RESUMEN
We present the experimental end-station TRIXS dedicated to time-resolved soft x-ray resonant inelastic x-ray scattering (RIXS) experiments on solid samples at the free-electron laser FLASH. Using monochromatized ultrashort femtosecond XUV/soft x-ray photon pulses in combination with a synchronized optical laser in a pump-probe scheme, the TRIXS setup allows measuring sub-picosecond time-resolved high-resolution RIXS spectra in the energy range from 35 eV to 210 eV, thus spanning the M-edge (M1 and M2,3) absorption resonances of 3d transition metals and N4,5-edges of rare earth elements. A Kirkpatrick-Baez refocusing mirror system at the first branch of the plane grating monochromator beamline (PG1) provides a focus of (6 × 6) µm2 (FWHM) at the sample. The RIXS spectrometer reaches an energy resolution of 35-160 meV over the entire spectral range. The optical laser system based on a chirped pulse optical parametric amplifier provides approximately 100 fs (FWHM) long photon pulses at the fundamental wavelength of 800 nm and a fluence of 120 mJ/cm2 at a sample for optical pump-XUV probe measurements. Furthermore, optical frequency conversion enables experiments at 400 nm or 267 nm with a fluence of 80 and 30 mJ/cm2, respectively. Some of the first (pump-probe) RIXS spectra measured with this setup are shown. The measured time resolution for time-resolved RIXS measurements has been characterized as 287 fs (FWHM) for the used energy resolution.
RESUMEN
The entatic state denotes a distorted coordination geometry of a complex from its typical arrangement that generates an improvement to its function. The entatic-state principle has been observed to apply to copper electron-transfer proteins and it results in a lowering of the reorganization energy of the electron-transfer process. It is thus crucial for a multitude of biochemical processes, but its importance to photoactive complexes is unexplored. Here we study a copper complex-with a specifically designed constraining ligand geometry-that exhibits metal-to-ligand charge-transfer state lifetimes that are very short. The guanidine-quinoline ligand used here acts on the bis(chelated) copper(I) centre, allowing only small structural changes after photoexcitation that result in very fast structural dynamics. The data were collected using a multimethod approach that featured time-resolved ultraviolet-visible, infrared and X-ray absorption and optical emission spectroscopy. Through supporting density functional calculations, we deliver a detailed picture of the structural dynamics in the picosecond-to-nanosecond time range.
Asunto(s)
Complejos de Coordinación/química , Cobre/química , Procesos Fotoquímicos , Teoría Funcional de la Densidad , Transporte de Electrón , Estructura MolecularRESUMEN
We report about the development and implementation of a new setup for time-resolved X-ray absorption fine structure spectroscopy at beamline P11 utilizing the outstanding source properties of the low-emittance PETRA III synchrotron storage ring in Hamburg. Using a high intensity micrometer-sized X-ray beam in combination with two positional feedback systems, measurements were performed on the transition metal complex fac-Tris[2-phenylpyridinato-C2,N]iridium(III) also referred to as fac-Ir(ppy)3. This compound is a representative of the phosphorescent iridium(III) complexes, which play an important role in organic light emitting diode (OLED) technology. The experiment could directly prove the anticipated photoinduced charge transfer reaction. Our results further reveal that the temporal resolution of the experiment is limited by the PETRA III X-ray bunch length of â¼103 ps full width at half maximum (FWHM).
RESUMEN
The effect of short-term (6 months) administration of conjugated equine estrogen (Premarin) on content and composition of the aortic sterols in male shite Carneau pigeons while they were on a cholesterol-free grain diet was investigated. Estrogen treatment resulted in a 38% increase (P less than 0.05) in free sterol concentration, with a 28.8% concomitant decrease (P less than 0.05) in the percent of cholesteryl esters. The total sterol concentration remained unchanged. This finding suggests that estrogens might influence the synthetic or hydrolytic (or both) processes that control the concentration of cholesteryl esters in the aorta. Fatty acid composition of steryl esters did not change significantly. The cholesterol content of plasma showed a mild reduction (14%) whereas the triglycerides increased significantly (30%).
Asunto(s)
Aorta/metabolismo , Ésteres del Colesterol/metabolismo , Colesterol/análogos & derivados , Estrógenos Conjugados (USP)/farmacología , Esteroles/metabolismo , Animales , Arteriosclerosis/sangre , Colesterol/sangre , Columbidae , Perros , Triglicéridos/sangreRESUMEN
Cholesteryl ester hydrolase activity was measured in the microsomal and supernatant fractions of the aorta of atherosclerosis-susceptible White Carneau and atherosclerosis-resistant Show Racer pigeons while on their normal cholesterol-free diets. Enzyme activities from both fractions showed fatty acid specificities for the hydrolysis of different cholesteryl esters in the following decreasing order: Linoleate greater than oleate greater than palmitate. At 9 months of age (the period of lipid accumulation) the microsomal enzyme activity in the Show Racer breed was significantly higher (P less than 0.001) than in the White Carneau breed, while the supernatant enzyme was slightly higher (P less than 0.05) in the White Carneaux at this age. In older birds (3 years of age) these differences in enzyme activities disappeared.
