The First Example of Dinuclear Co(III) Complexes Containing Crown Ether Moieties

The new dinuclear, octahedral cobalt(III) complexes have been synthesized and then their ability to interact with 4,4′-trimethylene dipyridine investigated. The ¹H and ¹³C-NMR, IR and elemental analysis data indicated that the cobalt(III) complexes are dinuclear.     

Preparation and antimicrobial properties of LL‐37 peptide immobilized lignin/caprolactone polymer film

The use of biopolymers has gained priority in tissue engineering and biotechnology, both as dressing material and for enhancing treatment efficiency. There is a demand for new biopolymers designed with protease inhibitors and antimicrobials. LL‐37 is an important antimicrobial peptide in human skin and exhibits a broad spectrum of antimicrobial activity against bacteria, fungi, and viral pathogens. Using lignin which is an abundant carbohydrate polymer in nature and a polyacrylic acid, we prepared a lignin/caprolactone biodegradable film by plastifying caprolactone and polyacyrlic acid. Lignin/caprolactone biodegradable film was activated with CDI and then immobilized LL‐37 peptide. The structure was elucidated in terms of its functional groups by attenuated total reflectance‐fourier transform infrared spectroscopy (ATR‐FTIR), and the morphology of the lignin/caprolactone biodegradable film was characterized by scanning electron microscopy (SEM) before and after the immobilization process. The amount of LL‐37 immobilized was determined by ELISA method. It was found that 97% of LL‐37 peptide was successfully immobilized onto the lignin/caprolactone biodegradable film. Antimicrobial activity was determined in the lignin/caprolactone biodegradable film samples by quantitative antimicrobial activity method. According to the results, LL‐37 immobilized lignin/caprolactone biodegradable film samples were effective on test organisms; Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli. In bio‐compatibility assays, the ability to support tissue cell integration was detected by using 3 T3 mouse fibroblasts. Samples were examined under transverse microscope, non‐immobilized sample showed a huge cellular death, whereas LL‐37 immobilized lignin/caprolactone biodegradable film had identical cellular growth with the control group. This dual functional lignin/caprolactone biodegradable film with enhanced antibacterial properties and increased tissue cell compatibility may be used to design new materials for various types of biological applications.     

Optimization and Validation of RP-LC/UV–VIS Detection Method for Simultaneous Determination of Fat-Soluble Anti-Oxidant Vitamins, all-trans-Retinol and α-Tocopherol in Human Serum: Effect of Experimental Parameters

A versatile isocratic reversed-phase liquid chromatographic/ultraviolet–visible detection method for simultaneous determination of all-trans-retinol and α-tocopherol in human serum was developed and validated after optimization of various chromatographic conditions and other experimental parameters. Analytes were separated on a Kromasil 100 RP₁₈ (150 × 4.6 mm, 5 μm) analytical column protected by a Perkin Elmer RP₁₈ (30 × 4.6 mm, 10 μm) guard cartridge. The mobile phase, methanol–water (96:04 v/v) was pumped at a flow rate of 2.2 mL min^?1 and the column eluents were monitored at the wavelength of 292 nm using retinyl acetate (1.0 μg mL^?1) as the internal standard for both analytes. Sample preparation was based on protein precipitation and stabilization with 2,6-bis(1,1-dimethylethyl)-4-methylphenol/ethanol and a two step extraction process using n-hexane followed by dichloromethane as extraction solvents. Sample size was kept 20 μL and separation of analytes was achieved in less than 7 min. The present method demonstrated acceptable values for specificity/selectivity, linearity within the expected concentration range, recovery, precision, sensitivity, stability of solutions, robustness, and system suitability specifications and tests. The method was used for monitoring all-trans-retinol and α-tocopherol concentrations in human serum samples and could also be applied to other sample matrices such as brain slices and cosmetic products if attention is paid to the extraction procedure.     

Tandem nitrosation/cycloaddition of heterocyclic enamines using nitrolic acids

The reaction of alkylidenepyrrolidines with nitrolic acids gives rise to the formation of novel 3,7a-disubstituted (1,2,4-oxadiazol-5-yl)-5,6,7,7a-tetrahydropyrrolo[1,2-d][1,2,4]oxadiazoles. A plausible mechanism for this reaction is proposed, which features nitrosation of the enamine by the nitrous acid that is liberated from the nitrolic acid.     

