Electrochemical and theoretical evaluation of the interaction between dna and amodiaquine: evidence of the guanine adduct formation

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

Crystallographic studies on the binding of isonicotinyl-NAD adduct to wild-type and isoniazid resistant 2-trans-enoyl-ACP (CoA) reductase from Mycobacterium tuberculosis

The resumption of tuberculosis led to an increased need to understand the molecular mechanisms of drug action and drug resistance, which should provide significant insight into the development of newer compounds. Isoniazid (INH), the most prescribed drug to treat TB, inhibits an NADH-dependent enoyl-acyl carrier protein reductase (InhA) that provides precursors of mycolic acids, which are components of the mycobacterial cell wall. InhA is the major target of the mode of action of isoniazid. INH is a pro-drug that needs activation to form the inhibitory INH-NAD adduct. Missense mutations in the inhA structural gene have been identified in clinical isolates of Mycobacterium tuberculosis resistant to INH. To understand the mechanism of resistance to INH, we have solved the structure of two InhA mutants (121V and S94A), identified in INH-resistant clinical isolates, and compare them to INH-sensitive WT InhA structure in complex with the INH-NAD adduct. We also solved the structure of unliganded INH-resistant S94A protein, which is the first report on apo form of InhA. The salient features of these structures are discussed and should provide structural information to improve our understanding of the mechanism of action of, and resistance to, INH in M. tuberculosis. The unliganded structure of InhA allows identification of conformational changes upon ligand binding and should help structure-based drug design of more potent antimycobacterial agents. (c) 2007 Elsevier B.V. All rights reserved.

Structural characterization of an etheno-2 '-deoxyguanosine adduct modified by tetrahydrofuran

The reaction of 2'-deoxyguanosine with the alpha,beta-unsaturated aldehydes trans-2-octenal, trans-2-nonenal, trans-2-decenal, trans,trans-2,4-nonadienal, and trans,trans-2,4-decadienal in THF gives rise to three novel adducts: 3-(2'-deoxy-beta-D-erythro-pentafuranosyl)-7-[3-hydroxy-1-(3(2'-deoxy-beta-D-erythro-pentafuranosyl)-3,5-dihydro-imidazo[1,2-alpha]purin-9-one-7-yl)-propyl] -3,5-dihydro-imidazo[1,2-alpha]purin-9-one (M) and 3-(2'-deoxy-beta-D-erythro-pentafuranosyl)-7-(tetrahydrofuran-2-yl)-3,5-dihydro-imidazo[1,2-alpha]purin-9-one (A8 and A9), which are not observed in the absence of THF. These adducts were isolated from in vitro reactions by reversed-phase HPLC and fully characterized on the basis of spectroscopic measurements. Adduct A7 consists of two 1,N-2-etheno-2'-deoxyguanosine (1,N-2-epsilondGuo) residues linked to a hydroxy-carbon side chain; adducts A8 and A9 are interconvertible 1,N-2-epsilondGuo derivatives bearing a THF moiety. The proposed reaction mechanism involves the electrophilic attack on 1,N-2-epsilondGuo by the carbonyl of 4-hydroxy-butanal, generated via ring opening of alpha-hydroxy-THF (THF-OH), yielding adducts A8 and A9. A further combination of these adducts with another 1,N-2-epsilondGuo produces the double adduct A7. These findings demonstrate that reactions of unsaturated aldehydes in the presence of THF produce novel condensation 1,N-2-epsilondGuo-THF adducts. Further studies would indicate the relevance of these adducts in THF toxicity.

Kinetic parameters for thermal decomposition of supramolecular polymers derived from flunixin-meglumine adducts

Meglumine, (2R,3R,4R,5S)-6-methylaminohexane-1,2,3,4,5-pentol, is a carbohydrate derived from sorbitol in which the hydroxyl group in position one is replaced by a methylamine group. It forms binary adducts with substances having carboxyl groups, which have in common the presence of hydrogen bonding as the main force in the stabilization of these species. During melting, adducts of meglumine with flunixin (2-[[2-methyl-3-(trifluoromethyl)phenyl]amino]pyridine-3-carboxylic acid) polymerize or self-assemble in amorphous supramolecular structures with molecular weights around 2.0 x 10(5) kDa. DSC curves, in a first heating, show isomorphic transitions where the last one at 137 A degrees C for the flunixin-meglumine adduct originated the supramolecular amorphous polymers with glass transition around 49.5 A degrees C. The kinetic parameters for the thermal decomposition step of the polymers were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15, and 20 A degrees C min(-1), the E (alpha) and B (alpha) terms could be determined and, consequently, the pre-exponential factor, A(alpha), as well as the kinetic model, g(alpha).

