Estudo da atividade antibacteriana do picolinato de sacarose em Escherichia coli.Escherichia coli.

Os sucroésteres são empregados como surfactantes, tensoativos, substitutos de gordura e antibióticos. Este trabalho tem como objetivo sintetizar um novo sucroéster derivado do ácido picolínico (ácido 2-piridinocarboxílico), o picolinato de sacarose, e estudar sua atividade antibacteriana in vitrosobre a bactéria Gram-negativa patogênica Escherichia coli. A síntese do picolinato de sacarose foi processada a partir da transesterificação da sacarose com picolinato de metila em condição anidra à 80oC, utilizando dimetil sulfóxido (DMSO) como solvente e K2CO3 como catalisador. A separação dos isômeros formados foi realizada por HPLC no modo semipreparativo e cinco frações cromatográficas foram coletadas e aplicadas em testes de atividade antibacteriana, por disco-difusão em meio sólido, nas concentrações de 150; 300; 450; 600; 750 e 900 μg/mL. As frações 2, 4 e 6 foram ativas contra E.coli. e a fração 4 (900 μg/mL) foi a mais eficiente, sendo selecionada para testes em sinergia com EDTA nas concentrações de 250, 500 e 750 μg/mL, com melhor resultado quando empregado EDTA em 750 μg/mL. Neste caso, os discos apresentaram halos de inibição de crescimento igual ao da Tetraciclina (30 μg/mL) e superior aos produzidos pelos discos com Gentamicina (10 μg/mL). A fração 4 foi caracterizada por FTIR e espectrometria de massas (ESI-MS) e os resultados indicam que se trata sucroéster monossubstituído. Palavras-chave:Sucroquímica. Sucroéster. Sacarose. Picolinato de sacarose. Escherichia coli. Antibiograma por disco-difusão. ABSTRACT Study of antimicrobial activity of sucrose picolinate against Escherichia coli Sucrose esters are generally used as surfactants, fat substitutes and antibiotics. The aim of the present study was to synthesize new sucrose esters derived from picolinic acid (2-pyridine carboxylic acid) and study in vitro antimicrobial activity on the Gramnegative pathogenic bacterium Escherichia coli. The synthesis of sucrose picolinate was performed through the transesterification of sucrose with methyl picolinate under anhydrous conditions at 80 oC using dimethyl sulfoxide (DMSO) as the solvent and K2CO3as the catalyst. The separation of the formed isomers was performed by HPLC in a semi-preparative chromatograph system. Five fractions were collected and applied to a disc-diffusion antibiogram in solidmedium tests at concentrations of 150, 300, 450, 600, 750 and 900 μg/mL. Fractions 2, 4 and 6 were active against E. coli. Fraction 4 (900 μg/mL) was the most efficient and was selected for the determination of antimicrobial activity in synergistic tests with EDTA at concentrations of 250, 500 and 750 μg/mL. The best result was obtained with 750 μg/mL of EDTA. Fraction 4 was characterized as a monosubstituted sucrose ester by FTIR and mass spectrometry (ESI-MS). Keywords: Sucrochemistry. Sucrose. Chromium picolinate sucrose. Escherichia coli. Susceptibility testing by disk diffusion.

Light-Induced Structural Change in Iridium Complexes Studied by Electron Spin Resonance

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da acessibilidade aos sítios ativos e desativação na desidratação do glicerol utilizando catalisadores zeolíticos lamelares

Pós-graduação em Química - IQ

Mecanismos da infertilidade causada por Gossipol em ratos e efeito protetor da vitamina E

Pós-graduação em Ciência e Tecnologia Animal - FEIS

On the stability of the RuCl2(triphenylphosphine)(2)(amine) complexes: Ligand substituent effects of cyclic and acyclic amines

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Asymmetric and Symmetric Triazenido Cyclopalladated Complexes: Synthesis, Structural Analysis and DFT Calculations

The reaction of [Pd{dmba}(l-N3)]2 (dmba = N,N-dimethylbenzylamine) with 1-(2-fluorophenyl)-3-(4- nitrophenyl)triazenido (L1 ) or 1,3-bis(4-nitrophenyl)triazenido (L2 ) anions, in methanol, and subsequent treatment with pyridine (py) allows the preparation of the corresponding cyclopalladated compounds [Pd(dmba)(L1 )(py)] (1) and [Pd(dmba)(L2 )(py)]py (2). The acentric mononuclear entities of (1) and (2) are connected by weak intermolecular non-classical CAHC hydrogen bonds, which results in 2-D arrangements by translation, along the [1 0 0] and [0 01] crystallographic directions, respectively.

