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1.
Molecules ; 24(21)2019 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-31717733

RESUMO

The reaction of hydroxyl radical (HO•) with DNA produces many primary reactive species and many lesions as final products. In this study, we have examined the optical spectra of intermediate species derived from the reaction of HO• with a variety of single- and double-stranded oligodeoxynucleotides and ct-DNA in the range of 1 µs to 1 ms by pulse radiolysis using an Intensified Charged Coupled Device (ICCD) camera. Moreover, we applied our published analytical protocol based on an LC-MS/MS system with isotopomeric internal standards to enable accurate and precise measurements of purine lesion formation. In particular, the simultaneous measurement of the four purine 5',8-cyclo-2'-deoxynucleosides (cPu) and two 8-oxo-7,8-dihydro-2'-deoxypurine (8-oxo-Pu) was obtained upon reaction of genetic material with HO• radicals generated either by γ-radiolysis or Fenton-type reactions. Our results contributed to the debate in the literature regarding absolute level of lesions, method of HO• radical generation, 5'R/5'S diastereomeric ratio in cPu, and relative abundance between cPu and 8-oxo-Pu.


Assuntos
DNA/química , Radical Hidroxila/química , Oligodesoxirribonucleotídeos/química , Animais , Dano ao DNA/genética , Humanos , Peróxido de Hidrogênio/química , Ferro/química , Purinas/química
2.
J Phys Chem B ; 123(17): 3688-3698, 2019 05 02.
Artigo em Inglês | MEDLINE | ID: mdl-30964986

RESUMO

The photoreduction by amines and N-phenylglycine, NPG, of six styrylquinoxalin-2(1 H)-ones derivatives substituted in the styryl moiety, R-SQ, was studied by using flash photolysis. The photoreaction is initiated via a single electron transfer from the electron donor (amines or NPG) to R-SQ excited triplet state, 3R-SQ*, with the formation of a triplet state radical ion pair or a charge transfer exciplex, 3[CRIP/CTE]. These species live longer than the respective 3R-SQ* and have very similar transient spectra. In the presence of NPG, these 3[CRIP/CTE] evolve on µs time scale to the respective hydrogenated radicals, R-SQH•, whose transient spectra and reaction rate constants with NPG are reported. The identity of these hydrogenated radicals was supported by the spectra obtained with the α-H donor triethylamine and previous pulse radiolysis studies in 2-propanol. Our findings allow proposing a radical chain reaction mechanism that explains the observed spectral behavior and rationalizes formation of the main product formed by binding of four PhNHCH2• derived from NPG decarboxylation.

3.
Talanta ; 177: 122-141, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29108567

RESUMO

The monitoring of Advanced Oxidation/Reduction Processes (AO/RPs) for the evaluation of the yield and mechanisms of decomposition of perfluorinated compounds (PFCs) is often a more difficult task than their determination in the environmental, biological or food samples with complex matrices. This is mostly due to the formation of hundreds, or even thousands, of both intermediate and final products. The considered AO/RPs, involving free radical reactions, include photolytic and photocatalytic processes, Fenton reactions, sonolysis, ozonation, application of ionizing radiation and several wet oxidation processes. The main attention is paid to the most commonly occurring PFCs in the environment, namely PFOA and PFOS. The most powerful and widely exploited method for this purpose is without a doubt LC/MS/MS, which allows the identification and trace quantitation of all species with detectability and resolution power depending on the particular instrumental configurations. The GC/MS is often employed for the monitoring of volatile fluorocarbons, confirming the formation of radicals in the processes of C‒C and C‒S bonds cleavage. For the direct monitoring of radicals participating in the reactions of PFCs decomposition, the molecular spectrophotometry is employed, especially electron paramagnetic resonance (EPR). The UV/Vis spectrophotometry as a detection method is of special importance in the evaluation of kinetics of radical reactions with the use of pulse radiolysis methods. The most commonly employed for the determination of the yield of mineralization of PFCs is ion-chromatography, but there is also potentiometry with ion-selective electrode and the measurements of general parameters such as Total Organic Carbon and Total Organic Fluoride. The presented review is based on about 100 original papers published in both analytical and environmental journals.