Structure Elucidation and Absolute Stereochemistry of Isomeric Monoterpene Chromane Esters

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

Structural aspects, thermal behavior, and stability of a self-assembled supramolecular polymer derived from flunixin-meglumine supramolecular adducts

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of surface conditioning methods on the microtensile bond strength of resin composite to composite after aging conditions

Objectives. This study evaluated the effect of two different surface conditioning methods on the repair bond strength of a bis-GMA-adduct/bis-EMA/TEGDMA based resin composite after three aging conditions.Methods. Thirty-six composite resin blocks (Esthet X, Dentsply) were prepared (5 mm x 6 mm x 6 mm) and randomly assigned into three groups for aging process: (a) immersion in citric acid (pH 3.0 at 37 degrees C, 1 week) (CA); (b) boiling in water for 8h (BW) and (c) thermocycling (x5000, 5-55 degrees C, dwell time: 30s) (TC). After aging, the blocks were assigned to one of the following surface conditioning methods: (1) silica coating (30 mu m SiOx) (CoJet, 3M ESPE) + silane (ESPE-Sil) (CJ), (2) phosphoric acid + adhesive resin (Single Bond, 3M ESPE) (PA). Resin composite (Esthet.X (R)) was bonded to the conditioned substrates incrementally and light polymerized. The experimental groups formed were as follows: Gr1:CA + PA; Gr2:CA + CJ Gr3:BW + PA; Gr4: BW + CJ; Gr5:TC + PA; Gr6: TC + CJ. The specimens were sectioned in two axes (x and y) with a diamond disc under coolant irrigation in order to obtain non-trimmed bar specimens (sticks, 10 mm x 1 mm x 1 mm) with 1 mm(2) of bonding area. The microtensile test was accomplished in a universal testing machine (crosshead speed: 0.5 mm min(-1)).Results. The means and standard deviations of bond strength (MPa +/- S.D.) per group were as follows: Gr1: 25.5 +/- 10.3; Gr2: 46.3 +/- 10.1; Gr3: 21.7 +/- 7.1; Gr4: 52.3 +/- 15.1; GrS: 16.1 +/- 5.1; Gr6, 49.6 +/- 13.5. The silica coated groups showed significantly higher mean bond values after all three aging conditions (p < 0.0001) (two-way ANOVA and Tukey tests, alpha = 0.05). The interaction effect revealed significant influence of TC aging on both silica coated and acid etched groups compared to the other aging methods (p < 0.032). Citric acid was the least aggressive aging medium.Significance. Chairside silica coating and silanization provided higher resin-resin bond strength values compared to acid etching with phosphoric acid followed by adhesive resin applications. Thermocycling the composite substrates resulted in the lowest repair bond strength compared to citric acid challenge or boiling in water. (C) 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Kinetic parameters for thermal decomposition of supramolecular polymers derived from diclofenac-meglumine supramolecular adducts

Meglumine is an aminocarbohydrate able to form supramolecular adducts with organic acids. The recognition is based on hydrogen bonds and the structures resulting from the complexation have high solubility in water. This property has been exploited by the pharmaceutical industry in the improvement of existing drugs, and the successful example of this approach involves the poorly soluble non-steroidal anti-inflammatory drugs (NSAIDs). Investigation of the thermal behavior of adduct obtained from meglumine and the NSAID diclofenac revealed that a polymer-like material is formed from the self-assembly of diclofenac-meglumine adducts in the melt. This polymer showed a high molecular weight around 2.0×105kDa. The kinetic parameters for the thermal decomposition step of the polymer were determined by the Capela-Ribeiro non-linear isoconversional method. From data for the TG curves in nitrogen atmosphere and heating rates of 5, 10, 15 and 20°Cmin-1, the Eα and Bα terms could be determined, and consequently the pre-exponential factor, Aα, as well as the kinetic model, g(α). © 2012 Elsevier B.V.

