5,484 research outputs found
Polyacrylamide Electrogeneration at High-Current Densities and Different Water Content in DMF/NaN03 Solutions
ABSTRACT Polyacrylamide was electrogenerated in dimethyl formamide at high current densities and different water content. The polymerization rate (Rp) was proportional to i 1.2 [H20]-04 over current densities between 40 and 140 mA 9 cm -2, and water content between 0.12 and 5.7M. Polymerization begins after an induction time for the current flow. The formation and growth of a polyaerylamide film on the electrode during the induction period was followed by microgravimetry and identified by FTIR specular reflectance spectroscopy. The oxidation of water through the polyacrylamide film is proposed as the origin of the water's order dependence and the diminution of the average viscosimetric molar mass when the water content rises. Those aspects are included in a partial model of the interracial reactions
A CerberusâInspired AntiâInfective Multicomponent Gatekeeper Hydrogel against Infections with the Emerging âSuperbugâ Yeast Candida auris
Infrared Excess in the Be Star Delta Scorpii
We present infrared photometric observations of the Be binary system delta
Scorpii obtained in 2006. The J,H and K magnitudes are the same within the
errors compared to observations taken 10 months earlier. We derive the infrared
excess from the observation and compare this to the color excess predicted by a
radiative equilibrium model of the primary star and its circumstellar disk. We
use a non-LTE computational code to model the gaseous envelope concentrated in
the star's equatorial plane and calculate the expected spectral energy
distribution and Halpha emission profile of the star with its circumstellar
disk. Using the observed infrared excess of delta Sco, as well as Halpha
spectroscopy bracketing the IR observations in time, we place constraints on
the radial density distribution in the circumstellar disk. Because the disk
exhibits variability in its density distribution, this work will be helpful in
understanding its dynamics.Comment: 12 pages, 14 figures, to be published in PASP May 200
Aspergillus ocratoxigĂȘnicos em uvas e no solo de cultivo da variedade Sauvignon Blanc no Nordeste brasileiro.
A ocratoxina A (OTA) Ă© um metabĂłlito secundĂĄrio de fungos freqĂŒentemente encontrado como contaminante de uvas, vinhos e suco de uva, sendo considerada uma das micotoxinas mais prejudiciais para a saĂșde humana. Este estudo teve como objetivo avaliar a incidĂȘncia de AspergillusocratoxigĂȘnicos em uvas e no solo de cultivo da variedade Sauvignon Blanc utilizada para produção de vinho no nordeste brasileiro. As amostras de uva e de solo foram coletadas em uma regiĂŁo vitivinĂcola do SubmĂ©dio SĂŁo Francisco (Casa Nova, Bahia). Para o isolamento de fungos das uvas e sementes utilizou-se a TĂ©cnica de Plaqueamento Direto em meio de cultura DRBC (Dicloran Rosa Bengal Cloranfenicol); para a amostra de solo foi utilizada a tĂ©cnica de espalhamento superficial, em DG 18 (Dichloran 18% Glycerol Agar), a partir de diluiçÔes seriadas. Selecionou-se para obtenção de culturas puras apenas os fungos do gĂȘnero Aspergillus que foram identificados por caracterĂsticas morfolĂłgicas e avaliados, quanto Ă produção de OTA, pelo MĂ©todo Plug Agar. Das uvas foram isoladas e identificadas as seguintes espĂ©cies A. foetidus, A. tubingensis e A. sp.. Destes isolados nenhum foi ocratoxigĂȘnico. Dos vinte e nove isolados obtidos do solo, quatro foram ocratoxigĂȘnicos (A. niger agregado (1), A. carbonarius agregado (2) e A. carbonarius (1)), o que realça a importĂąncia de evitar durante a colheita o contato das uvas com o solo, visto que este pode representar uma fonte de contaminação com esta micotoxina para as uvas e vinhos. Palavras-chaves: Fungos ocratoxigĂȘnicos, Uvas, Aspergillus, Ocratoxina A, Solo, Sauvignon Blan
Fungos ocratoxigĂȘnicos em solo de cultivo de uvas vinĂferas no Nordeste brasileiro.
