A 1H, 13C and 15N NMR study in solution and in the solid state of six N-substituted pyrazoles and indazoles

Three N-substituted pyrazoles and three N-substituted indazoles [1-(4-nitrophenyl)-3,5-dimethylpyrazole (1), 1-(2,4-dinitrophenyl)-3,5-dimethylpyrazole (2), 1-tosyl-pyrazole (3), 1-p-chlorobenzoylindazole (4), 1-tosylinda-zole (5) and 2-(2-hydroxy-2-phenylethyl)-indazole (6)] have been studied by NMR spectroscopy in solution (1H, 13C, 15N) and in the solid state (13C, 15N). The chemical shifts have been compared with GIAO/DFT calculated absolute shieldings. Some discrepancies have been analyzed.     

A further study on the combined use of internal standard and isotope-labeled derivatization reagent for expansion of linear dynamic ranges in liquid chromatography-electrospray mass spectrometry

The combined use of a so-called internal standard and the isotope-labeled derivatization reagent for the quantification of analytes for liquid chromatography-mass spectrometry (LC/MS) was further studied. The sample solution (containing the analytes and an internal standard) was derivatized with the light form of the derivatization reagent, 7-(N,N-dimethylaminosulfonyl)-4-(aminoethyl)piperazino-2,1,3-benzoxadiazole (DBD-PZ-NH(2)) or 7-(N,N-dimethylaminosulfonyl)-4-piperazino-2,1,3-benzoxadiazole (DBD-PZ). A standard solution of the analytes (containing an internal standard) was derivatized with the isotope (d(6))-labeled derivatization reagent, DBD-PZ-NH(2) (D) or DBD-PZ (D), and served as the isotope-labeled internal standards. The peak heights of the targeted analytes derivatives in the sample solution were corrected using those of the internal standard and the heavy form derivatives of the standards, and the calibration curves were constructed. The curve bending of the calibration curves caused by the ion suppression at the ion source was suppressed and the linear dynamic ranges of the calibration curves were expanded. The derivatives of DBD-PZ-NH(2) were about 10 times more sensitively detected than those of DBD-PZ derivatives and, therefore, DBD-PZ-NH(2) might be suitable for sensitive detection.     

Biosurfactant production by Rhodococcus erythropolis grown on glycerol as sole carbon source

The production of biosurfactant by Rhodococcus erythropolis during the growth on glycerol was investigated. The process was carried out at 28 degrees C in a 1.5-L bioreactor using glycerol as carbon source. The bioprocess was monitored through measurements of biosurfactant concentration and glycerol consumption. After 51 h of cultivation, 1.7 g/L of biosurfactant, surface, and interfacial tensions values (with n-hexadecane) of 43 and 15 mN/m, respectively, 67% of Emulsifying Index (E (24)), and 94% of oil removal were obtained. The use of glycerol rather than what happens with hydrophobic carbon source allowed the release of the biosurfactant, originally associated to the cell wall.     

Global effects of mistranslation from an editing defect in mammalian cells

Aminoacyl-tRNA synthetases prevent mistranslation, or genetic code ambiguity, through specialized editing reactions. Mutations that disrupt editing in bacteria adversely affect cell growth and viability, and recent work in the mouse supports the idea that translational errors caused by an editing defect lead to a neurological disease-like phenotype. To further investigate the connection of mistranslation to cell pathology, we introduced an inducible transgene expressing an editing-deficient valyl-tRNA synthetase into mammalian cells. Introducing mistranslation precipitated a disruption of cell morphology and membrane blebbing, accompanied by activation of caspase-3, consistent with an apoptotic response. Addition of a noncanonical amino acid that is misactivated, but not cleared, by the editing-defective enzyme exacerbated these effects. A special ambiguity-detecting sensor provided direct readout of mistranslation in vivo, supporting the possibility that decreased translational fidelity could be associated with disease.     

Hybrid rylene arrays via combination of Stille coupling and C-H transformation as high-performance electron transport materials

Hybrid rylene arrays have been prepared via a combination of Stille coupling and C-H transformation. The ability to extend the π system along the equatorial axis of rylenes not only leads to broadened light absorption but also increases the electron affinity, which can facilitate electron injection and transport with ambient stability.     

