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1.
Hemoglobin ; 46(3): 184-186, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35543019

RESUMO

Hb Dhonburi (also known as Hb Neapolis) (HBB: c.380T>G) is an unstable hemoglobin (Hb) variant that cannot be detected by high performance liquid chromatography (HPLC) or capillary electrophoresis (CE) in routine laboratory diagnosis. This could lead to prenatal misdiagnosis unless a molecular analysis is applied. Here, we report a Thai couple with a positive result for the dichlorophenolindophenol precipitation (DCIP) screening test. After routine laboratory investigation, the female was diagnosed with heterozygous Hb E (HBB: c.79G>A) during pregnancy; however, the male, whose case we present herein, was suspected to carry a rare heterozygous ß-thalassemia (ß-thal). Therefore, they were designated as a couple at-risk for having a fetus with a serious thalassemia genotype: compound heterozygosity for Hb E with ß-thal (Hb E/ß-thal). Based on the result of the DCIP test, his DNA was sequenced for a causative mutation and revealed heterozygosity for a rare Hb variant, Hb Dhonburi. Theoretically, this couple was not at risk for Hb E/ß-thal. Furthermore, this case demonstrates for the first time that in addition to a common Hb variant, i.e. Hb E, Hb Dhonburi (Hb Neapolis) also gives positive DCIP results, even in the heterozygous state.


Assuntos
Hemoglobinas Anormais , Talassemia beta , 2,6-Dicloroindofenol , Feminino , Hemoglobinas Anormais/genética , Heterozigoto , Humanos , Masculino , Mutação , Gravidez , Talassemia beta/diagnóstico , Talassemia beta/genética
2.
J Biol Inorg Chem ; 26(1): 1-11, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33146770

RESUMO

The interaction of Tb3+ and La3+ cations with different photosystem II (PSII) membranes (intact PSII, Ca-depleted PSII (PSII[-Ca]) and Mn-depleted PSII (PSII[-Mn]) membranes) was studied. Although both lanthanide cations (Ln3+) interact only with Ca2+-binding site of oxygen-evolving complex (OEC) in PSII and PSII(-Ca) membranes, we found that in PSII(-Mn) membranes both Ln3+ ions tightly bind to another site localized on the oxidizing side of PSII. Binding of Ln3+ cations to this site is not protected by Ca2+ and is accompanied by very effective inhibition of Mn2+ oxidation at the high-affinity (HA) Mn-binding site ([Mn2+ + H2O2] couple was used as a donor of electrons). The values of the constant for inhibition of electron transport Ki are equal to 2.10 ± 0.03 µM for Tb3+ and 8.3 ± 0.4 µM for La3+, whereas OEC inhibition constant in the native PSII membranes is 323 ± 7 µM for Tb3+. The value of Ki for Tb3+ corresponds to Ki for Mn2+ cations in the reaction of diphenylcarbazide oxidation via HA site (1.5 µM) presented in the literature. Our results suggest that Ln3+ cations bind to the HA Mn-binding site in PSII(-Mn) membranes like Mn2+ or Fe2+ cations. Taking into account the fact that Mn2+ and Fe2+ cations bind to the HA site as trivalent cations after light-induced oxidation and the fact that Mn cation bound to the HA site (Mn4) is also in trivalent state, we can suggest that valency may be important for the interaction of Ln3+ with the HA site.


Assuntos
Lantânio/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Térbio/metabolismo , 2,6-Dicloroindofenol/química , Sítios de Ligação , Cálcio/metabolismo , Transporte de Elétrons/efeitos dos fármacos , Transporte de Elétrons/efeitos da radiação , Cinética , Luz , Manganês/metabolismo , Oxirredução/efeitos dos fármacos , Oxigênio/metabolismo , Complexo de Proteína do Fotossistema II/química , Proteínas de Plantas/metabolismo , Ligação Proteica , Spinacia oleracea/enzimologia , Tilacoides/química
3.
J Biol Inorg Chem ; 25(2): 199-212, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32060650