XYZH systems as potential 1,3-dipoles. Part 62: 1,3-Dipolar cycloaddition reactions of metallo-azomethine ylides derived from α-iminophosphonates

Metallo-azomethine ylides, generated from iminophosphonates in combination with LiBr or AgOAc and bases Et₃N, DBU, t-butyl tetramethylguanidine(BTMG) undergo cycloaddition to give dialkyl pyrrolidine-2-phosphonates along with the corresponding Michael adduct in some cases. Cycloadditions with the chiral dipolarophile 5R-(1′R,2′S,5′R-menthyloxy)-2-(5H)-furanone (MOF) afforded enantiopure cycloadducts.     

In situ palladium/N-heterocyclic carbene complex catalyzed carbonylative cross-coupling reactions of arylboronic acids with 2-bromopyridine under CO pressure: efficient synthesis of unsymmetrical arylpyridine ketones and their antimicrobial activities

Transition Metal Chemistry - The carbonylative Suzuki cross-coupling of 2-bromopyridine with various boronic acids to prepare unsymmetrical arylpyridine ketones has been carried out using...     

Platinum species in the pores of NaX, NaY and NaA zeolites studied using EPR, XAS and FTIR spectroscopies

The results of X-band EPR, X-ray absorption and Fourier transform infrared spectroscopy on Pt(NH(3))(4)(2+) exchanged NaX, NaY and NaA zeolites reveal after oxygen calcination at 573 K that diamagnetic Pt(2+) is not the only product. Calcination provides Pt(3+) cations, but depending on the heating rate, the decomposition of amino groups during calcination also produces hydrogen that reduces Pt(3+) to Pt(2+) and Pt(+). NaX (Si/Al = 1.23) has a more negative framework charge than NaY (Si/Al = 2.31), so Pt(3+) can be stabilized only in NaX, whereas lower oxidation states of Pt such as Pt(+) can be stabilized in both, NaX and NaY, and neither of the paramagnetic Pt cations are stabilized in NaUSY (Si/Al = 3). The autoreduction process allows controlling the number of Pt(3+) and Pt(+) in the NaX zeolite by changing the calcination heating rate: a heating rate of 1.25 K min(-1) gives only Pt(+), but 0.5 K min(-1) gives a Pt(3+)/Pt(+) ratio close to 1. The structure of the support is also important for the synthesis of Pt species. While isolated paramagnetic Pt ions were stabilized in faujasite zeolites (NaX and NaY), a paramagnetic Pt dimer was obtained in a Linde type A zeolite (LTA, Si/Al = 1) by applying the same preparation methods. The fraction of paramagnetic Pt species which were characterized by X-band EPR spectroscopy amounts to 2-18% of the total Pt in the zeolites, the remaining Pt must be diamagnetic.     

Inactivation of Escherichia coli by alternative electric current in rivers discharged into sea

Inactivation effect of alternative electric current on Escherichia coli ATCC 25922 and fecal E. coli MAAG 1405 found resistant to antibiotics was examined in water samples collected from Ayamama River, Sar?su River, and their discharge points into sea and from Black Sea and Marmara Sea. In addition to water samples, lauryl sulfate broth was used as an organic rich medium. Both test strains were inactivated within 1–3 min in media containing marine waters (1 A), 5–10 min in Ayamama River water (1 A), 5 min in Sar?su River water (0.5 A), 20–35 min in lauryl sulfate broth (1 A) by applying alternative electric current.     

Prediction of retention times and peak widths in temperature-programmed gas chromatography using the finite element method

Optimization of separations in gas chromatography is often a time-consuming task. However, computer simulations of chromatographic experiments may greatly reduce the time required. In this study, the finite element method was used to predict the retention times and peak widths of three analytes eluting from each of four columns during chromatographic separations with two temperature programs. The data acquired were displayed in predicted chromatograms that were then compared to experimentally acquired chromatograms. The differences between the predicted and measured retention times were typically less than 0.1%, although the experimental peak widths were typically 10% larger than expected from the idealized calculations. Input data for the retention and peak dispersion calculations were obtained from isothermal experiments, and converted to thermodynamic parameters.     

The scattering of a plane wave by two parallel semi-infinite overlapping screens with dielectric loading

The diffraction of a plane electromagnetic wave by two parallel, overlapping, perfectly conducting half-planes with a dielectric loading is considered by using the Fourier transform technique in conjunction with the mode-matching method. This mixed method of formulation enables one to obtain directly two uncoupled modified Wiener–Hopf equations instead of a matrix one. When the overlap length is set to zero and the dielectric loading is removed, the results are shown to coincide exactly with those obtained previously by Abrahams [1]. Numerical results showing the effects of the dielectric loading on the transmitted field are also presented.