RESUMO
Low-dimensional electronic systems have traditionally been obtained by electrostatically confining electrons, either in heterostructures or in intrinsically nanoscale materials such as single molecules, nanowires and graphene. Recently, a new method has emerged with the recognition that symmetry-protected topological (SPT) phases, which occur in systems with an energy gap to quasiparticle excitations (such as insulators or superconductors), can host robust surface states that remain gapless as long as the relevant global symmetry remains unbroken. The nature of the charge carriers in SPT surface states is intimately tied to the symmetry of the bulk, resulting in one- and two-dimensional electronic systems with novel properties. For example, time reversal symmetry endows the massless charge carriers on the surface of a three-dimensional topological insulator with helicity, fixing the orientation of their spin relative to their momentum. Weakly breaking this symmetry generates a gap on the surface, resulting in charge carriers with finite effective mass and exotic spin textures. Analogous manipulations have yet to be demonstrated in two-dimensional topological insulators, where the primary example of a SPT phase is the quantum spin Hall state. Here we demonstrate experimentally that charge-neutral monolayer graphene has a quantum spin Hall state when it is subjected to a very large magnetic field angled with respect to the graphene plane. In contrast to time-reversal-symmetric systems, this state is protected by a symmetry of planar spin rotations that emerges as electron spins in a half-filled Landau level are polarized by the large magnetic field. The properties of the resulting helical edge states can be modulated by balancing the applied field against an intrinsic antiferromagnetic instability, which tends to spontaneously break the spin-rotation symmetry. In the resulting canted antiferromagnetic state, we observe transport signatures of gapped edge states, which constitute a new kind of one-dimensional electronic system with a tunable bandgap and an associated spin texture.
RESUMO
Twisted bilayer graphene (TBLG) is one of the simplest van der Waals heterostructures, yet it yields a complex electronic system with intricate interplay between moiré physics and interlayer hybridization effects. We report on electronic transport measurements of high mobility small angle TBLG devices showing clear evidence for insulating states at the superlattice band edges, with thermal activation gaps several times larger than theoretically predicted. Moreover, Shubnikov-de Haas oscillations and tight binding calculations reveal that the band structure consists of two intersecting Fermi contours whose crossing points are effectively unhybridized. We attribute this to exponentially suppressed interlayer hopping amplitudes for momentum transfers larger than the moiré wave vector.
RESUMO
Autoimmune blistering skin diseases, including pemphigus vulgaris, rarely involve the esophagus. We report a case of exfoliative esophagitis with pemphigus vulgaris. A sloughing esophageal cast observed by endoscopy was dissected esophageal squamous epithelium in all layers. Our case is the fifth case of pemphigus vulgaris associated with esophageal cast formation recorded in the medical literature. Prednisolone was administered, and both the pemphigus vulgaris and exfoliative esophagitis improved. Upon findings of exfoliative esophagitis by endoscopic examination, we should consider the coexistence of blistering skin diseases, including pemphigus vulgaris.
Assuntos
Esofagite/complicações , Pênfigo/complicações , Epitélio/patologia , Esofagite/patologia , Esôfago/patologia , Feminino , Humanos , Pessoa de Meia-Idade , Pênfigo/patologiaRESUMO
Serological immunoscreening was used to identify a gene encoding heat shock protein-70 from Babesia gibsoni (BgHSP-70) that showed high homology with HSP-70s from other apicomplexan parasites. This gene corresponded to a full-length cDNA containing an open reading frame of 1968 bp predicted to result in a 70-kDa mature protein consisting of 656 amino acids. Analysis of the expression levels of BgHSP-70 indicated elevated transcription from cultured parasites incubated at 40 degrees C for 1 h, but not at 30 degrees C. Interestingly, antiserum raised against recombinant BgHSP-70 protein reacted specifically not only with a 70-kDa protein of B. gibsoni but also with a corresponding native protein of B. microti (BmHSP-70), indicating the high degree of conservation of this protein. The BmHSP-70 gene was then isolated and characterized and the immunoprotective properties of recombinant BgHSP-70 (rBgHSP-70) and rBmHSP-70 were compared in vitro and in vivo. Both proteins had potent mitogenic effects on murine and canine mononuclear cells as evidenced by high proliferative responses and IFN-gamma production after stimulation. Immunization regimes in BALB/c and C57BL/6 mice using rBgHSP-70 and rBmHSP-70 elicited high antibody levels, with concurrent significant reductions in peripheral parasitaemias. Taken together, these results emphasize the potential of HSP-70s as a molecular adjuvant vaccine.