RESUMO

Methanol dehydrogenases (MDH) have recently taken the spotlight with the discovery that a large portion of these enzymes in nature utilize lanthanides in their active sites. The kinetic parameters of these enzymes are determined with a spectrophotometric assay first described by Anthony and Zatman 55 years ago. This artificial assay uses alkylated phenazines, such as phenazine ethosulfate (PES) or phenazine methosulfate (PMS), as primary electron acceptors (EAs) and the electron transfer is further coupled to a dye. However, many groups have reported problems concerning the bleaching of the assay mixture in the absence of MDH and the reproducibility of those assays. Hence, the comparison of kinetic data among MDH enzymes of different species is often cumbersome. Using mass spectrometry, UV-Vis and electron paramagnetic resonance (EPR) spectroscopy, we show that the side reactions of the assay mixture are mainly due to the degradation of assay components. Light-induced demethylation (yielding formaldehyde and phenazine in the case of PMS) or oxidation of PES or PMS as well as a reaction with assay components (ammonia, cyanide) can occur. We suggest here a protocol to avoid these side reactions. Further, we describe a modified synthesis protocol for obtaining the alternative electron acceptor, Wurster's blue (WB), which serves both as EA and dye. The investigation of two lanthanide-dependent methanol dehydrogenases from Methylorubrum extorquens AM1 and Methylacidiphilum fumariolicum SolV with WB, along with handling recommendations, is presented. Lanthanide-dependent methanol dehydrogenases. Understanding the chemistry of artificial electron acceptors and redox dyes can yield more reproducible results.


Assuntos
2,6-Dicloroindofenol/química , Oxirredutases do Álcool/química , Elétrons , Metilfenazônio Metossulfato/química , Fenazinas/química , Tetrametilfenilenodiamina/química , 2,6-Dicloroindofenol/metabolismo , Oxirredutases do Álcool/metabolismo , Methylobacterium extorquens/enzimologia , Metilfenazônio Metossulfato/metabolismo , Estrutura Molecular , Fenazinas/metabolismo , Tetrametilfenilenodiamina/metabolismo , Verrucomicrobia/enzimologia
4.
Biochemistry (Mosc) ; 85(8): 908-919, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33045951

RESUMO

Elevation of intracellular Zn2+ following ischemia contributes to cell death by affecting mitochondrial function. Zn2+ is a differential regulator of the mitochondrial enzyme lipoamide dehydrogenase (LADH) at physiological concentrations (Ka = 0.1 µM free zinc), inhibiting lipoamide and accelerating NADH dehydrogenase activities. These differential effects have been attributed to coordination of Zn2+ by LADH active-site cysteines. A detailed kinetic mechanism has now been developed for the diaphorase (NADH-dehydrogenase) reaction catalyzed by pig heart LADH using 2,6-dichlorophenol-indophenol (DCPIP) as a model quinone electron acceptor. Anaerobic stopped-flow experiments show that two-electron reduced LADH is 15-25-fold less active towards DCPIP reduction than four-electron reduced enzyme, or Zn2+-modified reduced LADH (the corresponding values of the rate constants are (6.5 ± 1.5) × 103 M-1·s-1, (9 ± 2) × 104 M-1·s-1, and (1.6 ± 0.5) × 105 M-1·s-1, respectively). Steady-state kinetic studies with different diaphorase substrates show that Zn2+ accelerates reaction rates exclusively for two-electron acceptors (duroquinone, DCPIP), but not for one-electron acceptors (benzoquinone, ubiquinone, ferricyanide). This implies that the two-electron reduced form of LADH, prevalent at low NADH levels, is a poor two-electron donor compared to the four-electron reduced or Zn2+-modified reduced LADH forms. These data suggest that zinc binding to the active-site thiols switches the enzyme from one- to two-electron donor mode. This zinc-activated switch has the potential to alter the ratio of superoxide and H2O2 generated by the LADH oxidase activity.


Assuntos
Di-Hidrolipoamida Desidrogenase/metabolismo , Elétrons , Miocárdio/metabolismo , NADH Desidrogenase/metabolismo , Zinco/metabolismo , 2,6-Dicloroindofenol/metabolismo , Animais , Domínio Catalítico , Escherichia coli/enzimologia , Peróxido de Hidrogênio/metabolismo , Cinética , Oxirredução , Superóxidos/metabolismo , Suínos , Tiorredoxina Dissulfeto Redutase/metabolismo
5.
J Biol Chem ; 293(15): 5431-5446, 2018 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-29487133