Assuntos
Técnicas de Química Analítica/métodos , Poluentes Ambientais/análise , Poluentes Ambientais/química , Fluorcarbonetos/análise , Fluorcarbonetos/química , Radicais Livres/química , Humanos , Oxirredução , Volatilização
4.
Chemistry ; 23(26): 6380-6390, 2017 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-28263437

RESUMO

A shape-persistent molecule, featuring four bipyridinium units, has been synthesized that upon reduction undergoes intermolecular pimerization because of the rigid architecture of the molecule. The pimerization process has been investigated by a variety of techniques, such as absorption measurements, EPR spectroscopy, as well as gamma and pulse radiolysis, and compared with the behavior of a model compound. Computational studies have also been performed to support the experimental data. The most interesting feature of the tetramer is that pimerization occurs only above a threshold concentration of monoreduced species, on the contrary to the model compound. Furthermore, there is an increase of the apparent pimerization constant by increasing the concentration of reduced bipyridinium units. These results have been interpreted by the fact that pimerization is favored in the tetrahedrally shaped molecule because of a cooperative mechanism. Each multiply reduced molecule can indeed undergo multiple intermolecular interactions that enhance the stabilization of the system, also leading to hierarchical supramolecular growth. The resulting supramolecular system formed by such intermolecular pimerization should exhibit a diamond-like structure, as suggested by a simplified modeling approach. The intermolecular nature of the pimerization process occurring in the tetramer has been demonstrated by measuring the corresponding bimolecular rate constant by pulsed radiolysis experiments.

6.
Top Curr Chem (Cham) ; 374(5): 60, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27573502

RESUMO

The most important contributions of radiation chemistry to some selected technological issues related to water-cooled reactors, reprocessing of spent nuclear fuel and high-level radioactive wastes, and fuel evolution during final radioactive waste disposal are highlighted. Chemical reactions occurring at the operating temperatures and pressures of reactors and involving primary transients and stable products from water radiolysis are presented and discussed in terms of the kinetic parameters and radiation chemical yields. The knowledge of these parameters is essential since they serve as input data to the models of water radiolysis in the primary loop of light water reactors and super critical water reactors. Selected features of water radiolysis in heterogeneous systems, such as aqueous nanoparticle suspensions and slurries, ceramic oxides surfaces, nanoporous, and cement-based materials, are discussed. They are of particular concern in the primary cooling loops in nuclear reactors and long-term storage of nuclear waste in geological repositories. This also includes radiation-induced processes related to corrosion of cladding materials and copper-coated iron canisters, dissolution of spent nuclear fuel, and changes of bentonite clays properties. Radiation-induced processes affecting stability of solvents and solvent extraction ligands as well oxidation states of actinide metal ions during recycling of the spent nuclear fuel are also briefly summarized.


Assuntos
Energia Nuclear , Cerâmica/química , Peróxido de Hidrogênio/química , Cinética , Nanopartículas/química , Nanoporos , Reatores Nucleares , Oxirredução , Solventes/química , Água/química
7.
J Phys Chem B ; 117(46): 14385-99, 2013 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-24147795

RESUMO

Hydrophobic room-temperature ionic liquids (ILs) hold promise as replacements for molecular diluents for processing of used nuclear fuel as well as for the development of alternative separations processes, provided that the solvent can be made resistant to ionizing radiation. We demonstrate that 1-benzylpyridinium cations are uniquely suited as radiation resistant cations due to the occurrence of charge delocalization in both their reduced and oxidized forms in the ILs. It is suggested that the excess electron and hole in the latter ILs are stabilized through the formation of π-electron sandwich dimers that are analogous to the well-known dimer radical cations of aromatic molecules. This charge delocalization dramatically reduces the yield of fragmentation by deprotonation and the loss of benzyl arms, thereby providing a synthetic path to radiation resistant ILs that are suitable for nuclear fuel processing.

8.
Photochem Photobiol ; 89(6): 1417-26, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23647175

RESUMO

Photoreduction of 7H-benzo[e]perimidin-7-one (3-AOIA, A1) and its 2-methyl derivative (2-Me-3-AOIA, A2) by non-H-donating amines (1,4-diazabicyclo[2.2.2]octane [DABCO]; 2,2,6,6-tetramethylpiperidine [TMP]), and a hydrogen-donating amine (triethylamine [TEA]), has been studied in deaerated neat acetonitrile solutions using laser flash photolysis (LFP) and steady-state photolysis. The triplet excited states of A1 and A2 were characterized by a strong absorption band with λmax = 440 nm and lifetimes of 20 and 27 µs respectively. In the presence of tertiary amines, both triplet excited states were quenched with rate constants close to the diffusional limit (kq ranged between 10(9) and 10(10) M(-1) s(-1)). The transient absorption spectra observed after quenching with DABCO and TMP were characterized by maxima located at 460 nm and broad shoulders in the range of 500-600 nm. These transient species are attributed to solvent-separated radical ion pairs and/or to isolated radical anions. In the presence of TEA, these transients undergo proton transfer, leading to the neutral hydrogenated radicals, protonated over the N1- and O-atoms. Transient absorption spectra of these transients were characterized by maxima located at 400 and 520 nm and 430 nm respectively. Additional support for these spectral assignments was provided by pulse radiolysis (PR) experiments in acetonitrile and 2-propanol solutions.


