On the mechanisms of dissolution of montroydite [HgO(s)]: dependence of the dissolution rate on pH, temperature, and stirring rate

The dissolution behavior of montroydite (HgO) has been studied using a fully automated system. Dissolution data under equilibrium conditions are in agreement with previously published data and indicate that HgO solubility is relatively high and constant between pH 4 and 10.1 and increases markedly at pH<4. The dissolution rate also has similar behavior: it is relatively high and constant between pH 4 and 10.1 and increases sharply at pH<4. The dissolution process obeys a three-dimensional contraction or attrition mechanism. The dissolution rate increases with increasing temperature and stirring rate and is the result of mixed transport and reaction control. The rate of HgO dissolution is considerably higher than that of other divalent metal oxides at low pH. This high rate is due to the ability of Hg(II) to rapidly exchange its ligands. Data suggest that montroydite will only occur in nature in highly contaminated sites and indicate that Hg oxidation products that are formed at the liquid Hg/water interface may dissolve rapidly.     

4-Isoxazolines and pyrroles from allenoates

The synthesis of 4-isoxazolines via 1,3-dipolar cycloaddition of nitrones generated from allenoates and the subsequent thermal rearrangement to pyrroles is reported. The selection of the reaction conditions allowed the isolation of the initial 1,3-dipolar cycloadducts, the 4-isoxazolines, or the pyrrole derivatives. The isomerization of the parent system (4-isoxazoline) was examined by carrying out quantum chemical calculations and corroborated the favourability of the 4-isoxazoline rearrangement to five-membered heterocycles via 2-acylaziridine intermediates.     

Glycosylated VCAM-1 isoforms revealed in 2D western blots of HUVECs treated with tumoral soluble factors of breast cancer cells

Background  

Several common aspects of endothelial phenotype, such as the expression of cell adhesion molecules, are shared between metastasis and inflammation. Here, we analyzed VCAM-1 variants as biological markers of these two types of endothelial cell activation. With the combination of 2-DE and western blot techniques and the aid of tunicamycin, we analyzed N-glycosylation variants of VCAM-1 in primary human endothelial cells stimulated with either TNF or tumoral soluble factors (TSF's) derived from the human breast cancer cell line ZR75.30.     

Redesigning Nature: Ruthenium Flavonoid Complexes with Antitumour,Antimicrobial and Cardioprotective Activities

Flavonoids are a class of natural polyphenolic compounds sharing a common 2-phenyl-3,4-dihydro-2H-1-benzopyran (flavan) backbone. Typically known for their antioxidant activity, flavonoids are also being investigated regarding antitumour and antimicrobial properties. In this review, we report on the complexation of both natural and synthetic flavonoids with ruthenium as a strategy to modulate the biological activity. The ruthenoflavonoid complexes are divided into three subclasses, according to their most prominent bioactivity: antitumour, antimicrobial, and protection of the cardiovascular system. Whenever possible the activity of the ruthenoflavonoids is compared with that of commercial drugs for a critical assessment of the feasibility of using them in future clinical applications.     

Fluorescence Detection by Intensity Change Based Sensors: A Theoretical Model

According to Fluorescence Detection by Intensity Changes (FDIC) the fluorescence intensity of many fluorophores depends on the non-covalent (specific and/or non-specific) interactions these fluorophores would be able to establish with the solvent and, more interestingly, with other surrounding molecules. This latter effect is the basis of FDIC for analytical purposes. In this paper, a preliminary study of FDIC applications using a fluorophore supported in a solid medium (sensor film) is presented. First, a mathematical model relating the analyte concentration with the immobilized fluorophore fluorescence is deduced. The model includes all the different mechanisms explaining this relationship: index of refraction or dielectric constant modification, scattering coefficient alteration and sensor film volume increase. Then, the very first experimental results are presented, using different fluorophores and solid supports. The best results were obtained using polyacrylamide (PAA) polymers and coralyne as the fluorophore. This sensor film is applied for albumin and polyethylenglycol determination and the results are compared with those obtained using coralyne in solution. Albumin quenches the coralyne fluorescence in both cases (solution and film), while PEG quenches coralyne fluorescence in films but increases it in solution. These results suggest that the outstanding fluorescence change mechanism is sensor films is the film volume increases, which is different than those observed in solution.     

