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1.
J Chem Phys ; 151(12): 125102, 2019 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-31575191

RESUMO

We present an analytical model for the role of hydrogen bonding on the spin-orbit coupling of a model DNA molecule. Here, we analyze in detail the electric fields due to the polarization of the hydrogen bond on the DNA base pairs and derive, within a tight binding analytical band folding approach, an intrinsic Rashba coupling which should dictate the order of the spin active effects in the chiral-induced spin selectivity effect. The coupling found is ten times larger than the intrinsic coupling estimated previously and points out to the predominant role of hydrogen bonding in addition to chirality in the case of biological molecules. We expect similar dominant effects in oligopeptides, where the chiral structure is supported by hydrogen-bonding and bears on orbital carrying transport electrons.


Assuntos
DNA/química , Modelos Químicos , Transporte de Elétrons , Ligações de Hidrogênio , Oligopeptídeos/química
2.
Bioresour Technol ; 291: 121858, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31377515

RESUMO

The improved performances during anaerobic degradation of phenol to methane with Fe(OH)3 were usually inapparent, due to its lower solubility (unaccessible to dissimilatory iron reduction) and more positive reduction potential of Fe(III)/Fe(II) (unfavorable for enriching Fe(III)-reducing bacteria [IRBs]). In this study, citrate, the organic chelates, were used to solubilize Fe(III) with the aim of improving the phenol degradation and declining the reduction potential of Fe(III)/Fe(II). Results showed that, in the co-occurrence of citrate and Fe(OH)3, the degradation rates of phenol were about 1.3-fold rapider than that with sole Fe(OH)3. Analysis of cyclic voltammetry demonstrated that the reduction potential of Fe(III)/Fe(II) in the form of Fe(OH)3 (-0.41 to -0.28 V vs Ag/AgCl) declined to -0.61 to -0.41 V. As a result, the Fe(III)-reducing genera, such as Petrimonas and Shewanella, which held a great potential of proceeding syntrophic metabolism via direct interspecies electron transfer (DIET), were significantly enriched.


Assuntos
Quelantes/farmacologia , Compostos Férricos/metabolismo , Ferro/metabolismo , Metano/metabolismo , Fenol/metabolismo , Anaerobiose , Bacteroides/efeitos dos fármacos , Bacteroides/metabolismo , Transporte de Elétrons , Oxirredução , Fenóis/metabolismo , Shewanella/efeitos dos fármacos , Shewanella/metabolismo
3.
Phys Chem Chem Phys ; 21(32): 17971-17977, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31384846

RESUMO

The electron-hole injection from a family of spiropyran photoswitches into A/T-duplex DNA has been investigated at the molecular level for the first time. Multiscale computations coupled with automatized quantitative wavefunction analysis reveal a pronounced directionality and regioselectivity towards the template strand of the duplex DNA. Our findings suggest that this directional and regioselective photoinduced electron-hole transfer could thus be exploited to tailor the charge transport processes in DNA in specific applications.


Assuntos
Benzopiranos/química , DNA/química , Indóis/química , Substâncias Intercalantes/química , Nitrocompostos/química , Transporte de Elétrons , Luz , Modelos Moleculares , Conformação de Ácido Nucleico , Oxirredução , Processos Fotoquímicos , Prótons , Termodinâmica
4.
Bioresour Technol ; 291: 121881, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31394488

RESUMO

To understand the effect of inoculum concentration on direct interspecies electron transfer (DIET) for methanogenesis, batch-type anaerobic bioreactors with different inoculum concentrations were operated with and without supplemented granular activated carbon (GAC). With decrease in inoculum concentration, GAC-supplemented bioreactors showed faster methane production rates and reduced lag times. Geobacter species were specifically enriched on the GAC surfaces under lower inoculum concentration conditions. Together, the relative abundance of aceticlastic methanogens (competitors of Geobacter species for acetate) gradually decreased when the inoculum concentration increased. These results suggested that the specific enrichment of Geobacter species by outcompeting with aceticlastic methanogens through low inoculum concentrations on GAC surfaces accelerated methanogenesis by DIET via GAC in anaerobic bioreactors. Taken together, the results of this study suggested that inoculum concentration is an important factor in stimulating DIET for methane production.


