Synthesis of a fluorescent xanthenic derivative useful for labeling amine residues

The 2,5-dioxopyrrolidin-1-yl-4-(3-hydroxy-6-oxo-6H-xanthen-9-yl)-3-methylbenzoate has been synthesized as an amine-reactive derivative able to yield stable covalently labeled biopolymers. The new derivative has been used to label polyribocytidilic acid (5'), poly(C), amine residues. TG-II-poly(C) exhibits monoexponential decay at the physiological pH range. In addition, both steady-state fluorescence intensity and fluorescence decay are also sensitive to solution pH. The large decrease in steady-state fluorescence upon hybridization allows it to be used as a nucleic acid probe in a homogeneous assay format. In summary, we report an efficient synthesis to obtain labeled RNA from commercially available materials in excellent yields.     

Car-Parrinello MD simulations for the Na+ -phenylalanine complex in aqueous solution

Car-Parrinello molecular dynamics (CPMD) calculations are presented for a Na (+)(Phe) complex in aqueous solution and for various stable Na (+)(Phe) complexes and Na (+)(H 2O) n clusters in the gas phase (with up to six water molecules). The CPMD results are compared to available experimental and ab initio reference data, to DFT results obtained with various combinations of density functionals and basis sets, and to previous classical mechanics MD simulations. The agreement with the reference data in the gas phase validates the CPMD method, showing that it is a valid approach for studying these systems and that it describes correctly the competing Na (+)-Phe and Na (+)-H 2O interactions. Analysis of MD trajectories reveals that the Na (+)(Phe) complex in aqueous solution maintains a stable configuration in which the Na (+) cation hovers above the phenyl ring, at an average distance of 3.85 A from the ring center, while remaining strongly bound to one of the carboxylic oxygens of Phe. Constrained MD simulations indicate that the free energy barrier opposing dissociation of the complex exceeds 5.5 kcal/mol. We thus confirm that "cation- pi" interactions between alcali cations and the pi ring, combined with other kinds of interactions, may allow aromatic amino acids to overcome the competition with water in binding a cation.     

Cellular adhesion, proliferation and viability on conducting polymer substrates

This work reports a comprehensive study about cell adhesion and proliferation on the surface of different electroactive substrates formed by pi-conjugated polymers. Biological assays were performed considering four different cellular lines: two epithelial and two fibroblasts. On the other hand, the electroactivity of the three conducting systems was determined in physiological conditions. Results indicate that the three substrates behave as a cellular matrix, even though compatibility with cells is larger for PPy and the 3-layered system. Furthermore, the three polymeric systems are electro-compatible with the cellular monolayers.     

Chemistry and biology of the aeruginosin family of serine protease inhibitors

The aeruginosins have been isolated from marine sponges and cyanobacterial waterblooms, sources that are phylogenetically distinct and the bodies of water are geographically well-separated. The aeruginosins comprise a central hydroxy- (or dihydroxy-) octahydroindole carboxamide core unit, onto which are appended unusual amino acids on the carboxy and amino termini as part of the linear peptide array. Potent inhibitory activity of serine proteases in vitro is exhibited by some of the aeruginosins as a result of the presence and proper deployment of three important pharmacophoric subunits: a P1 arginine mimetic, and two hydrophobic residues with interaction sites designated as P2 and P3. In this article, we provide the first comprehensive review on the chemistry and biology of the aeruginosins, with an emphasis on their sources, structural revisions, and total syntheses.     

NADH Electrooxidation Using Bis(1,10-phenanthroline-5,6-dione) (2,2'-bipyridine)ruthenium(II)-Exchanged Zirconium Phosphate Modified Carbon Paste Electrodes

We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10‐phenanthroline‐5,6‐dione)(2,2′‐bipyridine)ruthenium(II) ([Ru(phend)₂bpy]²⁺) exchanged into the inorganic layered material zirconium phosphate (ZrP). X‐Ray powder diffraction showed that the interlayer distance of ZrP increases upon [Ru(phend)₂bpy]²⁺ intercalation from 10.3 Å to 14.2 Å. The UV‐vis and IR spectroscopies results showed the characteristic peaks expected for [Ru(phend)₂bpy]²⁺. The UV‐vis spectrophotometric results indicate that the [Ru(phend)₂bpy]²⁺ concentration inside the ZrP layers increased as a function of the loading level. The exchanged [Ru(phend)₂bpy]²⁺ exhibited luminescence even at low concentration. Modified CPEs were constructed and analyzed using cyclic voltammetry. The intercalated mediator remained electroactive within the layers (E°′=–38.5 mV vs. Ag/AgCl, 3.5 M NaCl) and electrocatalysis of NADH oxidation was observed. The kinetics of the modified CPE shows a Michaelis–Menten behavior. This CPE was used for the oxidation of NADH in the presence of Bakers' yeast alcohol dehydrogenase. A calibration plot for ethanol is presented.     

Viscum album aqueous extract induces NOS-2 and NOS-3 overexpression in Guinea pig hearts

Viscum album L. aqueous extract, on the Langendorff isolated and perfused heart model, decreases coronary vascular resistance, when compared to control group (36.00 +/- 2.00 vs. 15.80 +/- 1.96 dyn s cm-5). Our data support the fact that this mechanism involves NOS-2 and NOS-3 overexpression (4.65 and 7.89 times over control, respectively), which is correlated with increases in NO (6.24 +/- 2.49 vs. 147.95 +/- 2.79 pmol) and cGMP production (43.94 +/- 2.00 vs. 74.81 +/- 1.96 pmol mg-1 of tissue), compared to control values. Such an effect is antagonized by gadolinium(III) chloride, L-NAME and ODQ. Therefore, coronary vasodilator effect elicited by V. album L. aqueous extract is mediated by the NO/sGC pathway.     

