Lignin peroxidase initiates O2-dependent self-propagating chemical reactions which accelerate the consumption of 1-(3′,4′-dimethoxyphenyl)propene

2000 ◽  
Vol 347 (2) ◽  
pp. 585-591 ◽  
Author(s):  
Rimko TEN HAVE ◽  
Maurice C. R. FRANSSEN ◽  
Jim A. FIELD
Keyword(s):  
Chemical Reactions ◽  
Lignin Peroxidase ◽  
Metal Ion ◽  
Consumption Rate ◽  
Peroxyl Radicals ◽  
Side Chain ◽  
Coupling Reactions ◽  
Air Atmosphere ◽  
Aromatic Substrates ◽  
Consumption Rates

Lignin peroxidase (LiP) has been used to study the Cα-Cβ cleavage of the propylene side chain in 1-(3ʹ,4ʹ-dimethoxyphenyl)propene (DMPP) to 3,4-dimethoxybenzaldehyde (veratraldehyde, VAD). Under an air atmosphere, LiP oxidized DMPP to VAD (27.8%) and 1-(3ʹ,4ʹ-dimethoxyphenyl)propan-2-one (DMPA, 8.7%), after 10 min of incubation. Dissolved O2 was rapidly consumed during DMPP conversion, of which one-third was converted into superoxide. The remaining two-thirds of the consumed O2 was involved in Cα-Cβ cleavage of DMPP to VAD and in self-propagating chemical reactions stimulating the consumption of DMPP. The involvement of peroxyl radicals, in the chemical consumption of DMPP, was confirmed by using the well-known peroxyl radical reductant Mn2+. This metal ion severely inhibited the DMPP consumption rate under air, but did not affect the lower enzymic DMPP consumption rate under N2. The substoichiometric requirement of LiP for H2O2 during DMPP oxidation could be explained in part by dismutation of superoxide, but more importantly by direct chemical reactions of DMPP-derived peroxyl radicals with fresh DMPP. Another VAD-producing route was found by incubating the DMPP oxidation product, DMPA, with LiP. Under air the molar yield of VAD was 29.7%. In the absence of O2, the Cα-Cβ cleavage of DMPA to VAD was strongly inhibited and side-chain coupling products (dimers) were formed instead. As a whole, the results suggest two new roles of O2 in LiP-mediated oxidation of aromatic substrates. First, O2 is responsible for the formation of reactive peroxyl intermediates, which can directly react with other substrate molecules and thereby accelerate consumption rates. Secondly, O2 can prevent coupling reactions by lowering the pool of carbon-centred radicals accumulating during LiP catalysis.

Synthesis of covalent organic frameworks via in situ salen skeleton formation for catalytic applications

2019 ◽  
Vol 7 (10) ◽  
pp. 5482-5492 ◽  
Author(s):  
He Li ◽  
Xiao Feng ◽  
Pengpeng Shao ◽  
Jian Chen ◽  
Chunzhi Li ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Metal Ion ◽  
Cycloaddition Reactions ◽  
Styrene Epoxidation ◽  
Facile Synthesis ◽  
Air Atmosphere ◽  
Catalytic Applications ◽  
Isolation Effects ◽  
Skeleton Formation

A facile synthesis of COF-salen via in situ salen skeleton formation under air atmosphere is described herein. COF-salen–M prepared via metal ion coordination could efficiently catalyse chemical reactions, e.g. styrene epoxidation, epoxide hydration and cycloaddition reactions of epoxides with CO2. More interestingly, both cooperation and isolation effects were observed in COF-salen–M.

scholarly journals Biosynthesis of the modified tetrapyrroles—the pigments of life

2020 ◽  
Vol 295 (20) ◽  
pp. 6888-6925 ◽  
Author(s):  
Donald A. Bryant ◽  
C. Neil Hunter ◽  
Martin J. Warren
Keyword(s):  
Chemical Reactions ◽  
Metal Ion ◽  
Side Chain ◽  
Vitamin B ◽  
Metal Chelation ◽  
Macrocyclic Compounds ◽  
Comparative Biochemistry ◽  
Chain Composition ◽  
Almost All ◽  
Life On Earth

