Xi,
CRelevant articles and documents
All total 40 Articles be found
All total 40 Articles be found-
Warneford,Hardy
, (1926)
-
Discovery and Biosynthesis of Bolagladins: Unusual Lipodepsipeptides from Burkholderia gladioli Clinical Isolates**
Challis, Gregory L.,Dashti, Yousef,Jian, Xinyun,Mahenthiralingam, Eshwar,Mullins, Alex J.,Nakou, Ioanna T.,Webster, Gordon
, (2020)
Two Burkholderia gladioli strains isolated from the lungs of cystic fibrosis patients were found to produce unusual lipodepsipeptides containing a unique citrate-derived fatty acid and a rare dehydro-β-alanine residue. The gene cluster responsible for the
SYNTHESIS OF 4-(HYDROXYMETHYL)TETRAHYDRO-4-PYRANOL - A NEW INTERMEDIATE FOR THE PREPARATION OF SYNTHETIC CITRIC ACID
Gevorkyan, A. A.,Kazaryan, P. I.,Sargysyan, M. S.,Petrosyan, K. A.,Mkrtumyan, S. A.
, p. 712 - 713 (1983)
The hydroxylation of 4-methylenetetrahydropyran with hydrogen peroxide in the presence of various acidic catalysts was investigated.The oxidation of 4-(hydroxymethyl)tetrahydro-4-pyranol with concentrated nitric acid leads to citric acid in 50percent yield.
Absolute stereochemical course of the 3-carboxymuconate cycloisomerases from Pseudomonas putida and Acinetobacter colcoaceticus: Analysis and implications
Chari,Whitman,Kozarich,et al.
, p. 5514 - 5519 (1987)
The absolute stereochemical course of the 3-carboxymuconate cycloisomerases [EC 5.5.1.2; 2-carboxy-5-oxo-2,5-dihydrofuran-2-acetate lyase (decyclizing)] from Pseudomonas putida and Acinetobacter calcoaceticus has been determined by chemical and 1H NMR methods. The product of the enzyme-catalyzed reaction in 2H2O was detected by NMR and trapped by catalytic hydrogenation to afford 5-[2H]homocitrate lactone. Subsequent chemical degradation of the monodeuteriated homocitrate lactone gave (2r,3S)-2-[2H]citrate as determined by 1H NMR analysis. The product of the cycloisomerase reaction was established as (4R,5R)-5-[2H]-4-carboxymuconate, indicating that the lactonization proceeded by an anti addition - the mechanistic and stereochemical antipode of the previously studied muconate cycloisomerase from P. putida and 3-carboxymuconate cycloisomerase from Neurospora crassa. The anti addition probably represents the lower energy pathway for the reaction and suggests that the evolutionary relationship between the two classes of cycloisomerases is more remote than previously believed.
Kusnetzow
, p. 341 (1925)
Stern et al.
, (1956)
Cyanide as a primordial reductant enables a protometabolic reductive glyoxylate pathway
Krishnamurthy, Ramanarayanan,Pulletikurti, Sunil,Yadav, Mahipal,Yerabolu, Jayasudhan R.
, p. 170 - 178 (2022/02/11)
Investigation of prebiotic metabolic pathways is predominantly based on abiotically replicating the reductive citric acid cycle. While attractive from a parsimony point of view, attempts using metal/mineral-mediated reductions have produced complex mixtures with inefficient and uncontrolled reactions. Here we show that cyanide acts as a mild and efficient reducing agent mediating abiotic transformations of tricarboxylic acid intermediates and derivatives. The hydrolysis of the cyanide adducts followed by their decarboxylation enables the reduction of oxaloacetate to malate and of fumarate to succinate, whereas pyruvate and α-ketoglutarate themselves are not reduced. In the presence of glyoxylate, malonate and malononitrile, alternative pathways emerge that bypass the challenging reductive carboxylation steps to produce metabolic intermediates and compounds found in meteorites. These results suggest a simpler prebiotic forerunner of today’s metabolism, involving a reductive glyoxylate pathway without oxaloacetate and α-ketoglutarate—implying that the extant metabolic reductive carboxylation chemistries are an evolutionary invention mediated by complex metalloproteins. [Figure not available: see fulltext.].
Catalytic Oxidation of VOCs over SmMnO3 Perovskites: Catalyst Synthesis, Change Mechanism of Active Species, and Degradation Path of Toluene
Liu, Lizhong,Sun, Jiangtian,Ding, Jiandong,Zhang, Yan,Jia, Jinping,Sun, Tonghua
, p. 14275 - 14283 (2019/10/17)
Highly active samarium manganese perovskite oxides were successfully prepared by employing self-molten-polymerization, coprecipitation, sol-gel, and impregnation methods. The physicochemical properties of perovskite oxides were investigated by XRD, N2 adsorption-desorption, XPS, and H2-TPR. Their catalytic performances were compared via the catalytic oxidation of toluene. The perovskite prepared by self-molten-polymerization possessed the highest catalytic capacity, which can be ascribed to its higher oxygen adspecies concentration (Olatt/Oads = 0.53), higher surface Mn4+/Mn3+ ratio (Mn4+/Mn3+ = 0.95), and best low-temperature reducibility (H2 consumption = 0.27; below 350 °C). The most active catalyst also exhibited good cycling and long-term stability for toluene oxidation. After a multistep cycle reaction and a long-term reaction of 42 h, the toluene conversion maintained above 99.9% at 270 °C. Mechanistic study hinted that lattice oxygen was involved in toluene oxidation. The oxidation reaction was dependent on the synergism of lattice oxygen, adsorbed oxygen, and oxygen vacancies. The degradation pathway of toluene, researched by diffuse reflectance infrared Fourier transform spectroscopy and online mass spectrometry technologies, demonstrated that a series of organic byproducts existed at a relatively low temperature. This work provides an efficient and practical method for selecting highly active catalysts and for exploring the catalytic mechanism for the removal of atmospheric environmental pollution.
