RESUMO
The recently discovered novel concept of self-terminating, oxidative radical cyclizations, through which alkynes can be converted into carbonyl compounds under very mild reaction conditions using O-centered inorganic and organic radicals as oxidants, is described.
Assuntos
Radicais Livres/química , Oxidantes/química , Alcinos/química , Ciclização , Radical Hidroxila/química , Modelos Químicos , Estrutura Molecular , Nitratos/química , Oxirredução , Espécies Reativas de Oxigênio/químicaAssuntos
Bacteriemia/diagnóstico , Portador Sadio , Leucocidinas/genética , Infecções Estafilocócicas/diagnóstico , Staphylococcus aureus/genética , Adolescente , Antibacterianos , Bacteriemia/tratamento farmacológico , Bacteriemia/genética , Toxinas Bacterianas , DNA Bacteriano , Quimioterapia Combinada/uso terapêutico , Exotoxinas , Seguimentos , Humanos , Masculino , Nasofaringe/metabolismo , Reação em Cadeia da Polimerase/métodos , Medição de Risco , Infecções Estafilocócicas/tratamento farmacológico , Infecções Estafilocócicas/genética , Staphylococcus aureus/classificação , Resultado do TratamentoRESUMO
Here, we describe an activity assay for sialyltransferases based on surface plasmon resonance (SPR). Different natural and synthetic oligosaccharides serving as acceptor substrates for the sialyltransferase ST3Gal-III (EC 2.4.99.6) were immobilized or synthesized on SPR chips. The chip was then exposed to different concentrations of a reaction mixture of ST3Gal-III and CMP-Neu5Ac either by injection or by external application of the reaction mixture to the chip surface. The binding of two lectins, one that specifically recognizes the unmodified acceptor, the other the sialylated oligosaccharide, was utilized to determine the extent of enzymatic turnover. In order to obtain enzymatic activities, the SPR data were correlated to data obtained from a classical radio assay. After regeneration, that is, cleavage of the sialic acid residues by using a sialidase, the chip is available for new experiments. The technique allows the rapid determination of sialyltransferase activity with only nanomolar quantities of acceptor substrates and should be of particular value in cases in which a large variety of samples, including cell lysates, have to be screened for their enzymatic activities.
Assuntos
Sialiltransferases/metabolismo , Ressonância de Plasmônio de Superfície/métodos , Estrutura Molecular , Polissacarídeos/metabolismo , Estreptavidina , Especificidade por SubstratoRESUMO
OBJECTIVE: To evaluate whether the mean gastric residual volume (GRV) and green gastric residuals (GR) themselves are significant predictors of feeding intolerance in the early enteral feeding advancement in extremely low birth weight (ELBW; <1000 g) infants. DESIGN: Ninety-nine ELBW infants were fed following a standardized protocol (day 3--14). At 48 hours of age, milk feeding was started (12 mL/kg/d increments, 12 meals per day). GR were checked before each feeding, and a GRV up to 2 mL/3 mL in infants less-than-or-equal750 g/>750 g was tolerated. In cases of increased GRV, feedings were reduced or withheld. The color of GR was assessed as clear, milky, green-clear, green-cloudy, blood-stained, or hemorrhagic. Multiple regression analysis was used to study the effect of the mean GRV and the color of GR on the feeding volume on day 14 (V14). RESULTS: The median V14 was 103 mL/kg/d (0--166). V14 increased with an increasing percentage of milky GR, whereas the mean GRV and the color green did not have a significant effect. CONCLUSIONS: 1) Early enteral feeding could be established in ELBW infants. The critical GRV seems to be above 2 mL/3 mL because there was no significant negative correlation between the mean GRV and V14. 2) Green GR were not negatively correlated with V14 and should not slow down the advancement of feeding volumes in absence of other clinical signs and symptoms.