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Flexible high-resolution broadband sum-frequency generation vibrational spectroscopy for intrinsic spectral line widths
No full textThe difficulty in achieving high spectral resolution and accurate line shape in sum-frequency generation vibrational spectroscopy (SFG-VS) has restricted its use in applications requiring precise detection and quantitative analysis. Recently, the development of high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS) with sub-wavenumber resolution generated by synchronizing two independent amplifier lasers have opened new opportunities for probing an intrinsic SFG response. Here, we present a new flexible approach to achieve HR-BB-SFG-VS. In this system, two regeneration amplifiers shared the same oscillator laser as the seed, and a time-asymmetric visible pulse with a nearly Lorentzian line shape filtered by an etalon was used to overlap with a femtosecond broadband infrared pulse. This Lorentzian line shape of the visible pulse can greatly simplify the spectral fitting and analysis. We also demonstrated that the single-sided long visible pulse provided both high spectral resolution (1.4 cm(-1)) and effective suppression of the non-resonant background by detuning the time delay between visible and infrared pulses in SFG-VS measurements. With this new SFG setup, a pair of spectral splittings by 3.1 +/- 0.7 and 3 +/- 0.2 cm 1 for the symmetric and antisymmetric stretching of the CH3 group was resolved at the CH3CN/TiO2(110) surface, which are tentatively attributed to two different orientational methyl groups. These technological advancements can help broaden the applications of HR-BB-SFG-VS and provide solid ground for a better understanding of complex molecular structures and dynamics at interfaces. Published under license by AIP Publishing
Recent Recent advances in alkoxylation chemistry of polyoxometalates: From synthetic strategies, structural overviews to functional applications
No full textPolyoxometalates (POMs), an exceptional family of coordination clusters consisting of Mo, W, V, etc. early transition metal ions in their highest oxidation states, have received significant attention over recent years due to their structural versatility and unique and diverse chemical and physical properties. The functionalization of POMs with organic ligands provides a novel strategy to precisely incorporate POMs with advanced functional organic moieties on their surfaces and enhance their compatibility in organic media. Among the various organically functionalized synthetic strategies for POM-based organic-inorganic hybrid materials, alkoxylation of POMs stands for one of the hottest topics during the past decades, since the diverse and tunable alkoxyl ligands are able to anchor on the surface of many POMs clusters, forming novel and flexible organically functionalized POM clusters, which can be further exploited as building blocks to design various functionalized POM-based hybrids with charming catalytic properties, and biomedicine, energy, or functional materials applications. In this review, recent advances in alkoxylation chemistry of POMs from synthetic strategies, structural overviews to their functional applications have been discussed. (C) 2017 Elsevier B.V. All rights reserved
N-Acetylcysteine alleviates gut dysbiosis and glucose metabolic disorder in high-fat diet-fed mice
No full textBackground: N-Acetylcysteine (NAC), an antioxidative reagent for clinical diseases, shows potential in the treatment of diabetes and other metabolic diseases. However, it is unknown how NAC modulates the gut microbiota of mice with metabolic syndrome. The aim of the present study was to demonstrate the preventive effect of NAC on intestinal dysbiosis and glucose metabolic disorder.
Methods: Mice (C57BL/6J strain) were fed either a normal chow diet (NCD), NCD plus NAC, a high-fat diet (HFD), or HFD plus NAC for 5 months, after which glucose levels, circulating endotoxins and key metabolism-related proteins were determined. Fecal samples were analyzed by 16S rRNA sequencing. A novel analysis was performed to predict functional changes in gut microbiota. In addition, Spearman's correlation analysis was performed between metabolic biomarkers and bacterial abundance.
Results: Treatment with NAC significantly reversed the glucose intolerance, fasting glucose concentrations, and gains in body weight and plasma endotoxin in HFD-fed mice. Further, NAC upregulated occludin and mucin glycoprotein levels in the proximal colon of HFD-treated mice. Noticeably, NAC promoted the growth of beneficial bacteria (i.e. Akkermansia, Bifidobacterium, Lactobacillus and Allobaculum) and decreased populations of diabetes-related genera, including Desulfovibrio and Blautia. In addition, NAC may affect the metabolic pathways of intestinal bacteria, including lipopolysaccharide biosynthesis, oxidative stress, and bacterial motility. Finally, the modified gut microbiota was closely associated with the metabolic changes in NAC-treated HFD-fed mice.
Conclusions: N-Acetylcysteine may be a potential drug to prevent glucose metabolic disturbances by reshaping the structure of the gut microbiota