Modified tetrapyrroles are large macrocyclic compounds, consisting of diverse conjugation and metal chelation systems and imparting an array of colors to the biological structures that contain them. Tetrapyrroles represent some of the most complex small molecules synthesized by cells and are involved in many essential processes that are fundamental to life on Earth, including photosynthesis, respiration, and catalysis. These molecules are all derived from a common template through a series of enzyme-mediated transformations that alter the oxidation state of the macrocycle and also modify its size, its side-chain composition, and the nature of the centrally chelated metal ion. The different modified tetrapyrroles include chlorophylls, hemes, siroheme, corrins (including vitamin B12), coenzyme F430, heme d1, and bilins. After nearly a century of study, almost all of the more than 90 different enzymes that synthesize this family of compounds are now known, and expression of reconstructed operons in heterologous hosts has confirmed that most pathways are complete. Aside from the highly diverse nature of the chemical reactions catalyzed, an interesting aspect of comparative biochemistry is to see how different enzymes and even entire pathways have evolved to perform alternative chemical reactions to produce the same end products in the presence and absence of oxygen. Although there is still much to learn, our current understanding of tetrapyrrole biogenesis represents a remarkable biochemical milestone that is summarized in this review.

Base-Free Synthesis and Synthetic Application of Novel 3-(organochalcogenyl)prop-2-yn-1-yl Esters: Promising Anticancer Agents

Synthesis ◽  
2021 ◽  
Author(s):  
Fabiane Gritzenco ◽  
Jean Carlo Kazmierczak ◽  
Thiago Anjos ◽  
Adriane Sperança ◽  
Maura Luise Bruckchem Peixoto ◽  
...  
Keyword(s):  
Anticancer Agents ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Chalcogen Bond ◽  
Cross Coupling Reactions ◽  
Air Atmosphere ◽  
Carbon Carbon Bonds ◽  
Palladium Catalyzed ◽  
Synthetic Application

This manuscript portrays the CuI-catalyzed Csp-chalcogen bond formation through cross-coupling reactions of propynyl esters and diorganyl dichalcogenides by using DMSO as solvent, at room temperature, under base-free and open-to-air atmosphere. Generally, the reactions have proceeded very smoothly, being tolerant to range of substituents present in both substrates, affording the novel 3-(organochalcogenyl)prop-2-yn-1-yl esters in moderate to good yields. Noteworthy, the 3-(butylselanyl)prop-2-yn-1-yl benzoate proved to be useful as synthetic precursor in palladium-catalyzed Suzuki and Sonogashira type cross-coupling reactions by replacing the carbon-chalcogen bond by new carbon-carbon bonds. Moreover, the 3-(phenylselanyl)prop-2-yn-1-yl benzoate has shown promising in vitro activity against glioblastoma cancer cells.

Room-Temperature, Water-Promoted, Radical-Coupling Reactions of Phenols with tert-Butyl Nitrite

Synlett ◽  
2017 ◽  
Vol 28 (16) ◽  
pp. 2153-2156 ◽  
Author(s):  
Wen-Ting Wei ◽  
Hongze Liang ◽  
Wen-Ming Zhu ◽  
Weida Liang ◽  
Yi Wu ◽  
...  
Keyword(s):  
Room Temperature ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Phenol Derivative ◽  
Tert Butyl ◽  
Radical Coupling ◽  
Air Atmosphere ◽  
Cross Coupling Reaction ◽  
Temperature Water

A radical–radical cross-coupling reaction of phenols with tert-butyl nitrite has been developed with the use of water as an additive. This method allows the construction of C–N bonds under an air atmosphere at room temperature, providing the ortho-nitrated phenol derivative in moderate to good yields.

A simple and efficient synthesis of 5′-(2H3)olivetol

1987 ◽  
Vol 65 (1) ◽  
pp. 189-190 ◽  
Author(s):  
Michel Girard ◽  
David B. Moir ◽  
John W. ApSimon
Keyword(s):  
Title Compound ◽  
Cross Coupling ◽  
Side Chain ◽  
Coupling Reactions ◽  
Efficient Synthesis ◽  
Cross Coupling Reactions

The title compound 1 was prepared in 13% overall yield starting from the commercially available and inexpensive 3,5-dimethoxybenzoic acid (4). The n-pentyl side chain was elaborated from cross-coupling reactions between halides.

Estimating oxygen consumption rates of arteriolar walls under physiological conditions in rat skeletal muscle

2005 ◽  
Vol 289 (1) ◽  
pp. H295-H300 ◽  
Author(s):  
Masahiro Shibata ◽  
Shigeru Ichioka ◽  
Akira Kamiya
Keyword(s):  
Vascular Tone ◽  
Consumption Rate ◽  
Vascular Wall ◽  
Surrounding Tissue ◽  
Phosphorescence Quenching ◽  
Physiological Conditions ◽  
First Order ◽  
Vascular Walls ◽  
Consumption Rates

