Preparation of bow tie–type methacrylated poly(caprolactone‐co‐lactic acid) scaffolds: effect of collagen modification on cell growth

A branched methacrylated poly(caprolactone‐co‐lactic acid) and methacrylated poly(tetramethylene ether glycol) (PTMG‐IEM) resins were synthesized. ¹H‐NMR spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) spectroscopy, and gel permeation chromatography confirmed the chemical structures of copolymers. The photoinitiated polymerization of formulation composed of various amounts of methacrylated poly(caprolactone‐co‐lactic acid), PTMG‐IEM, poly(ethylene glycol) diacrylate, water, and photoinitiator were performed. The curing reactions were followed by photo‐DSC (Differential scanning calorimetry). Gel fraction was calculated from the insoluble part and found as ≥93%. Swelling and contact angles were measured, and all increased with the increasing amount of PTMG‐IEM in network formulations. In vitro degradation studies were performed at 37 °C in phosphate‐buffered saline (pH 7.4). Collagen‐modified polymers were also prepared and introduced as a bioactive moiety to modify the polymer to enhance cell affinity. To compare the cell adhesion affinity to the polymer with and without collagen, cell growth experiments were performed. The results showed that collagen improves the cell adhesion onto the polymer surface. With the increasing amount of collagen, cell viability increases 86% (ECV304, p < 0.05) and 83% (3 T3, p < 0.05). Copyright © 2011 John Wiley & Sons, Ltd.     

Epimeric Isopavine N-Oxides from Roemeria refracta

Roemeria refracta DC. (Papaveraceae) of Turkish origin yielded two novel epimeric N-oxides, (?)-(5R, 11S,14R)-reframidine N-oxide ( = (?)-(5R, 11S,14R)-11,12-dihydro-14-methyl-11,5-(iminomethano)-5H -cyclohepta[1, 2-f: 4, 5-f′]bis[1,3]benzodioxole 14-oxide; 1 ) and (?)-(5R, 11S, 14S)-reframidine N-oxide ( = (?)-(5R, 11S, 14S)-11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxole 14-oxide; 2 ). The isolated (?)-roelactamine ( = (?)-11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxol-15-one, 4 ) is the first natural isopavinoid incorporating a lactam group. The epimeric (?)-15-(2-oxopropyl)reframidines ( = (?)-1-[11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxol-15-y1]propan-2-ones; 5/6 ) and the epimeric (?)-ethyl (reframidin-15-yl)acetates ( = (?)-ethyl [11, 12-dihydro-14-methyl-11, 5-(iminomethano)-5H-cyclohepta[1, 2-f:4, 5-f′]bis[1, 3]benzodioxol-15-y1]acetates; 7/8 ) are probably artifacts. (±)-Coclaurine ( 9 ), (±)-N-methylcoclaurine ( 10 ), (?)-roemeridine ( 11 ), and N-feruloyltyramine ( 12 ) are also isolated from R. refracta together with the previously reported bases. Specific ¹³C-NMR assignments are reported for the first time for the isopavines.     

Kinetics and modeling of (R,S)‐1‐phenylethanol acylation over lipase

The kinetics of the acylation of (R,S)‐1‐phenylethanol was investigated using lipase as a catalyst. The main parameters were temperature, reaction atmosphere, different acyl donors, and different amounts of acyl donor as well as the presence of some additives in the reaction mixture. The initial reaction rate increased with increasing temperature and with a decreasing amount of an acyl donor. The activated esters, such as isopropenyl‐ and vinyl acetate, exhibited very high acylation rates for R‐1‐phenylethanol, whereas low rates were obtained with ethyl acetate and 2‐methoxyethyl acetate. The addition of water and acetophenone decreased the acylation rate. A kinetic model was developed based on a sequential step mechanism, in which enzyme was reacting in the first step with an acyl donor followed by the reaction of a modified enzyme complex with the reactant, R‐1‐phenylethanol. Comparison with experimental data obtained at different temperatures allowed simplification of this model, leading to a kinetic equation with just one apparent parameter. The influence of the amount of acyl donor, ethyl acetate, could be quantitatively described by taking into account the competitive inhibition of the ethanol produced. The rate constants and apparent activation energy for experiments performed under different temperatures and the amounts of acylation agent were determined. The apparent activation energy was 24.5 kJ/mol. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 629–639, 2010     

Formation of spiro and ansa derivatives in the reaction of 2,2,3,3,4,4-hexafluoropentane-1,5-diol with cyclotriphosphazene: Comparison with 2,2,3,3-tetrafluorobutane-1,4-diol