Assuntos
Transporte de Elétrons , Metano/biossíntese , Microbiota , Reatores Biológicos , Euryarchaeota/metabolismo , Geobacter/metabolismo
5.
Bioresour Technol ; 291: 121877, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376672

RESUMO

Bioelectrochemical conversion of CO2 to CH4 is a promising way to increase the calorific value of biogas produced during anaerobic digestion. There are two groups of methanogens enriched in these systems, hydrogenotrophs and acetoclastic methanogens that can also directly accept electrons from an electrode or another microorganism. In this study, a microbial electrolysis cell (MEC) poised at -500 mV (vs. SHE) was operated for biogas upgrading. Methane content in the biogas increased from 71% to >90%, and 8.2% of the CO2 was converted to methane. Methanothrix, an acetoclastic methanogen that can participate in direct electron transfer (DET), and Azonexus, an acetate-oxidizing electrogen, were enriched on the cathode. Transcriptomics revealed that Methanothrix on the cathode were using the CO2 reduction pathway, while Methanothrix in the bulk sludge were using the acetate decarboxylation pathway for production of methane. These results show that stimulation of DET in MEC enhances biogas-upgrading processes.


Assuntos
Biocombustíveis , Methanosarcinaceae , Eletrodos , Eletrólise , Transporte de Elétrons , Elétrons , Metano/metabolismo , Esgotos
6.
Chem Commun (Camb) ; 55(72): 10776-10779, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31432809

RESUMO

Herein, we present a dual-site ratiometric fluorescent probe based on the ICT-PET-FRET mechanism for the detection of pH in the ER. The probe showed a highly sensitive response to pH in the range of 5.0-7.2, and could be applied for the quantitative measurement of the pH values in the ER during ER stress and dexamethanose-induced stimulation.


Assuntos
Retículo Endoplasmático/metabolismo , Transferência Ressonante de Energia de Fluorescência , Corantes Fluorescentes/química , Dexametasona/farmacologia , Transporte de Elétrons , Retículo Endoplasmático/efeitos dos fármacos , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Humanos , Concentração de Íons de Hidrogênio
7.
Bioresour Technol ; 292: 121926, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31409520

RESUMO

Anaerobic digestion is the most widely adopted biological waste treatment processes with renewable energy production. The effects of adding metal nanoparticles (NPs) on improving digestion performance are well noted. This paper reviewed the traditional view on the cytotoxicity of NPs to living organisms and the contemporary view of mechanisms for enhancement in anaerobic digestion performance in the presence of metal NPs. The complicated interactions acquire further studies for comprehending the physical and chemical interactions of metal NPs to the constituent compounds and to the living cells, and the involvement of mechanisms such as direct interspecies electron transfer for better design and control of the "NP strategy" for anaerobic digestion performance enhancement.


Assuntos
Nanopartículas Metálicas , Anaerobiose , Transporte de Elétrons
8.
Bioresour Technol ; 292: 121995, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31430670

RESUMO

Introducing oxygen-containing functional groups is a common and convenient method to increase the hydrophilicity of bioelectrodes. In this study, the effect of oxygen-containing functional groups on biofilm was systematically studied to understand how the electron transfer between electrochemically active bacteria (EAB) and bioelectrode was boosted. After electrolysis pretreatment in sulfuric and nitric acid mixture, the oxygen content of the carbon fiber brushes increased from 4.6% to 30.9%. Comparing with the control, the maximum power density increased by 27.7%, while the anode resistance decreased by 21.8%, because charge transfer resistance significantly reduced. The analysis results showed that the content of c-type cytochromes (c-Cyts) in the EAB biofilm was four times higher than that in the control, while the biomass just slightly increased and the bacteria community was similar with that of the control. These findings suggested that the fundamental reason for the enhanced extracellular electron transfer between EAB and electrode was the increased c-Cyts.


Assuntos
Fontes de Energia Bioelétrica , Biofilmes , Citocromos , Eletrodos , Transporte de Elétrons , Elétrons , Oxigênio
9.
Phys Chem Chem Phys ; 21(33): 18105-18118, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31396604

