Topological Line Defects around Graphene Nanopores for DNA Sequencing

Topological line defects in graphene represent an ideal way to produce highly controlled structures with reduced dimensionality that can be used in electronic devices. In this work we propose using extended line defects in graphene to improve nucleobase selectivity in nanopore-based DNA sequencing devices. We use a combination of QM/MM and non-equilibrium Green's functions methods to investigate the conductance modulation, fully accounting for solvent effects. By sampling over a large number of different orientations generated from molecular dynamics simulations, we theoretically demonstrate that distinguishing between the four nucleobases using line defects in a graphene-based electronic device appears possible. The changes in conductance are associated with transport across specific molecular states near the Fermi level and their coupling to the pore. Through the application of a specifically tuned gate voltage, such a device would be able to discriminate the four types of nucleobases more reliably than that of graphene sensors without topological line defects.Comment: 6 figures and 6 page

Antimicrobial activity and acute and chronic toxicity of the essential oil of Lippia origanoides

Currently, there is a growing interest in medicinal plants, because of an increased demand for alternate therapies. In this study, the antimicrobial activity and toxicity of the essential oil of Lippia origanoides (L. origanoides) were investigated. The essential oil of L. origanoides was extracted by steam-dragging distillation and its constituents were identified by chromatography coupled with mass spectrometry. Among the 15 compounds identified, the most abundant were carvacrol (29.00%), o-cymene (25.57%), and thymol methyl ether (11.50%). The essential oil was studied in antimicrobial assays to determine the MIC and MBC. The results indicated that a concentration of 120μL/mL of oil was sufficient to inhibit the growth of the following microorganisms: Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923) and Salmonella cholerasuis (ATCC 10708). Acute and chronic toxic effects of orally administered oil were investigated in Wistar rats by using standard methods. Doses of 30, 60 and 120mg/kg of the essential oil did not induce significant changes in weight, behavior or hematological and biochemical parameters in the animals. There were no signs of any histopathological changes to the liver, kidneys or heart of the treated rats, suggesting that Lippia origanoides oil is non-toxic after oral administration in acute or chronic toxicity studies. The results obtained in this study show that the essential oil of L. origanoides has a high safety margin, with no detectable toxic effects in rats treated with doses to 120mg/kg. In addition, L. origanoides oil demonstrated potent antimicrobial activity against S. aureus, E. coli and S. cholerasuis. Based on these findings, this essential oil may have practical application as a veterinary antimicrobial

Chemical diversity of the volatiles of Lippia rotundifolia Cham. (Verbenaceae) in Minas Gerais, Brazil

Lippia rotundifolia is an aromatic species, native and endemic to rocky fields, which are isolated by small mountains. It is little known about their chemical composition. Because of that we aimed to study the chemical diversity of volatiles released from rosemary leaves (Lippia rotundifolia Cham.) coming from 11 populations of the Minas Gerais, Brazil. The material for chemical analysis was obtained from the accessions in the active germplasm bank of the Instituto de Ciências agrárias of the Universidade Federal de Minas Gerais. A total of 67 compounds were detected by HS-CG-MS. Most volatiles were detected in the São Gonçalo do Rio das Pedras accession, with 40 compounds, whereas in the Santana do Riacho accession only 5 compounds were detected. Volatiles myrcene, linalool and caryophyllene were detected in the majority of the accessions. We concluded that Lippia rotundifolia presents high chemical variability. The volatiles mircene, linalool and caryophyllene are the most frequent, detected in most of the accessions. Due to some accession to present predominance of monoterpenes, others sesquiterpenes, studies of molecular analysis are necessary for associate the chemotypes, since environmental variation influence the gene expression of the secondary metabolites

Essential oil in the taxonomy of Ocimum selloi benth

Chemical composition analysis of the essential oil from the leaves and flowers of two accessions of Ocimum selloi Benth, cultivated at the Federal University of Viçosa was carried out. For accession A the major component was identified as estragole and represented 94,95% and 92,54% of the oil from the leaves and flowers respectively. For accession B, the oil from the leaves and flowers was constituted by 65,49% and 66,18% of methyleugenol, respectively. For both accessions several minor constituents were also identified. The phenotypic and chemical differences observed between these two accessions suggest the existence of two chemicaly distinct varieties for Ocimum selloi Benth

Determinação do coeficiente de cultura (Kc) e eficiência do uso de água do alecrim-pimenta irrigado

Objetivou-se com este estudo determinar os coeficientes de cultura (Kc), a eficiência do uso de água (EUA) do alecrim-pimenta contemplando a produção de biomassa e óleo essencial. O experimento foi conduzido em lisímetro de drenagem, no Instituto de Ciências Agrárias da Universidade Federal de Minas Gerais, em Montes Claros, MG. O delineamento experimental utilizado foi em blocos casualizados, cujos tratamentos correspondiam a sete lâminas de água (0,5; 0,75; 1,0; 1,2; 1,4; 1,65 e 1,9 ETo), e três repetições. A evapotranspiração potencial de referência utilizada no cálculo das lâminas de irrigação foi obtida pelo método de Penman-Monteith. Os tratamentos foram submetidos à análise de regressão. Os resultados indicam que o alecrim-pimenta apresenta resposta positiva ao aumento da lâmina d'água aplicada. O tratamento responsável pelo maior índice de eficiência do uso da água, foi o tratamento 6 (1,65 ETo), com 1,26 kg m-3 para a produção de matéria fresca em função da lâmina aplicada. A produtividade de óleo essencial foi de 59,12 kg ha-1 aos 120 dias após transplantio, para o tratamento 7 (1,9 ETo). Os coeficientes de cultura (Kc) médios determinados em todo o ciclo da cultura, variaram de 0,98 na fase inicial, 1,20 no desenvolvimento vegetativo e 1,52 no florescimento