Bioaccumulation pattern of lanthanides in pteridophytes and magnoliophytes species from Atlantic Forest

The availability of chemical elements for plants is mainly dependent on the nature of the soil and characteristics of each species. The transfer factors of lanthanides from the soil to the tree leaves of the Atlantic Forest, Brazil, were calculated for one fern species (Alsophila sternbergii—Pteridophyta division) and four magnoliophytes species (Bathysa australis, Euterpe edulis, Garcinia gardneriana and Guapira opposita—Magnoliophyta division) obtained in two areas of Serra do Mar State Park and collected in two different seasons. Samples were analyzed by instrumental neutron activation analysis (INAA). The soil-to-plant transfer factor (TF = C_plant:C_soil) in magnoliophytes species was correlated to the mass fraction of lanthanides in the soil, described by a exponential model (TF = a.C_soil^−b). Despite the tree fern Alsophila sternbergii presented a hyperaccumulation of lanthanides, this species did not have a significant relationship between TF and mass fraction in soil. Results indicated that plants of Magnoliophyta division selected the input of lanthanides from the soil, while the same was not observed in Alsophila sternbergii.     

Fluorescence of a Benzothienopyridopyrimidone in Solution and in Lipid Vesicles

Fluorescence properties of a biologically active benzothienopyridopyrimidone in solution and in lipid vesicles are reported. Assays at different pH values (0.5–10) allowed the determination of pK _a = 2.0, showing that this compound may be useful as a pH indicator for pH ≤ 4. In lipid vesicles, benzothienopyridopyrimidone locates in a water-rich environment, indicating that it can be carried in the hydrophilic region of liposomes for drug delivery applications.     

Fluorescence Studies on Potential Antitumoral Heteroaryl and Heteroannulated Indoles in Solution and in Lipid Membranes

Fluorescence properties of three potential antitumoral compounds, a 3-(dibenzothien-4-yl)indole 1, a phenylbenzothienoindole 2 and a 3-(dibenzofur-4-yl)indole 3, were studied in solution and in lipid aggregates of dipalmitoyl phosphatidylcholine (DPPC), dioleoyl phosphatidylethanolamine (DOPE) and egg yolk phosphatidylcholine (Egg-PC). The 3-(dibenzofur-4-yl)indole 3 exhibits the higher fluorescence quantum yields in all solvents studied (0.32 ≤ Φ_F ≤ 0.51). All the compounds present a solvent sensitive emission, with significant red shifts in alcohols. The results point to an ICT character of the excited state, more pronounced for compound 1. Fluorescence (steady-state) anisotropy measurements of the compounds incorporated in lipid aggregates of DPPC, DOPE and Egg-PC indicate that the three compounds are deeply located in the lipid bilayer, feeling the difference between the rigid gel phase and fluid phases.     

Some aspects of acylation of cellulose under homogeneous solution conditions

Commercially available cellulose (Avicell PH101) was successfully acylated under homogeneous solution conditions by the following procedure: 2.0 g of cellulose were stirred with 75 mL of N,N‐dimethylacetamide for 1 h at 150°C, 3.5 g of LiCl were added, the temperature was raised to 170°C, ca. 18.5 mL of the solvent were distilled and the suspension was cooled to room temperature and stirred overnight. The temperature of the clear cellulose solution was raised to 110°C, kept at that temperature for 1 h, an acid anhydride was added and the solution stirred at 110°C for additional 4 h. Acetates, propionates, butyrates, and acetate/propionate mixed ester were prepared with excellent control of the degree of substitution, DS, 1 to 3 for acetates, 2 and 3 for propionates and butyrates, and 3 for acetate/propionate. The degree of polymerization of cellulose is negligibly affected under these reaction conditions. The distribution of the acetyl moiety among the three OH groups of the anhydroglucose unit shows a preference for the C₆ position. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1357–1363, 1999     

Flexibility of the triblock copolymers modulating their penetration and expulsion mechanism in Langmuir monolayers of dihexadecyl phosphoric acid

The surface activity of the poly–[block (ethylene oxide)]–poly [block (propylene oxide)]–poly [block (ethylene oxide)] copolymers (EO)_x–(PO)_y–(EO)_x adsorbed together with dihexadecyl phosphoric acid (DHP), a synthetic phospholipid, is analyzed from their surface pressure and surface potential isotherms. The block copolymers of (EO)_x–(PO)_y–(EO)_x with variable molecular weight (1100–14 000) were dissolved in the subphase for DHP monolayers. The concentration of the copolymers within the aqueous subphase were selected to render an initial surface tension of 60 mN/m. The simultaneous adsorption of the copolymer and DHP is attested by the observation of a liquid expanded state at large areas, absent for pure DHP monolayers. Above some critical surface pressure all copolymers cited above are expelled from the interface. The surface potential isotherms, which give information on the component of the molecular dipole moment normal to the plane of the monolayer, are interpreted in terms of changes in the copolymer conformation as well as in terms of the copolymer desorption from the air–liquid interface. For an equal hydrophobic/hydrophilic ratio, the size of the chains or molecular weight is decisive in the mechanism of the copolymer expulsion from the air–liquid interface.     