Reaction of cyclophosphazene, N₃P₃Cl₆ (1), with the sodium derivative of the fluorinated diol, 2,2,3,3,4,4-hexafluoropentane-1,5-diol (2), in THF solution at room temperature afforded five isolated products, whose structures have been characterised by X-ray crystallography and ¹H, ¹⁹F and ³¹P NMR spectroscopy: the mono-spiro compound, N₃P₃Cl₄(OCH₂CF₂CF₂CF₂CH₂O) (3), its ansa isomer (4), a di-spiro derivative N₃P₃Cl₂(OCH₂CF₂CF₂CF₂CH₂O)₂ (5), its spiro-ansa (6) isomer and the tri-spiro compound N₃P₃(OCH₂CF₂CF₂CF₂CH₂O)₃ (7). Quantitative ³¹P NMR measurements of the soluble portion of the reaction mixture show that in the reaction of (1) with the sodium derivative of the fluorinated pentanediol (2) there is a small preference for spiro compounds compared to ansa compounds (ratio ca. 1.3:1), similar to the analogous reaction of (1) with the sodium derivative of the fluorinated butanediol where there is a slightly greater proportion of spiro compared to ansa compounds (ratio ca. 1.5:1). The relative proportions of spiro and ansa compounds is likely to depend on the fine balance in stabilities of the different medium-sized rings in the fluorinated pentanediol (spiro, 8- and ansa, 10-membered rings) compared to the fluorinated butanediol (spiro, 7- and ansa, nine-membered rings) derivatives of cyclophosphazene.     

Comparison of high-performance liquid chromatography of cyclotriphosphazene derivatives with one or two equivalent stereogenic centres

High-performance liquid chromatographic (HPLC) methods have been developed for investigating the stereogenic properties of two analogous series of dibenzylamino derivatives of cyclotriphosphazene containing either one or two equivalent stereogenic centres. Separation of the enantiomers of all the racemic compounds has been investigated by chiral HPLC using Whelk-01 and Chiralcel OD columns. In all cases, conditions for separation of enantiomers have been found using a Whelk-01 column with different ratios of tetrahydrofuran in n-hexane as the mobile phase. It is found that both the separation factor (alpha) and resolution factor (R(S)) of molecules with two equivalent stereogenic centres are greater than those for analogues with only one centre.     

2‐Meth­oxy‐4‐[(5‐oxo‐2‐phenyl‐4,5‐dihydro‐1,3‐oxazol‐4‐yl­idene)meth­yl]­phenyl 4‐methyl­benzene­sulfonate

Mol­ecules of the title compound, C₂₄H₁₉NO₆S, adopt the Z configuration and have a distorted tetra­hedral geometry around the S atom. The oxazolone, 2‐phenyl and methoxy­phenyl rings are approximately coplanar. The C atom between the methoxy­phenyl and oxazolone rings displays a distorted trigonal bonding geometry. Pairs of mol­ecules are linked into dimers through weak C—H⋯O hydrogen bonds.     

A Pseudo-Pareto Distribution and Concomitants of Its Order Statistics

Pareto distributions are very flexible probability models with various forms and kinds. In this paper, a new bivariate Pseudo-Pareto distribution and its properties are presented and discussed. Main variables, order statistics and concomitants of this distribution are studied and their importance for risk and reliability analysis is explained. Joint and marginal distributions, complementing cumulative distributions and hazard functions of the variables are derived. Numerical illustrations, graphical displays and interpretations for the obtained distributions and derived functions are provided. An implementation example on defaultable bonds is performed.     

in vitro Selection of Aptamer for Imidacloprid Recognition as Model Analyte and Construction of a Water Analysis Platform

Pesticide use in agriculture is one of the threats to water safety. Therefore, detection of pesticide residues is crucial for human health. Compared to conventional chromatographic methods, aptasensors are promising tools for fast, cheap and sensitive detection of environmental contaminants. To the best of our knowledge, such an aptasensor has not been reported for imidacloprid (Imi) which is one of the most widely used pesticides. In order to meet this demand, we initially selected two novel aptamers designated as ‘Apta‐1’ and ‘Apta‐2’ by graphene oxide‐SELEX (GO‐SELEX) method. Then, these aptamers were used to fabricate the gold electrode‐based aptasensor platforms and characterized by using electrochemical methods such as cyclic voltammetry, and electrochemical impedance spectroscopy as well as X‐Ray photoelectron spectroscopy. It was found that the limit of detection value of Apta‐1 based sensor for the Imi was found better than Apta‐2 based system, although linear ranges were similar. Based on that finding, Apta‐1 based system was further tested against possible interference molecules. The proposed platform was successfully used for detection of very low concentrations of Imi in the range of ng/mL. Thus, it eliminates the need for sample pre‐treatment and enables a practical analysis in real wastewater samples.     

Utilization of cascade chemo-bio catalysis for the synthesis of R -1-phenylethyl acetate

Liquid phase tert-butylation of m-cresol was carried out using 12-tungstosilicic acid supported on neutral alumina by varying different parameters. The reaction has also been carried out by using calcined samples under optimized conditions. The present catalyst shows an excellent activity of 93.2%, conversion of 100% selectivity for the o-isomer, an important industrial product.