Microwave-Assisted Extraction of Curcuma longa L. Oil: Optimization,Chemical Structure and Composition,Antioxidant Activity and Comparison with Conventional Soxhlet Extraction

Curcuma root (Curcuma longa L.) is a very important plant in gastronomy and medicine for its unique antiseptic, anti-inflammatory, antimicrobial and antioxidant properties. Conventional methods for the extraction of curcuma oil require long extraction times and high temperatures that can degrade the active substances. Therefore, the objectives of the present study were: (i) first, to optimize the extraction yield of curcuma oil by applying a Box-Behnken experimental design using surface response methodology to the microwave-assisted extraction (MAE) technique (the independent variables studied were reaction time (10–30 min), microwave power (150–200 W) and curcuma powder/ethanol ratio (1:5–1:20; w/v); and, (ii) second, to assess the total phenolic content (TPC) and their antioxidant activity of the oil (at the optimum conditions point) and compare with the conventional Soxhlet technique. The optimum conditions for the MAE were found to be 29.99 min, 160 W and 1:20 w/v to obtain an optimum yield of 10.32%. Interestingly, the oil extracted by microwave-assisted extraction showed higher TPC and better antioxidant properties than the oil extracted with conventional Soxhlet technique. Thus, it was demonstrated that the method applied for extraction influences the final properties of the extracted Curcuma longa L. oil.     

Midkine Interaction with Chondroitin Sulfate Model Synthetic Tetrasaccharides and Their Mimetics: The Role of Aromatic Interactions

Midkine (MK) is a neurotrophic factor that participates in the embryonic central nervous system (CNS) development and neural stem cell regulation, interacting with sulfated glycosaminoglycans (GAGs). Chondroitin sulfate (CS) is the natural ligand in the CNS. In this work, we describe the interactions between a library of synthetic models of CS-types and mimics. We did a structural study of this library by NMR and MD (Molecular Dynamics), concluding that the basic shape is controlled by similar geometry of the glycosidic linkages. Their 3D structures are a helix with four residues per turn, almost linear. We have studied the tetrasaccharide-midkine complexes by ligand observed NMR techniques and concluded that the shape of the ligands does not change upon binding. The ligand orientation into the complex is very variable. It is placed inside the central cavity of MK formed by the two structured beta-sheets domains linked by an intrinsically disordered region (IDR). Docking analysis confirmed the participation of aromatics residues from MK completed with electrostatic interactions. Finally, we test the biological activity by increasing the MK expression using CS tetrasaccharides and their capacity in enhancing the growth stimulation effect of MK in NIH3T3 cells.     

Encapsulation of Cyano(cyclopentadienyl) Complexes of Iron with β-cyclodextrin

Inclusion compounds have been prepared comprising g -cyclodextrin (CD) molecules as the host and half-sandwich cyano complexes of iron as the guests. High yields of crystalline one-to-one adducts were obtained by treatment of CpFe(CO) 2 CN and K[CpFe(CO)(CN) 2 ] with g -CD. In the case of CpFe(dppe)CN [dppe=bis(diphenylphosphine)ethane], a non-stoichiometric product is obtained and it is evident that the organometallic guests are easily liberated from the host cavities. The products were characterized in the solid-state by elemental analysis, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), FTIR and CP MAS NMR ( 13 C, 31 P) spectroscopy. Additional information concerning the possible structure of the inclusion compounds was obtained from ab initio calculations using a two-layer approximation. The best organometallic- g -CD interaction is obtained with deep inclusion of the cyclopentadienyl ring, a geometry that is not possible in the case of the CpFe(dppe)CN system due to the size and orientation of the dppe ligand.     

Nearness results for real tridiagonal 2‐Toeplitz matrices

In this article, we extend the results for Toeplitz matrices obtained by Noschese, Pasquini, and Reichel. We study the distance d, measured in the Frobenius norm, of a real tridiagonal 2‐Toeplitz matrix T to the closure of the set formed by the real irreducible tridiagonal normal matrices. The matrices in , whose distance to T is d, are characterized, and the location of their eigenvalues is shown to be in a region determined by the field of values of the operator associated with T, when T is in a certain class of matrices that contains the Toeplitz matrices. When T has an odd dimension, the eigenvalues of the closest matrices to T in are explicitly described. Finally, a measure of nonnormality of T is studied for a certain class of matrices T. The theoretical results are illustrated with examples. In addition, known results in the literature for the case in which T is a Toeplitz matrix are recovered.     

Microwave‐assisted three‐component synthesis and in vitro antifungal evaluation of 6‐cyano‐5,8‐dihydropyrido[2,3‐d]pyrimidin‐4(3H)‐ones

The reaction of 6‐aminopyrimidin‐4‐ones 1 with benzaldehydes 2 and β‐aminocrotononitrile 3 or benzoylacetonitrile 4 under microwave irradiation in dry media yields the 6‐cyano‐5,8‐dihydropyrido[2,3‐d]‐pyrimidinones 5a‐t . The structure of the synthesized compounds was determined on the basis of nmr measurements, especially by ¹H,¹H?, ¹H,¹³C COSY, DEPT and NOESY experiments. In contrast with other pyrido‐[2,3‐d]pyrimidine derivatives, these compounds did not show any antifungal in vitro activity up to 250 μg/mL.