Understanding factors controlling depolymerization and polymerization in catalytic degradation of β-ether linked model lignin compounds by versatile peroxidase

2017 ◽  
Vol 19 (9) ◽  
pp. 2145-2154 ◽  
Author(s):  
Jijiao Zeng ◽  
Matthew J. L. Mills ◽  
Blake A. Simmons ◽  
Michael S. Kent ◽  
Kenneth L. Sale
Keyword(s):  
Structural Features ◽  
Catalytic Degradation ◽  
Versatile Peroxidase ◽  
Reaction Conditions ◽  
Linked Model

Insights into reaction conditions and structural features of lignin that facilitate its versatile peroxidase catalyzed depolymerization.

A close look at the structural features and reaction conditions that modulate the synthesis of low and high molecular weight fructans by levansucrases

2019 ◽  
Vol 219 ◽  
pp. 130-142 ◽  
Author(s):  
Maria Elena Ortiz-Soto ◽  
Jaime R. Porras-Domínguez ◽  
Jürgen Seibel ◽  
Agustín López-Munguía
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Structural Features ◽  
Reaction Conditions

scholarly journals Di-tungsten Bis-carbene Complexes Linked by Condensed Heteroaromatic Spacers

2007 ◽  
Vol 62 (3) ◽  
pp. 419-426 ◽  
Author(s):  
Marilé Landmana ◽  
Helmar Görls ◽  
Chantelle Crause ◽  
Hubert Nienaber ◽  
Andrew Olivier ◽  
...  
Keyword(s):  
Structural Features ◽  
Crystallographic Data ◽  
Reaction Conditions ◽  
Carbene Complexes

The 2,7-dilithiated substrates of 3,6-dimethylthieno[3,2-b]thiophene, N,N′-dimethylpyrrolo[3,2- b]pyrrole and N-methylthieno[3,2-b]pyrrole were reacted with W(CO)6 to give, after subsequent alkylation with Et3OBF4, the ditungsten biscarbene complexes [(CO)5W{C(OEt)XXC(OEt)} W(CO)5] (XX = condensed heteroaromatic spacers). Sites of attack during the dilithiation of the condensed rings were studied and compared, and the yields of the desired ditungsten biscarbene complexes optimized by changing the reaction conditions according to the role of the heteroatoms in the rings. The crystallographic data of the three ditungsten biscarbene complexes are reported and their structural features compared. The methyl substituents on the condensed heteroaromatic rings play an important role in determining the molecular configurations.

scholarly journals Unravelling the diversity of glycoside hydrolase family 13 α-amylases from Lactobacillus plantarum WCFS1

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Laura Plaza-Vinuesa ◽  
Oswaldo Hernandez-Hernandez ◽  
F. Javier Moreno ◽  
Blanca de las Rivas ◽  
Rosario Muñoz
Keyword(s):  
Lactobacillus Plantarum ◽  
Glycoside Hydrolase ◽  
Catalytic Efficiency ◽  
Hydrolytic Activity ◽  
Structural Features ◽  
Biochemical Properties ◽  
Glycoside Hydrolase Family ◽  
Reaction Conditions ◽  
Genes Encoding ◽  
Hydrolysis Of

Abstract Background α-Amylases specifically catalyse the hydrolysis of the internal α-1, 4-glucosidic linkages of starch. Glycoside hydrolase (GH) family 13 is the main α-amylase family in the carbohydrate-active database. Lactobacillus plantarum WCFS1 possesses eleven proteins included in GH13 family. Among these, proteins annotated as maltose-forming α-amylase (Lp_0179) and maltogenic α-amylase (Lp_2757) were included. Results In this study, Lp_0179 and Lp_2757 L. plantarum α-amylases were structurally and biochemically characterized. Lp_2757 displayed structural features typical of GH13_20 subfamily which were absent in Lp_0179. Genes encoding Lp_0179 (Amy2) and Lp_2757 were cloned and overexpressed in Escherichia coli BL21(DE3). Purified proteins showed high hydrolytic activity on pNP-α-D-maltopyranoside, being the catalytic efficiency of Lp_0179 remarkably higher. In relation to the hydrolysis of starch-related carbohydrates, Lp_0179 only hydrolysed maltopentaose and dextrin, demonstrating that is an exotype glucan hydrolase. However, Lp_2757 was also able to hydrolyze cyclodextrins and other non-cyclic oligo- and polysaccharides, revealing a great preference towards α-1,4-linkages typical of maltogenic amylases. Conclusions The substrate range as well as the biochemical properties exhibited by Lp_2757 maltogenic α-amylase suggest that this enzyme could be a very promising enzyme for the hydrolysis of α-1,4 glycosidic linkages present in a broad number of starch-carbohydrates, as well as for the investigation of an hypothetical transglucosylation activity under appropriate reaction conditions.

