Preparation of Oxysterols by C-H Oxidation of Dibromocholestane with Ru(Bpga) Catalyst.
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ABSTRACT:
SUBMITTER: Fujii Y
PROVIDER: S-EPMC8746986 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The rutile SnxTi1-xO2 (x = 0, 0.33, 0.5, 0.67, 1) solid solution was synthesized by a one-step hydrothermal method, in which tetrabutyl titanate and Tin (IV) chloride pentahydrate were used as raw materials. A series of Ru/SnxTi1-xO2 were then prepared by the impregnation process in RuCl3 to investigate the performance and stability of CO and C3H8 oxidation. These catalysts were characterized through XRD, N2 adsorption-desorption, FT-IR, TEM, XPS, H2-TPR, and O2-TPD techniques. The effect of Sn/Ti molar ratio and hydrothermal condition on the low-temperature catalytic oxidized performance and stability of Ru/SnxTi1-xO2 were investigated. The results indicated that Ru/Sn0.67Ti0.33O2 catalyst showed an excellent activity and stability at low temperatures. The CO conversion reached 50% at 180 °C and 90% at 240 °C. Besides, the C3H8 conversion reached 50% at 320 °C, the complete conversion of C3H8 realized at 500 °C, and no deactivation occurs after 12?h of catalytic reaction. The excellent low-temperature activity and stability of the Ru/Sn0.67Ti0.33O2 were attributed to the following factors. Firstly, XRD results showed that Sn4+ was successfully introduced into the lattice of TiO2 to replace Ti4+ forming a homogeneous solid solution (containing -Sn4+-O-Ti4+- species), which was consistent with TEM and N2 adsorption-desorption results. The introduction of Sn could suppress the growth of anatase crystal and promote the formation of rutile phase, and this phase transition was helpful to improve the low-temperature activity of the catalysts. Secondly, TEM images showed that ultrafine Ru nanoparticles (~ 5?nm) were dispersed on Sn0.67Ti0.33O2 support, suggesting that the formation of SnxTi1-xO2 solid solution was beneficial to the dispersion of Ru particles.
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Project description:Recent studies suggest that 7-dehydrocholesterol (7-DHC)-derived oxysterols play important roles in the pathophysiology of Smith-Lemli-Opitz syndrome (SLOS), a metabolic disorder that is caused by defective 3β-hydroxysterol-Δ(7)-reductase (DHCR7). Although 14 oxysterols have been identified as the primary products of 7-DHC autoxidation in organic solution, the metabolic fate of these oxysterols in a biological environment has not yet been elucidated. Therefore, we incubated these primary 7-DHC oxysterols in control Neuro2a and control human fibroblast cells and identified metabolites of these oxysterols by HPLC-MS. We also incubated Dhcr7-deficient Neuro2a cells and fibroblasts from SLOS patients with isotopically labeled 7-DHC (d(7)-7-DHC). The observation of matching d(0)- and d(7) peaks in HPLC-MS confirmed the presence of true metabolites of 7-DHC after excluding the possibility of ex vivo oxidation. The metabolites of primary 7-DHC oxysterols were found to contribute to the majority of the metabolic profile of 7-DHC in cells. Furthermore, based on this new data, we identified three new 7-DHC-derived metabolites in the brain of Dhcr7-KO mice. Our studies suggest that 7-DHC peroxidation is a major source of oxysterols observed in cells and in vivo and that the stable metabolites of primary 7-DHC oxysterols can be used as markers of 7-DHC peroxidation in these biological systems.
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