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1.
Phys Chem Chem Phys ; 22(9): 5057-5069, 2020 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-32073000

RESUMO

Graph theory-based reaction pathway searches (ACE-Reaction program) and density functional theory calculations were performed to shed light on the mechanisms for the production of [an + H]+, xn+, yn+, zn+, and [yn + 2H]+ fragments formed in free radical-initiated peptide sequencing (FRIPS) mass spectrometry measurements of a small model system of glycine-glycine-arginine (GGR). In particular, the graph theory-based searches, which are rarely applied to gas-phase reaction studies, allowed us to investigate reaction mechanisms in an exhaustive manner without resorting to chemical intuition. As expected, radical-driven reaction pathways were favorable over charge-driven reaction pathways in terms of kinetics and thermodynamics. Charge- and radical-driven pathways for the formation of [yn + 2H]+ fragments were carefully compared, and it was revealed that the [yn + 2H]+ fragments observed in our FRIPS MS spectra originated from the radical-driven pathway, which is in contrast to the general expectation. The acquired understanding of the FRIPS fragmentation mechanism is expected to aid in the interpretation of FRIPS MS spectra. It should be emphasized that graph theory-based searches are powerful and effective methods for studying reaction mechanisms, including gas-phase reactions in mass spectrometry.


Assuntos
Teoria da Densidade Funcional , Radicais Livres/química , Oligopeptídeos/química , Análise de Sequência de Proteína/métodos , Sequência de Aminoácidos , Óxidos N-Cíclicos/química , Gases/química , Cinética , Espectrometria de Massas , Simulação de Dinâmica Molecular , Termodinâmica
2.
J Phys Chem Lett ; 11(4): 1305-1309, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-31967478

RESUMO

G-Quadruplexes are formed by guanine rich DNA/RNA sequences in the presence of metal ions, which occupy the central cavity of these four-stranded structures. We show that these metal ions have a significant effect on the photogeneration and the reactivity of guanine radicals. Transient absorption experiments on G-quadruplexes formed by association of four TGGGGT strands in the presence of K+ reveal that the quantum yield of one-photon ionization at 266 nm (8.1 × 10-3) is twice as high as that determined in the presence of Na+. Replacement of Na+ with K+ also suppresses one reaction path involving deprotonated radicals, (G-H2)• → (G-H1)• tautomerization. Such behavior shows that the underlying mechanisms are governed by dynamical processes, controlled by the mobility of metal ions, which is higher for Na+ than for K+. These findings may contribute to our understanding of the ultraviolet-induced DNA damage and optimize optoelectronic devices based on four-stranded structures, beyond DNA.


Assuntos
Quadruplex G , Guanina/química , Potássio/química , Dano ao DNA/efeitos da radiação , Radicais Livres/química , Radicais Livres/metabolismo , Íons/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Fótons , Teoria Quântica , Raios Ultravioleta
3.
Chemphyschem ; 21(1): 43-50, 2020 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-31709709

RESUMO

The role of tyrosine radicals as mediators of electron transfer reactions in enzymes is well established, as is the involvement of histidine as a binding partner. But how environmental factors affect these reactions remains poorly explored. In the study presented here, kinetic data on the influence of the protonation state of the reactants on the reduction of transient histidine radicals by tyrosine were obtained in neutral and basic aqueous solution (pH 6-12) using time-resolved chemically induced dynamic nuclear polarization (CIDNP). The histidine radicals were generated in the photo-induced reaction with the photosensitizer 3,3',4,4'-tetracarboxy benzophenone. From model simulations of the detected CIDNP kinetics, pH dependent second-order rate constants of the reduction of histidine radicals were obtained for four possible combinations of the amino acids and their N-acetyl derivatives, and also for the systems histidine-phenylalanine dipeptide/N-acetyl tyrosine, and N-acetyl histidine/tyrosine-glutamine dipeptide. The pH dependences of the rate constant of the reduction reaction are explained accounting for the protonation states of reactants, and also protonation state of the equilibrium form of the product - reduced form of histidine radical, which is histidine with neutral or a positively charged imidazole.