RESUMO

Heme cytotoxicity is minimized by a two-step catabolic reaction that generates biliverdin (BV) and bilirubin (BR) tetrapyrroles. The second step is regulated by two non-redundant biliverdin reductases (IXα (BLVRA) and IXß (BLVRB)), which retain isomeric specificity and NAD(P)H-dependent redox coupling linked to BR's antioxidant function. Defective BLVRB enzymatic activity with antioxidant mishandling has been implicated in metabolic consequences of hematopoietic lineage fate and enhanced platelet counts in humans. We now outline an integrated platform of in silico and crystallographic studies for the identification of an initial class of compounds inhibiting BLVRB with potencies in the nanomolar range. We found that the most potent BLVRB inhibitors contain a tricyclic hydrocarbon core structure similar to the isoalloxazine ring of flavin mononucleotide and that both xanthene- and acridine-based compounds inhibit BLVRB's flavin and dichlorophenolindophenol (DCPIP) reductase functions. Crystallographic studies of ternary complexes with BLVRB-NADP+-xanthene-based compounds confirmed inhibitor binding adjacent to the cofactor nicotinamide and interactions with the Ser-111 side chain. This residue previously has been identified as critical for maintaining the enzymatic active site and cellular reductase functions in hematopoietic cells. Both acridine- and xanthene-based compounds caused selective and concentration-dependent loss of redox coupling in BLVRB-overexpressing promyelocytic HL-60 cells. These results provide promising chemical scaffolds for the development of enhanced BLVRB inhibitors and identify chemical probes to better dissect the role of biliverdins, alternative substrates, and BLVRB function in physiologically relevant cellular contexts.


Assuntos
Inibidores Enzimáticos , Oxirredutases atuantes sobre Doadores de Grupo CH-CH , 2,6-Dicloroindofenol/química , 2,6-Dicloroindofenol/farmacologia , Coenzimas/química , Coenzimas/metabolismo , Simulação por Computador , Cristalografia por Raios X , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Células HL-60 , Humanos , Niacinamida/química , Niacinamida/metabolismo , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/antagonistas & inibidores , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo
6.
Photosynth Res ; 137(3): 421-429, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29767343

RESUMO

The peculiarities of interaction of cyanobacterial photosystem I with redox mediators 2,6-dichlorophenolindophenol (DCPIP) and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) were investigated. The higher donor efficiency of the reduced DCPIP form was demonstrated. The oxidized form of DCPIP was shown to be an efficient electron acceptor for terminal iron-sulfur cluster of photosystem I. Likewise methyl viologen, after one-electron reduction, DCPIP transfers an electron to the molecular oxygen. These results were discussed in terms of influence of these interactions on photosystem I reactions with the molecular oxygen and natural electron acceptors.


Assuntos
2,6-Dicloroindofenol/metabolismo , Complexo de Proteína do Fotossistema I/fisiologia , Tetrametilfenilenodiamina/metabolismo , Transporte de Elétrons , Luz , Oxirredução , Oxigênio/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Synechocystis/metabolismo
7.
Q Rev Biophys ; 48(4): 437-44, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26537403

RESUMO

Using high-resolution mass spectrometry, we have studied the synthesis of isoquinoline in a charged electrospray droplet and the complexation between cytochrome c and maltose in a fused droplet to investigate the feasibility of droplets to drive reactions (both covalent and noncovalent interactions) at a faster rate than that observed in conventional bulk solution. In both the cases we found marked acceleration of reaction, by a factor of a million or more in the former and a factor of a thousand or more in the latter. We believe that carrying out reactions in microdroplets (about 1-15 µm in diameter corresponding to 0·5 pl - 2 nl) is a general method for increasing reaction rates. The mechanism is not presently established but droplet evaporation and droplet confinement of reagents appear to be two important factors among others. In the case of fused water droplets, evaporation has been shown to be almost negligible during the flight time from where droplet fusion occurs and the droplets enter the heated capillary inlet of the mass spectrometer. This suggests that (1) evaporation is not responsible for the acceleration process in aqueous droplet fusion and (2) the droplet-air interface may play a significant role in accelerating the reaction. We argue that this 'microdroplet chemistry' could be a remarkable alternative to accelerate slow and difficult reactions, and in conjunction with mass spectrometry, it may provide a new arena to study chemical and biochemical reactions in a confined environment.


