Interfacial photoreactions of Cr(VI) and oxalate on lepidocrocite surface under oxic and acidic conditions: Reaction mechanism and potential implications for contaminant degradation in surface waters

Lytic polysaccharide monooxygenases (LPMOs) are copper-center enzymes that are involved in the oxidative cleavage of the glycosidic bond in crystalline cellulose and other polysaccharides. The LPMO reaction is initiated by the addition of a reductant and oxygen to ultimately form an unknown activated copper–oxygen species that is responsible for polysaccharide-substrate H-atom abstraction. Given the sensitivity of metalloproteins to radiation damage, neutron protein crystallography provides a nondestructive technique for structural characterization while also informing on the positions of H atoms. Neutron cryo-crystallography permits the trapping of catalytic intermediates, thereby providing insight into the protonation states and chemical nature of otherwise short-lived species in the reaction mechanism. To characterize the reaction-mechanism intermediates of LPMO9D from Neurospora crassa, a cryo-neutron diffraction data set was collected from an ascorbate-reduced crystal. A second neutron diffraction data set was collected at room temperature from an LPMO9D crystal exposed to low-pH conditions to probe the protonation states of ionizable groups involved in catalysis under acidic conditions.

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Use of Phenacyl Thiosalicylates for the Preparation of 3-Hydroxybenzo[b]thiophene Derivatives

Synlett ◽

10.1055/s-0036-1591875 ◽

2018 ◽

Vol 29 (06) ◽

pp. 810-814 ◽

Cited By ~ 1

Author(s):

Miroslav Soural ◽

Patricia Trapani ◽

Lubomír Kvapil ◽

Pavel Hradil

Keyword(s):

Reaction Mechanism ◽

Nmr Spectroscopy ◽

Reaction Intermediates ◽

Detailed Reaction Mechanism ◽

Acidic Conditions ◽

Thiophene Derivatives ◽

Phenacyl Esters

In this work, we attempted to synthesize thioflavonols using rearrangement of phenacyl thiosalicylates prepared by two different approaches and subjected to cyclization under acidic conditions. Contrary to our expectations, the isolated products were identified as (3-hydroxybenzo[b]thiophen-2-yl)(phenyl)methanones. The detailed reaction mechanism was elucidated by characterization of all reaction intermediates with HPLC and NMR spectroscopy. The applicability of the reaction using different phenacyl esters was tested.

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Water treatment with a fixed bed catalytic ozonation process

Water Science & Technology ◽

10.2166/wst.1997.0151 ◽

1997 ◽

Vol 35 (4) ◽

pp. 353-360 ◽

Cited By ~ 16

Author(s):

F. P. Logemann ◽

J. H. J. Annee

Keyword(s):

Reaction Mechanism ◽

Fixed Bed ◽

Catalytic Ozonation ◽

Solid Catalyst ◽

Oh Radicals ◽

Radical Scavengers ◽

Industrial Plants ◽

Alkaline Conditions ◽

Acidic Conditions ◽

Ozonation Process

Progress in developing the fixed bed, catalytic ozonation process “ECOCLEAR” continues. Experimental evidence supports a reaction mechanism that predominantly takes place at the surface of the solid catalyst. This sets “ECOCLEAR” apart from all other advanced oxidation techniques which depend on the presence of ·OH radicals in the aqueous phase. The catalytic ozonation process requires less ozone, is substantially less affected by dissolved radical scavengers such as (bi)carbonates and is equally effective under both highly acidic conditions – when ·OH radicals are not formed – as well as under highly alkaline conditions. Results of industrial plants in operation are given.

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Oxygen reduction reaction mechanism and kinetics on M-NxCy and M@N-C active sites present in model M-N-C catalysts under alkaline and acidic conditions

Journal of Solid State Electrochemistry ◽

10.1007/s10008-019-04436-w ◽

2019 ◽

Cited By ~ 3

Author(s):

Ricardo Sgarbi ◽

Kavita Kumar ◽

Frédéric Jaouen ◽

Andrea Zitolo ◽

Edson A. Ticianelli ◽

...

Keyword(s):

Reaction Mechanism ◽

Oxygen Reduction Reaction ◽

Oxygen Reduction ◽

Active Sites ◽

Reduction Reaction ◽

Acidic Conditions ◽

Mechanism And Kinetics

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Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.16.136 ◽

2020 ◽

Vol 16 ◽

pp. 1636-1648

Author(s):

Csilla Hargitai ◽

Györgyi Koványi-Lax ◽

Tamás Nagy ◽

Péter Ábrányi-Balogh ◽

András Dancsó ◽

...

Keyword(s):

Reaction Mechanism ◽

Dft Calculations ◽

Single Crystal ◽

Structure Elucidation ◽

Computational Study ◽

Nmr Studies ◽

X Ray ◽

Product Distributions ◽

Acidic Conditions

Treatment of alkoxy-substituted o-(pivaloylaminomethyl)benzaldehydes under acidic conditions resulted in the formation of the regioisomeric aldehydes and/or dimer-like products. Detailed NMR studies and single-crystal X-ray measurements supported the structure elucidation of the compounds. DFT calculations were also carried out to clarify the reaction mechanism, and to explain the observed product distributions and structural variances in the dimer-like products. Studies on the transformation of unsubstituted o-(pivaloylaminomethyl)benzaldehyde under similar conditions were presented as well.

