RESUMO
The acidity characteristics of zeolite are highly significant, and understanding the acidic properties is essential for developing new types of zeolite catalysts. Zeolite membranes were synthesized using metakaolin, sodium hydroxide, and alumina with a molar ratio of 6Al2Si2O7:12NaOH:2Al2O3 as the starting ingredients. X-ray diffraction, scanning electron microscopy, and infrared spectroscopy were used for this study. N2 adsorption measurements determined the surface areas of the SOD zeolite membrane (115 m2/g) and the LTA membrane (150 m2/g). The units of absorbed water vapor were 40 and 60 wt% for the SOD membrane and the LTA membrane, respectively. The strength and number of acid sites of the synthesized LTA and SOD zeolite membranes were determined by temperature-programmed desorption of ammonia. As a result, the value of the total acidity of the LTA zeolite membrane is in the range of 0.08 × 1019 units/m2 while that of the sodalite membrane is an order of magnitude lower and is 0.006 × 1019 units/m2. The apparent activation energy values for desorption of ammonia from LTA and SOD zeolite membranes were calculated using data on the kinetics of desorption of ammonia at different heating rates. It was found that at temperatures below 250 °C, the degree of conversion of the activation energy values is no more than 35 kJ/mol, which corresponds to the desorption of physically bound ammonia. An increase in the activation values up to 70 kJ/mol (for SOD) and up to 80 kJ/mol (for LTA) is associated with the desorption of chemically bound ammonia from the samples.
RESUMO
We investigated the association between biomarkers of dermal exposure, naphthyl-keratin adducts (NKA), and urine naphthalene biomarker levels in 105 workers routinely exposed to jet-fuel. A moderate correlation was observed between NKA and urine naphthalene levels (p = 0.061). The NKA, post-exposure breath naphthalene, and male gender were associated with an increase, while CYP2E1*6 DD and GSTT1-plus (++/+-) genotypes were associated with a decrease in urine naphthalene level (p < 0.0001). The NKA show great promise as biomarkers for dermal exposure to naphthalene. Further studies are warranted to characterize the relationship between NKA, other exposure biomarkers, and/or biomarkers of biological effects due to naphthalene and/or PAH exposure.
Assuntos
Biomarcadores/análise , Hidrocarbonetos/análise , Queratinas/análise , Naftalenos/análise , Exposição Ocupacional/análise , Adolescente , Adulto , Poluentes Ocupacionais do Ar/análise , Poluentes Ocupacionais do Ar/intoxicação , Aeronaves , Biomarcadores/química , Citocromo P-450 CYP2E1/genética , Ensaio de Imunoadsorção Enzimática , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Genótipo , Glutationa Transferase/genética , Humanos , Hidrocarbonetos/intoxicação , Queratinas/química , Masculino , Militares , Naftalenos/química , Naftalenos/urina , Exposição Ocupacional/efeitos adversos , Hidrocarbonetos Policíclicos Aromáticos/intoxicação , Análise de Regressão , Pele/metabolismo , Teratogênicos/análise , Adulto JovemAssuntos
Surtos de Doenças , Raposas , Vírus da Raiva/isolamento & purificação , Raiva/veterinária , Animais , Bovinos , Análise por Conglomerados , Epidemiologia Molecular , Dados de Sequência Molecular , Mongólia , Proteínas do Nucleocapsídeo/genética , Filogenia , RNA Viral/genética , Raiva/epidemiologia , Vírus da Raiva/classificação , Vírus da Raiva/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Federação Russa , Análise de Sequência de DNA , Homologia de Sequência , Topografia MédicaRESUMO
Reaction of 10-cyanotetrahydrobenzo[b][1,6]naphthyridines (1-6) with activated alkynes affords stable benzo[b]pyrrolo[2,1-f][1,6]naphthyridine-4-ium ylides (7-14) in moderate yields. A proposed mechanism for their formation consists of a new tandem multistage process.
RESUMO
VceC is the outer membrane component of the major facilitator (MF) VceAB-VceC multiple-drug-resistant (MDR) efflux pump of Vibrio cholerae. TolC is the outer membrane component of the resistance-nodulation-division AcrAB-TolC efflux pump of Escherichia coli. Although these proteins share little amino acid sequence identity, their crystal structures can be readily superimposed upon one another. In this study, we have asked if TolC and VceC are interchangeable for the functioning of the AcrAB and VceAB pumps. We have found that TolC can replace VceC to form a functional VceAB-TolC MDR pump, but VceC cannot replace TolC to form a functional AcrAB-VceC pump. However, we have been able to isolate gain-of-function (gof) VceC mutants which can functionally interface with AcrAB. These mutations map to four different amino acids located at the periplasmic tip of VceC. Chemical cross-linkage experiments indicate that both wild-type and gof mutant VceC can physically interact with the AcrAB complex, suggesting that these gof mutations are not affecting the recruitment of VceC to the AcrAB complex but rather its ability to functionally interface with the AcrAB pump.
Assuntos
Proteínas da Membrana Bacteriana Externa/genética , Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Escherichia coli/genética , Lipoproteínas/metabolismo , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Antibacterianos/farmacologia , Resistência a Múltiplos Medicamentos , Escherichia coli/efeitos dos fármacos , Escherichia coli/metabolismo , Genótipo , Proteínas de Membrana Transportadoras , Testes de Sensibilidade Microbiana , Modelos Moleculares , Mutagênese Sítio-Dirigida , Mutação , Plasmídeos , Conformação ProteicaRESUMO
Herein, we identify vceC as a component of a vceCAB operon, which codes for the Vibrio cholerae VceAB multiple-drug resistance (MDR) efflux pump, and vceR, which codes for a transcriptional autoregulatory protein that negatively regulates the expression of the vceCAB operon and is modulated by some of the substrates of this MDR efflux pump.
Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Proteínas da Membrana Bacteriana Externa/genética , Genes Reguladores , Óperon , Vibrio cholerae/genética , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/biossíntese , Proteínas da Membrana Bacteriana Externa/biossíntese , Proteínas de Bactérias/genética , Sítios de Ligação , Farmacorresistência Bacteriana Múltipla/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Bombas de Íon/genética , Proteínas de Membrana/genética , Mutagênese Insercional , Fases de Leitura Aberta , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Two new rabies-related viruses were discovered in Russia during 2002. Viruses were isolated from bats in Eastern Siberia near Baikal Lake and in the western Caucasus Mountains. After preliminary antigenic and genetic characterization, we found that both viruses should be considered as new putative lyssavirus genotypes.