Assuntos
Espectrometria de Massas/métodos , 2,6-Dicloroindofenol/química , Aceleração , Aerossóis , Animais , Ácido Ascórbico/química , Fenômenos Biofísicos , Citocromos c/química , Cavalos , Substâncias Macromoleculares , Maltose/química , Miocárdio/metabolismo , Soluções , Solventes/química , Espectrometria de Massas por Ionização por Electrospray , Água/química
8.
Prikl Biokhim Mikrobiol ; 53(2): 244-50, 2017.
Artigo em Russo | MEDLINE | ID: mdl-29509379

RESUMO

The maximal rates and effective constants of 2,6-dichlorphenolindophenol and oxygen reduction by bacterim Gluconobacter oxydans in bacterial fuel cells under different conditions were evaluated. In an open-circuit mode, the rate of 2,6-dichlorphenolindophenol reduction coupled with ethanol oxidation under oxygen and nirogen atmospheres were 1.0 and 1.1 µM s­1 g­1, respectively. In closed-circuit mode, these values were 0.4 and 0.44 µM s­1 g­1, respectively. The initial rate of mediator reduction with the use of membrane fractions of bacteria in oxygen and nitrogen atmospheres in open-circuit mode were 6.3 and 6.9 µM s­1 g­1, whereas these values in closed-circuit mode comprised 2.2 and 2.4 µM s­1 g­1, respectively. The oxygen reduction rates in the presence and absence of 2,6-dichlorphenolindophenol were 0.31 and 0.32 µM s­1 g­1, respectively. The data obtained in this work demonstrated independent electron transfer from bacterial redox centers to the mediator and the absence of competition between the redox mediator and oxygen. The results can make it possible to reduce costs of microbial fuel cells based on activity of acetic acid bacteria G. oxydans.


Assuntos
2,6-Dicloroindofenol/química , Fontes de Energia Bioelétrica , Etanol/metabolismo , Gluconobacter oxydans/metabolismo , Oxigênio/química , Transporte de Elétrons , Glucose/metabolismo , Cinética , Nitrogênio/química , Oxirredução
9.
Drug Metab Dispos ; 44(7): 967-74, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26856346

RESUMO

The NADPH dehydrogenase quinone oxido-reductase 1 (NQO1) enzyme is an antioxidant and metabolic enzyme that performs two electron reduction of quinones and other chemicals. Based on the physiologic role(s) of NQO1, we hypothesized that expression and activity of this enzyme would vary with age and other demographic variables. Cytosols from 117 archived human livers were investigated for changes in NQO1 with age, sex, obesity, and ethnicity. Protein expression but not activity of NQO1 was weakly negatively correlated with age (Spearman r = -0.2, P = 0.03). No sex differences were observed for either protein expression or activity and for ethnicity; Caucasians had greater NQO1 activity than Asians (P < 0.05). Overweight children had statistically significantly higher NQO1 activity as compared with ideal weight children (P < 0.05) although this difference was not observed in adults. These findings establish that NQO1 is approximately as active in children as adults. However, modeled NQO1 clearance (both allometric and physiologically based pharmacokinetics) predicted maturation at 23 to 26 years. This is almost certainly an overestimate, with error in the model resulting from a small sample size and inability to scale for age-related changes in hepatic cellularity and/or cytosolic protein content, and indicates a delay in reaching maximum clearance through the NQO1 pathway that is affected by physiologic development as much, or more than, biochemical development. Obesity may increase hepatic NQO1 activity in children, which is likely a protective mechanism in oxidative stress, but may also have significant implications for drug and chemical disposition in obese children.


Assuntos
2,6-Dicloroindofenol/farmacocinética , Envelhecimento/metabolismo , Fígado/enzimologia , NAD(P)H Desidrogenase (Quinona)/metabolismo , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Envelhecimento/etnologia , Povo Asiático , Criança , Pré-Escolar , Citosol/enzimologia , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Modelos Biológicos , Obesidade Infantil/enzimologia , Fatores Sexuais , Especificidade por Substrato , População Branca , Adulto Jovem
10.
Langmuir ; 32(31): 7796-805, 2016 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-27400072