RESUMO

With the emergence of drug-resistant Plasmodium falciparum, the treatment of malaria has become a significant challenge; therefore, the development of antimalarial drugs acting on new targets is extremely urgent. In Plasmodium falciparum, type II nicotinamide adenine dinucleotide (NADH) dehydrogenase (NDH-2) is responsible for catalyzing the transfer of two electrons from NADH to flavin adenine dinucleotide (FAD), which in turn transfers the electrons to coenzyme Q (CoQ). As an entry enzyme for oxidative phosphorylation, NDH-2 has become one of the popular targets for the development of new antimalarial drugs. In this study, reliable motion trajectories of the NDH-2 complex with its co-factors (NADH and FAD) and inhibitor, RYL-552, were obtained by comparative molecular dynamics simulations. The influence of cofactor binding on the global motion of NDH-2 was explored through conformational clustering, principal component analysis and free energy landscape. The molecular interactions of NDH-2 before and after its binding with the inhibitor RYL-552 were analyzed, and the key residues and important hydrogen bonds were also determined. The results show that the association of RYL-552 results in the weakening of intramolecular hydrogen bonds and large allosterism of NDH-2. There was a significant positive correlation between the angular change of the key pocket residues in the NADH-FAD-pockets that represents the global functional motion and the change in distance between NADH-C4 and FAD-N5 that represents the electron transfer efficiency. Finally, the possible non-competitive inhibitory mechanism of RYL-552 was proposed. Specifically, the association of inhibitors with NDH-2 significantly affects the global motion mode of NDH-2, leading to widening of the distance between NADH and FAD through cooperative motion induction; this reduces the electron transfer efficiency of the mitochondrial respiratory chain. The simulation results provide useful theoretical guidance for subsequent antimalarial drug design based on the NDH-2 structure and the respiratory chain electron transfer mechanism.


Assuntos
Antimaláricos/química , Cetonas/química , NADH Desidrogenase/antagonistas & inibidores , Plasmodium falciparum/enzimologia , Proteínas de Protozoários/antagonistas & inibidores , Proteínas de Protozoários/química , Quinolinas/química , Transporte de Elétrons , Flavina-Adenina Dinucleotídeo/química , Ligações de Hidrogênio , Modelos Moleculares , Estrutura Molecular , NAD/química , NADH Desidrogenase/química , Oxirredução , Ligação Proteica , Relação Estrutura-Atividade , Termodinâmica
10.
Bioresour Technol ; 291: 121847, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31357044

RESUMO

Effects of magnetite on methane production and fate of antibiotic resistance genes (ARGs) during anaerobic digestion (AD) of swine manure were investigated. Results showed that methane production was increased by maximum 16.1%, and magnetite could enhance the acetoclastic methanogenesis not hydrogenotrophic methanogenesis reflected by the functional gene quantification and microbial community analysis. The propionate degradation rate was improved, and it was syntrophic oxidized into H+/e-/CO2 for direct interspecies electron transfer (DIET) and acetate, where DIET was further enhanced by magnetite and the acetate was transformed into methane through syntrophic acetate oxidation (SAO) pathway. Magnetite mainly influenced the ARGs at the interim period of AD, where ARGs especially ermF were significantly enriched. Magnetite did not influence the total ARGs abundance at the end, although the tetM was enriched and mefA was reduced finally. Statistical analysis indicated that magnetite influenced the ARGs fate mainly through the changes of microbial community.


Assuntos
Óxido Ferroso-Férrico/farmacologia , Esterco , Metano/biossíntese , Anaerobiose/efeitos dos fármacos , Animais , Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/genética , Transporte de Elétrons , Microbiota/efeitos dos fármacos , Oxirredução , Suínos
11.
BMC Bioinformatics ; 20(1): 377, 2019 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-31277574

RESUMO

BACKGROUND: Electron transport chain is a series of protein complexes embedded in the process of cellular respiration, which is an important process to transfer electrons and other macromolecules throughout the cell. It is also the major process to extract energy via redox reactions in the case of oxidation of sugars. Many studies have determined that the electron transport protein has been implicated in a variety of human diseases, i.e. diabetes, Parkinson, Alzheimer's disease and so on. Few bioinformatics studies have been conducted to identify the electron transport proteins with high accuracy, however, their performance results require a lot of improvements. Here, we present a novel deep neural network architecture to address this problem. RESULTS: Most of the previous studies could not use the original position specific scoring matrix (PSSM) profiles to feed into neural networks, leading to a lack of information and the neural networks consequently could not achieve the best results. In this paper, we present a novel approach by using deep gated recurrent units (GRU) on full PSSMs to resolve this problem. Our approach can precisely predict the electron transporters with the cross-validation and independent test accuracy of 93.5 and 92.3%, respectively. Our approach demonstrates superior performance to all of the state-of-the-art predictors on electron transport proteins. CONCLUSIONS: Through the proposed study, we provide ET-GRU, a web server for discriminating electron transport proteins in particular and other protein functions in general. Also, our achievement could promote the use of GRU in computational biology, especially in protein function prediction.