Assuntos
Histidina/química , Prótons , Tirosina/química , Radicais Livres/química , Concentração de Íons de Hidrogênio , Cinética , Estrutura Molecular , Oxirredução , Espectroscopia de Prótons por Ressonância Magnética
4.
Chemistry ; 26(4): 823-829, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31658386

RESUMO

Mechanistic studies with 5-ethyl-3-methyllumiflavinium (Fl+ ) perchlorate, a biomimetic model for flavoenzyme monoamine oxidase B (MAO-B) catalysis, and the tertiary, allyl amine 1-methyl-4-(1-methyl-1 H-pyrrol-2-yl)-1,2,3,6-tetrahydropyridine (MMTP) reveal that proton-coupled electron transfer (PCET) may be an important pathway for MAO catalysis. The first step involves a single-electron transfer (SET) leading to the free radicals Fl. and MMTP. , the latter produced by deprotonation of the initially formed and highly acidic MMTP.+ . Molecular oxygen (O2 ) is found to play a hitherto unrecognized role in the early steps of the oxidation. MMTP and several structurally similar tertiary amines are the only tertiary amines oxidized by MAO, and their structural/electronic properties provide the key to understanding this behavior. A general hypothesis about the role of SET in MAO catalysis, and the recognition that PCET occurs with appropriately substituted substrates is presented.


Assuntos
Aminas/química , Radicais Livres/metabolismo , Monoaminoxidase/química , Biomimética , Catálise , Transporte de Elétrons , Radicais Livres/química , Oxirredução , Prótons
5.
Chemistry ; 26(7): 1633-1639, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31724757

RESUMO

Convenient and sensitive detection of biomolecules is of great significance to disease diagnosis. In this work, a metal-free photoinduced atom transfer radical polymerization (photoATRP) by a reductive quenching pathway as a novel strategy is applied to achieve lung cancer DNA detection. Thiolated PNA is exploited to specifically recognize target DNA, and the initiator of photoATRP is linked to the electrode surface via phosphate-Zr4+ -carboxylate. Under the excitation of blue light, the reductive quenching pathway is activated with eosin Y (EY) as photoredox catalyst and N,N,N',N'',N'-pentamethyldiethylenetriamine (PMDETA) as electron donor, and numerous polymeric chains are formed. Under optimal conditions, the linear range of this strategy is from 0.1 pm to 10 nm (R2 =0.989) with a limit of detection (LOD) of 1.4 fm (14 zmol in 10 µL). The variety of possible light sources for photoATRP and simple operation endow this biosensor with great potential for practical applications.


Assuntos
Técnicas Biossensoriais/métodos , DNA/química , Radicais Livres/química , Neoplasias Pulmonares/genética , Metais/química , Polímeros/química , Catálise , DNA/genética , Eletrodos , Humanos , Limite de Detecção , Neoplasias Pulmonares/química , Polimerização
6.
Phytochemistry ; 170: 112218, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31812108

RESUMO

The vast majority of previous studies dealing with antioxidant potency of (poly)phenols does not investigate the fate of phenoxyl radical obtained after single free radical scavenging. We investigated possible pathways of inactivation of ferulic acid phenoxyl radical (FAPR) using DFT method. Direct coupling with a set of 10 physiologically important free radicals, H-atom donation and dimerization were analysed by estimation of Gibbs free energy changes related to these processes. The former two processes are thermodynamically feasible to inactivate more dangerous free radicals such as hydroxyl, alkoxyl and carbon-centered radicals. Among dimerization reactions, the least energy demanding is formation of C-5-C-5 dimer of ferulic acid (FA), which has higher antiradical potency than FA itself. Obtained results reveal that FAPR, a priori considered as stable and unreactive, may contribute to the overall antioxidant activity of FA. This is a beneficial behavior, which makes FA a particularly valuable protector against oxidative stress. Hence, the contribution of phenoxyl radicals to the antioxidant activity of (poly)phenolic compounds should be taken into account, what has been scarcely considered until now.


Assuntos
Antioxidantes/farmacologia , Ácidos Cumáricos/farmacologia , Fenóis/farmacologia , Compostos Fitoquímicos/farmacologia , Antioxidantes/química , Ácidos Cumáricos/química , Teoria da Densidade Funcional , Radicais Livres/química , Radicais Livres/farmacologia , Estrutura Molecular , Estresse Oxidativo/efeitos dos fármacos , Fenóis/química , Compostos Fitoquímicos/química
7.
Food Chem ; 311: 126010, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31869648