RESUMO

The development of artificial photosynthesis has focused on the efficient coupling of reaction at photoanode and cathode, wherein the production of hydrogen (or energy carriers) is coupled to the electrons derived from water-splitting reactions. The natural photosystem II (PSII) complex splits water efficiently using light energy. The PSII complex is a large pigment-protein complex (20 nm in diameter) containing a manganese cluster. A new photoanodic device was constructed incorporating stable PSII purified from a cyanobacterium Thermosynechococcus vulcanus through immobilization within 20 or 50 nm nanopores contained in porous glass plates (PGPs). PSII in the nanopores retained its native structure and high photoinduced water splitting activity. The photocatalytic rate (turnover frequency) of PSII in PGP was enhanced 11-fold compared to that in solution, yielding a rate of 50-300 mol e(-)/(mol PSII·s) with 2,6-dichloroindophenol (DCIP) as an electron acceptor. The PGP system realized high local concentrations of PSII and DCIP to enhance the collisional reactions in nanotubes with low disturbance of light penetration. The system allows direct visualization/determination of the reaction inside the nanotubes, which contributes to optimize the local reaction condition. The PSII/PGP device will substantively contribute to the construction of artificial photosynthesis using water as the ultimate electron source.


Assuntos
2,6-Dicloroindofenol/química , Proteínas de Bactérias/química , Cianobactérias/enzimologia , Vidro/química , Nanoporos , Oxigênio/química , Complexo de Proteína do Fotossistema II/química , Porosidade
11.
Appl Microbiol Biotechnol ; 100(2): 697-706, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26452496

RESUMO

The discovery of novel fungal lignocellulolytic enzymes is essential to improve the breakdown of plant biomass for the production of second-generation biofuels or biobased materials in green biorefineries. We previously reported that Ustilago maydis grown on maize secreted a diverse set of lignocellulose-acting enzymes including hemicellulases and putative oxidoreductases. One of the most abundant proteins of the secretome was a putative glucose-methanol-choline (GMC) oxidoreductase. The phylogenetic prediction of its function was hampered by the few characterized members within its clade. Therefore, we cloned the gene and produced the recombinant protein to high yield in Pichia pastoris. Functional screening using a library of substrates revealed that this enzyme was able to oxidize several aromatic alcohols. Of the tested aryl-alcohols, the highest oxidation rate was obtained with 4-anisyl alcohol. Oxygen, 1,4-benzoquinone, and 2,6-dichloroindophenol can serve as electron acceptors. This GMC oxidoreductase displays the characteristics of an aryl-alcohol oxidase (E.C.1.1.3.7), which is suggested to act on the lignin fraction in biomass.


Assuntos
Oxirredutases do Álcool/genética , Oxirredutases do Álcool/metabolismo , Lignina/metabolismo , Ustilago/enzimologia , 2,6-Dicloroindofenol/metabolismo , Benzoquinonas/metabolismo , Biomassa , Transporte de Elétrons , Oxigênio/metabolismo , Filogenia , Pichia/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Ustilago/metabolismo
12.
J Environ Sci (China) ; 43: 26-39, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27155406

RESUMO

Highly active mesoporous TiO2 of about 6nm crystal size and 280.7m(2)/g specific surface areas has been successfully synthesized via controlled hydrolysis of titanium butoxide at acidic medium. It was characterized by means of XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), FT-IR (Fourier transform infrared spectroscopy), TGA (thermogravimetric analysis), DSC (differential scanning calorimetry) and BET (Brunauer-Emmett-Teller) surface area. The degradation of dichlorophenol-indophenol (DCPIP) under ultraviolet (UV) light was studied to evaluate the photocatalytic activity of samples. The effects of different parameters and kinetics were investigated. Accordingly, a complete degradation of DCPIP dye was achieved by applying the optimal operational conditions of 1g/L of catalyst, 10mg/L of DCPIP, pH of 3 and the temperature at 25±3°C after 3min under UV irradiation. Meanwhile, the Langmuir-Hinshelwood kinetic model described the variations in pure photocatalytic branch in consistent with a first order power law model. The results proved that the prepared TiO2 nanoparticle has a photocatalytic activity significantly better than Degussa P-25.