Assuntos
Complexo de Proteínas da Cadeia de Transporte de Elétrons/química , Redes Neurais (Computação) , Software , Transporte de Elétrons , Humanos , Matrizes de Pontuação de Posição Específica
12.
Phys Chem Chem Phys ; 21(28): 15805-15814, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31282513

RESUMO

Electron transfer is the most fundamental reaction in chemistry, yet its exact mechanistic details are often complex. Laccases are important electron-transfer enzymes of substantial utility in bleaching, bioremediation, catalytic synthesis, and enzymatic fuel cells. These multi-copper oxidases catalyze the one-electron oxidation of substrates by outer-sphere electron transfer to a copper T1 site, and subsequent intramolecular electron transfer to a tri-nuclear copper site where O2 is reduced to water. Understanding the molecular mechanism of the first, supposedly rate-determining pure electron transfer step is of major fundamental and technological interest. It is widely thought that the difference in the half potentials of the substrate and the T1 copper enables the powerful electron abstraction from nearby substrates. However, the reorganization energy during electron transfer could also contribute to catalytic turnover. To explore this, we computed the self-exchange reorganization energies of 54 substrates with experimentally known activity or kcat data using density functional theory. We show that the energy costs of changing the substrate geometries during electron removal correlate significantly with experimental activity data with a physically meaningful direction of correlation. This means that substrate electronic reorganization, rather than only potential differences, plays a role in the activity of electron transfer proteins such as laccases. This finding is consistent with the Marcus theory and suggests that the first electron transfer step from substrate to T1 is rate-determining in the real enzymes; the electronic reorganization energies can rationalize "good" vs. "bad" laccase substrates, which has not previously been possible.


Assuntos
Lacase/metabolismo , Modelos Moleculares , Transporte de Elétrons , Metabolismo Energético , Oxirredução
13.
Phys Chem Chem Phys ; 21(31): 17072-17081, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31313765

RESUMO

The repair of sun-induced DNA lesions by photolyases is driven by a photoinduced electron transfer from a fully reduced FAD to the damaged DNA. A chain of several aromatic residues connecting FAD to solvent ensures the prior photoreduction of the FAD cofactor. In PhrA, a class III CPD photolyase, two branching tryptophan charge transfer pathways have been characterized. According to previous experiments, both pathways play a role in the FAD photoreduction. To provide a molecular insight to the charge transfer abilities of both pathways, we perform multiscales simulations where the protein motion and the positive charge are simultaneously propagated. Our computational approach reveals that one pathway drives a very fast charge transfer whereas the other pathway provides a very good thermodynamic stabilization of the positive charge. During the simulations, the positive charge firstly moves on the fast triad, while a reorganization of the close FAD˙- environment occurs. Then, backward transfers can lead to the propagation of the positive charge on the second pathway. After one nanosecond, we observe a nearly equal probability to find the charge at ending tryptophan of either pathway; eventually the charge distribution will likely evolve towards a charge stabilization on the last tryptophan of the slowest pathway. Our results highlight the role the protein environment, which manages the association of a kinetic and a thermodynamic pathways to trigger a fast and efficient FAD photoreduction.


Assuntos
Reparo do DNA , Desoxirribodipirimidina Fotoliase/química , Modelos Moleculares , Transporte de Elétrons , Flavina-Adenina Dinucleotídeo/química , Cinética , Oxirredução , Processos Fotoquímicos , Conformação Proteica , Termodinâmica , Triptofano/química
14.
Bioresour Technol ; 289: 121762, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31311731

RESUMO

In this work, glucose addition (0.7 g l-1) almost doubled hydrogen yield of Chlorella pyrenoidosa (121.1 ml l-1 vs 65.5 ml l-1), with a positive correlation between hydrogen production and glucose consumption (-0.977, P < 0.01). When the electrons transport from water photolysis to algal hydrogenase was inhibited, the hydrogen productivity declined by 21.1%; whereas it dramatically decreased by 70.9% when the algal nicotinamide adeninedinucleotide dehydrogenase (NADH) was inhibited. Therefore, in the presence of glucose, the electrons for algae based hydrogen production would be mainly from glucose glycolysis rather than water photolysis. Further deuterated-glucose trial indicated that the glucose might serve as an electron donor for algal hydrogenases. Finally, a tentative electron transport route from glucose to algal hydrogenase was proposed, hoping to provide more scientific direction for further algae-based hydrogen production improvement.