Assuntos
Babesia/genética , Babesia/imunologia , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico HSP70/imunologia , Proteínas de Protozoários/genética , Proteínas de Protozoários/imunologia , Animais , Anticorpos Antiprotozoários , Babesia microti/genética , Babesia microti/imunologia , Proliferação de Células , Células Cultivadas , DNA de Protozoário/genética , Cães , Perfilação da Expressão Gênica , Proteínas de Choque Térmico HSP70/química , Temperatura Alta , Interferon gama/metabolismo , Leucócitos Mononucleares/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Peso Molecular , Fases de Leitura Aberta , Parasitemia/prevenção & controle , Proteínas de Protozoários/química , Vacinas Protozoárias/imunologia , Vacinas Sintéticas/imunologiaRESUMO
Three cDNAs encoding rhoptry-associated protein 1 (RAP-1) homologues were found in the Babesia gibsoni EST database. Based on similarities to BgRAP-1a, which was identified previously by serological screening of a cDNA merozoite library, the two new genes were designated BgRAP-1b (33.7%) and BgRAP-1c (57%). Mice antiserum raised against each recombinant protein reacted specifically with B. gibsoni parasites as determined by Western blotting, which showed native molecular sizes of the BgRAP-1a (51 kDa), BgRAP-1b (53 kDa) and BgRAP-1c (47 kDa) consistent with predictable molecular weights. Immunofluoresence using these antibodies revealed localization of all BgRAP-1s within the matrix of merozoites; however, BgRAP-1a appeared to diverge from the other two when it was found secreted into the cytoplasm of infected erythrocytes. Apical localization of all 3 BgRAP-1s during the extracellular stage of the parasite combined with their ability to bind a canine erythrocyte membrane fraction was suggestive of a role for these proteins in erythrocyte attachment. Lastly, the ability of these recombinant proteins to be used as diagnostic reagents was tested by ELISA and the sensitivities of BgRAP-1a and BgRAP-1c were found increased through N-terminal truncation. Taken together, our data suggest divergent roles for the 3 BgRAP-1s in the merozoite stage of B. gibsoni.
Assuntos
Babesiose/veterinária , Doenças do Cão/diagnóstico , Proteínas de Protozoários , Animais , Babesia/classificação , Babesia/genética , Babesia/imunologia , Babesia/metabolismo , Babesiose/diagnóstico , Babesiose/parasitologia , Western Blotting , DNA de Protozoário/análise , Doenças do Cão/parasitologia , Cães , Ensaio de Imunoadsorção Enzimática , Imunofluorescência , Camundongos , Microscopia Confocal , Dados de Sequência Molecular , Proteínas de Protozoários/genética , Proteínas de Protozoários/imunologia , Proteínas de Protozoários/metabolismo , Análise de Sequência de DNARESUMO
Peptidases of parasitic protozoa are currently under intense investigation in order to identify novel virulence factors, drug targets, and vaccine candidates, except in Babesia. Leucine aminopeptidases in protozoa, such as Plasmodium and Leishmania, have been identified to be involved in free amino acid regulation. We report here the molecular and enzymatic characterization, as well as the localization of a leucine aminopeptidase, a member of the M17 cytosolic aminopeptidase family, from B. gibsoni (BgLAP). A functional recombinant BgLAP (rBgLAP) expressed in Escherichia coli efficiently hydrolysed synthetic substrates for aminopeptidase, a leucine substrate. Enzyme activity of the rBgLAP was found to be optimum at pH 8.0 and at 37 degrees C. The substrate profile was slightly different from its homologue in P. falciprum. The activity was also strongly dependent on metal divalent cations, and was inhibited by bestatin, which is a specific inhibitor for metalloprotease. These results indicated that BgLAP played an important role in free amino acid regulation.