Asunto(s)
Aorta/enzimología , Arteriosclerosis/enzimología , Hidrolasas de Éster Carboxílico/metabolismo , Microsomas/enzimología , Esterol Esterasa/metabolismo , Envejecimiento , Animales , Aorta/crecimiento & desarrollo , Arteriosclerosis/genética , Columbidae , Modelos Animales de Enfermedad , Especificidad de la Especie , Fracciones Subcelulares/enzimologíaRESUMEN
The in vitro effects of prostaglandins E1 and F1alpha on the activity of cholesteryl ester synthetase and cholesteryl ester hydrolase activities of the pigeon aorta were examined. It was found that prostaglandin E1 markedly inhibited the cholesteryl ester hydrolase activity in the supernatant fraction and slightly inhibited the cholesteryl ester synthetase activity. Prostaglandin F1alpha, however, modestly stimulated the cholesteryl ester hydrolase activity both in the microsomal and in the supernatant fraction of the aorta. These observations strongly warrant further studies on the role of prostaglandins in atherogenesis.
Asunto(s)
Aorta/enzimología , Hidrolasas de Éster Carboxílico/metabolismo , Colesterol 7-alfa-Hidroxilasa/metabolismo , Prostaglandinas Sintéticas/farmacología , Esteroide Hidroxilasas/metabolismo , Esterol Esterasa/metabolismo , Animales , Colesterol 7-alfa-Hidroxilasa/antagonistas & inhibidores , Ésteres del Colesterol , Columbidae , Relación Dosis-Respuesta a Droga , Concentración de Iones de Hidrógeno , Microsomas/enzimología , Prostaglandinas E/farmacología , Prostaglandinas F/farmacología , Esterol Esterasa/antagonistas & inhibidoresRESUMEN
Early changes in cholesteryl ester metabolism of the aorta during the regression of naturally occurring atherosclerotic lesions in pigeon aorta by ileal bypass surgery were examined. Three months after surgery, there was a decrease (50%) in the content of cholesteryl esters in the aorta. Increases in the activity of cholesteryl ester hypdrolase in the lysosomal (P less than 0.05) and the supernatant (P less than 0.01) fractions of the aorta also occurred at this time. There were no differences in the activity of cholesteryl ester synthetase and in the plasma levels of cholesterol and triglycerides between the ileal bypass group and the controls. These results suggest that ileal bypass surgery decreases the level of cholesteryl esters in the aorta, probably because of enhanced cholesteryl ester hydrolysis.
Asunto(s)
Aorta/química , Arteriosclerosis/cirugía , Ésteres del Colesterol/análisis , Intestino Delgado/cirugía , Animales , Arteriosclerosis/enzimología , Columbidae , Esterol Esterasa/metabolismoAsunto(s)
Productos Lácteos/normas , Leche , Animales , Tecnología de Alimentos/normas , Leche/análisisRESUMEN
AIMS/HYPOTHESIS: We sought to determine whether pioglitazone and metformin alter NEFA-induced insulin resistance in type 2 diabetes and, if so, the mechanism whereby this is effected. METHODS: Euglycaemic-hyperinsulinaemic clamps (glucose approximately 5.3 mmol/l, insulin approximately 200 pmol/l) were performed in the presence of Intralipid-heparin (IL/H) or glycerol before and after 4 months of treatment with pioglitazone (n = 11) or metformin (n = 9) in diabetic participants. Hormone secretion was inhibited with somatostatin in all participants. RESULTS: Pioglitazone increased insulin-stimulated glucose disappearance (p < 0.01) and increased insulin-induced suppression of glucose production (p < 0.01), gluconeogenesis (p < 0.05) and glycogenolysis (p < 0.05) during IL/H. However, glucose disappearance remained lower (p < 0.05) whereas glucose production (p < 0.01), gluconeogenesis (p < 0.05) and glycogenolysis (p < 0.05) were higher on the IL/H study day than on the glycerol study day, indicating persistence of NEFA-induced insulin resistance. Metformin increased (p < 0.001) glucose disappearance during IL/H to rates present during glycerol treatment, indicating protection against NEFA-induced insulin resistance in extrahepatic tissues. However, glucose production and gluconeogenesis (but not glycogenolysis) were higher (p < 0.01) during IL/H than during glycerol treatment with metformin, indicating persistence of NEFA-induced hepatic insulin resistance. CONCLUSIONS/INTERPRETATION: We conclude that pioglitazone improves both the hepatic and the extrahepatic action of insulin but does not prevent NEFA-induced insulin resistance. In contrast, whereas metformin prevents NEFA-induced extrahepatic insulin resistance, it does not protect against NEFA-induced hepatic insulin resistance.
Asunto(s)
Diabetes Mellitus Tipo 2/tratamiento farmacológico , Diabetes Mellitus Tipo 2/fisiopatología , Ácidos Grasos no Esterificados/farmacología , Resistencia a la Insulina/fisiología , Metformina/uso terapéutico , Tiazolidinedionas/uso terapéutico , Glucemia/efectos de los fármacos , Glucemia/metabolismo , Índice de Masa Corporal , Péptido C/sangre , Emulsiones Grasas Intravenosas/farmacología , Femenino , Glucagón/sangre , Gluconeogénesis/efectos de los fármacos , Glucosa/metabolismo , Técnica de Clampeo de la Glucosa , Glicerol/farmacología , Heparina/farmacología , Humanos , Insulina/sangre , Insulina/fisiología , Masculino , Persona de Mediana Edad , PioglitazonaRESUMEN
On cholesterol-free diets, the total fecal steroid excretion was significantly lower in atherosclerosis-susceptible Whit Carneau pigeons than in atherosclerosis-resistant Show Racer pigeons, with major differences in the neutral sterol fraction.