The electrochemical reduction of the purines guanine and adenine at platinum electrodes in several room temperature ionic liquids

The reduction of guanine was studied by microelectrode voltammetry in the room temperature ionic liquids (RTILs) N-hexyltriethylammonium bis (trifluoromethanesulfonyl) imide [N6,2,2,2][N(Tf)2], 1-butyl-3-methylimidazolium hexafluorosphosphate [C4mim][PF6], N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide [C4mpyrr][N(Tf)2], 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C4mim][N(Tf)2], N-butyl-N-methyl-pyrrolidinium dicyanamide [C4mpyrr][N(NC)2] and tris(P-hexyl)-tetradecylphosphonium trifluorotris(pentafluoroethyl)phosphate [P14,6,6,6][FAP] on a platinum microelectrode. In [N6,2,2,2][NTf2] and [P14,6,6,6][FAP], but not in the other ionic liquids studied, guanine reduction involves a one-electron, diffusion-controlled process at very negative potential to produce an unstable radical anion, which is thought to undergo a dimerization reaction, probably after proton abstraction from the cation of the ionic liquid. The rate of this subsequent reaction depends on the nature of the ionic liquid, and it is faster in the ionic liquid [P14,6,6,6][FAP], in which the formation of the resulting dimer can be voltammetrically monitored at less negative potentials than required for the reduction of the parent molecule. Adenine showed similar behaviour to guanine but the pyrimidines thymine and cytosine did not; thymine was not reduced at potentials less negative than required for solvent (RTIL) decomposition while only a poorly defined wave was seen for cytosine. The possibility for proton abstraction from the cation in [N6,2,2,2][NTf2] and [P14,6,6,6][FAP] is noted and this is thought to aid the electrochemical dimerization process. The resulting rapid reaction is thought to shift the reduction potentials for guanine and adenine to lower values than observed in RTILs where the scope for proton abstraction is not present. Such shifts are characteristic of so-called EC processes where reversible electron transfer is followed by a chemical reaction. © 2009 Elsevier B.V.

Dermatose responsiva à biotina em cão

Os transtornos da pele e dos pelos são parte importante na prática clínica de pequenos animais. Numerosos fatores nutricionais afetam a homeostase, a qualidade e o aspecto da pelagem. As vitaminas do complexo B incluem compostos hidrossolúveis necessários como coenzimas em diversas funções celulares envolvidas no metabolismo energético e na síntese tecidual. A biotina, em especial, é necessária nas reações de carboxilação, participando da síntese de ácidos graxos, aminoácidos e purinas pelo tecido epitelial. Uma cadela com quadro de cistite recorrente e tumor venéreo transmissível foi tratada com antibioticoterapia prolongada e quimioterapia. Após alguns meses de tratamento, foram observadas lesões no plano nasal e nos coxins plantar e palmar, caracterizadas por hiperceratose, espessamento, fissuras, sangramento e inflamação. O paciente recebeu suplementação de 15mg de biotina por via oral (equivalente a 1,4mg kg-1 de peso corporal), uma vez por dia, durante 60 dias, havendo importante regressão das lesões. Sugere-se que, sob antibioticoterapia e doença, a síntese intestinal de biotina possa não ter sido suficiente, sendo necessária sua suplementação.

Teores de proteína bruta para bovinos alimentados com feno de capim-tifton 85: parâmetros ruminais, eficiência de síntese microbiana e degradabilidade in situ

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

Lower levels of oxidative DNA damage and apoptosis in lymphocytes from patients undergoing surgery with propofol anesthesia

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

Influence of diet on oxidative DNA damage, uracil misincorporation and DNA repair capability

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

Structure of human PNP complexed with ligands

Purine nucleoside phosphorylase (PNP) is a key enzyme in the purine-salvage pathway, which allows cells to utilize preformed bases and nucleosides in order to synthesize nucleotides. PNP is specific for purine nucleosides in the beta-configuration and exhibits a strong preference for purines containing a 6-keto group and ribosyl-containing nucleosides relative to the corresponding analogues. PNP was crystallized in complex with ligands and data collection was performed using synchrotron radiation. This work reports the structure of human PNP in complex with guanosine (at 2.80 angstrom resolution), 3' deoxyguanosine (at 2.86 angstrom resolution) and 8-azaguanine (at 2.85 angstrom resolution). These structures were compared with the PNP-guanine, PNP-inosine and PNP-immucillin-H complexes solved previously.

Kinetics and crystal structure of human purine nucleoside phosphorylase in complex with 7-methyl-6-thio-guanosine

Purine nucleoside phosphorylase (PNP) catalyzes the reversible phosphorolysis of nucleosides and deoxynucleosides, generating ribose 1-phosphate and the purine base, which is an important step of purine catabolism pathway. The lack of such an activity in humans, owing to a genetic disorder, causes T-cell impairment, and drugs that inhibit this enzyme may have the potential of being utilized as modulators of the immunological system to treat leukemia, autoimmune diseases, and rejection in organ transplantation. Here, we describe kinetics and crystal structure of human PNP in complex with 7-methyl-6-thio-guanosine, a synthetic substrate, which is largely used in activity assays. Analysis of the structure identifies different protein conformational changes upon ligand binding, and comparison of kinetic and structural data permits an understanding of the effects of atomic substitution on key positions of the synthetic substrate and their consequences to enzyme binding and catalysis. Such knowledge may be helpful in designing new PNP inhibitors. © 2005 Elsevier Inc. All rights reserved.

Influence of experimental canine ehrlichiosis on the E-ADA activity and purine levels in serum and possible functional correlations with pathogenesis

The aim of this study was to evaluate adenosine deaminase activity and purines levels in serum of dogs experimentally infected by Ehrlichia canis. Banked serum samples of dogs divided into two groups with five animals each: healthy animals and animals infected by E. canis. The concentration of purines (adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), adenosine, inosine, hypoxanthine, xanthine and uric acid), and adenosine deaminase (E-ADA) activity in sera were evaluated. Samples were collected on days 12 and 30 post-infection (PI). The E-ADA activity showed a significant reduction on day 12 PI, and increased on day 30 PI in dogs infected with E. canis. On day 12, an increase in seric concentration of ATP, ADP and adenosine was verified, and different levels of hypoxanthine, xanthine and uric acid had a drastic reduction in infected compared healthy dogs (P< 0.05). However, on day 30 PI, the levels of seric ADP and AMP decreased, unlike the concentration of xanthine and uric acid that increased significantly in infected dogs (P< 0.05). Therefore, the activity of E-ADA and purine levels are altered in experimental canine ehrlichiosis, probably with the purpose of modulating the pathogenesis of the disease related to immune response, oxidative stress and coagulation disorders in acute phase. © 2013 Elsevier B.V.

Polimorfismos gênicos e danos no DNA em indivíduos com obesidade mórbida

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito da suplementação com licopeno no estresse oxidativo decorrente da prenhez

Pós-graduação em Fisiopatologia em Clínica Médica - FMB

Comparison of oxidative stress in ASA physical status I patients scheduled for minimally invasive surgery under balanced or intravenous anesthesia

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

Polimorfismos dos genes ADA e CNTNAP2 em indivíduos com Transtornos do Espectro do Autismo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Oxidative DNA damage in diabetic and mild gestational hyperglycemic pregnant women

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

Virginiamycin via mineral supplementation and sward height in growing Nelore young bulls

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