Bromazepam determination in human plasma by high-performance liquid chromatography coupled to tandem mass spectrometry: a highly sensitive and specific tool for bioequivalence studies

A rapid, sensitive and specific method to quantify bromazepam in human plasma using diazepam as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by liquid-liquid extraction using diethyl ether-hexane (80 : 20, v/v). The extracts were analyzed by high-performance liquid chromatography (HPLC) coupled to electrospray tandem mass spectrometry (MS/MS). Chromatography was performed isocratically on a Genesis C(18) analytical column (100 x 2.1 mm i.d., film thickness 4 microm). The method had a chromatographic run time of 5.0 min and a linear calibration curve over the range 5.0-150 ng ml(-1) (r(2) > 0.9952). The limit of quantification was 5 ng ml(-1). This HPLC/MS/MS procedure was used to assess the bioequivalence of two bromazepam 6 mg tablet formulations (bromazepam from Medley SA Indústria Farmacêutica as the test formulation and Lexotan from Produtos Roche Químico e Farmacêutico SA as the reference formulation). A single 6 mg dose of each formulation was administered to 24 healthy volunteers (12 males and 12 females). The study was conducted using an open, randomized, two-period crossover design with a 3 week washout interval. Since the 90% CI for C(max), AUC(last), AUC(0-240 h) (linear) and AUC((0- infinity )) ratios were all inside the 80-125% interval proposed by the US Food and Drug Administration, it was concluded that the bromazepam formulation from Medley is bioequivalent to the Lexotan formulation for both the rate and the extent of absorption.     

Flow nephelometric analysis of protein-tannin interactions

The interaction of tannins from different sources (grape skin, grape seed and wine) with bovine serum albumin (BSA) was studied using a continuous flow method with nephelometric detection. The tannin samples were mixed in a reaction chamber with increasing BSA concentration and the resulting tannin-BSA insoluble aggregates passed through a flow cell where the turbidity was monitored. Based on this technique, the tannin specific activity (TSA) of wine can be directly determined from different wine flows without previous dilutions or any other treatment. The maximum amount of insoluble aggregates formed with BSA and wine or grape skin tannins seemed to remain constant even with the addition of an excess of protein, whereas a decrease in the amount of insoluble aggregates with an excess of BSA was observed in the case of grape seed tannins. It should be noted that BSA was used in these experiments as a model protein and only as an analytical reagent since bovine additives are not allowed in wine.     

Adsorption of detergent-solubilized and phospholipase C-solubilized alkaline phosphatase at air/liquid interfaces

To investigate the influence of a hydrophobic anchor on protein adsorption, equilibrium and dynamic aspects of the adsorption of two different solubilized forms of rat osseous plate alkaline phosphatase on Langmuir monolayers of dimyristoylphosphatidic acid (DMPA) were studied. Surface pressure and surface potential measurements at air/liquid interfaces were carried out using the detergent-solubilized form (DSAP) of alkaline phosphatase, which holds a glycosylphosphatidylinositol (GPI) hydrophobic anchor, and the glycosylphosphatidylinositol-specific phospholipase C-solubilized form (PLSAP), lacking the GPI anchor. Similar surface transitions observed for both DMPA and DMPA/PLSAP mixed monolayers indicate that the presence of PLSAP does not promote significant changes in surface packing of the DMPA monolayer. However, PLSAP interacts with the polar portion of the phospholipid even at high lateral compression. The presence of the GPI anchor increases the adsorption of DSAP at a plain air/liquid interface and also enables the penetration of the protein into the DMPA monolayers. The penetration is dependent on both time and surface pressure. Up to 20 mN/m, the surface pressure increases smoothly indicating a diffusion followed by an adsorption process. Above 20 mN/m, after a fast increase, the surface pressure slowly decays to equilibrium values quite close to the initial surface pressures. The results indicate that the molecular packing of the lipid layer drives the enzyme adsorption to the interface either through the GPI anchor or by the polypeptide moiety.