To examine the effects of vascular tone reduction on O2 consumption of the vascular wall, we determined the O2 consumption rates of arteriolar walls under normal conditions and during vasodilation induced by topical application of papaverine. A phosphorescence quenching technique was used to quantify intra- and perivascular Po2 in rat cremaster arterioles with different branching orders. Then, the measured radial Po2 gradients and a theoretical model were used to estimate the O2 consumption rates of the arteriolar walls. The vascular O2 consumption rates of functional arterioles were >100 times greater than those observed in in vitro experiments. The vascular O2 consumption rate was highest in first-order (1A) arterioles, which are located upstream, and sequentially decreased downstream in 2A and 3A arterioles under normal conditions. During papaverine-induced vasodilation, on the other hand, the O2 consumption rates of the vascular walls decreased to similar levels, suggesting that the high O2 consumption rates of 1A arterioles under normal conditions depend in part on the workload of the vascular smooth muscle. These results strongly support the hypothesis that arteriolar walls consume a significant amount of O2 compared with the surrounding tissue. Furthermore, the reduction of vascular tone of arteriolar walls may facilitate an efficient supply of O2 to the surrounding tissue.

scholarly journals Comparative Study of a Powerplant Life Consumption Rate When Installed in Two Different Aircraft Variants

Aerospace ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 327
Author(s):  
Ioannis Templalexis ◽  
Ioannis Lionis ◽  
Nikolaos Christou
Keyword(s):  
Air Force ◽  
Consumption Rate ◽  
Low Cycle Fatigue ◽  
Rotor Blades ◽  
Parameter Method ◽  
Great Level ◽  
Consumption Rates ◽  
Life Consumption ◽  
Mission Profile ◽  
Engine Life

The Hellenic Air Force (HAF) operates both EMB-145 and EMB-135 LR versions of Embraer aircraft, used in surveillance and civil missions respectively. These aircraft are equipped with the same version of Rolls Royce, AE 3007 turbofan engine. This study aims to quantify and compare the life consumption rate of this engine when installed in each of the two aircraft variants. Two typical missions, one for each variant, were constructed based on mission profile data dictated by the aircraft commanders. For each mission profile segment, corresponding engine data were matched out of the engine recordings archives held by the Hellenic Air Force. The life consumption rate was based on the Low Cycle Fatigue (LCF) and creep cumulative detrimental effect on the rotor blades of the 1st High-Pressure Turbine stage. For the LCF, the rainflow method was used to determine the respective loading cycles, whereas the Larson - Miller parameter method was used to determine the consumed life fractions due to creep. The main conclusion of the study was that the engine when installed in the EMB-145 military variant, is much more loaded. Despite the fact absolute life consumption values could hide a great level of uncertainty, the comparative outcomes wherein errors are, to a certain extent, cancelled out, could be used as a rule of thumb when monitoring engine life consumption rates.

scholarly journals Design and Analysis of a Modified-atmosphere Package for Minimally Processed Romaine Lettuce

1996 ◽  
Vol 121 (4) ◽  
pp. 722-729 ◽  
Author(s):  
Kevin I. Segall ◽  
Martin G. Scanlon
Keyword(s):  
Shelf Life ◽  
Consumption Rate ◽  
Modified Atmosphere Packaging ◽  
Modified Atmosphere ◽  
Packaging Film ◽  
Romaine Lettuce ◽  
Minimally Processed ◽  
Headspace Gas ◽  
Consumption Rates ◽  
Critical Choice

The first goal of this study was to determine the packaging film O2 permeability required to maintain a steady-state O2 concentration of 3% in modified-atmosphere packaging (MAP) of minimally processed romaine lettuce (Lactuca sativa L.). The second goal of the study was to determine the extent to which MAP could preserve lettuce quality and consequently extend product shelf life. Oxygen consumption rates of commercially prepared lettuce samples were determined in a closed system for each of three atmospheres (3% O2 combined with either 6%, 10%, or 14% CO2). Enzymatic, quadratic, and linear mathematical models were compared to determine which best described the respiratory data. The linear model was the most suitable and was used to predict the O2 consumption rate of the minimally processed romaine lettuce under the desired package headspace gas concentrations. The predicted O2 consumption rate was used to calculate the necessary O2 permeability for the packaging film. Packages (21.6 × 25.4 cm) were constructed from a polypropylene-polyethylene-laminate film with the appropriate O2 permeability. Packaged samples were stored under three modified atmospheres (MAs) (3% O2 combined with either 6%, 10%, or 14% CO2) for 20 days, and headspace gas concentrations, lettuce appearance, and color were evaluated every other day. Growth of pectinolytic and lactic acid bacteria was also studied. The O2 consumption rate of the lettuce decreased with increasing CO2 levels. The O2 levels in the MA packages equilibrated at 7% to 11%. Compared to a control atmosphere of air, MAP delayed the development of tissue discoloration. Preliminary results indicated no effect of MAP on microbial growth. Of the three CO2 levels, 10% was slightly more effective than 6% and 14%. Critical choice of packaging permeabilities combined with MAP maintained the quality of minimally processed romaine lettuce and thereby increased shelf life by about 50%.