Caracterização e estudo do comportamento térmico dos adutos flunixina-meglumina e diclofenaco-meglumina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Polióis de substratos vegetais quimicamente modificados com trimetilolpropano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Design, synthesis and characterization of a hexapeptide bio-inspired by acetylcholinesterase and its interaction with pesticide dichlorvos

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

Identification of Sudan III-(deoxy)-guanosine adducts formed in situ in a reaction with no catalyst

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

2 '-Deoxyguanosine, 2 '-deoxycytidine, and 2 '-deoxyadenosine adducts resulting from the reaction of tetrahydrofuran with DNA bases

A recent study showed that tetrahydrofuran (THF), a widely used solvent, is carcinogenic in experimental animals. Despite its carcinogenic activity, there is a paucity of information regarding cellular toxicity, biomolecular damage, and genotoxicity induced by THF. We describe here the structural characterization of adducts produced by the reaction of oxidized THF with 2'-deoxyguanosine (dGuo-THF 1 and dGuo-THF 2), 2'-deoxyadenosine (dAdo-THF), and 2'-deoxycytidine (dCyd-THF). Adducts were isolated from in vitro reactions by reverse-phase HPLC and fully characterized on the basis of spectroscopic measurements. The stable derivatives obtained by the reduction of adducts with NaBH4 ( the case of dGuo-THF 1, dCyd-THF, and dAdo-THF) and the stable adduct dGuo-THF 2 were used as standards for optimization of chromatographic separations for adduct detection in DNA through HPLC/ESI/MSMS. Using this methodology, we successfully detected the four adducts in calf thymus DNA reacted with oxidized THF. The present study also provides evidence that rat liver microsomal monooxigenases oxidize THF to the reactive electrophilic compounds that are able to damage the DNA molecule, as indicated by a significant increase in adduct dGuo-THF 1 level when NADPH was added to the THF/ microsomes/dGuo incubation mixtures. Our data point to DNA-THF adducts as possible contributing factors to the toxicological effects of THF exposure.

Formation of 1,N-6-etheno-2 '-deoxyadenosine adducts by trans,trans-2,4-decadienal

trans,trans-2,4-Decadienal (DDE) is an important breakdown product of lipid peroxidation. This aldehyde is cytotoxic to mammalian cells and is known to be implicated in DNA damage. Therefore, attempts were made in this work to assess the reactivity of DDE with 2'-deoxyadenosine (dAdo). It was shown that DDE is able to bind to 2'-deoxyadenosine, yielding highly fluorescent products. Besides 1,N-6-etheno-2'-deoxyadenosine (epsilon dAdo), two other related adducts, 1-[3-(2-deoxy-beta-D-erythro-pentofuranosyl)3H-imidazo[2,1-i]purin-7-yl]-1,2,3-octanetriol and 1-[3-(2-deoxy-beta-D-erythro-pentofuranosyl)-3H-imidazo[2,1-i]purin-7-yl]-1,2-heptanediol, were isolated by reverse phase high-performance liquid chromatography and characterized on the basis of their UV, fluorescence, nuclear magnetic resonance, and mass spectrometry features. The reaction mechanism for the formation of the DDE-2'-deoxyadenosine adducts involves 2,4-decadienal epoxidation and subsequent addition to the N-2 amino group of 2'-deoxyadenosine, followed by cyclization at the N-1 site. Adducts differ by the length of carbon side chain and the number of hydroxyl groups. The present data indicate that DDE can be epoxidized by peroxides, and the resulting products are able to form several adducts with 2'-deoxyadenosine and/or DNA. Endogenous DNA adduct formation can contribute to the already reported high cytotoxicity of DDE to mammalian cells.

Magnetically drivable nano-bio-conjugate mimicking free curcumin redox behavior

Curcumin possesses wide-ranging anti-inflammatory and anti-cancer properties and its biological activity can be correlated to its potent antioxidant capacity. Novel maghemite (gamma-Fe3O4) nanoparticles, characterized by a diameter of about 10 nm and possessing peculiar colloidal properties and surface interactions, called Surface Active Maghemite Nanoparticles (SAMN), were superficially modified with curcumin by simple incubation, due to the presence of under-coordinated Fe(III) atoms on nanoparticle surface. The resulting curcumin-modified SAMNs (SAMN@curcumin) were characterized by transmission electron microscopy (TEM), FTIR, Mossbauer, EPR and UV-Vis spectroscopy. The redox properties of bound curcumin were tested by electrochemistry. Finally, SAMN@curcumin was studied in the presence of different electroactive substances, namely hydroquinone, NADH and ferrocyanide, in order to assess its electrochemical behavior. Moreover, SAMN@curcumin was electrochemically tested in the presence of one of the most diffuse reactive oxygen specie, such as hydrogen peroxide, demonstrating its stability. SAMN@curcumin in which curcumin is firmly bound, but still retaining its redox features represents a feasible adduct: a magnetically drivable nano-bio-conjugate mimicking free Curcumin redox behavior. The proposed nanostructured material could be exploited as magnetic drivable curcumin vehicle for biomedical applications.