Effect of Perylene as Electron Acceptor and poly(tetrabromo-p-phenylene Diselenide) as “Buffer Layer” on Heterojunction Solar Cells Performances

Summary : Perylene derivatives, that behave as liquid crystal and might be used as electron acceptors, and poly(tetrabromo-p-phenylenediselenide) (PTBrPDSe) were synthesized with the purpose of using the polymer as buffer layer in solar cells. It was demonstrated that perylene compounds of N,N′-diheptyl-3,4,9,10-perylentetracarboxyldiimide (PTCDI-C7) and N,N′-diundecyl-3,4,9,10-perylentetracarboxyldiimide (PTCDI-C11) enabled obtaining photovoltaic effect when coupled with copper phthalocyanine (CuPc). The power conversion efficiency of the cells prepared from these perylenes is similar, whatever the x value. However this efficiency is smaller than the one achieved when the couple CuPc/C₆₀ (fullerene) is used. More precisely, the best efficiency was obtained when a PTBrPDSe/Au buffer layer is introduced between the ITO anode and the CuPc. It was established that the presence of the thin PTBrPDSe layer allows improving the shunt resistance and consequently the cells performance.     

Solubility of β-carotene in ethanol- and triolein-modified CO2

Modification of an experimental device and methodology improved speed and reproducibility of measurement of solubility of β-carotene in pure and modified SuperCritical (SC) CO₂ at (313 to 333) K. Solubilities of β-carotene in pure CO₂ at (17 to 34) MPa ranged (0.17 to 1.06) μmol/mol and agreed with values reported in literature. The solubility of β-carotene in CO₂ modified with (1.2 to 1.6) % mol ethanol increased by a factor of 1.7 to 3.0 as compared to its solubility in pure CO₂ under equivalent conditions. The concentration of triolein in equilibrated ternary (CO₂ + β-carotene + triolein) mixtures having excess triolein reached values (0.01 to 0.39) mmol/mol corresponding to its solubility in pure SC CO₂ under equivalent conditions. Under these conditions, the solubility of β-carotene in triolein-modified CO₂ increased by a factor of up to 4.0 in relation with its solubility in pure CO₂ at comparable system temperature and pressure, reaching an uppermost value of 3.3 μmol/mol at 333 K and 32 MPa. Unlike in the case of ethanol, where enhancements in solubility where relatively independent on system conditions, solubility enhancements using triolein as co-solvent increased markedly with system pressure, being larger than using (1.2 to 1.6) % mol ethanol at about (24 to 28) MPa, depending on system temperature. The increase in the solubility β-carotene in SC CO₂ as a result of using ethanol or triolein as co-solvent apparently does not depend on the increase in density associated with the dissolution of the co-solvent in CO₂. Enhancements may be due to an increase in the polarizability of SC CO₂, which possibly growths markedly as triolein dissolves in it when the system pressure becomes higher.     

Effect of Wood Content on The Thermal Behavior and on The Molecular Dynamics of Wood/Plastic Composites

Summary: In the last decades, the growing environmental awareness has resulted in a renewed interest in the use of natural materials for different applications. In this context, the use of wood in plastic to obtain composites has grown significantly. In the present work, heartwood and sapwood from Angelim Pedra (Hymenolobiun petraeum) were used to prepare PVC/wood composites. To study the composites with different wood types and filler contents the molecular dynamic was investigated through low field NMR by poton spin- lattice relaxation time measurements (T₁H) and the thermal behavior was characterized by means of differential scanning calorimetry (DSC) focusing the glass transition temperature and thermogravimetric analyses (TGA) observing the changes in the thermal stability. It was found that increasing addition of wood flour (sapwood and heartwood) caused a small but progressive improvement of the decomposition temperature of the composites, whereas the glass transition temperature remains practically unchanged. In the molecular dynamic behavior, a gradual decrease in T₁H values was observed with increasing sapwood and heartwood content, indicating that the composites became less rigid. The distribution curves of the domains showed a better interaction and phase dispersion between the composite components with higher filler content.     

A simple method for determination of erythritol,maltitol, xylitol,and sorbitol in sugar‐free chocolates by capillary electrophoresis with capacitively coupled contactless conductivity detection

In this work, a novel and simple analytical method using capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C⁴D) is proposed for the determination of the polyols erythritol, maltitol, xylitol, and sorbitol in sugar‐free chocolate. CE separation of the polyols was achieved in less than 6 min, and it was mediated by the interaction between the polyols and the borate ions in the background electrolyte, forming negatively charged borate esters. The extraction of the polyols from the samples was simply obtained using ultra‐pure water and ultrasonic energy. Linearity was assessed by calibration curves that showed R² varying from 0.9920 to 0.9976. The LOQs were 12.4, 15.9, 9.0, and 9.0 μg/g for erythritol, maltitol, xylitol, and sorbitol, respectively. The accuracy of the method was evaluated by recovery tests, and the obtained recoveries varied from 70 to 116% with standard deviations ranging from 0.2 to 19%. The CE‐C⁴D method was successfully applied for the determination of the studied polyols in commercial samples of sugar‐free chocolate.