RESUMO

This study reports enhanced efficacy of encapsulated α-Terpineol to control fungal, aflatoxin B1 (AFB1) and free radicals mediated deterioration of stored maize samples. The α-Terpineol loaded chitosan nanoemulsion (α-TCsNe) was characterized through SEM, FTIR and XRD techniques. The α-TCsNe exhibited enhanced antifungal activity against aflatoxin secreting strain of Aspergillus flavus (AF-LHP-S1) and 12 other food borne moulds as well as AFB1 production at 0.4 and 0.3 µL/mL, respectively. Further, α-TCsNe inhibited ergosterol synthesis, methylglyoxal (the aflatoxin enhancer) content and enhanced cellular contents release. α-TCsNe showed enhanced radical scavenging activity with IC50 value equivalent to 39.57 and 6.23 µL/mL for DPPH and ABTS, respectively. In addition, α-TCsNe completely inhibited AFB1 production in stored maize samples during in situ investigation. Overall, α-TCsNe holds a promising potential and can be recommended as a novel antifungal preservative to improve the shelf-life of stored maize samples against fungal and aflatoxin contamination.


Assuntos
Aflatoxina B1/metabolismo , Aspergillus flavus/efeitos dos fármacos , Quitosana/química , Radicais Livres/química , Aflatoxina B1/análise , Antifúngicos/química , Antifúngicos/farmacologia , Antioxidantes/química , Aspergillus flavus/metabolismo , Cromatografia Líquida de Alta Pressão , Emulsões/química , Armazenamento de Alimentos , Zea mays/metabolismo
8.
Food Chem ; 311: 125962, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31869645

RESUMO

Effect of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) on oxidation stability of stripped peanut oil (SPO) and bulk peanut oil (BPO) was investigated by EPR. Impact of commercial lecithin and cephalin on BPO oxidation was also studied. PC < 1000 ppm could not affect SPO oxidation but obviously accelerated oxidation above 1000 ppm. PE acted as antioxidant below 250 ppm, had no effect at 500 and 1000 ppm but behaved prooxidative properties above 2500 ppm. It suggested that there was a threshold value for PC and PE to act as prooxidant in SPO, which above the CMC yet not just at the CMC. PC (500 ppm) and PE (100-500 ppm) decreased BPO oxidation rate through reducing the formation of peroxyl and carbon-centered radicals. 250, 500 ppm PC from lecithin and 100, 250 ppm PE from cephalin possessed antioxidant abilities in BPO during Schaal oven test, demonstrating the results obtained with EPR.


Assuntos
Óleo de Amendoim/química , Fosfatidiletanolaminas/química , Antioxidantes/química , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/química , Radicais Livres/metabolismo , Peroxidação de Lipídeos
9.
Chemosphere ; 240: 124921, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726593

RESUMO

The interplay of phenolic molecules with 3d transition metals, such as Fe and Cu, and their oxide surfaces, provide important fingerprints for environmental burdens associated with thermal recycling of e-waste and subsequent generation of notorious dioxins compounds and phenoxy-type Environmental Persistent Free Radicals (EPFRs). DRIFTS and EPR measurements established a strong interaction of the phenol molecule with transition metal oxides via synthesis of phenolic- and catecholic-type EPFRs intermediates. In this contribution, we comparatively examined the dissociative adsorption of a phenol molecule, as the simplest model for phenolic-type compounds, on Cu and Fe surfaces and their partially oxidized configurations through accurate density functional theory (DFT) studies. The underlying aim is to elucidate the specific underpinning mechanism forming phenoxy- or phenolate-type EFPRs. Simulated results show that, the phenol molecule undergoes fission of its hydroxyl's O-H bond via accessible activation energies. These values are lower by 46.5-74.1% when compared with the analogous gas phase value. Physisorbed molecules of phenol incur very low binding energies in the range of -2.1 to -5.5 over clean Cu/Fe and their oxides surfaces. Molecular attributes based on charge transfer and geometrical features are in accord with the very weak interaction in physisorbed states. Thermo-kinetic parameters established over the temperature region of 300 and 1000 K, exhibit a lower activation energy for scission of phenolic's O-H bonds over the oxide surfaces in reference to their pure surfaces (24.7 and 43.0 kcal mol-1vs 38.4 and 47.0 kcal mol-1).