A Recent Review on Drug Modification Using 1,2,3-triazole

2020 ◽  
Vol 14 (2) ◽  
pp. 71-87
Author(s):  
Adarsh Sahu ◽  
Preeti Sahu ◽  
Ramkishore Agrawal
Keyword(s):  
Structural Features ◽  
Molecular Hybridization ◽  
Molecular Fragments ◽  
Reaction Conditions ◽  
Widespread Occurrence ◽  
Drug Discovery And Development ◽  
Bioisosteric Replacement ◽  
Anti Cancer ◽  
Medicinal Properties ◽  
Drug Modification

Motivated by evidence garnered from literature probing the use of triazoles in drug discovery and development, we reported the utilization of bioisosteric replacement and molecular hybridization in this review. Bio-isosteric replacement has played a significant role in modulating rapid and versatile strategy in synthesizing molecules with multifaceted medicinal properties. Molecular hybridization seeks to conjugate two molecular fragments with diverse applications under very mild reaction conditions. In this regard, 1,2,3-triazole is a well-known scaffold with widespread occurrence in medicinal compounds. It is characterized to have several bioactivities such as anti-microbial, anti-cancer, anti-viral, analgesic, anti- inflammatory effects. Furthermore, the structural features of 1,2,3-triazoles enable it to mimic different functional groups justifying its use as bio-isostere for the synthesis of new molecules of medicinal interest, which we have reported briefly.

scholarly journals Exploring the scope of DBU-promoted amidations of 7-methoxycarbonylpterin

2020 ◽  
Vol 16 ◽  
pp. 509-514 ◽  
Author(s):  
Anna R Bockman ◽  
Jeffrey M Pruet
Keyword(s):  
Reaction Kinetics ◽  
Structural Features ◽  
Product Formation ◽  
Reaction Conditions ◽  
First Order ◽  
First Order Kinetics ◽  
Synthetic Utility ◽  
Pseudo First Order ◽  
Pteridine Derivatives

The synthetic utility of pterins is often hampered by the notorious insolubility of this heterocycle, slowing the development of medicinally relevant pteridine derivatives. Reactions which expedite the development of new pterins are thus of great importance. Through a dual role of diazabicycloundecene (DBU), 7-carboxymethylpterin is converted to the soluble DBU salt, with additional DBU promoting an ester-to-amide transformation. We have explored this reaction to assess its scope and identify structural features in the amines which significantly affect success, monitored the reaction kinetics using a pseudo-first order kinetics model, and further adapted the reaction conditions to allow for product formation in as little as 5 min, with yields often >80%.

Postconsumer Plastic Waste Over Post-Use Cracking Catalysts for Producing Hydrocarbon Fuels

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Yeuh-Hui Lin ◽  
Ta-Tung Wei ◽  
Mu-Hoe Yang ◽  
Sheau-Long Lee
Keyword(s):  
Catalyst Deactivation ◽  
Ambient Pressure ◽  
Reaction System ◽  
Catalytic Degradation ◽  
Plastic Waste ◽  
Conservation Of Resources ◽  
Reaction Conditions ◽  
Fcc Catalyst ◽  
Fcc Catalysts ◽  
Cracking Catalysts