Assuntos
2,6-Dicloroindofenol/química , Nanopartículas/química , Processos Fotoquímicos , Titânio/química , Cinética , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Modelos Químicos , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
13.
J Nanosci Nanotechnol ; 15(9): 6550-8, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26716211

RESUMO

Stable mixed dispersion of TiO2 and SiO2 was developed and hybrid TiO2/SiO2 layers were fabricated by the direct inkjet patterning technique. The prepared layers were tested for photoinduced hydrophilicity and their photocatalytic activity was tested using stearic acid and dichloroindophenol as model compounds. The antimicrobial activity of prepared layers was tested and evaluated by the traditional plate counting method according to ISO 27447:2009, using Escherichia coli CCM 3988. Material printing proved to be well suited for the deposition of this complex nanoparticulate ink and samples with variable thickness were conveniently fabricated. Printed layers are able to change their surface properties from hydrophobic to superhydrophilic and also decompose the model contaminants rapidly.


Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Dióxido de Silício/química , Dióxido de Silício/farmacologia , Titânio/química , Titânio/farmacologia , 2,6-Dicloroindofenol , Escherichia coli/efeitos dos fármacos , Interações Hidrofóbicas e Hidrofílicas , Nanotecnologia , Oxirredução , Fotoquímica , Impressão , Ácidos Esteáricos
14.
J Enzyme Inhib Med Chem ; 30(5): 796-9, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25672529

RESUMO

Ellman's method is a standard protocol for the determination of cholinesterases activity. Though the method is ready for laboratory purposes, it has some drawbacks as well. In the current article, 2,6-dichloroindophenol acetate is performed as a chromogenic substrate suitable for acetylcholinesterase (AChE) activity examination. Michaelis constant and maximal velocity for 2,6-dichloroindophenol acetate were determined (38.0 µM and 244 pkat) and compared to the values for acetythiocholine (K(m) 0.18 mM; V(max) 5.1 nkat). Docking for 2,6-dichloroindophenol acetate and human AChE was done as well. In conclusion, 2,6-dichloroindophenol acetate seems to be suitable chromogenic substrate for AChE and spectrophotometry and based on this it can be easily performed whenever AChE activity should be tested.


Assuntos
2,6-Dicloroindofenol/farmacologia , Acetatos/farmacologia , Acetilcolinesterase/metabolismo , Inibidores da Colinesterase/farmacologia , 2,6-Dicloroindofenol/síntese química , 2,6-Dicloroindofenol/química , Acetatos/síntese química , Acetatos/química , Inibidores da Colinesterase/síntese química , Inibidores da Colinesterase/química , Relação Dose-Resposta a Droga , Humanos , Estrutura Molecular , Relação Estrutura-Atividade
15.
Plant Cell Physiol ; 55(7): 1266-75, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24853102

RESUMO

PSII generates strong oxidants used for water oxidation. The secondary electron donor, Y(Z), is Tyr161 on PSII reaction center D1 protein and mediates electron transfer from the oxygen-evolving Mn(4)CaO(5) cluster to the primary electron donor, P680. The latest PSII crystal structure revealed the presence of a hydrogen bond network around Y(Z), which is anticipated to play important roles in the electron and proton transfer reactions. Y(Z) forms a hydrogen bond with His190 which in turn forms a hydrogen bond with Asn298 on D1 protein. Although functional roles of Y(Z) and His190 have already been characterized, little is known about the functional role of Asn298. Here we have generated 19 mutants from a green alga Chlamydomonas reinhardtii, in which the Asn298 has been substituted by each of the other 19 amino acid residues. All mutants showed significantly impaired or no photosynthetic growth. Seven mutants capable of photosynthetic growth showed oxygen-evolving activity although at a significantly reduced rate. Interestingly the oxygen-evolving activity of these mutants was markedly photosensitive. The 19 mutants accumulated PSII at variable levels and showed a light-induced electron transfer reaction from 1,5-diphenylcarbazide (DPC) to 2,6-dichlorophenolindophenol (DCIP), suggesting that Asn298 is important for the function and photoprotection of the Mn(4)CaO(5) cluster.


