Direct electrochemical synthesis and characterization of copper(II), iron(II) and iron(III) complexes with 1- and 2-substituted pyridines

Summary The electrochemical oxidation of anodic metals (iron and copper) in MeCN solutions of 2-pyridinone (HOPy), 1-hydroxy-2-pyridinethione (HPT), 2-pyridinemethanethiol-1-oxide (HPMTO) or its dimer 2,2-dithiodimethyldipyridine-1,1-dioxide (PMTO)₂, gave the simple complexes Fe(OPy)₂ · H₂O, Cu(OPy)₂ · 3H₂O, Fe(PT)₂ · 3H₂O, Fe(PT)₃, Cu(PT)₂, Fe(PMTO)₂·3H₂O and Cu(PMTO)₂·H₂O, respectively. When 1,10-phenanthroline (phen) was added to the electrolytic phase, only two mixed complexes were obtained: Cu(OPy)₂phen·3H₂O and Fe(PT)₂phen·2H₂O. The possible molecular structures of the complexes were studied on the basis of their i.r. spectra and magnetic properties.     

Diastereoselective synthesis of cularine alkaloids via enium ions and an easy entry to isoquinolines by aza-Wittig electrocyclic ring closure

In preliminary communications, we reported the diastereoselective synthesis of cularine and sarcocapnine via the intramolecular ring closure of nitrenium and oxenium ions, a new highly diastereoselective reductive methylation with (+)-8-phenylmenthyl chloroacetate followed by reduction with sodium borohydride, and a facile entry to the isoquinoline precursors by aza-Wittig electrocyclic ring closure. We now report the full details of the syntheses of (+)-O-demethylcularine, (+)-cularine, (+)-sarcocapnidine, (+)-sarcocapnine, and (+)-crassifoline and describe different methods of synthesis of their precursors.     

Electric field induced electron transfer at the adsorbate-surface interface. Effect of the type of metal surface

The ab initio two-state model for electron transfer induced by an external electric field has been applied to the chloride oxidation on Cu, Rh, Pd, Ag, Pt and Au (001) surface models. The two electronic states involved in the model represent physical situations where the electron transferred from the chloride anion to the metal surface lies either on the halide or on the metal substrate. The model assumes that electron transfer takes place when these two states become degenerate and this is achieved by applying an external electric field. Two different situations representing either ultrahigh vacuum or electrochemical conditions have been considered. For the former the present study shows that electric field necessary to achieve degeneracy of the two electronic states is directly related to the metal surface work function whereas for the latter, it is found to be rather insensitive to the metal surface.     

Development of Neuropeptide Y and Cell-Penetrating Peptide MAP Adsorbed onto Lipid Nanoparticle Surface

Functionalization of nanoparticles surfaces have been widely used to improve diagnostic and therapeutic biological outcome. Several methods can be applied to modify nanoparticle surface; however, in this article we focus toward a simple and less time-consuming method. We applied an adsorption method on already formulated nanostructured lipid carriers (NLC) to functionalize these nanoparticles with three distinct peptides sequences. We selected a cell-penetrating peptide (CPP), a lysine modified model amphipathic peptide (Lys(N₃)-MAP), CPP/drug complex, and the neuropeptide Y. The aim of this work is to evaluate the effect of several parameters such as peptide concentration, different types of NLC, different types of peptides, and incubation medium on the physicochemical proprieties of NLC and determine if adsorption occurs. The preliminary results from zeta potential analysis indicate some evidence that this method was successful in adsorbing three types of peptides onto NLC. Several non-covalent interactions appear to be involved in peptide adsorption with the possibility of three adsorption peptide hypothesis that may occur with NLC in solution. Moreover, and for the first time, in silico docking analysis demonstrated strong interaction between CPP MAP and NPY Y1 receptor with high score values when compared to standard antagonist and NPY.     

Development and validation of a rapid RP‐HPLC method for analysis of (−)‐copalic acid in copaíba oleoresin

The Copaifera species (Leguminoseae) are popularly known as ‘copaíba’ or ‘copaíva’ and are grown in the states of Amazonas, Pará and Ceará in northern Brazil. The oleoresins obtained from these species have been extensively used owing to their pharmacological potential and their application in cosmetic and pharmaceutical preparations. In the present study, the development and validation of a novel, rapid and efficient RP‐HPLC methodology for the analysis of the diterpene (?)‐copalic acid (CA), pointed out as the only chemical marker of the Copaifera genus, are described. The regression equation (Y = 26,707x ? 29,498) was obtained with good linearity (r² = 0.9993) and the limits of quantification and detection were 9.182 and 3.032 µg/mL, respectively. The precision and the accuracy of the method were adequate (lower than 4%). Finally, the validation parameters evaluated were satisfactorily met, so the developed method represents a suitable tool for application in the quality control of such natural products. Further studies aiming to develop analytical methodologies for each Copaifera species using a more representative number of chemical markers should be performed. Copyright © 2012 John Wiley & Sons, Ltd.     

Ultrastructure of the Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) midgut

The insect midgut has ultimately been the focus of researches tempting to control insect pests because alterations in the insect gut may affect not only its development, but also physiological events such as nutrient absorption and transformation. The objective of the present work was to describe morphologically, histochemically, and ultrastructurally the larva midgut of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), a cotton key pest in Brazil. Light and electronic transmission microscopy was used to obtain images from midgut sections of late fourth-instar larvae of A. argillacea. In general, the morphology, histochemistry, and ultrastructure characteristics of A. argillacea midgut follow that described in the literature for other lepidopteran species. However, the results showed a mitochondrial polymorphism and branched microvilli, which suggest an ultrastrucutural and physiological modification possibly associated with a high absorption and secretion activity by the columnar cells of this species. This intense activity may favor a faster response related to the action of ingested microbial agents and/or toxins, and can explain the high susceptibility of A. argillacea to the agents of control such as the toxin of Bacillus thuringiensis.     

Comparative assessment of computational methods for the determination of solvation free energies in alcohol‐based molecules

The determination of differences in solvation free energies between related drug molecules remains an important challenge in computational drug optimization, when fast and accurate calculation of differences in binding free energy are required. In this study, we have evaluated the performance of five commonly used polarized continuum model (PCM) methodologies in the determination of solvation free energies for 53 typical alcohol and alkane small molecules. In addition, the performance of these PCM methods, of a thermodynamic integration (TI) protocol and of the Poisson–Boltzmann (PB) and generalized Born (GB) methods, were tested in the determination of solvation free energies changes for 28 common alkane‐alcohol transformations, by the substitution of an hydrogen atom for a hydroxyl substituent. The results show that the solvation model D (SMD) performs better among the PCM‐based approaches in estimating solvation free energies for alcohol molecules, and solvation free energy changes for alkane‐alcohol transformations, with an average error below 1 kcal/mol for both quantities. However, for the determination of solvation free energy changes on alkane‐alcohol transformation, PB and TI yielded better results. TI was particularly accurate in the treatment of hydroxyl groups additions to aromatic rings (0.53 kcal/mol), a common transformation when optimizing drug‐binding in computer‐aided drug design. © 2013 Wiley Periodicals, Inc.