Assuntos
Radicais Livres/química , Fenol/química , Fenóis/química , Adsorção , Catecóis , Dioxinas , Radical Hidroxila , Oxirredução , Óxidos/química , Temperatura Ambiente , Elementos de Transição
10.
Ecotoxicol Environ Saf ; 188: 109891, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31740236

RESUMO

The study focuses on degradation efficiency of non-radical activation and radical activation systems of persulfate (PS) to degrade imidacloprid (IMI) by using sodium persulfate (SPS) as PS source. Copper oxide (CuO)-SPS and CuO/biochar (BC)-SPS were selected as PS non-radical activation systems, and pyrite (PyR)-SPS was selected as PS radical activation system. The degradation by CuO-SPS, CuO/BC-SPS and PyR-SPS systems was investigated from acidic to basic conditions (pH 3.0-11.0). Highest degradation by CuO-SPS and CuO/BC-SPS systems was achieved over pH 11.0. In contrast, highest degradation by PyR-SPS system was achieved over pH 3.0, however, PyR-SPS system was also found effective up to pH 9.0. It was found that degradation was more efficient in PS radical activation system, indicating that IMI could be oxidized by radicals rather than by activated PS. Electron paramagnetic resonance (EPR) analysis was carried out to investigate the generation of sulfate (SO4-) and hydroxyl (OH) radicals, which indicated the presence of SO4- and OH in CuO-SPS, CuO/BC and PyR-SPS systems. However, free radical quenching analysis indicated that radicals were main reactive oxygen species for degradation. The lower degradation in PS non-radical activation systems was probably resulted from radicals existed as minor reactive oxygen species. The findings indicated that non-radical oxidation systems showed low reality for degradation and good degradation could be achieved by radical oxidation system. The degradation was also carried out in real waters to investigate the potential applicability of applied systems, which supported PyR-SPS system for effective degradation.


Assuntos
Carvão Vegetal/química , Cobre/química , Radicais Livres/química , Neonicotinoides/análise , Nitrocompostos/análise , Compostos de Sódio/química , Sulfatos/química , Poluentes Químicos da Água/análise , Concentração de Íons de Hidrogênio , Radical Hidroxila/química , Ferro/química , Modelos Teóricos , Oxirredução , Sulfetos/química , Purificação da Água
11.
Food Chem ; 309: 125714, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31671375

RESUMO

Evaluation on the oxidative stability of oils, based on the tendency of free radicals production, can be operated by using electron spin resonance (ESR) spectroscopy. Induction Periods (IP) can be determined by Boltzmann equation fitting under accelerated conditions (heated). The IPs were compared with IPs of Rancimat method, and high linear correlation was found between these two methods (r = 0.996 and 0.985 separately), suggesting that ESR method can predict the oxidative stabilities provided by the Rancimatt method. This study indicated that ESR provided a sensitive method to evaluate the oxidative stability of edible oils.


Assuntos
Espectroscopia de Ressonância de Spin Eletrônica , Óleos Vegetais/química , Radicais Livres/química , Óleo de Palmeira/química , Óleo de Amendoim/química , Marcadores de Spin , Temperatura Ambiente
12.
Chemosphere ; 239: 124815, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526994

RESUMO

In this study, Pd-BiVO4 bearing highly dispersed Pd nanoparticles was prepared from pure BiVO4 using an impregnation method. The pure BiVO4 and Pd-BiVO4 catalysts were characterized by X-ray diffraction, scanning electron microscopy, UV-visible diffuse reflection, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that the prepared catalysts had a monoclinic scheelite structure and exhibited a flake-like morphology. Pd-BiVO4 showed a distinct response in the visible light region, with an extended absorption edge at 550 nm. According to the Scherrer formula, the nanocrystal particle sizes of the BiVO4 and Pd-BiVO4 catalysts were 35 and 28 nm, respectively. Highly dispersed Pd nanoparticles with sizes of 2.5 ±â€¯0.5 nm were observed on the BiVO4 surface. Two Pd valence states, Pd(II) and Pd(0), were identified in a 2:1 ratio. Pd-BiVO4 exhibited excellent activity for paracetamol (PCT) degradation, with 100% removal achieved in 1 h under visible light irradiation. During degradation, the mineralization ratio reached up to 40% total organic carbon removal. Two highly active species, namely, hydroxyl and superoxide radicals, were determined by electron spin resonance (ESR). Furthermore, the potential degradation of PCT in this system was proposed based on intermediate information obtained using HPLC-MS and Gauss analysis. The high dispersion and small size of Pd nanoparticles might favor the removal of emerging contaminants using the Pd-BiVO4 photocatalytic system.