Assuntos
Babesia/enzimologia , Leucil Aminopeptidase/metabolismo , Sequência de Aminoácidos , Animais , Anticorpos Antiprotozoários , Clonagem Molecular , Etiquetas de Sequências Expressas , Regulação da Expressão Gênica/fisiologia , Leucil Aminopeptidase/química , Camundongos , Camundongos Endogâmicos ICR , Dados de Sequência Molecular , Filogenia , Especificidade por SubstratoRESUMO
BACKGROUND: Outbreaks of vancomycin-resistant enterococcus (VRE) are a serious problem in hospitals. Inferring the transmission route is an important factor to institute appropriate infection control measures; however, the methodology has not been fully established. AIM: To reconstruct and evaluate the transmission model using sequence variants extracted from whole genome sequencing (WGS) data and epidemiological information from patients involved in a VRE outbreak. METHODS: During a VRE outbreak in our hospital, 23 samples were collected from patients and environmental surfaces and analysed using WGS. By combining genome alignment information with patient epidemiological data, the VRE transmission route was reconstructed using a Bayesian approach. With the transmission model, evaluation and further analyses were performed to identify risk factors that contributed to the outbreak. FINDINGS: All VREs were identified as Enterococcus faecium belonging to sequence type 17, which consisted of two VRE genotypes: vanA (N = 8, including one environmental sample) and vanB (N = 15). The reconstruction model using the Bayesian approach showed the transmission direction with posterior probability and revealed transmission through an environmental surface. In addition, some cases acting as VRE spreaders were identified, which can interfere with appropriate infection control. Vancomycin administration was identified as a significant risk factor for spreaders. CONCLUSION: A Bayesian approach for transmission route reconstruction using epidemiologic data and genomic variants from WGS can be applied in actual VRE outbreaks. This may contribute to the design and implementation of effective infection control measures.
Assuntos
Transmissão de Doença Infecciosa , Enterococcus faecium/isolamento & purificação , Infecções por Bactérias Gram-Positivas/epidemiologia , Infecções por Bactérias Gram-Positivas/transmissão , Epidemiologia Molecular , Enterococos Resistentes à Vancomicina/isolamento & purificação , Sequenciamento Completo do Genoma , Adulto , Idoso , Idoso de 80 Anos ou mais , Teorema de Bayes , Infecção Hospitalar/epidemiologia , Infecção Hospitalar/transmissão , Surtos de Doenças , Enterococcus faecium/classificação , Enterococcus faecium/genética , Feminino , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , Tipagem Molecular , Fatores de Risco , Enterococos Resistentes à Vancomicina/classificação , Enterococos Resistentes à Vancomicina/genéticaRESUMO
Two-dimensional (2D) materials offer a promising platform for exploring condensed matter phenomena and developing technological applications. However, the reduction of material dimensions to the atomic scale poses a challenge for traditional measurement and interfacing techniques that typically couple to macroscopic observables. We demonstrate a method for probing the properties of 2D materials via nanometer-scale nuclear quadrupole resonance (NQR) spectroscopy using individual atomlike impurities in diamond. Coherent manipulation of shallow nitrogen-vacancy (NV) color centers enables the probing of nanoscale ensembles down to approximately 30 nuclear spins in atomically thin hexagonal boron nitride (h-BN). The characterization of low-dimensional nanoscale materials could enable the development of new quantum hybrid systems, combining atomlike systems coherently coupled with individual atoms in 2D materials.
RESUMO
The outer membrane protein OpcP1 of Burkholderia (formerly Pseudomonas) cepacia is one of the subunits forming the porin oligomer OpcPO by non-covalent association. OpcP1 was cleaved with lysyl endopeptidase and the N-terminal amino acid (aa) sequences of the polypeptide fragments were determined. Based on the sequence information, we cloned the opcP gene on a 10-kb EcoRI DNA fragment of the B. cepacia ATCC25416 chromosome. Nucleotide (nt) sequencing revealed a 1086-bp open reading frame (ORF), encoding a 361-aa polypeptide with a signal sequence of 20 residues. The predicted opcP gene encoded a mature protein of Mr 35,696, which agrees well with the value observed previously on SDS-PAGE. The opcP was sub-cloned into pTrc99A and introduced into Escherichia coli. Immunoblot analysis using murine antiserum specific to OpcP1 visualized the protein expressed in the E. coli cells after induction by isopropyl beta-D-thiogalactopyranoside (IPTG).
Assuntos
Proteínas da Membrana Bacteriana Externa/biossíntese , Proteínas da Membrana Bacteriana Externa/genética , Burkholderia cepacia/genética , Escherichia coli/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Dados de Sequência Molecular , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/genética , Análise de Sequência de DNA , Homologia de Sequência de AminoácidosRESUMO
A putative mature human neutrophil chemotactic factor (NCF) corresponding to the C-terminal 72 amino acids of its precursor was directly produced in Escherichia coli by recombinant DNA technology. Human NCF was present in both the soluble and insoluble protein fractions of the homogenate of host cells, and it was partially purified as a water-soluble polypeptide from both fractions, separately. The partially purified NCF preparation was highly purified to an endotoxin-free homogeneous polypeptide by means of CM-Sepharose CL-6B column chromatography and gel filtration on Toyopearl HW-55. No difference between the human NCF preparations purified from both starting materials could be found concerning purity, primary structure, solubility, molecular weight, and chemotactic activity for human neutrophils. The amino acid sequence of recombinant human NCF was identical to the sequence deduced from the cDNA sequence. A methionine residue due to the translation initiation codon was removed. Recombinant human NCF was found to be biologically active and to exhibit chemotactic activity for human neutrophils in vitro and cause a neutrophil infiltration in vivo in mice.
