Search results for " kinetic"
showing 10 items of 416 documents
Why Are Some Enzymes Dimers? Flexibility and Catalysis in Thermotoga maritima Dihydrofolate Reductase
2019
[Image: see text] Dihydrofolate reductase from Thermotoga maritima (TmDFHFR) is a dimeric thermophilic enzyme that catalyzes the hydride transfer from the cofactor NADPH to dihydrofolate less efficiently than other DHFR enzymes, such as the mesophilic analogue Escherichia coli DHFR (EcDHFR). Using QM/MM potentials, we show that the reduced catalytic efficiency of TmDHFR is most likely due to differences in the amino acid sequence that stabilize the M20 loop in an open conformation, which prevents the formation of some interactions in the transition state and increases the number of water molecules in the active site. However, dimerization provides two advantages to the thermophilic enzyme: …
Changes in ewe milk fatty acids following turning out to pasture
2008
Abstract Ten Comisana dairy ewes were selected to observe time of changing in milk fatty acids as a result of switching from stall to pasture feeding. At first, ewes were subjected to a stall-feeding period of 30 days (pre-experimental phase). After which, ewes were abruptly turned out to a vetch and oats pasture as their sole feed (experimental phase). Individual milk samples were collected on experimental days 0 (the last day of stall feeding), 1–4, 8, 11, 17 and 23. Milk and feeds fatty acid composition was determined by gas chromatography. The sudden passage from a stall to a pasture diet significantly modified the fatty acid profile of ewe milk. Medium- and long-chain fatty acids were …
Polymerisationskinetische und konduktometrische messungen an polystyrylionenpaaren in einem größeren temperaturbereich
1974
Messungen der Bruttogeschwindigkeitskonstante von Polystyryl-Natrium in 3-Methyltetrahydrofuran (3-Me-THF) in Abhangigkeit von der Konzentration der “lebenden” Kettenenden und der Natriumionen ergeben, das die Monomeraddition wie in anderen polaren Losungsmitteln nach einem Mehrwegmechanismus erfolgt. Der Ubergang vom Kontakt- zum solvatgetrennten Ionenpaar wird in einem Temperaturbereich von — 110 bis +85°CC mit Hilfe kinetischer Messungen im Stromungsrohr und durch Leitf ahigkeitsmessungen verfolgt. Analog zu entsprechenden Untersuchungen in Tetrahydrofuran kann dabei die Polymerisation uber jeweils eine Art von Ionenpaaren fast vollstandig isoliert beobachtet werden. Die thermodynamische…
TEMPERATURE DEPENDENCE OF THE OZONE ABSORPTION KINETICS IN AQUEOUS PHENOL SOLUTIONS
1978
(1978). TEMPERATURE DEPENDENCE OF THE OZONE ABSORPTION KINETICS IN AQUEOUS PHENOL SOLUTIONS. Chemical Engineering Communications: Vol. 2, No. 4-5, pp. 219-221.
Multisensory integration as a strategy to compensate for sodium and fat reduction in food
2012
Multisensory integration as a strategy to compensate for sodium and fat reduction in food. Forum Jeunes chercheurs
From the Classical Boltzmann Equation to the Generalized Kinetic models of Biological Systems
2017
This paper deal with the classical Boltzmann Equation generalized to model populations in complex biological system. In particular, the populations refer to the cells of the immune system and to those of an aggressive host (cancer cells) in a human being. We will focus with the study of a spatially homogeneous continuous model, and derivation of the macroscopic model. The paper starts from a simple description of the classical Boltzmann equation and goes to the mathematical approach proposed to model the large systems of interacting entities focusing the competition between immune system and cancer cells.
On the mechanistic behavior of highly efficient palladium-tetraphosphine catalytic systems for cross-coupling reactions: first spectroscopic and elec…
2008
Electrochemical studies carried out in conjunction with 31P NMR spectroscopy on the palladium(II)/palladium(0) halogeno complexes of the tetraphosphine 1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′-di...
Calcium efflux from human erythrocyte ghosts
1970
The passive Ca efflux from human red cell ghosts was studied in media of differing ion compositions and compared to the ATP-dependent Ca efflux. Cells were loaded with(45)Ca during reversible hemolysis, and the loss of radioactivity into the non-radioactive incubation medium was measured, usually for 3 hr at 37°C. Analysis of the efflux curves revealed that(45)Ca efflux followed the kinetics of a simple two-compartment system. In the concentration range between 0 and 1MM Ca in the external solution ([Ca(++)] o ), the rate constant of passive Ca efflux (k min(-1), fraction of(45)Ca lost per minute into the medium) increased from 0.00732 to 0.0150 min(-1). There was no further increase at hig…
Molecular docking and oxidation kinetics of 3-phenyl coumarin derivatives by human CYP2A13
2021
CYP2A13 enzyme is expressed in human extrahepatic tissues, while CYP2A6 is a hepatic enzyme. Reactions catalysed by CYP2A13 activate tobacco-specific nitrosamines and some other toxic xenobiotics in lungs.To compare oxidation characteristics and substrate-enzyme active site interactions in CYP2A13 vs CYP2A6, we evaluated CYP2A13 mediated oxidation characteristics of 23 coumarin derivatives and modelled their interactions at the enzyme active site.CYP2A13 did not oxidise six coumarin derivatives to corresponding fluorescent 7-hydroxycoumarins. The Km-values of the other coumarins varied 0.85���97 ��M, Vmax-values of the oxidation reaction varied 0.25���60 min���1, and intrinsic clearance var…
In vitro glucuronidation of 7-hydroxycoumarin derivatives in intestine and liver microsomes of Beagle dogs
2019
Beagle dog is a standard animal model for evaluating nonclinical pharmacokinetics of new drug candidates. Glucuronidation in intestine and liver is an important first-pass drug metabolic pathway, especially for phenolic compounds. This study evaluated the glucuronidation characteristics of several 7-hydroxycoumarin derivatives in beagle dog's intestine and liver in vitro. To this end, glucuronidation rates of 7-hydroxycoumarin (compound 1), 7-hydroxy-4-trifluoromethylcoumarin (2), 6-methoxy-7-hydroxycoumarin (3), 7-hydroxy-3-(4-tolyl)coumarin (4), 3-(4-fluorophenyl)coumarin (5), 7-hydroxy-3-(4-hydroxyphenyl)coumarin (6), 7-hydroxy-3-(4-methoxyphenyl)coumarin (7), and 7-hydroxy-3-(1H-1,2,4-t…