Assuntos
Acetaminofen/efeitos da radiação , Poluentes Ambientais/química , Luz , Nanopartículas Metálicas/química , Paládio/química , Fotólise/efeitos da radiação , Vanadatos/química , Acetaminofen/química , Bismuto/química , Catálise , Poluentes Ambientais/efeitos da radiação , Radicais Livres/química , Microscopia Eletrônica , Fotólise/efeitos dos fármacos , Análise Espectral
13.
Mutat Res ; 782: 108283, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31843137

RESUMO

Immuno-spin trapping detection of DNA radicals with the nitrone spin trap 5,5-dimethyl-1-pyrrloine N-oxide (DMPO) has made important contributions towards the understanding of DNA radicalization and genotoxicity at sites of inflammation. At sites of inflammation, one-electron oxidants and chloramines decay induce oxidation of genomic DNA, genotoxicity and cell transformation. Radicalization of DNA can result in either single- or double-strand breaks, or end-oxidation products at the sugar or bases. If not repaired, these modifications can lead to mutations and cell transformation. If trapped with DMPO, DNA-centered radical decay and subsequent formation of end-oxidation products are blocked. Herein we discuss recent literature regarding the use of immuno-spin trapping with DMPO to study DNA-centered radicals and their involvement in genotoxicity. This technique has shown the critical role of DNA radicalization in 8-oxo-dG formation and DNA strand breaks in isolated DNA, cells and in whole animals. Combination of technologies, including immuno-spin trapping and powerful chromatographic and sequencing techniques are needed to move forward the field towards the detection of specific genes that are susceptible to oxidative damage in cells located at sites of inflammation. This is important in order to provide novel information about genotoxicity mechanisms, as well as therapeutic possibilities of DMPO or its derivatives for preventing DNA-centered radical-mediated carcinogenesis.


Assuntos
Óxidos N-Cíclicos/efeitos adversos , Dano ao DNA/efeitos dos fármacos , DNA/efeitos dos fármacos , Radicais Livres/química , Mutagênicos/efeitos adversos , Óxidos de Nitrogênio/efeitos adversos , Óxidos de Nitrogênio/química , Animais , Inflamação/genética , Detecção de Spin/métodos
14.
Chem Asian J ; 14(23): 4352-4357, 2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31777169

RESUMO

A maleimide-based acyclic enediyne with salicylaldiminato substituents at the alkyne termini was synthesized, which was further chelated with three kinds of metal-ions, CuII , ZnII , and MgII , and form metalloenediynes. The cycloaromatization of this thermally inactive enediyne ligand was greatly accelerated through the coordination with metal ions. Specifically, the CuII -metalloenediyne showed an extremely low onset temperature of 55 °C and underwent spontaneous cycloaromatization at ambient temperature to produce free radicals, followed by generation of reactive oxygen species in the physiological environment. The metalloenediyne exhibited excellent DNA cleavage ability and high cytotoxicity towards HeLa cells, with half-maximal inhibitory concentration values comparable to many commercial antitumor agents. The combination of the electron-withdrawing effect of the maleimide moiety at the ene position and metal coordination at the yne termini provides a new inspiration for designing and synthesizing highly efficient enediyne antitumor agents.


Assuntos
Enedi-Inos/química , Radicais Livres/metabolismo , Antineoplásicos/química , Antineoplásicos/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Clivagem do DNA/efeitos dos fármacos , Radicais Livres/química , Células HeLa , Humanos , Ligantes , Maleimidas/química , Metais/química , Espécies Reativas de Oxigênio/metabolismo
15.
J Chem Phys ; 151(20): 201102, 2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31779325

RESUMO

Throughout nature, both free radicals and transient radical reaction intermediates are vital to many biological functions. Coenzyme B12 is a case in point. This organometallic cofactor generates a radical pair upon activation in its dependent enzymes by substrate binding and following photolysis. The resulting cob(ii)alamin/5'-deoxyadenosyl radical pair has unusual magnetic properties that present a challenge to detailed investigation at ambient temperatures. Here, we use femtosecond transient absorption spectroscopy adapted for magnetic field exposure to reveal that the spin dynamics of the B12 radical pair are sufficiently fast for magnetic field effects to be observed on the ultrafast reaction kinetics. Moreover, the large difference in g-values between the radicals of the pair means that effects of the Δg mechanism are observed for the first time for a radical pair system exposed to magnetic fields below 1 T. Spin dynamic simulations allow a value of the cob(ii)alamin radical g-value (2.105) at ambient temperature to be extracted and, because the spin dynamic time scale is faster than the diffusional rotation of the cob(ii)alamin radical, the observed value corresponds to the anisotropic g|| value for this radical.