Assuntos
Chlorella/metabolismo , Hidrogênio/metabolismo , Hidrogenase/metabolismo , Transporte de Elétrons , Elétrons , Glucose/metabolismo , Fotólise
15.
Ecotoxicol Environ Saf ; 182: 109413, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31284121

RESUMO

The effects of rhamnolipids (RLs) produced and further purified from Burkholderia thailandensis, on the unicellular microalgae Dunaliella tertiolecta were investigated, in terms of RLs ability to affect algal growth, photosynthetic apparatus structure and energy flux, round and through photosystems II and I. Specifically, 24-48 h RLs-treated algae (RLs at concentrations ranged from 5 to 50 mg L-1) showed significantly decreased levels of growth rate, while increased levels of Chl a and b were obtained only in 72-96 h RLs-treated algae. Similarly, although no changes were obtained in the Chl a/b ratio and almost all chlorophyll fluorescence parameters over time, yields of electron transport (ϕR0, ϕE0) and respective performance index (PItotal) were negatively affected at 72 and 96 h. Based on those findings, it seems that the inhibitory effect of RLs on the algae growth rate after 24 and 48 h and the gradual attenuation of the phenomenon (after 72 h of exposure), may indicate the initial response of the organism, as well as algae ability to overcome, since RLs showed no effects on algae photosynthetic ability. Those findings reveal for the first time that RLs from Burkholderia thailandensis are not harmful for Dunaliella tertiolecta. However, further studies with the use of more aquatic species could be essential for assessing the RLs-mediated effects on aquatic biota.


Assuntos
Burkholderia/fisiologia , Clorófitas/fisiologia , Glicolipídeos/toxicidade , Clorofíceas , Clorófitas/efeitos dos fármacos , Transporte de Elétrons , Fotossíntese , Complexo de Proteína do Fotossistema II
16.
Chemosphere ; 233: 905-912, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31340418

RESUMO

We investigated the interconnected roles of reactive oxygen species (ROS) generated upon seed exposure to glyphosate and/or gibberellic acid (GA3), and the possible interaction between the herbicide and the plant hormone during germination of sorghum seeds. GA3 decreased antioxidant enzyme activity in embryos, and the over accumulation of hydrogen peroxide (H2O2) in 1000 mM GA3-treated seeds resulted in the lowest germinability among treatments. The deleterious effects of glyphosate on germination rate, in contrast, were not related to H2O2 accumulation, but to its interference with the mitochondrial electron transport chain. However, interactions among glyphosate, GA3 and H2O2 during seed germination were observed. Similar to paclobutrazol, glyphosate appears to interfere with the de novo synthesis of gibberellin, which modulates seed germination through oxidative metabolism. Seeds experiencing increased oxidative status due to GA3 (100 mM) or H2O2 (50 mM) applications had the effects of glyphosate on germination rate reversed. Since decreased ATP synthesis is a secondary effect of glyphosate, increased H2O2 concentrations in embryos must facilitate germination by decreasing the energy required by ATP-demanding metabolism. Our results showed that glyphosate affect seed germination of sorghum, and that the herbicide interacts with oxidative and gibberellin metabolisms.


Assuntos
Germinação/efeitos dos fármacos , Giberelinas/metabolismo , Glicina/análogos & derivados , Herbicidas/farmacologia , Peróxido de Hidrogênio/metabolismo , Reguladores de Crescimento de Planta/metabolismo , Sorghum/metabolismo , Antioxidantes/metabolismo , Grão Comestível/metabolismo , Transporte de Elétrons/efeitos dos fármacos , Glicina/farmacologia , Sementes/efeitos dos fármacos
17.
Biochemistry (Mosc) ; 84(5): 520-528, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31234766

RESUMO

In our recent X-ray study, we demonstrated that substitution of the natural leucine residue M196 with histidine in the reaction center (RC) from Rhodobacter (Rba.) sphaeroides leads to formation of a close contact between the genetically introduced histidine and the primary electron donor P (bacteriochlorophylls (BChls) PA and PB dimer) creating a novel pigment-protein interaction that is not observed in native RCs. In the present work, the possible nature of this novel interaction and its effects on the electronic properties of P and the photochemical charge separation in isolated mutant RCs L(M196)H are investigated at room temperature using steady-state absorption spectroscopy, light-induced difference FTIR spectroscopy, and femtosecond transient absorption spectroscopy. The results are compared with the data obtained for the RCs from Rba. sphaeroides pseudo-wild type strain. It is shown that the L(M196)H mutation results in a decrease in intensity and broadening of the long-wavelength Qy absorption band of P at ~865 nm. Due to the mutation, there is also weakening of the electronic coupling between BChls in the radical cation P+ and increase in the positive charge localization on the PA molecule. Despite the significant perturbations of the electronic structure of P, the mutant RCs retain high electron transfer rates and quantum yield of the P+QA- state (QA is the primary quinone acceptor), which is close to the one observed in the native RCs. Comparison of our results with the literature data suggests that the imidazole group of histidine M196 forms a π-hydrogen bond with the π-electron system of the PB molecule in the P dimer. It is likely that the specific (T-shaped) spatial organization of the π-hydrogen interaction and its potential heterogeneity in relation to the bonding energy is, at least partially, the reason that this type of interaction between the protein and the pigment and quinone cofactors is not realized in the native RCs.


