18983-82-9Relevant articles and documents
Product channels in the 193-nm photodissociation of HCNO (fulminic acid)
Feng, Wenhui,Hershberger, John F.
, p. 18 - 23 (2016)
IR diode laser spectroscopy was used to detect the products of HCNO (fulminic acid) photolysis at 193 nm. Six product channels are energetically possible at this photolysis wavelength: O + HCN, H + NCO/CNO, CN + OH, CO + NH, NO + CH and HNCO. In some experiments, isotopically labeled 15N18O, C2D6 or C6H12 reagents were included into the photolysis mixture in order to suppress and/or redirect possible secondary reactions. HCN, OC18O, 15N15NO, CO, DCN and HNCO molecules were detected upon laser photolysis of HCNO/reagents/buffer gas mixtures. Analysis of the yields of product molecules leads to the following photolysis quantum yields: φ1a (O + HCN) = 0.38 ± 0.04, φ1b (H + (NCO)) = 0.07 ± 0.02, φ1c (CN + OH) = 0.24 ± 0.03, φ1d (CO + NH(a1Δ)) 1e (HNCO) = 0.02 ± 0.01 and φ1f (CH + NO) = 0.21 ± 0.1, respectively.
New Strategy for in Vitro Determination of Carbonic Anhydrase Activity from Analysis of Oxygen-18 Isotopes of CO2
Ghosh, Chiranjit,Mandal, Santanu,Pal, Mithun,Pradhan, Manik
, p. 1384 - 1387 (2018)
The oxygen-18 isotopic (18O) composition in CO2 provides an important insight into the variation of rate in isotopic fractionation reaction regulated by carbonic anydrase (CA) metalloenzyme. This work aims to employ an 18O-isotope ratio-based analytical method for quantitative estimation of CA activity in erythrocytes for clinical testing purposes. Here, a new method has been developed that contains the measurements of 18O/16O isotope ratios during oxygen-18 isotopic exchange between 12C16O16O and H218O of an in vitro biochemical reaction controlled by erythrocytes CA and estimation of enzymatic activity of CA from the isotopic composition of CO2. We studied the enrichments of 18O-isotope of CO2 with increments of CA activities during isotopic fractionation reaction. To check the influence of subject-specific body temperature, pH, H218O, and cellular produced CO2 on this reaction, we performed the in vitro experiments in closed containers with variations of those parameters. Finally, we mimicked the exchange reaction at 5% [CO2], 5‰ [H2 18O], pH of 7.4, and temperature of 37 °C to create the physiological environment equivalent to that of the human body and monitored the exchange kinetics with variations of CA activities, and subsequently, we derived the quantitative relation between the 18O-isotope of CO2 and CA activity in erythrocytes. This assay may be applicable for rapid and simple quantification of carbonic anhydrase activity which is very important to prevent the carbonic-anhydrase-associated disorders in human.