Assuntos
Aminas/química , Aporfinas/química , Radiólise de Impulso , Oxirredução , Fotoquímica
9.
Faraday Discuss ; 154: 353-63; discussion 439-64, 465-71, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22455029

RESUMO

On time scales of a nanosecond or less, radiolytically-generated excess electrons in ionic liquids undergo solvation processes and reactions that determine all subsequent chemistry and the accumulation of radiolytic damage. Using picosecond pulse radiolysis detection methods, we observed and quantified the solvation response of the electron in 1-methyl-1-butyl-pyrrolidinium bis (trifluoromethylsulfonyl)amide and used it to understand electron scavenging by a typical solute, duroquinone.


Assuntos
Elétrons , Líquidos Iônicos/química , Termodinâmica , Radioquímica , Solubilidade , Fatores de Tempo
10.
J Photochem Photobiol B ; 103(1): 22-8, 2011 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-21300556

RESUMO

The thermostability of glucose oxidase entrapped in silica gel obtained by sol-gel method was studied by thermostimulated fluorescence of FAD at pH 5 and 7 and compared with that of the native enzyme in the solution and at the presence of ethanol. The unfolding temperatures were found to be lower for the enzyme immobilised in gel as compared with the native enzyme but higher as for the enzyme at the presence of ethanol. In gel, the thermal denaturation of glucose oxidase is independent on pH while in solution the enzyme is more stable at pH 5. The investigation the enzyme in different environment by steady-state fluorescence of FAD and tryptophan, synchronous fluorescence and time-resolved fluorescence of tryptophan indicates that the state of the molecule (tertiary structure and molecular dynamics) is different in gel and in solution. The ethanol produced during gel precursor hydrolysis is not the main factor influencing the thermostability of the enzyme but more important are interactions of the protein with the gel lattice.


Assuntos
Enzimas Imobilizadas/química , Fluorometria/métodos , Glucose Oxidase/química , Sílica Gel/química , Temperatura , Aspergillus niger/enzimologia , Estabilidade Enzimática/efeitos dos fármacos , Etanol/farmacologia , Desdobramento de Proteína/efeitos dos fármacos , Soluções , Espectrometria de Fluorescência
11.
Mol Biol Rep ; 35(1): 65-71, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17661161

RESUMO

Due to the variant functions that estrogens play in the regulation of reproduction, development of the mammary gland, growth and differentiation of cells, estrogen receptors and their genes are considered as a candidates for the markers of production and functional traits in farm animals, including cattle. In the earliest study, a 2853-bp bovine ER gene 5'-region was PCR amplified and sequenced. Moreover, for the first time, a polymorphism was described within 5' region of the bovine ERalpha gene--A/G transition lying upstream at position 2591 from acceptor splice site +85, possibly within its promoter--which could be recognized with RFLP-BglI. In other study we are found second polymorphism-A/G transition at position 1213 from acceptor splice site +85, located in promoter for exon B. We have examined the specific mRNA expression of ERalpha in various genotypes using real-time RT-PCR. We used four animals from each genotype group--AG, GG for BglI and AA, AG for SnaBI--to analyse liver ERalpha expression at the level of Real-time PCR. Liver samples were taken from the 16 young Friesian bulls of the different ERalpha genotypes, slaughtered at the local abattoir. As shown by Real-Time PCR, on the livers of animals with different genotype ERalpha mRNA for BglI polymorphism we didn't found variability, but for SnaBI we have found variability between AG and AA genotypes.