Assuntos
Asparagina/metabolismo , Chlamydomonas reinhardtii/genética , Oxigênio/metabolismo , Fotossíntese , Complexo de Proteína do Fotossistema II/metabolismo , 2,6-Dicloroindofenol/metabolismo , Substituição de Aminoácidos , Chlamydomonas reinhardtii/metabolismo , Chlamydomonas reinhardtii/efeitos da radiação , Clorofila/metabolismo , Difenilcarbazida/metabolismo , Transporte de Elétrons , Cinética , Luz , Manganês/metabolismo , Mutagênese Sítio-Dirigida , Mutação , Oxirredução , Complexo de Proteína do Fotossistema II/química , Complexo de Proteína do Fotossistema II/genética
16.
Anal Chem ; 86(18): 9315-21, 2014 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-25160559

RESUMO

Double-barrel wire-in-a-capillary electrospray emitters prepared from theta-glass capillaries were used to mix solutions during the electrospray process. The relative flow rate of each barrel was continuously monitored with internal standards. The complexation reaction of 18-crown-6 and K(+), introduced from opposite barrels, reaches equilibrium during the electrospray process, suggesting that complete mixing also occurs. A simplified diffusion model suggests that mixing occurs in less than a millisecond, and contributions of turbulence, estimated from times of coalescing ballistic microdroplets, suggest that complete mixing occurs within a few microseconds. This mixing time is 2 orders of magnitude less than in any mixer previously coupled to a mass spectrometer. The reduction of 2,6-dichloroindophenol by l-ascorbic acid was performed using the theta-glass emitters and monitored using mass spectrometry. On the basis of the rate constant of this reaction in bulk solution, an apparent reaction time of 274 ± 60 µs was obtained. This reaction time is an upper limit to the droplet lifetime because the surface area to volume ratio and the concentration of reagents increase as the droplet evaporates and some product formation occurs in the Taylor cone prior to droplet formation. On the basis of increases in reaction rates measured by others in droplets compared to rates in bulk solution, the true droplet lifetime is likely 1-3 orders of magnitude less than the upper limit, i.e., between 27 µs and 270 ns. The rapid mixing and short droplet lifetime achieved in these experiments should enable the monitoring of many different fast reactions using mass spectrometry.


Assuntos
Vidro/química , Espectrometria de Massas por Ionização por Electrospray/métodos , 2,6-Dicloroindofenol/análise , 2,6-Dicloroindofenol/química , Ácido Ascórbico/análise , Ácido Ascórbico/química , Éteres de Coroa/química , Encefalinas/análise , Oxirredução , Potássio/química , Espectrometria de Massas por Ionização por Electrospray/instrumentação
17.
Langmuir ; 30(29): 8990-4, 2014 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-25029217

RESUMO

Photosystem I (PSI) is a photoactive electron-transport protein found in plants that participates in the process of photosynthesis. Because of PSI's abundance in nature and its efficiency with charge transfer and separation, there is a great interest in applying the protein in photoactive electrodes. Here, we developed a completely organic, transparent, conductive electrode using reduced graphene oxide (RGO) on which a multilayer of PSI could be deposited. The resulting photoactive electrode demonstrated current densities comparable to that of a gold electrode modified with a multilayer film of PSI and significantly higher than that of a graphene electrode modified with a monolayer film of PSI. The relatively large photocurrents produced by integrating PSI with RGO and using an opaque, organic mediator can be applied to the facile production of more economic solar energy conversion devices.


Assuntos
2,6-Dicloroindofenol/química , Grafite/química , Complexo de Proteína do Fotossistema I/química , Eletrodos , Transporte de Elétrons , Ferricianetos/química , Ferrocianetos/química , Oxirredução , Óxidos , Compostos de Rutênio/química , Energia Solar
18.
J Allergy Clin Immunol ; 132(3): 696-703.e10, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23683465

RESUMO

BACKGROUND: Phl p 4 is a major pollen allergen but exhibits lower allergenicity than other major allergens. The natural protein is glycosylated and shows cross-reactivity with related and structurally unrelated allergens. OBJECTIVE: We sought to determine the high-resolution crystal structure of Phl p 4 and to evaluate the immunologic properties of the recombinant allergen in comparison with natural Phl p 4. METHODS: Different isoallergens of Phl p 4 were expressed, and the nonglycosylated mutant was crystallized. The specific role of protein and carbohydrate epitopes for allergenicity was studied by using IgE inhibition and basophil release assays. RESULTS: The 3-dimensional structure was determined by using x-ray crystallography at a resolution of 1.9 Å. The allergen is a glucose dehydrogenase with a bicovalently attached flavin adenine dinucleotide. Glycosylated and nonglycosylated recombinant Phl p 4 showed identical inhibition of IgE binding, but compared with natural Phl p 4, all recombinant isoforms displayed a reduced IgE-binding inhibition. However, the recombinant protein exhibited an approximately 10-fold higher potency in basophil release assays than the natural protein. CONCLUSION: The crystal structure reveals the compact globular nature of the protein, and the observed binding pocket implies the size of the natural substrate. Plant-derived cross-reactive carbohydrate determinants (CCDs) appear to reduce the allergenicity of the natural allergen, whereas the Pichia pastoris-derived glycosylation does not. Our results imply yet undescribed mechanism of how CCDs dampen the immune response, leading to a novel understanding of the role of CCDs.