A Structural Mimic of Carbonic Anhydrase in a Metal-Organic Framework
Wright, Ashley M.,Wu, Zhenwei,Zhang, Guanghui,Mancuso, Jenna L.,Comito, Robert J.,Day, Robert W.,Hendon, Christopher H.,Miller, Jeffrey T.,Dinc?, Mircea
, p. 2894 - 2901 (2018)
Metal-organic frameworks (MOFs) have exciting potential for biomimetic studies of enzymes, yet construction of high-fidelity models at the metal nodes is challenging. Nonetheless, biomimetic MOFs have significant advantages, such as increased stability and ease of separation, over their enzymatic and homogeneous counterparts, making them particularly attractive for industrial applications. Here, we demonstrate biomimetic behavior of Zn hydroxide moieties inside a MOF with structural and reactivity characteristics of carbonic anhydrase. Similar to the biological system, the MOF binds CO2 by an insertion mechanism into the Zn–OH bond, leading to significant adsorption of CO2 (3.41 mmol/g). In reactivity mimicking that of the enzyme, the material also catalyzes the oxygen isotope exchange between water and carbon dioxide. Overall, these results provide the strongest evidence yet of metal nodes in MOFs bearing high structural fidelity to enzymatic active sites. The nodes of metal-organic frameworks are attractive sites for mimicking metalloenzymes, primarily through their site isolation and similar ligand fields. In this article, the metal-organic framework MFU-4l is shown to mimic the active site of carbonic anhydrase with high structural fidelity and reactivity. The material adsorbs high quantities of carbon dioxide at low pressures and mimics critical features of carbonic anhydrase, such as isotopic exchange of oxygen atoms from water and carbon dioxide. Mimicking metalloenzymes at the node of a metal-organic framework (MOF) has the potential to impart enzyme-like catalytic activity within a heterogeneous material. Carbonic anhydrase, one of nature's fastest enzymes, catalyzes the hydrolysis of carbon dioxide into bicarbonate and protons. Notably, carbonic anhydrase mimics have been proposed as potential catalysts for carbon capture and sequestration from the environment. Here, we demonstrate that the metal node of MFU-4l, a MOF featuring a metal node with a N3ZnX coordination environment, can be functionalized to give a mimic of carbonic anhydrase. This work describes a well-defined example of a metal node within a MOF with high structural fidelity to an enzyme active site. It has potential applicability to applications such as CO2 capture and sequestration and also important gas separations involving CO2.
The effect of water on the heterogeneously catalyzed selective oxidation of acrolein: An isotope study
Petzold, Tina,Blickhan, Nina,Drochner, Alfons,Vogel, Herbert
, p. 2053 - 2058 (2014)
The effect of water on the selective gas phase oxidation of acrolein to acrylic acid on a Mo/V/W mixed oxide catalyst was studied by performing steady-state isotopic transient kinetic analysis experiments with H 218O. Experiments were performed in the temperature range of 90-345C at ambient pressure. It could be shown that acrolein exchanges its carbonylic oxygen with oxygen from water even at low temperatures (200C), the oxygen atoms of the water molecules incorporate into all oxidation products such as acrylic acid, carbon monoxide, and carbon dioxide.
Anion-Receptor Mediated Oxidation of Carbon Monoxide to Carbonate by Peroxide Dianion
Nava, Matthew,Lopez, Nazario,Müller, Peter,Wu, Gang,Nocera, Daniel G.,Cummins, Christopher C.
, p. 14562 - 14565 (2015)
The reactivity of peroxide dianion O22- has been scarcely explored in organic media due to the lack of soluble sources of this reduced oxygen species. We now report the finding that the encapsulated peroxide cryptate, [O2?mBDCA-5t-H6]2- (1), reacts with carbon monoxide in organic solvents at 40 °C to cleanly form an encapsulated carbonate. Characterization of the resulting hexacarboxamide carbonate cryptate by single crystal X-ray diffraction reveals that carbonate dianion forms nine complementary hydrogen bonds with the hexacarboxamide cryptand, [CO3?mBDCA-5t-H6]2- (2), a conclusion that is supported by spectroscopic data. Labeling studies and 17O solid-state NMR data confirm that two-thirds of the oxygen atoms in the encapsulated carbonate derive from peroxide dianion, while the carbon is derived from CO. Further evidence for the formation of a carbonate cryptate was obtained by three methods of independent synthesis: treatment of (i) free cryptand with K2CO3; (ii) monodeprotonated cryptand with PPN[HCO3]; and (iii) free cryptand with TBA[OH] and atmospheric CO2. This work demonstrates CO oxidation mediated by a hydrogen-bonding anion receptor, constituting an alternative to transition-metal catalysis.