Assuntos
Fatores Quimiotáticos/biossíntese , Proteínas Recombinantes/biossíntese , Sequência de Aminoácidos , Animais , Movimento Celular , Fatores Quimiotáticos/isolamento & purificação , Fatores Quimiotáticos/fisiologia , Quimiotaxia de Leucócito , Escherichia coli/metabolismo , Humanos , Interleucina-8 , Camundongos , Dados de Sequência Molecular , Neutrófilos/fisiologiaRESUMO
Overproduction of the Pseudomonas aeruginosa outer membrane protein OprM was observed in the nalidixix acid (NalB-type) multidrug-resistant strains. To clarify the involvement of OprM in the resistance, transposon mutants were isolated from strain PAO4141 and its OprM-overexpressed mutant KG2113 and were screened for OprM production by immunoblot assays using murine polyclonal antiserum resulting from immunization with purified OprM. Two OprM-deficient mutants from PAO4141 and one from KG2113 were identified. Determination of the susceptibilities of these mutants to antimicrobial agents demonstrated that OprM was involved not only in the acquired resistance, but also in the intrinsic resistance of P. aeruginosa to quinolones, cephems, penicillins, tetracycline, and chloramphenicol.
Assuntos
Proteínas da Membrana Bacteriana Externa/genética , Resistência a Múltiplos Medicamentos/genética , Ácido Nalidíxico/farmacologia , Pseudomonas aeruginosa/genética , Proteínas da Membrana Bacteriana Externa/imunologia , Proteínas da Membrana Bacteriana Externa/isolamento & purificação , Resistência Microbiana a Medicamentos , Testes de Sensibilidade Microbiana , Mutagênese InsercionalRESUMO
A method based upon the polymerase chain reaction (PCR) for detecting genes encoding the Fc receptors of Staphylococcus aureus and streptococci is described. Primers were designed from the nucleotide sequences of the five Fc receptor genes encoding protein A, protein G, protein H, FcRA and protein V. Amplification products corresponding in size to the protein A and protein G genes were detected in S. aureus strain Cowan 1 and Streptococcus pyogenes strain G148, respectively, as expected. Str. pyogenes strain AR1 was shown to possess the type H receptor gene. Two clinical isolates of Str. pyogenes, strains IP-28 and ES-21L, were shown to possess genes for Fc receptor types FcRA and protein G, respectively. The identification of all these products was confirmed by restriction endonuclease analysis. Amplification of protein H genes from two other clinical isolates of streptococci, MS-4 and MS-38, yielded a product larger than expected and with a different restriction fragment pattern to strain AR1, indicating a new type of Fc receptor gene. This PCR method provides a DNA-based method for the determination of Fc receptor type in S. aureus and streptococci.
Assuntos
Reação em Cadeia da Polimerase , Receptores Fc/genética , Staphylococcus aureus/genética , Streptococcus/genética , Proteínas de Bactérias/genética , Proteínas de Transporte/genética , Primers do DNA/química , DNA Bacteriano/análise , DNA Bacteriano/química , Eletroforese em Gel de Ágar , Proteínas de Membrana/genética , Receptores de IgG/genética , Mapeamento por Restrição , Proteína Estafilocócica A/genética , Staphylococcus aureus/metabolismo , Streptococcus/metabolismoRESUMO
van der Waals heterostructures constitute a new class of artificial materials formed by stacking atomically thin planar crystals. We demonstrated band structure engineering in a van der Waals heterostructure composed of a monolayer graphene flake coupled to a rotationally aligned hexagonal boron nitride substrate. The spatially varying interlayer atomic registry results in both a local breaking of the carbon sublattice symmetry and a long-range moiré superlattice potential in the graphene. In our samples, this interplay between short- and long-wavelength effects resulted in a band structure described by isolated superlattice minibands and an unexpectedly large band gap at charge neutrality. This picture is confirmed by our observation of fractional quantum Hall states at ± 5/3 filling and features associated with the Hofstadter butterfly at ultrahigh magnetic fields.