Assuntos
Alérgenos/química , Alérgenos/imunologia , Phleum/imunologia , Proteínas de Plantas/química , Proteínas de Plantas/imunologia , Pólen/imunologia , 2,6-Dicloroindofenol/metabolismo , Alérgenos/metabolismo , Sequência de Aminoácidos , Basófilos/imunologia , Glucose 1-Desidrogenase/química , Glucose 1-Desidrogenase/imunologia , Glucose 1-Desidrogenase/metabolismo , Imunoglobulina E/sangue , Dados de Sequência Molecular , Proteínas de Plantas/metabolismo , Pólen/química , Conformação Proteica , Proteínas Recombinantes/imunologia
19.
Prikl Biokhim Mikrobiol ; 50(6): 570-7, 2014.
Artigo em Russo | MEDLINE | ID: mdl-25726665

RESUMO

Acetic acid bacteria Gluconobacter oxydans subsp. industrius RKM V-1280 were immobilized into a synthetic matrix based on polyvinyl alcohol modified with N-vinylpyrrolidone and used as biocatalysts for the development ofbioanodes for microbial fuel cells. The immobilization method did not significantly affect bacterial substrate specificity. Bioanodes based on immobilized bacteria functioned stably for 7 days. The maximum voltage (fuel cell signal) was reached when 100-130 µM of an electron transport mediator, 2,6-dichlorophenolindophenol, was added into the anode compartment. The fuel cell signals reached a maximum at a glucose concentration higher than 6 mM. The power output of the laboratory model of a fuel cell based on the developed bioanode reached 7 mW/m2 with the use of fermentation industry wastes as fuel.


Assuntos
2,6-Dicloroindofenol/química , Fontes de Energia Bioelétrica , Gluconobacter oxydans/química , Glucose/metabolismo , Polímeros/química , 2,6-Dicloroindofenol/metabolismo , Biocatálise , Células Imobilizadas , Eletrodos , Transporte de Elétrons , Fermentação , Gluconobacter oxydans/metabolismo , Glucose/química , Resíduos Industriais , Oxirredução , Álcool de Polivinil/química , Pirrolidinonas/química
20.
Diagn Microbiol Infect Dis ; 108(2): 116139, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-37984109

RESUMO

The Viracor CMV-T-cell immunity Panel (TCIP) measures %CMV-specific CD4+ and CD8+ T-cells. In this blinded clinical study, we evaluated the performance of the TCIP in predicting CMV events. Prospectively enrolled donor or recipient CMV-seropositive kidney transplant recipients (KTR) were evaluated with monthly TCIP testing until either discontinuation of valganciclovir prophylaxis or CMV DNAemia prompting treatment initiation. Also, prospectively enrolled KTR with low-level untreated DNAemia or after completion of treatment were evaluated for progression or relapse of CMV infection. Among 46 KTR, those with CMV events had significantly lower %CMV-specific CD8+ T-cells (p = 0.024), and the CMV protection ROC AUC was significant (AUC 0.78, p = 0.026). The positive predictive values of CD4+ and CD8+ T-cell positivity >0.2 % for CMV protection were: 96.3 % for CMV DNAemia prompting treatment initiation, 92.6 % for any DNAemia, 100 % for DNAemia >1000 IU/mL. The TCIP could be a useful adjunct tool in individualized management of CMV infection.


Assuntos
2,6-Dicloroindofenol/análogos & derivados , Infecções por Citomegalovirus , Citomegalovirus , Humanos , Citomegalovirus/genética , Linfócitos T CD8-Positivos , Estudos Prospectivos , Infecções por Citomegalovirus/diagnóstico , Infecções por Citomegalovirus/prevenção & controle , Infecções por Citomegalovirus/tratamento farmacológico , DNA Viral , Antivirais/uso terapêutico , Transplantados
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