Ocratoxina A (OTA) Ă© um metabĂłlito secundĂĄrio de origem fĂșngica que tem recebido atenção crescente devido ao potencial perigo para os seres humanos e animais. Este estudo teve como objetivo avaliar a incidĂȘncia de fungos ocratoxigĂȘnicos do gĂȘnero Aspergillus em solos de cultivo de uvas vinĂferas no nordeste brasileiro. Foram coletadas amostras de solo de cultivo de trĂȘs variedades de uvas vinĂferas, Cabernet Sauvignon, Grenache e Petit Verdot de uma regiĂŁo vitivinĂcola do nordeste brasileiro. Para o isolamento de fungos foi utilizada a tĂ©cnica de espalhamento superficial, em DG 18 (Dichloran 18% Glycerol Agar), a partir de diluiçÔes seriadas. Selecionou-se para obtenção de culturaspuras apenas os fungos do gĂȘnero Aspergillus que foram identificados por caracterĂsticas morfolĂłgicas e avaliados, quanto Ă produção de OTA, pelo MĂ©todo Plug Agar. Das amostras de solo foram isoladas e identificadas as seguintes espĂ©cies A. foetidus, A. aculeatus, A. niger, A. tubingensis, A. carbonariuse A. ibericus. Dos vinte e quatro isolados fĂșngicos obtidos quatro foram ocratoxigĂȘnicos (A. niger (1), A. tubingensis (1) e A. carbonarius (2)), o que evidĂȘncia a importĂąncia de evitar durante a colheita o contato das uvas com o solo, visto que este pode representar uma fonte de contaminação com esta micotoxina para as uvas e vinhos.Palavras-chaves: Fungos ocratoxigĂȘnicos, Uvas vinĂferas, Aspergillus, Ocratoxina A, Sol
6-Deoxyhexoses froml-Rhamnose in the Search for Inducers of the Rhamnose Operon: Synergy of Chemistry and Biotechnology
In the search for alternative nonâmetabolizable inducers in the l ârhamnose promoter system, the synthesis of fifteen 6âdeoxyhexoses from l ârhamnose demonstrates the value of synergy between biotechnology and chemistry. The readily available 2,3âacetonide of rhamnonolactone allows inversion of configuration at C4 and/or C5 of rhamnose to give 6âdeoxyâd âallose, 6âdeoxyâd âgulose and 6âdeoxyâl âtalose. Highly crystalline 3,5âbenzylidene rhamnonolactone gives easy access to l âquinovose (6âdeoxyâl âglucose), l âolivose and rhamnose analogue with C2 azido, amino and acetamido substituents. Electrophilic fluorination of rhamnal gives a mixture of 2âdeoxyâ2âfluoroâl ârhamnose and 2âdeoxyâ2âfluoroâl âquinovose. Biotechnology provides access to 6âdeoxyâl âaltrose and 1âdeoxyâl âfructose
Altered drug susceptibility during host adaptation of a <i>Plasmodium falciparum</i> strain in a non-human primate model
Infections with Plasmodium falciparum, the most pathogenic of the Plasmodium species affecting man, have been reduced in part due to artemisinin-based combination therapies. However, artemisinin resistant parasites have recently emerged in South-East Asia. Novel intervention strategies are therefore urgently needed to maintain the current momentum for control and elimination of this disease. In the present study we characterize the phenotypic and genetic properties of the multi drug resistant (MDR) P. falciparum Thai C2A parasite strain in the non-human Aotus primate model, and across multiple passages. Aotus infections with C2A failed to clear upon oral artesunate and mefloquine treatment alone or in combination, and ex vivo drug assays demonstrated reduction in drug susceptibility profiles in later Aotus passages. Further analysis revealed mutations in the pfcrt and pfdhfr loci and increased parasite multiplication rate (PMR) across passages, despite elevated pfmdr1 copy number. Altogether our experiments suggest alterations in parasite population structure and increased fitness during Aotus adaptation. We also present data of early treatment failures with an oral artemisinin combination therapy in a pre-artemisinin resistant P. falciparum Thai isolate in this animal model
Increased Activities against Biofilms of the Pathogenic Yeast Candida albicans of Optimized Pom-1 Derivatives
Antimicrobial peptides (AMPs) are an alternative group for the therapy of infectious diseases, with activity against a wide range of diverse pathogens. However, classical AMPs have significant side effects in human cells due to their unspecific pore formation in biomembranes. Nevertheless, AMPs are promising therapeutics and can be isolated from natural sources, which include sea and freshwater molluscs. The AMPs identified in these organisms show promising antimicrobial activities, as pathogens are mainly fought by innate defence mechanisms. An auspicious candidate among molluscs is the Cuban freshwater snail Pomacea poeyana, from which the peptides Pom-1 and Pom-2 have been isolated and studied. These studies revealed significant antimicrobial activities for both AMPs. Based on the activities determined, Pom-1 was used for further optimization. In order to meet the emerging requirements of improved anti-biofilm activity against naturally occurring Candida species, the six derivatives Pom-1A to F were developed and investigated. Analysis of the derivatives acting on the most abundant naturally occurring Candida yeast Candida albicans (C. albicans) revealed a strong anti-biofilm activity, especially induced by Pom-1 B, C, and D. Furthermore, a moderate decrease in the metabolic activity of planktonic yeast cells was observed
Combination of Six Individual Derivatives of the Pom-1 Antibiofilm Peptide Doubles Their Efficacy against Invasive and Multi-Resistant Clinical Isolates of the Pathogenic Yeast Candida albicans
In previous studies, derivatives of the peptide Pom-1, which was originally extracted from the freshwater mollusk Pomacea poeyana, showed an exceptional ability to specifically inhibit biofilm formation of the laboratory strain ATCC 90028 as a model strain of the pathogenic yeast Candida albicans. In follow-up, here, we demonstrate that the derivatives Pom-1A to Pom-1F are also active against biofilms of invasive clinical C. albicans isolates, including strains resistant against fluconazole and/or amphotericin B. However, efficacy varied strongly between the isolates, as indicated by large deviations in the experiments. This lack of robustness could be efficiently bypassed by using mixtures of all peptides. These mixed peptide preparations were active against biofilm formation of all the isolates with uniform efficacies, and the total peptide concentration could be halved compared to the original MIC of the individual peptides (2.5 ”g/mL). Moreover, mixing the individual peptides restored the antifungal effect of fluconazole against fluconazole-resistant isolates even at 50% of the standard therapeutic concentration. Without having elucidated the reason for these synergistic effects of the peptides yet, both the gain of efficacy and the considerable increase in efficiency by combining the peptides indicate that Pom-1 and its derivatives in suitable formulations may play an important role as new antibiofilm antimycotics in the fight against invasive clinical infections with (multi-) resistant C. albicans
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