Performance evaluation of throat type updraft biomass gasifier using different biomass fuels

2021 ◽  
Vol 45 (03) ◽  
pp. 6-12
Author(s):  
D. K. Vyas ◽  
J. Sravankumar ◽  
J. J. Chavda
Keyword(s):  
Power Generation ◽  
Carbon Monoxide ◽  
Chemical Process ◽  
Consumption Rate ◽  
Calorific Value ◽  
Producer Gas ◽  
Saw Dust ◽  
Consumption Rates ◽  
Maize Cobs ◽  
Agro Residues

A biomass gasifier converts solid fuel such as wood waste, saw-dust briquettes and agro-residues into a gaseous fuel through a thermo-chemical process and the resultant gas can be used for thermal and power generation applications. The present research aims to evaluate the updraft biomass gasifier using different biomass for thermal application. The capacity of updraft gasifier was a 5-10 kg.h-1 and three types of biomass: maize cobs, sized wood and saw dust briquettes were used as fuel for producing producer gas by thermal application. The maximum carbon monoxide (CO), hydrogen (H2) and Methane (CH4) found were 14.8, 12.7 and 3.9%, 14.6, 13.7 and 3.9 % and 14.2, 13.5 and 3.9% at 5 kg.h-1 biomass consumption rate, respectively using maize cobs, sized wood and saw dust briquettes as fuel. The maximum and minimum producer gas calorific value was found 1120 and 1034 kcal.m-3; 1139 and 1034 kcal.m-3 and 1123 and 1036 kcal.m-3 at biomass consumption rate of 5 and 10 kg.h-1 using maize cobs, sized wood and saw dust briquettes as fuel respectively. The maximum gasifier efficiency of 77.94, 70.26 and 69.60% was found at the biomass consumption rate of 5 kg.h-1 using maize cobs, sized wood and saw dust briquettes as fuel, respectively. The minimum gasifier efficiency of 72.72, 64.49 and 64.90 % was found at the biomass consumption rate of 10 kg.h-1 using maize cobs, sized wood and saw dust briquettes as fuel in the system, respectively. The maximum overall thermal efficiency of 29.60, 30.65 and 23.69 % were found at the biomass consumption rates of 8, 7 and 7 kg.h-1 using maize cobs, sized wood and saw dust briquettes, respectively.

A comparison of the gill physiology of two euryhaline crab species, Callinectes sapidus and Callinectes similis: energy production, transport-related enzymes and osmoregulation as a function of acclimation salinity

1995 ◽  
Vol 198 (2) ◽  
pp. 349-358 ◽  
Author(s):  
S Piller ◽  
R Henry ◽  
J Doeller ◽  
D Kraus
Keyword(s):  
Oxygen Consumption ◽  
Energy Production ◽  
Consumption Rate ◽  
Callinectes Sapidus ◽  
Crab Species ◽  
Ion Concentrations ◽  
Low Salinity ◽  
Consumption Rates ◽  
Cytochrome Content ◽  
Mitochondrial Cytochromes

Callinectes sapidus and C. similis co-occur in estuarine waters above 15 salinity. Callinectes sapidus also inhabits more dilute waters, but C. similis is rarely found below 15 . Previous work suggests that C. sapidus may be a better hyperosmoregulator than C. similis. In this study, energy metabolism and the levels of transport-related enzymes in excised gills were used as indicators of adaptation to low salinity. Oxygen consumption rates and mitochondrial cytochrome content of excised gills increased in both species as acclimation salinity decreased, but to a significantly greater extent in C. similis gills. In addition, C. similis gills showed the same levels of carbonic anhydrase and Na+/K+-ATPase activities and the same degree of enzyme induction during low-salinity adaptation as has been reported for C. sapidus gills. However, hemolymph osmolality and ion concentrations were consistently lower in C. similis at low salinity than in C. sapidus. Therefore, although gills from low-salinity-acclimated C. similis have a higher oxygen consumption rate and more mitochondrial cytochromes than C. sapidus gills and the same level of transport-related enzymes, C. similis cannot homeostatically regulate their hemolymph to the same extent as C. sapidus.

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