Assuntos
Fotólise , Teoria Quântica , Vitamina B 12/química , Radicais Livres/química , Campos Magnéticos , Estrutura Molecular , Temperatura Ambiente
16.
Chemosphere ; 237: 124411, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31549633

RESUMO

Atmospheric oxidation of NHx-containing (x = 1, 2) compounds can produce N-center radicals, a precursor of toxic nitrosamines. The reaction rate constant (kO2) with O2 has been considered as an important parameter to determine the nitrosamines yield in the subsequent reactions of N-center radicals. However, available kO2 values of N-center radicals are limited. Here, a three-step scheme including mechanistic analysis and kinetics calculation of the reactions of 28 various N-center radicals with O2, and model development was taken to solve the kO2 data shortage. Mainly employed tools include highly cost-expensive coupled-cluster theory (CCSD(T)), kinetic model and statistics. The results indicate that the direct H-abstraction pathway is the most favorable for the reactions of all considered N-center radicals with O2. The specific molecular conformation and the C-H bond energy of the N-center radicals are two important factors to determine kO2 values. Based on the mechanistic understanding of kO2 values, a quantitative structure-activity relationship (QSAR) model of kO2 values was developed. The model has satisfactory goodness-of-fit, robustness and predictive ability. The determined kO2 values and the in silico methods provide a scientific base for assessing formation risk of toxic nitrosamines in the atmosphere.


Assuntos
Poluentes Atmosféricos/química , Radicais Livres/química , Oxigênio/química , Relação Quantitativa Estrutura-Atividade , Atmosfera/química , Simulação por Computador , Cinética , Modelos Químicos , Conformação Molecular , Nitrosaminas/química , Oxirredução
17.
Chemistry ; 25(69): 15779-15785, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31523878

RESUMO

A series of fluoroalkylated cyclic λ3 -iodanes and their hydrochloride salts was prepared and used in a combination with sodium ascorbate in buffer or aqueous methanol mixtures for radical fluoroalkylation of a range of substituted indoles, pyrroles, tryptophan or its derivatives, and Trp residues in peptides. As demonstrated on several peptides, the aromatic amino acid residues of Trp, Tyr, Phe, and His are targeted with high selectivity to Trp. The functionalization method is biocompatible, mild, rapid, and transition-metal-free. The proteins myoglobin, ubiquitin, and human carbonic anhydrase I were also successfully functionalized.


Assuntos
Aminoácidos Aromáticos/química , Indóis/química , Peptídeos/química , Proteínas/química , Pirróis/química , Alquilação , Aminoácidos Aromáticos/síntese química , Radicais Livres/síntese química , Radicais Livres/química , Halogenação , Humanos , Indóis/síntese química , Modelos Moleculares , Peptídeos/síntese química , Proteínas/síntese química , Pirróis/síntese química
18.
Environ Sci Pollut Res Int ; 26(31): 31675-31684, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31482528

RESUMO

Oxidative stress is an imbalance between free radicals and antioxidants which leads to reactive oxygen species (ROS) production in cells. Reactive oxygen species contains oxygen radicals that easily react with other molecules in the biological system. For decades, lead acetate (Pb(C2H3O2)2) is used as an additive for many widely used chemical products such as insecticides, hair dyes, and cosmetics; however, contact with lead acetate may irritate skin, eyes, and mucous membranes.In the present study, the antioxidant and anti-inflammatory effect of using ferulic acid to inhibit lead acetate-induced toxicity in rats is investigated. Lead acetate was orally given at a dose of 20 mg/kg body weight for 10 days, either alone or with ferulic acid at dose 25 mg/kg. Serum luteinizing hormone (LH), total testosterone, and follicle-stimulating hormone (FSH) levels were measured. Also, reactive oxygen species (ROS), lipid peroxidation (LPO), total antioxidant capacity (TAC), and catalase (CAT) activities were determined. In addition, histopathological changes of testes and kidney were examined. Results showed that administration of lead acetate induced oxidative stress through attenuation of luteinizing hormone, total testosterone, and follicle-stimulating hormone levels in serum. Moreover, the kidney and testes of lead acetate-treated animals exhibited elevation of ROS level, lipid peroxide levels, as well as lysosomal enzyme activity such acid phosphatase and N-acetyl-ß-glucosminidase. DNA fragmentation and histological changes were also observed in lead acetate-treated group. In contrast, ferulic acid treatment reduced the deleterious effects induced by lead acetate in both testes and kidney tissues. These results illustrated that ferulic acid has a protective action against toxicity caused by lead acetate in rats. In conclusions, ferulic acid may have future therapeutic relevance in the prevention of lead acetate-induced testicular and renal toxicity in rats.