The recycling of plastic waste is important both in the conservation of resources and the environment. A plastic waste (polyethylene(PE)/polypropylene(PP)/polystyrene(PS)/polyvinyl chloride(PVC)) was pyrolyzed over a series of post-use fluid catalytic cracking (FCC) catalysts using a fluidizing reaction system similar to the FCC process operating isothermally at ambient pressure. Experiments carried out with these catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A model based on kinetic considerations associated with chemical reactions and catalyst deactivation in the catalytic degradation of plastics has been developed. Greater product selectivity was observed with a hybrid catalyst (SAHA/CAT-R1) of amorphous silica-aluminas (SAHA) and a recycle FCC catalyst with regeneration (CAT-R1) with more than 68.6 wt. % olefins products. It is demonstrated that the catalytic degradation of postconsumer plastics over these recycled catalysts using fluidizing cracking reactions was shown to be a useful method for the production of potentially valuable hydrocarbons.

scholarly journals Riley Oxidation of Heterocyclic Intermediates on Paths to Hydroporphyrins—A Review

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1858 ◽  
Author(s):  
Pengzhi Wang ◽  
Jonathan S. Lindsey
Keyword(s):  
Structural Features ◽  
Reaction Conditions ◽  
Selenium Species ◽  
Broad Scope ◽  
Riley Oxidation ◽  
High Yields ◽  
Comparison Of The Results

Riley oxidation of advanced heterocyclic intermediates (dihydrodipyrrins and tetrahydrodipyrrins) is pivotal in routes to synthetic hydroporphyrins including chlorins, bacteriochlorins, and model (bacterio)chlorophylls. Such macrocycles find wide use in studies ranging from energy sciences to photomedicine. The key transformation (–CH3 → –CHO) is often inefficient, however, thereby crimping the synthesis of hydroporphyrins. The first part of the review summarizes 12 representative conditions for Riley oxidation across diverse (non-hydrodipyrrin) substrates. An interlude summarizes the proposed mechanisms and provides context concerning the nature of various selenium species other than SeO2. The second part of the review comprehensively reports the conditions and results upon Riley oxidation of 45 1-methyltetrahydrodipyrrins and 1-methyldihydrodipyrrins. A comparison of the results provides insights into the tolerable structural features for Riley oxidation of hydrodipyrrins. In general, Riley oxidation of dihydrodipyrrins has a broad scope toward substituents, but proceeds in only modest yield. Too few tetrahydrodipyrrins have been examined to draw conclusions concerning scope. New reaction conditions or approaches will be required to achieve high yields for this critical transformation in the synthesis of hydroporphyrins.

scholarly journals Pteridines CII Synthesis and Characterization of Dimeric Lumazines

Pteridines ◽  
1994 ◽  
Vol 5 (4) ◽  
pp. 121-141 ◽  
Author(s):  
Ashok Koul ◽  
Thomas Wagner ◽  
Wolfgang Pfleiderer
Keyword(s):  
Zinc Dust ◽  
Structural Features ◽  
Synthesis And Characterization ◽  
Reaction Conditions ◽  
X Ray ◽  
Dihydro Derivative ◽  
Elemental Analyses ◽  
Spectra Properties ◽  
Dimerization Reaction

Summary Reduction of 1.3-dimethyllumazine (1) by zinc dust in Ac2O/AcOH leads to the formation of 6-7 connected bis-Iumazinyl derivatives. Depending on the reaction conditions either 7 -(5-acetyl-5,6, 7,8-tetrahydro-1.3-dimethyllumazin- 6-yl)-l, 3-dimethyllumazin (3) or isomeric 7 -(5-acetyl-5.6. 7.8-tetrahydro-I. 3-dimethyllumazin- 6-yl)-5-acetyl-5,6,7,8-tetrahydro-I. 3-dimethyllumazines (2) are formed . Treatment of 3 with MeOH/HCl gave 4 which is oxidized by air to a very stable 7.8-dihydro derivative 5 showing unexpected spectra properties. Further oxidation by KMnO. afforded 6.1 -bis-I. 3-dimethyllumazinyl (6). The isomeric 6.6-(14) and 7.7 -bis-I. 3-dimethyllumazinyls (21) were also synthesized from 6-chloro-(1l) and I-chloro-I. 3-dimethyllu-mazine (18). respectively. in a nickel catalyzed dimerization reaction. The various structures were proven by spectral means. elemental analyses and an X-ray analysis of 2. Comparisons of the structural features are mainly based on UV data.

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