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Cytostatic Drug 6-Mercaptopurine Degradation on Pilot Scale Reactors by Advanced Oxidation Processes: UV-C/H2O2 and UV-C/TiO2/H2O2 Kinetics

Catalysts ◽

10.3390/catal11050567 ◽

2021 ◽

Vol 11 (5) ◽

pp. 567

Author(s):

Luis A. González-Burciaga ◽

Juan C. García-Prieto ◽

Manuel García-Roig ◽

Ismael Lares-Asef ◽

Cynthia M. Núñez-Núñez ◽

...

Keyword(s):

Advanced Oxidation Processes ◽

Pilot Scale ◽

Cytostatic Drug ◽

Contaminant Degradation ◽

Ph Values ◽

Initial Ph ◽

Acidic Conditions ◽

Kinetic Calculations ◽

Uv C ◽

By Products

6-Mercaptopurine (6-MP) is a commonly used cytostatic agent, which represents a particular hazard for the environment because of its low biodegradability. In order to degrade 6-MP, four processes were applied: Photolysis (UV-C), photocatalysis (UV-C/TiO2), and their combination with H2O2, by adding 3 mM H2O2/L (UV-C/H2O2 and UV-C/TiO2/H2O2 processes). Each process was performed with variable initial pH (3.5, 7.0, and 9.5). Pilot scale reactors were used, using UV-C lamps as radiation source. Kinetic calculations for the first 20 min of reaction show that H2O2 addition is of great importance: in UV-C experiments, highest k was reached under pH 3.5, k = 0.0094 min−1, while under UV-C/H2O2, k = 0.1071 min−1 was reached under the same initial pH; similar behavior was observed for photocatalysis, as k values of 0.0335 and 0.1387 min−1 were calculated for UV-C/TiO2 and UV-C/TiO2/H2O2 processes, respectively, also under acidic conditions. Degradation percentages here reported for UV-C/H2O2 and UV-C/TiO2/H2O2 processes are above 90% for all tested pH values. Ecotoxicity analysis of samples taken at 60 min in the photolysis and photocatalysis processes, suggests that contaminant degradation by-products present higher toxicity than the original compound.

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Habitat Association of Klebsiella Species

Infection Control ◽

10.1017/s0195941700062603 ◽

1985 ◽

Vol 6 (2) ◽

pp. 52-58 ◽

Cited By ~ 111

Author(s):

Susan T. Bagley

Keyword(s):

Drinking Water ◽

Gastrointestinal Tract ◽

Surface Waters ◽

Industrial Effluents ◽

Opportunistic Pathogen ◽

Habitat Associations ◽

Habitat Association ◽

Klebsiella Species ◽

Almost All ◽

Polluted Waters

AbstractThe genus Klebsiella is seemingly ubiquitous in terms of its habitat associations. Klebsiella is a common opportunistic pathogen for humans and other animals, as well as being resident or transient flora (particularly in the gastrointestinal tract). Other habitats include sewage, drinking water, soils, surface waters, industrial effluents, and vegetation. Until recently, almost all these Klebsiella have been identified as one species, ie, K. pneumoniae. However, phenotypic and genotypic studies have shown that “K. pneumoniae” actually consists of at least four species, all with distinct characteristics and habitats. General habitat associations of Klebsiella species are as follows: K. pneumoniae—humans, animals, sewage, and polluted waters and soils; K. oxytoca—frequent association with most habitats; K. terrigena— unpolluted surface waters and soils, drinking water, and vegetation; K. planticola—sewage, polluted surface waters, soils, and vegetation; and K. ozaenae/K. rhinoscleromatis—infrequently detected (primarily with humans).

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Identifying Sources of Sulfate Aerosols Reaching Whiteface Mountain, NY

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117546 ◽

1985 ◽

Vol 43 ◽

pp. 98-101

Author(s):

James S. Webber

Keyword(s):

Trace Metals ◽

Acid Deposition ◽

Surface Waters ◽

Dry Deposition ◽

Coal Combustion ◽

Public Awareness ◽

Sulfate Aerosols ◽

Wet And Dry Deposition ◽

Whiteface Mountain ◽

Toxic Trace Metals

INTRODUCTION“Acid rain” and “acid deposition” are terms no longer confined to the lexicon of atmospheric scientists and 1imnologists. Public awareness of and concern over this phenomenon, particularly as it affects acid-sensitive regions of North America, have increased dramatically in the last five years. Temperate ecosystems are suffering from decreased pH caused by acid deposition. Human health may be directly affected by respirable sulfates and by the increased solubility of toxic trace metals in acidified waters. Even man's monuments are deteriorating as airborne acids etch metal and stone features.Sulfates account for about two thirds of airborne acids with wet and dry deposition contributing equally to acids reaching surface waters or ground. The industrial Midwest is widely assumed to be the source of most sulfates reaching the acid-sensitive Northeast since S02 emitted as a byproduct of coal combustion in the Midwest dwarfs S02 emitted from all sources in the Northeast.

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Arylation of enelactams using TIPSOTf: reaction scope and mechanistic insight

Organic Chemistry Frontiers ◽

10.1039/d0qo01396j ◽

2021 ◽

Author(s):

Tomasz J. Idzik ◽

Zofia M. Myk ◽

Łukasz Struk ◽

Magdalena Perużyńska ◽

Gabriela Maciejewska ◽

...

Keyword(s):

Reaction Mechanism ◽

Multinuclear Nmr ◽

Mechanistic Insight ◽

Nmr Study ◽

Wide Range

Triisopropylsilyltrifluoromethanesulfonate can be effectively used for the arylation of a wide range of enelactams. The multinuclear NMR study provided deep insights into the reaction mechanism.

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