Reactivity of molecularly chemisorbed oxygen on a Au/TiO2 model catalyst
Stiehl, James D.,Gong, Jinlong,Ojifinni, Rotimi A.,Kim, Tae S.,McClure, Sean M.,Mullins, C. Buddie
, p. 20337 - 20343 (2006)
We present results of an investigation into the reactivity of molecularly chemisorbed oxygen with CO on a Au/TiO2 model catalyst at 77 K. We previously discovered that exposing the model catalyst sample to a radio-frequency-generated plasma jet of oxygen results in co-population of both atomically and molecularly ' chemisorbed oxygen species on the sample. We tested the reactivity of the molecularly chemisorbed oxygen by comparing the CO 2 produced from a sample populated with both species to the CO 2 produced from a sample that has been cleared of molecularly chemisorbed oxygen employing collision-induced desorption. Samples that are populated with both species consistently result in greater CO2 produced than samples with only atomic oxygen. We interpret this result to indicate that molecularly chemisorbed oxygen on the sample can directly participate in the CO oxidation reaction. The reactivity of molecularly chemisorbed oxygen has been investigated for five different gold coverages (0.5, 0.75, 1, 1.25, and 2 ML), and we observe that there is a greater fractional difference in the CO2 produced (difference between sample populated with both molecularly and atomically adsorbed oxygen and sample populated solely with atomically adsorbed oxygen) for the 1 ML Au coverage than for the other coverages for equivalent oxygen plasma-jet exposures. However, it is not possible to unambiguously conclude that this observation is directly related to a particle size effect on the chemistry since the absolute O2,a and Oa content on the various surfaces is different for all the coverages studied because of the plasma-jet technique that we employed for populating the surfaces with oxygen. Unfortunately, this precludes a direct comparison of the reactivity of molecular oxygen in the carbon monoxide oxidation reaction as a function of gold coverage and hence particle size.
A CO2-mediated base catalysis approach for the hydration of triple bonds in ionic liquids
Han, Buxing,Ke, Zhengang,Li, Ruipeng,Liu, Zhimin,Tang, Minhao,Wang, Yuepeng,Zeng, Wei,Zhang, Fengtao,Zhao, Yanfei
supporting information, p. 9870 - 9875 (2021/12/27)
Herein, we report a CO2-mediated base catalysis approach for the activation of triple bonds in ionic liquids (ILs) with anions that can chemically capture CO2 (e.g., azolate, phenolate, and acetate), which can achieve hydration of triple bonds to carbonyl chemicals. It is discovered that the anion-complexed CO2 could abstract one proton from proton resources (e.g., IL cation) and transfer it to the CN or CC bonds via a six-membered ring transition state, thus realizing their hydration. In particular, tetrabutylphosphonium 2-hydroxypyridine shows high efficiency for hydration of nitriles and CC bond-containing compounds under a CO2 atmosphere, affording a series of carbonyl compounds in excellent yields. This catalytic protocol is simple, green, and highly efficient and opens a new way to access carbonyl compounds via triple bond hydration under mild and metal-free conditions.
Rh/Ce0.25Zr0.75O2 Catalyst for Steam Reforming of Propane at Low Temperature
Yu, Lin,Sato, Katsutoshi,Nagaoka, Katsutoshi
, p. 1472 - 1479 (2019/02/09)
Solid oxide fuel cells (SOFCs) show high energy-conversion efficiency and thus emit less CO2 than conventional combustion engines. Although SOFCs can directly convert hydrocarbons such as liquefied petroleum gas, these fuels readily induce coking on the electrodes of fuel cell stacks. To avoid coking, hydrocarbons can be subjected to a preliminary endothermic steam-reforming step at a relatively low temperature using waste heat from the stack. Herein, we report that a Rh/Ce0.25Zr0.75O2 catalyst exhibited higher propane-steam-reforming activity than other Rh/Ce1?xZrxO2 catalysts and Rh/γ-Al2O3. Catalyst characterization revealed that Rh/Ce0.25Zr0.75O2 had excellent redox property and high H2O-adsorption activity, which contributed to the activation of steam and thus enhanced the propane-steam-reforming activity of this catalyst.
