detection limit of 50 nM. Selectivity of the sensor for cocaine relative to some potential inferring compounds was also investigated, and the results were promising. The proposed approach exhibited an extended dynamic range, low detection limit, good sensitivity, and a desirable selectivity, which provides an efficient application prospect for on-field cocaine sensing.     

Molecularly imprinted stir bar sorptive extraction coupled with high-performance liquid chromatography for trace analysis of naphthalene sulfonates in seawater

In this paper, a novel molecularly imprinted polymer coated stir bar has been used to selectively extract naphthalene sulfonates (NS_s) directly from seawater sample. 1-Naphthalene sulfonic acid (1-NS) was used as template molecule. The effects of different parameters were optimized on the extraction efficiency and the optimum conditions were established as: the absorption and desorption times were fixed, respectively, at 10 and 15 min, stirring speed was 700 rpm, pH was adjusted to 4.1, amount of NaCl was 1 mol L^?1 and extraction process was performed at a temperature of 50 °C. The linear ranges were 2–250 µg L^?1 for 3,6-NDS-1-OH (1-naphthol-3,6-disulfonic acid), 4–250 µg L^?1 for 2-NS (2-naphthalene sulfonate) and 3–250 µg L^?1 for 1-NS. The detection limits were within the range of 0.32–0.95 µg L^?1. Under optimum conditions, the detection limits of the NSs were 0.84, 0.95 and 0.32 µg L^?1 with the enrichment factor of 117-, 41- and 77-fold for 2-NS, 1-NS, and 6-NDS-1-OH, respectively. The repeatability of the method was satisfactory (0.53 ≤ RSD ≤6.0 %, n = 10). The method has been successfully applied for the analysis of trace amounts of three naphthalene sulfonates in seawater of Chabahar Bay.     

BF3·SiO2: an efficient alternative for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes

Silica-supported boron trifluoride (BF₃·SiO₂) is an efficient, readily available, and reusable catalyst for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes by condensation of 2-naphthol and aldehydes. This reaction under heating or sonication conditions is very simple, affording good to excellent yields of products.     

Synthesis,structure, and electrochemistry of <Emphasis Type="Italic">trans</Emphasis>-[Co<Superscript>III</Superscript>{(BA)<Subscript>2</Subscript>pn}(L)<Subscript>2</Subscript>]ClO<Subscript>4</Subscript> complexes

The structure, spectroscopic, and electrochemical properties of [Co{(BA)₂pn}(L)₂]ClO₄ complexes, where (BA)₂pn = N,N′-bis(benzoylacetone)-1,3-propylenediimine dianion and the two ancillary ligands (L) are pyridine, py (1), and 4-methylpyridine, 4-Mepy (2), have been investigated. These complexes have been characterized by elemental analyses, IR, UV–Vis and ¹H-NMR spectroscopy. The crystal structure of [Co{(BA)₂pn}(py)₂]ClO₄ (1) has been determined by X-ray diffraction. The coordination geometry around cobalt(III) is best described as a distorted octahedron. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial N(py)–cobalt bonds. This process becomes quasi-reversible upon the addition of excess py ligands. The second reduction step of Co^II/I shows reversible behavior and is not influenced by the nature of the axial ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

An Efficient Synthesis of 3H‐1,5‐Benzodiazepine Derivatives Catalyzed by Heteropolyacids as a Heterogeneous Recyclable Catalyst

3H‐1,5‐benzodiazepines were synthesized by the condensation of o‐phenylendiamine and various 1,3‐diketones in the presence of various heteropolyacid (HPA) catalysts under mild conditions in very good yields and with high selectivity.     

Characterization of hydrocortisone biometabolites and 18S rRNA gene in Chlamydomonas reinhardtii cultures

A unicellular microalga, Chlamydomonas reinhardtii, was isolated from rice paddy-field soil and water samples and used in the biotransformation of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25 degrees C for 14 days of incubation. The products obtained were chromatographically purified and characterized using spectroscopic methods. 11b,17 beta-Dihydroxyandrost-4-en-3-one (2), 11 beta-hydroxyandrost-4-en-3,17-dione (3), 11 beta,17 alpha,20 beta,21-tetrahydroxypregn-4-en-3-one (4) and prednisolone (5) were the main products of the bioconversion. The observed bioreaction features were the side chain degradation of the substrate to give compounds 2 and 3 and the 20-ketone reduction and 1,2-dehydrogenation affording compounds 4 and 5, respectively. A time course study showed the accumulation of product 2 from the second day of the fermentation and of compounds 3, 4 and 5 from the third day. All the metabolites reached their maximum concentration in seven days. Microalgal 18S rRNA gene was also amplified by PCR. PCR products were sequenced to confirm their authenticity as 18S rRNA gene of microalgae. The result of PCR blasted with other sequenced microalgae in NCBI showed 100% homology to the 18S small subunit rRNA of two Chlamydomonas reinhardtii spp.     

Modification of carbonic anhydrase II with acetaldehyde, the first metabolite of ethanol, leads to decreased enzyme activity

Background

Bacillus thuringiensis Cry1Aa insecticidal protein is the most active known B. thuringiensis toxin against the forest insect pest Lymantria dispar (gypsy moth), unfortunately it is also highly toxic against the non-target insect Bombyx mori (silk worm).

Results

Surface exposed hydrophobic residues over domains II and III were targeted for site-directed mutagenesis. Substitution of a phenylalanine residue (F328) by alanine reduced binding to the Bombyx mori cadherin by 23-fold, reduced biological activity against B. mori by 4-fold, while retaining activity against Lymantria dispar.

Conclusion

The results identify a novel receptor-binding epitope and demonstrate that virtual elimination of binding to cadherin BR-175 does not completely remove toxicity in the case of B. mori.     

H14[NaP5W30O110] as a heterogeneous recyclable catalyst for the air oxidation of thiols under solvent free conditions

The catalytic oxidation of thiols to the corresponding disulfides using Preyssler's catalyst H(14)[NaP(5)W(30)O(110)] has been studied. These highly selective oxidations gave good yields of the target disulfides.