Estudo das propriedades estímulo responsivas dos polímeros escovas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Glycerol dehydration catalyzed by MWW zeolites and the changes in the catalyst deactivation caused by porosity modification

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mechanisms involved in reproductive damage caused by gossypol in rats and protective effects of vitamin E

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Sínteses e caracterizações de materiais microporosos com estrutura cristalográfica mista e suas aplicações como catalisadores em reações de conversão de biomassa em produtos de química fina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photophysical properties of a fluorene-bipyridine copolymer and its complexes with europium

The synthesis and structural characterization of a europium complexed fluorene-bipyridine copolymer are described. A level of ion insertion of 80% in molar basis was achieved, and theoretical calculations showed that it required a twist of 179 degrees (49 kJ) between the pyridine units. Spectroscopy data showed that no electronic coupling between the main backbone and the complexation sites had occurred, but these hindered the interchain aggregation observed in the non complexed polymer. Preliminary electroluminescence studies showed that the EL and PL spectra are consistent, and that the ion had a trapping effect in the charge transport. (C) 2011 Elsevier B.V. All rights reserved.

Platinum nanoparticles incorporated in silsesquioxane for use in LbL films for the simultaneous detection of dopamine and ascorbic acid

We describe the preparation of platinum nanoparticles (PtNPs) using the 3-n-propylpyridinium silsesquioxane chloride (SiPy+Cl-) as a nanoreactor and stabilizer. The formation of PtNPs was monitored by UV-Vis spectroscopy by measuring the decrease in the intensity of the band at 375 nm, which is attributed to the electronic absorption of PtCl62- ions. TEM images of Pt-SiPy+Cl- nanohybrid indicated an average size of 3-40 nm for PtNPs. The Pt-SiPy+Cl- was used as a polycation in the preparation of layer-by-layer films (LbL) on a glass substrate coated with fluorine-doped tin oxide (FTO) alternating with the polyanion poly(vinyl sulfonic acid) (PVS). The films were electrochemically tested in sulfuric acid to confirm the deposition of Pt-SiPy+Cl- onto the LbL films, observing the adsorption and desorption of hydrogen (E-pa = 0.1 V) and by the redox process of formation for PtO with E-pa = 1.3 V and E-pc = 0.65 V. FTIR and Raman spectra confirmed the presence of the PVS and Pt-SiPy+Cl- in the LbL films. A linear increase in the absorbance in the UV-Vis spectra of the Pt-SiPy+Cl- at 258 nm (pi -> pi* transition of the pyridine groups) with a number of Pt-SiPy+Cl-/PVS or PVS/SiPy+Cl- bilayers (R = 0.992) was observed. These LbL films were tested for the determination of dopamine (DA) in the presence of ascorbic acid (AA) with a detection limit (DL) on the order of 2.6 x 10(-6) mol L-1 and a quantification limit (QL) of 8.6 x 10(-6) mol L-1. The films exhibited a good repeatability and reproducibility, providing a potential difference of 550 mV for the oxidation of DA with AA interferent.

Identification of novel components of NAD-utilizing metabolic pathways and prediction of their biochemical functions