Assuntos
Bovinos/genética , Receptor alfa de Estrogênio/genética , Regulação da Expressão Gênica , Fígado/metabolismo , Polimorfismo Genético , Regiões Promotoras Genéticas/genética , Animais , Sequência de Bases , Sítios de Ligação , Receptor alfa de Estrogênio/metabolismo , Dados de Sequência Molecular , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/metabolismo
12.
Mol Biol Rep ; 34(4): 207-11, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17661162

RESUMO

Estrogen receptors, similarly as other nuclear receptors, are transcription factors, which after binding to a proper ligand (17beta-estradiol, estron or estriol) are capable of regulating transcription of target genes. Due to the functions that estrogens play in the regulation of reproduction, development of the mammary gland, growth and differentiation of cells, estrogen receptors and their genes are considered as candidate markers for production and functional traits in farm animals. Known are two isoforms of the estrogen receptor-alpha and beta. They are encoded by separate genes located on different chromosomes. The typical feature of all genes coding for nuclear receptors, including the ER genes, is the complex structure of their 5' regions. In the 5' region of the ERalpha gene of different species are located alternative exons that code for transcripts of different length with different 5'-UTR (untranslated region). The mRNA variants are created by the alternative splicing of the primary transcripts. We sequenced a 2853 bp of the bovine ER gene 5' region, including exons A, B, C and their promoters. Moreover, we found several polymorphic sites, differing by single nucleotide substitutions (SNPs), in the 5' regulatory region and in the coding region of the bovine ERalpha gene.


Assuntos
Polimorfismo Genético , Receptores Estrogênicos/genética , Animais , Bovinos , Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/metabolismo , Receptor beta de Estrogênio/genética , Receptor beta de Estrogênio/metabolismo , Camundongos , Polimorfismo de Fragmento de Restrição , Regiões Promotoras Genéticas/genética , Ligação Proteica , Ratos , Receptores Estrogênicos/metabolismo , Ovinos , Suínos
13.
J Phys Chem B ; 111(18): 4685-92, 2007 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-17474696

RESUMO

Pairing of a Keggin or Lindqvist polyoxometalate (POM) anion with an appropriate tetraalkylphosphonium cation is shown to yield the first members of a new family of ionic liquids (ILs). Detailed characterization of one of them, an ambient-temperature "liquid POM" comprising the Lindqvist salt of the trihexyl(tetradecyl) phosphonium cation, by voltammetry, viscometry, conductimetry, and thermal analysis indicates that it exhibits conductivity and viscosity comparable to those of the one previously described inorganic-organic POM-IL hybrid but with substantially improved thermal stability.


Assuntos
Líquidos Iônicos/química , Compostos Organometálicos/química , Compostos Organofosforados/química , Varredura Diferencial de Calorimetria , Eletroquímica , Líquidos Iônicos/síntese química , Compostos Organometálicos/síntese química , Compostos Organofosforados/síntese química , Compostos de Amônio Quaternário/química , Espalhamento a Baixo Ângulo , Temperatura , Fatores de Tempo , Compostos de Tungstênio/química , Viscosidade , Difração de Raios X
14.
Dalton Trans ; (5): 529-31, 2007 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-17225903

RESUMO

The pairing of selected polyoxometalate (POM) anions with appropriate tetraalkylphosphonium cations is shown to yield an original family of ionic liquids, among them an ambient-temperature "liquid POM".


Assuntos
Líquidos Iônicos/química , Compostos de Tungstênio/química , Ânions , Catálise , Cátions , Eletroquímica , Compostos Organofosforados/química , Oxirredução , Solventes , Temperatura
15.
J Appl Genet ; 45(2): 225-36, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15131353

RESUMO

Due to the functions that estrogens play in the regulation of reproduction, development of the mammary gland, growth and differentiation of cells, estrogen receptors and their genes are considered candidates for the markers of production and functional traits in farm animals, including cattle. In the present study, on the basis of the sequences of the human, ovine, and porcine ER genes, available in the GenBank database, sets of PCR primers were designed and used to amplify the bovine ERalpha gene 5'-region. Seven overlapping fragments of the 5' region of the bovine ERalpha gene were amplified and then sequenced. Altogether, these fragments were composed in the 2853-bp sequence which was deposited in the GenBank database under accession no. AY340597. The sequenced fragment included the noncoding exons A, B, C, their putative promoters, and a part of the coding exon 1. A polymorphism within the 5' region of the bovine ERalpha gene-A/G transition, which could be recognized with RFLP-BglI, lying upstream to the exon C, was identified for the first time using this sequence.


Assuntos
Bovinos/genética , Polimorfismo Genético , Receptores Estrogênicos/genética , Região 5'-Flanqueadora/genética , Animais , Sequência de Bases , Primers do DNA , Bases de Dados de Ácidos Nucleicos , Receptor alfa de Estrogênio , Feminino , Amplificação de Genes , Masculino , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Análise de Sequência de DNA
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