Assuntos
Proteínas de Bactérias/metabolismo , Histidina/metabolismo , Leucina/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Rhodobacter sphaeroides/metabolismo , Proteínas de Bactérias/genética , Cristalografia por Raios X , Transporte de Elétrons , Histidina/genética , Cinética , Leucina/genética , Mutagênese Sítio-Dirigida , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Estrutura Terciária de Proteína , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/isolamento & purificação , Espectroscopia de Infravermelho com Transformada de Fourier
18.
Phys Chem Chem Phys ; 21(25): 13453-13461, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31187821

RESUMO

Radical pair formation and decay are implicated in a wide range of biological processes including avian magnetoreception. However, studying such biological radical pairs is complicated by both the complexity and relative fragility of natural systems. To resolve open questions about how natural flavin-amino acid radical pair systems are engineered, and to create new systems with novel properties, we developed a stable and highly adaptable de novo artificial protein system. These protein maquettes are designed with intentional simplicity and transparency to tolerate aggressive manipulations that are impractical or impossible in natural proteins. Here we characterize the ultrafast dynamics of a series of maquettes with differing electron-transfer distance between a covalently ligated flavin and a tryptophan in an environment free of other potential radical centers. We resolve the spectral signatures of the cysteine-ligated flavin singlet and triplet states and reveal the picosecond formation and recombination of singlet-born radical pairs. Magnetic field-sensitive triplet-born radical pair formation and recombination occurs at longer timescales. These results suggest that both triplet- and singlet-born radical pairs could be exploited as biological magnetic sensors.


Assuntos
Flavinas/química , Proteínas/química , Triptofano/química , Cisteína/química , Transporte de Elétrons , Radicais Livres/química , Cinética , Campos Magnéticos , Modelos Moleculares , Oxirredução
19.
Chem Commun (Camb) ; 55(53): 7695-7698, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31204743

RESUMO

We investigated the effects of a crowded environment on guanine oxidation in pyrene-modified oligonucleotides by photoinduced electron transfer. We observed drastic promotion of guanine oxidation in Ψ (psi; polymer- and salt-induced)-type DNA.


Assuntos
DNA/química , Guanina/química , Transporte de Elétrons , Oxirredução
20.
Chemosphere ; 232: 396-402, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31158634

RESUMO

Extracellular electron transfer from the biofilm surface to the electrode is the key step for the microbial fuel cell (MFC). More recently, graphene has attracted tremendous attentions for bioelectrochemical applications due to its good biocompatibility, high electrical conductivity and large surface area. In the current work, we report a facile and green synthesis of graphene-modified carbon paper (CP) as an efficient MFC anode through plant-mediated bioreduction coupled with self-assembly. Three-dimensional CFP uniformly wrapped by curled and wrinkled biosynthesized graphene enables more surface area for microbe adhesion and mass diffusion. Significantly, nontoxic and biodegradable biomolecules extracted from Eucalyptus leaves act as reducing agent and adsorb on the graphene, rendering the graphene surface become hydrophilic and biocompatible. Furthermore, the obtained graphene exhibit excellent bioelectrochemical interactions with the microbes. Equipped with the biosynthesized graphene-modified anode, the E. coli-catalyzed MFC delivered an enhanced maximum power density of 1158 mW/m2, 70% higher than a pristine graphene-modified one. This development provides not only a versatile and scalable synthesis strategy for biocompatible graphene-modified devices, but also indicates that biomolecules facilitate the extracellular electron transfer in bioelectrochemical process.


Assuntos
Fontes de Energia Bioelétrica , Biofilmes/crescimento & desenvolvimento , Escherichia coli/crescimento & desenvolvimento , Grafite/química , Adsorção , Condutividade Elétrica , Eletrodos , Transporte de Elétrons , Elétrons , Eucalyptus/química , Química Verde , Folhas de Planta/química , Propriedades de Superfície
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