Nicotinamide adenine dinucleotide (NAD) is a ubiquitous cofactor participating in numerous redox reactions. It is also a substrate for regulatory modifications of proteins and nucleic acids via the addition of ADP-ribose moieties or removal of acyl groups by transfer to ADP-ribose. In this study, we use in-depth sequence, structure and genomic context analysis to uncover new enzymes and substrate-binding proteins in NAD-utilizing metabolic and macromolecular modification systems. We predict that Escherichia coli YbiA and related families of domains from diverse bacteria, eukaryotes, large DNA viruses and single strand RNA viruses are previously unrecognized components of NAD-utilizing pathways that probably operate on ADP-ribose derivatives. Using contextual analysis we show that some of these proteins potentially act in RNA repair, where NAD is used to remove 2'-3' cyclic phosphodiester linkages. Likewise, we predict that another family of YbiA-related enzymes is likely to comprise a novel NAD-dependent ADP-ribosylation system for proteins, in conjunction with a previously unrecognized ADP-ribosyltransferase. A similar ADP-ribosyltransferase is also coupled with MACRO or ADP-ribosylglycohydrolase domain proteins in other related systems, suggesting that all these novel systems are likely to comprise pairs of ADP-ribosylation and ribosylglycohydrolase enzymes analogous to the DraG-DraT system, and a novel group of bacterial polymorphic toxins. We present evidence that some of these coupled ADP-ribosyltransferases/ribosylglycohydrolases are likely to regulate certain restriction modification enzymes in bacteria. The ADP-ribosyltransferases found in these, the bacterial polymorphic toxin and host-directed toxin systems of bacteria such as Waddlia also throw light on the evolution of this fold and the origin of eukaryotic polyADP-ribosyltransferases and NEURL4-like ARTs, which might be involved in centrosomal assembly. We also infer a novel biosynthetic pathway that might be involved in the synthesis of a nicotinate-derived compound in conjunction with an asparagine synthetase and AMPylating peptide ligase. We use the data derived from this analysis to understand the origin and early evolutionary trajectories of key NAD-utilizing enzymes and present targets for future biochemical investigations.

Tb3+-> Eu3+ Energy Transfer in Mixed-Lanthanide-Organic Frameworks

In this work, we report a theoretical and experimental investigation of the energy transfer mechanism in two isotypical 2D coordination polymers, (infinity)[(Tb1-xEux)(DPA)(HDPA)], where H(2)DPA is pyridine 2,6-dicarboxylic acid and x = 0.05 or 0.50. Emission spectra of (infinity)[(Tb0.95Eu0.05)(DPA)(HDPA)] and (infinity)[(Tb0.5Eu0.5)(DPA)(HDPA)], (I) and (2), show that the high quenching effect on Tb3+ emission caused by Eu3+ ion indicates an efficient Tb3+-> Eu3+ energy transfer (ET). The k(ET) of Tb3+-> Eu3+ ET and rise rates (k(r)) of Eu3+ as a function of temperature for (1) are on the same order of magnitude, indicating that the sensitization of the Eu3+5D0 level is highly fed by ET from the D-5(4) level of Tb3+ ion. The eta(ET) and R-0 values vary in the 67-79% and 7.15 to 7.93 angstrom ranges. Hence, Tb3+ is enabled to transfer efficiently to Eu3+ that can occupy the possible sites at 6.32 and 6.75 angstrom. For (2), the ET processes occur on average with eta(ET) and R-0 of 97% and 31 angstrom, respectively. Consequently, Tb3+ ion is enabled to transfer energy to Eu3+ localized at different layers. The theoretical model developed by Malta was implemented aiming to insert more insights about the dominant mechanisms involved in the ET between lanthanides ions. Calculated single Tb3+-> Eu3+ ETs are three orders of magnitude inferior to those experimentally; however, it can be explained by the theoretical model that does not consider the role of phonon assistance in the Ln(3+)-> Ln(3+) ET processes. In addition, the Tb3+-> Eu3+ ET processes are predominantly governed by dipole-dipole (d-d) and dipole-quadrupole (d-q) mechanisms.

Studies on Oxidative Couplings in H-Phosphonate Chemistry

In this thesis oxidative coupling of H-phosphonate and H phosphonothioate diesters with different alcohols and amines are presented. Since the reactions with alcohols previously have been particularly unfavourable due to competing side reactions, a modified protocol leading to high coupling yields of structurally diverse hydroxylic components was developed. The phosphorylation reaction was studied using 31P NMR spectroscopy and for the first time the previously only postulated reactive intermediate involved in these reactions was observed. The use of iodine in combination with a bulky chlorosilane in pyridine was found to have a profound effect on both the suppression of side reactions and the rate of the oxidative couplings, and led to a clean formation of phosphorylated products in high yields. This synthetic protocol was then extended to include coupling reactions with bis-functional reagents containing hexamethylene linkers to provide handles for derivatisations of oligonucleotides. A synthetic protocol consisting of the stereospecific oxidative coupling of amines with H-phosphonate diesters to produce phosphoroamidates was designed in such a way that it permitted control of the stereochemical outcome of the reactions. Based on a silylation-mediated reaction utilising phenyl H phosphonothioate monoester as a thiophosphonyl transferring agent, a method was developed and used for the preparation of H-phosphonothioate building blocks for the synthesis of DNA analogues.