Assuntos
Antioxidantes/metabolismo , Ácidos Cumáricos/análise , Dano ao DNA/efeitos dos fármacos , Radicais Livres/metabolismo , Rim/efeitos dos fármacos , Chumbo/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Hormônio Luteinizante/sangue , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Testículo/efeitos dos fármacos , Animais , Ácidos Cumáricos/química , Radicais Livres/química , Hormônio Luteinizante/química , Masculino , Ratos , Ratos Wistar , Espécies Reativas de Oxigênio/química
19.
Oxid Med Cell Longev ; 2019: 6528106, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31396304

RESUMO

In the cold environments of the interstellar medium, a variety of molecules in which a hydrogen (H) atom has been replaced by its heavier isotope deuterium (D) can be found. From its emergence, life had to counteract the toxic action of many agents, which posed a constant threat to its development and propagation. Oxygen-reactive species are archaic toxicants that lead to protein damage and genomic instability. Most of the oxidative lesions involve cleavage of C-H bonds and H abstraction. According to free radical chemistry principles, the substitution of D for H in oxidation-sensitive positions of cellular components should confer protection against the oxidative attack without compromising the chemical identity of the compounds. Here, we show that deuterated nucleosides and proteins protect from oxidative damage. Our data suggest a new, subtle but likely role of D in terrestrial life's evolution in that its inclusion in critical biomolecules might have facilitated their resistance during the infinite generations of life entities, cells, and organisms.


Assuntos
Deutério/química , Estresse Oxidativo , Sobrevivência Celular/efeitos dos fármacos , Sistema Livre de Células , Dano ao DNA/efeitos dos fármacos , Radicais Livres/química , Produtos Finais de Glicação Avançada/análise , Humanos , Células Jurkat , Nucleosídeos/química , Nucleosídeos/metabolismo , Nucleosídeos/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Carbonilação Proteica , Proteínas/química , Proteínas/metabolismo
20.
Environ Sci Pollut Res Int ; 26(28): 29234-29245, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31396866

RESUMO

To conduct a comprehensive ecological analysis on the solid residues derived from the thermal disposal of hyperaccumulator Pteris vittata, this study focused on the behaviors of As and Pb and the characteristics of environmentally persistent free radicals (EPFRs) in the solid residues under different thermal treatment conditions. The analysis results revealed that the concentrations of As in the biochars and bio-slag were approximately 350 and 1100 mg/kg, respectively. Moreover, the concentrations of Pb in the solid residues varied from 34 to 1050 mg/kg. According to the results of the modified BCR sequential extractions, As is more stable in the biochar while Pb is more stable in the combustion slags. In addition, As showed a higher volatilization temperature compared with Pb. The ecological risk assessment indicated that the correlation index between the contamination factor (Cf) of As and the risk index (R2 = 0.995) is considerably larger than the correlation index between the contamination factor of Pb and the risk index (R2 = 0.117), which implies that the pyrolysis method should be selected at priority. Moreover, the EPFR concentrations of the biochar declined by approximately 75 times when the pyrolysis temperature increased from 500 to 600 °C. This behavior indicated that high-temperature pyrolysis (> 600 °C) could simultaneously control both the heavy metal behavior and EPFR concentrations.


Assuntos
Carvão Vegetal/química , Radicais Livres/química , Metais Pesados/análise , Pteris/química , Gerenciamento de Resíduos/métodos , Arsênico/análise , Arsênico/química , Biodegradação Ambiental , Radicais Livres/análise , Chumbo/análise , Chumbo/química , Metais Pesados/química , Pirólise , Fatores de Risco , Poluentes do Solo/análise , Temperatura Ambiente , Termogravimetria , Volatilização
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