RESUMO
The 5' UTR is widely involved in gene expression via post-transcriptional regulation. However, a detailed profile of the 5' UTR for Toxoplasma gondii has not yet been demonstrated. To investigate the issue, we compared the predicted open reading frames (ORFs) and transcription start sites (TSSs) of T. gondii obtained by TSS-seq, a method that enables analysis of encyclopedic TSSs with next-generation sequencers. As a result, it was demonstrated that the mode length of the 5' UTR is between 120 and 140 nucleotides (nts) when a subset of genes with predicted signal peptides was examined. However, when genes without the signal peptide were examined, the length was extended to approximately 600 nts. Because additional information on the predicted signal peptide generates increased reliability to the 5' end estimation of each ORF, we believe that the former value was more reliable as a representative of the 5' UTR length of T. gondii. The discrepancy suggests that current predictions of the 5' end of the ORF were less accurate and considerably more discordant with the natural status. The 5' untranslated region (5' UTR) is defined as that between the 5' end of the transcripts and just in front of a start codon of an ORF. Therefore, the 5' UTR does not contain any information for a protein sequence; however, it is involved in the control of protein expression via the modulation of translational efficiency (Kozak, 1991b; Hughes, 2006).
Assuntos
Regiões 5' não Traduzidas/fisiologia , Toxoplasma/genética , Sítio de Iniciação de Transcrição/fisiologia , Etiquetas de Sequências Expressas , Modelos Genéticos , Fases de Leitura Aberta/fisiologia , Sinais Direcionadores de Proteínas/fisiologia , Proteínas de Protozoários/química , Proteínas de Protozoários/genéticaAssuntos
Técnicas de Genotipagem/métodos , Tipagem de Sequências Multilocus/métodos , Enterococos Resistentes à Vancomicina/classificação , Sequenciamento Completo do Genoma/métodos , Genes Bacterianos , Humanos , Reação em Cadeia da Polimerase , Análise de Sequência de DNA , Enterococos Resistentes à Vancomicina/genéticaAssuntos
Anti-Infecciosos/farmacologia , Genes Bacterianos , Resistência a Meticilina/genética , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/genética , 4-Quinolonas , Resistência Microbiana a Medicamentos/genética , Humanos , Testes de Sensibilidade Microbiana , PlasmídeosRESUMO
In this study we have attempted to quantify the thermal and photoperiodical responses of rice (Oryza sativa L.) flowering time QTLs jointly by a 'date-of-planting' field experiment of a mapping population, and a 'phenological model' analysis that separately parameterizes the two responses, based on daily temperature, daily photoperiod and flowering date. For this purpose, the 'three-stage Beta model', which parameterizes the sensitivity to temperature (parameter alpha), the sensitivity to photoperiod (parameter beta), and earliness under optimal conditions (10 h photoperiod at 30 degrees C) (parameter G), was applied to 'Nipponbare' x 'Kasalath' backcross inbred lines that were transplanted on five dates. QTLs for the beta value were detected in the four known flowering time QTL (Hd1, Hd2, Hd6 and Hd8) regions, while QTLs for the G value were detected only in the Hd1 and Hd2 regions. This result was consistent with previous reports on near-isogenic lines (NILs) of Hd1, Hd2 and Hd6, where these loci were involved in photoperiod sensitivity, and where Hd1 and Hd2 conferred altered flowering under both 10 and 14 h photoperiods, while Hd6 action was only affected by the 14 h photoperiod. Hd8 was shown to control photoperiod sensitivity for the first time. Interestingly, Hd1 and Hd2 were associated with a QTL for the alpha value, which might support the previous hypothesis that the process of photoinduction depends on temperature. These results demonstrate that our approach can effectively quantify environmental responses of flowering time QTLs without controlled environments or NILs.
Assuntos
Flores/crescimento & desenvolvimento , Oryza/fisiologia , Fotoperíodo , Temperatura , Modelos Biológicos , Oryza/genética , Fenótipo , Locos de Características QuantitativasRESUMO
DNA fragments of 8.5 kb containing the gyrA gene were cloned from Escherichia coli KL-16 and from four spontaneous gyrA mutants which showed various levels of resistance to quinolones. The gyrA gene was situated at about 4 kb in front of the nrdA gene and transcribed counterclockwise on the E. coli chromosome. It encoded a polypeptide of 875 amino acids with a molecular weight of about 97,000. The four gyrA mutations were located strikingly close to one another within a small region near the N-terminus of the gyrA polypeptide, i.e., nucleotide changes from C to T, from C to G, from G to T and from G to T at nucleotides 248, 248, 318 and 199, respectively, resulting in amino acid changes from Ser to Leu, from Ser to Trp, from Gln to His and from Ala to Ser at amino acids 83, 83, 106 and 67, respectively. These mutations were situated in the relatively hydrophilic regions of the GyrA polypeptide and close to Tyr at amino acid 122 which has been shown to be the site covalently bound to DNA.