Study on interactions of endocrine disruptors with estrogen receptor-beta using fluorescence polarization.

In this study, we developed a rapid, simple and homogeneous human recombinant estrogen receptor-beta (hrER-beta) binding assay method using fluorescence polarization (FP) by applying a fluorescent ligand, fluorescein-labeled estradiol (F-E2). A Scatchard plot and a Hill plot analysis of the saturation binding assay using F-E2 and hrER-beta were studied. F-E2 showed a high affinity for hrER-beta, the dissociation constant was 5.53 nM, indicating that F-E2 is applicable to the hrER-beta binding assay. Competitive binding assays using F-E2, in which the FP values decreased upon the addition of compounds (competitors) were carried out to evaluate the binding characteristics of compounds with and without biological activities to hrER-beta. Twenty-one compounds, such as hormones, pharmaceuticals, industrial chemicals and phytoestrogens, were examined. The obtained sigmoidal inhibition curves were transformed into pseudo-Hill plots and the concentrations at 50% inhibition (IC50) and Hill coefficients, the degree of cooperativity in ER-ligand binding, were obtained from the regression equations. Antagonists exhibited larger Hill coefficients than agonists, showing the correlation between the Hill coefficients and the estrogenic/antiestrogenic activities.     

Synthesis of New Heterocyclic Ring Systems via [1,3,5]Triazino[1,2‐a]benzimidazole Derivatives

Three new heterocyclic ring systems were synthesized from [1,3,5]triazino[l,2‐a]benzimidazole derivatives, which in turn were obtained by condensation of 2‐guanidinobenzimidazole with o‐substituted ben‐zaldehydes.     

Fluorescent oxidation products derived from DBD-thiocarbamoyl amino acid in the modified Edman sequencing analysis

The fluorescent product obtained by the oxidation of 7-N, N-dimethylaminosulfonyl-4-(2,1,3-benzoxadiazolyl) (DBD)-thiocarbamoyl (TC)-proline with NaNO(2)/H(+) in the modified Edman sequencing procedure was identified as the corresponding thiazolyl compound, N-[(8-dimethylaminosulfonyl)thiazolo[5,4, e]benzo[2,1,3]oxadiazol-5-yl]-L-proline, formed by the attack of the sulfur atom of the thiocarbamoyl group on the benzofurazan skeleton. The reaction mechanism for the formation of the fluorescent compound from DBD-TC primary and secondary amines is also discussed.     

Surface properties of silk fibroin films and their interaction with fibroblasts

There is a growing interest in the use of silk as a biomaterial for tissue engineering. Silk threads from Bombyx mori have a fibrous core of fibroin, the protein responsible for biocompatibility and bioactivity, which is surrounded by a family of "gummy" proteins, called sericins, which are almost completely removed during silk degumming. Three different methanol treatments on regenerated fibroin films were used to convert viscous solutions of Silk I to an insoluble crystalline form (Silk II), in an attempt to devise new processing protocols for the creation of a cell guiding fibroin surface. Human fibroblasts (MRC5 line) were used as probes of the cell-biomaterial interaction in the early stages of the process (1 h, 3 h, 6 h and 4 d after seeding). The effect of each treatment on cell adhesion, spreading and distribution was monitored by scanning electron microscopy (SEM) and was correlated to superficial properties (like roughness and crystallinity) and fibroin conformation by means of atomic force microscopy (AFM), used in both topographical and acoustic mode, and attenuated total internal reflection infrared spectroscopy (FTIR-ATR). It was found that traditional methanol treatments where fibroin films were soaked in methanol solution produced roughness patterns that affected only the very early stages of fibroblast adhesion (until 3 h from seeding), while the new treatment proposed could really dialogue with the cells. Its non-homogeneous surface can explain the existence of cells spreading in specific directions and the presence of cell repellent areas even 4 d after seeding.     

The effect of copolymerization on transition temperatures of polymeric materials

The relationship between transition temperatures and copolymer composition was studied by DSC. Three types of copolymers were studied: styrene-acrylonitrile (SAN), vinyl chloride-vinyl acetate (VC-VA), and ethylene vinyl acetate (EVA). SAN's and VC-VA's are amorphous copolymers, whereas EVA's are semi-crystalline copolymers. The variation of the glass transitions and the crystalline melting are discussed in this study.