Alcohol Oxidation at Platinum-Gas and Platinum-Liquid Interfaces: The Effect of Platinum Nanoparticle Size, Water Coadsorption and Alcohol Concentration

Alcohol oxidation reaction over platinum nanoparticles with size ranging from 2 to 8 nm deposited on mesoporous silica MCF-17 was studied in the gas and liquid phases. Among methanol, ethanol, 2- propanol, and 2-butanol oxidations, the turnover frequency increased as the nanoparticle size became large in both reaction phases. The activation energy in the gas phase was higher than that in the liquid phase. Water coadsorption decreased the turnover rate of all the gas and liquid phase oxidations except for the gas-phase 2-butanol case, while a certain amount of water promoted 2-propanol oxidation in the liquid phase. Sum frequency generation vibrational spectroscopy study and DFT calculation revealed that the alcohol molecules pack horizontally on the metal surface in low concentration and stand up in high concentration, which affects the dissociation of β-hydrogen of the alcohol as the critical step in alcohol oxidation

CD200-CD200R1 inhibitory signaling prevents spontaneous bacterial infection and promotes resolution of neuroinflammation and recovery after stroke

Abstract Background Ischemic stroke results in a robust inflammatory response within the central nervous system. As the immune-inhibitory CD200-CD200 receptor 1 (CD200R1) signaling axis is a known regulator of immune homeostasis, we hypothesized that it may play a role in post-stroke immune suppression after stroke. Methods In this study, we investigated the role of CD200R1-mediated signaling in stroke using CD200 receptor 1-deficient mice. Mice were subjected to a 60-min middle cerebral artery occlusion and evaluated at days 3 and 7, representing the respective peak and early resolution stages of neuroinflammation in this model of ischemic stroke. Infarct size and behavioral deficits were assessed at both time points. Central and peripheral cellular immune responses were measured using flow cytometry. Bacterial colonization was determined in lung tissue homogenates both after acute stroke and in an LPS model of systemic inflammation. Results In wild-type (WT) animals, CD200R1 was expressed on infiltrating monocytes and lymphocytes after stroke but was absent on microglia. Early after ischemia (72 h), CD200R1-knockout (KO) mice had significantly poorer survival rates and an enhanced susceptibility to spontaneous bacterial colonization of the respiratory tract compared to wild-type (WT) controls, despite no difference in infarct or neurological deficits. While the CNS inflammation was resolved by day 7 post-stroke in WT mice, brain-resident microglia and monocyte activation persisted in CD200R1-KO mice, accompanied by a delayed, augmented lymphocyte response. At this time point, CD200R1-KO mice displayed greater weight loss, more severe neurological deficits, and impaired motor function compared to WT. Systemically, CD200R1-KO mice exhibited signs of persistent infection including lymphopenia, T cell activation and memory conversion, and narrowing of the TCR repertoire. These findings were confirmed in a second model of acute neuroinflammation induced by systemic endotoxin challenge. Conclusion This study defines an essential role of CD200-CD200R1 signaling in stroke. Loss of CD200R1 led to high mortality, increased rates of post-stroke infection, and enhanced entry of peripheral leukocytes into the brain after ischemia, with no increase in infarct size. This suggests that the loss of CD200 receptor leads to enhanced peripheral inflammation that is triggered by brain injury.https://deepblue.lib.umich.edu/bitstream/2027.42/148133/1/12974_2019_Article_1426.pd

Molecular orientations change reaction kinetics and mechanism: A review on catalytic alcohol oxidation in gas phase and liquid phase on size-controlled Pt nanoparticles

Catalytic oxidation of alcohols is an essential process for energy conversion, production of fine chemicals and pharmaceutical intermediates. Although it has been broadly utilized in industry, the basic understanding for catalytic alcohol oxidations at a molecular level, especially under both gas and liquid phases, is still lacking. In this paper, we systematically summarized our work on catalytic alcohol oxidation over size-controlled Pt nanoparticles. The studied alcohols included methanol, ethanol, 1-propanol, 2-propanol, and 2-butanol. The turnover rates of different alcohols on Pt nanoparticles and also the apparent activation energy in gas and liquid phase reactions were compared. The Pt nanoparticle size dependence of reaction rates and product selectivity was also carefully examined. Water showed very distinct effects for gas and liquid phase alcohol oxidations, either as an inhibitor or as a promoter depending on alcohol type and reaction phase. A deep understanding of different alcohol molecular orientations on Pt surface in gas and liquid phase reactions was established using sum-frequency generation spectroscopy analysis for in situ alcohol oxidations, as well as density functional theory calculation. This approach can not only explain the entirely different behaviors of alcohol oxidations in gas and liquid phases, but can also provide guidance for future catalyst/process design