RESUMO
The combination of enhanced resolving power and improved duty cycle on a multireflecting time-of-flight mass spectrometer is described. Resolving power increases are achieved by extending the effective ion path length from 47 m to greater than 200 m. Path length increases are achieved through containment of ions within the analyzer for up to N = 5 passes using a pulsed deflection electrode. Resolving power was shown to increase from 220,000 to 402,000 (fwhm) at m/z 785 for N = 1 and N = 4 analyzer passes, respectively. Due to the timing of the pulsed deflection electrode, the approach is particularly suited to high resolution analysis over a targeted m/z range. Duty cycle enhancements are achieved for ions of the targeted m/z range via accumulation prior to orthogonal acceleration, providing signal improvements of 2 orders of magnitude. Achieving such high resolving powers at fast scan rates (30 Hz) can yield additional information such as fine isotope structure; when combined with ppb mass measurement accuracy, high confidence in analyte identification can be achieved. The technique is applied for N = 2 analyzer passes, demonstrating fine isotope structure for a typical UHPLC metabolite identification experiment at a 10 Hz acquisition rate. Additionally, mass spectrometry imaging data is acquired using DESI, demonstrating the improved image clarity achieved at >300,000 (fwhm).
Assuntos
Criptococose/diagnóstico , Cryptococcus gattii/isolamento & purificação , Infecções Oculares Fúngicas/diagnóstico , Retinite/diagnóstico , Administração Oral , Adulto , Anfotericina B/uso terapêutico , Antifúngicos/uso terapêutico , Corioidite/diagnóstico , Corioidite/microbiologia , Criptococose/tratamento farmacológico , Criptococose/microbiologia , Quimioterapia Combinada , Oftalmopatias/diagnóstico , Oftalmopatias/microbiologia , Infecções Oculares Fúngicas/tratamento farmacológico , Infecções Oculares Fúngicas/microbiologia , Fluconazol/uso terapêutico , Flucitosina/uso terapêutico , Infecções por HIV/diagnóstico , Humanos , Infusões Intravenosas , Masculino , Meningite Criptocócica/diagnóstico , Meningite Criptocócica/tratamento farmacológico , Meningite Criptocócica/microbiologia , Retinite/tratamento farmacológico , Retinite/microbiologia , Tomografia de Coerência Óptica , Corpo Vítreo/microbiologia , Corpo Vítreo/patologiaRESUMO
A novel mass spectrometry system is described here comprising a quadrupole-multireflecting time-of-flight design. The new multireflecting time-of-flight analyzer has an effective path length of 48 m and employs planar, gridless ion mirrors providing fourth-order energy focusing resulting in resolving power over 200â¯000 fwhm and sub-ppm mass accuracy. We show how these attributes are maintained with relatively fast acquisition speeds, setting the system apart from other high resolution mass spectrometers. We have integrated this new system into both liquid chromatography-mass spectrometry and mass spectrometry imaging workflows to demonstrate how the instrument characteristics are of benefit to these applications.
RESUMO
Three siblings developed bilateral, visually significant posterior subcapsular cataracts in their teenage years and were implanted with the SA40N Array Multifocal IOL. A recall examination was performed on the siblings at 12, 10, and 9 years, respectively, after implantation.
Assuntos
Extração de Catarata , Implante de Lente Intraocular/métodos , Visão Ocular/fisiologia , Adolescente , Adulto , Feminino , Humanos , Refração Ocular/fisiologia , Irmãos , Acuidade Visual/fisiologia , Adulto JovemRESUMO
This study elucidates the factors underlying the enhancement in efflux of human fibroblast unesterified cholesterol and phospholipid (PL) by lipid-free apolipoprotein (apo) A-I that is induced by cholesterol enrichment of the cells. Doubling the unesterified cholesterol content of the plasma membrane by incubation for 24 h with low density lipoprotein and lipid/cholesterol dispersions increases the pools of PL and cholesterol available for removal by apoA-I from about 0.8-5%; the initial rates of mass release of cholesterol and PL are both increased about 6-fold. Expression of the ATP binding cassette transporter A1 (ABCA1) is critical for this increased efflux of lipids, and cholesterol loading of the fibroblasts over 24 h increases ABCA1 mRNA about 12-fold. The presence of more ABCA1 and cholesterol in the plasma membrane results in a 2-fold increase in the level of specific binding of apoA-I to the cells with no change in binding affinity. Characterization of the species released from either control or cholesterol-enriched cells indicates that the plasma membrane domains from which lipids are removed are cholesterol-enriched with respect to the average plasma membrane composition. Cholesterol enrichment of fibroblasts also affects PL synthesis, and this leads to enhanced release of phosphatidylcholine (PC) relative to sphingomyelin (SM); the ratios of PC to SM solubilized from control and cholesterol-enriched fibroblasts are approximately 2/1 and 5/1, respectively. Biosynthesis of PC is critical for this preferential release of PC and the enhanced cholesterol efflux because inhibition of PC synthesis by choline depletion reduces cholesterol efflux from cholesterol-enriched cells. Overall, it is clear that enrichment of fibroblasts with unesterified cholesterol enhances efflux of cholesterol and PL to apoA-I because of three effects, 1) increased PC biosynthesis, 2) increased PC transport via ABCA1, and 3) increased cholesterol in the plasma membrane.