scholarly journals Amidation Reaction System: Kinetic Studies and Improvement by Product Removal

ACS Omega ◽  
2021 ◽  
Author(s):  
Issadaporn Wongwanichkangwarn ◽  
Sunun Limtrakul ◽  
Terdthai Vatanatham ◽  
Palghat A. Ramachandran
Keyword(s):  
Reaction System ◽  
Kinetic Studies ◽  
Product Removal ◽  
Amidation Reaction

Investigations into the Silica/Silane Reaction System

1997 ◽  
Vol 70 (4) ◽  
pp. 608-623 ◽  
Author(s):  
Udo Goerl ◽  
Andrea Hunsche ◽  
Arndt Mueller ◽  
H. G. Koban
Keyword(s):  
Silica Surface ◽  
Reaction System ◽  
Rolling Resistance ◽  
Kinetic Studies ◽  
Reaction Model ◽  
Secondary Reaction ◽  
Primary Reaction ◽  
Silanol Groups ◽  
Precipitated Silica ◽  
Low Concentrations

Abstract Silica in combination with organosilanes (e.g. [bis(3-triethoxysilylpropyl)tetrasulfane] = TESPT) has recently become more important in tire applications. Their use in tire treads leads to an improvement in rolling resistance and wet traction. The requirements for the attainment of these properties are, that the triethoxysilyl groups of TESPT react with the silanol groups on the silica surface during compounding, and the polymer active groups react with the polymer during cure. The reaction of precipitated silica with this silane was investigated. The influence of various parameters on the reaction type and the reaction kinetics was considered. The results of the investigation obtained using 29Si-CP/MAS solid state NMR spectroscopy agree well with a horizontal reaction model in which a single siloxane bond is first formed with the silica surface (primary reaction). It is followed by condensation reactions between silanol groups of silane molecules which are already bound to the silica surface (secondary reaction). The kinetic studies data show a clear difference between the fast primary reaction and the slow secondary reaction. Both reactions become more rapid in acidic and alkaline pH ranges. The primary reaction accelerates up to a particular H2O content after which the rate remains constant. The secondary reaction keeps on accelerating with rising H2O content. Modification with different silane concentrations showed a higher rate constant at low concentrations.

scholarly journals Biodegradation of 1,2,3-Trichloropropane to Valuable (S)-2,3-DCP Using a One-Pot Reaction System

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 3 ◽  
Author(s):  
Tadesse Fantaye Bogale ◽  
Ijaz Gul ◽  
Le Wang ◽  
Jiao Deng ◽  
Yong Chen ◽  
...  
Keyword(s):  
Batch Reactor ◽  
Scale Up ◽  
Environmental Pollutants ◽  
Reaction System ◽  
Liquid Waste ◽  
One Pot ◽  
Original Activity ◽  
Product Removal ◽  
Enantioselective Resolution ◽  
Carcinogenic Effects

1,2,3-trichloropropane (TCP) being one of the important environmental pollutants, has drawn significant concern due to its highly toxic and carcinogenic effects. In this study, we built a one-pot reaction system in which immobilized haloalkane dehalogenase (DhaA31) and halohydrin dehalognase (HheC) were used to catalyze the recalcitrant TCP to produce 2,3-dichloro-1-propanol (2,3-DCP) by removing epichlorohydrin (ECH). Since HheC displays a high R enantiopreference toward 2,3-DCP, the production of enantiopure (S)-2,3-DCP was expected. However, the enantioselective resolution of (R,S)-2,3-DCP by HheC was greatly inhibited by the circular reaction occurring between the product ECH and 1,3-dichloro-2-propanol (1.3-DCP). To resolve this problem, HZD-9 resin-based in situ product removal was implemented. Under the optimized conditions, TCP was completely consumed, resulting in optically pure (S)-2,3-DCP with enantiomer excess (e.e) > 99% and 40% yield (out of the 44% theoretical maximum). The scale-up resin-integrated reaction system was successfully carried out in 0.5 L batch reactor. Moreover, the system could be reused for 6 rounds with 64% of original activity retained, showing that it could be applied in the treatment of large volumes of liquid waste and producing enantiopure (S)-2,3-DCP.

scholarly journals The Role of Reaction Engineering in Bioprocess Development

2020 ◽  
Vol 74 (5) ◽  
pp. 378-381 ◽  
Author(s):  
Udo Kragl
Keyword(s):  
Reaction System ◽  
Short Review ◽  
Product Inhibition ◽  
Reaction Engineering ◽  
Kinetic Properties ◽  
Oxidation Reactions ◽  
Bioprocess Development ◽  
Product Removal ◽  
Reaction Cascades

This short review highlights the role of reaction engineering as a tool for bioprocess development. Selected examples are discussed that demonstrate the need to understand thermodynamic and kinetic properties of the reaction system in order to identify potential bottlenecks. For coupled enzyme systems and reaction cascades modelling as well as selection of suitable reactor configurations is discussed. For the problem of overcoming product inhibition examples are given, followed by selected examples for in situ product removal. Finally, two reactor concepts for oxidation reactions requiring oxygen are briefly presented.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

Tc-99m Labeled Complexes of Aldehydes and Glutamate as Cholescintigraphic Agents

1975 ◽  
Vol 14 (04) ◽  
pp. 330-338
Author(s):  
L. G. Colombetti ◽  
J. S. Arnold ◽  
W. E. Barnes
Keyword(s):  
Nuclear Medicine ◽  
Gall Bladder ◽  
Rose Bengal ◽  
Valence State ◽  
Monosodium Glutamate ◽  
Kinetic Studies ◽  
Scintillation Camera ◽  
Blood Clearance ◽  
Lower Valence ◽  
Wire Basket

SummaryTc-99m pyridoxylidene glutamate has proven to be an excellent biliary scanning agent, far superior in many respect to the commonly used 1-131 rose bengal. The preparation of the compound as previously reported by Baker et al is too time consuming and requires the use of an autoclave which is not available in most nuclear medicine departments. In our facility, we have been preparing similar compounds using several aldehydes and monosodium glutamate to make labeled complexes having the same pharmacological characteristics. The mixture of monosodium glutamate, aldehyde, and Tc-99m pertechnetate is made slightly alkaline, purged with helium, and placed in a sealed vial. The vial, which is protected by a wire basket, is then heated in a laboratory oven at 130° C for a period of 15 to 20 minutes. During this time, the technetium is reduced to a lower valence state and bound to the complex formed. Chromatographic data show that these compounds are chemically similar to that previously reported. The compounds prepared concentrate in the gall bladder of the rabbit in less than 10 minutes. Kinetic studies have been performed on dogs with a scintillation camera and small digital computer to measure rates of blood clearance, liver and gall bladder uptake, and excretion into the intestine. The aldehyde — glutamate complex promises to be a useful scanning agent for the diagnosis of biliary and hepatocellular diseases.

Factor V from Human Plasma

1961 ◽  
Vol 05 (01) ◽  
pp. 001-020
Author(s):  
Douglas M. Surgenor ◽  
Nancy A. Wilson ◽  
Anne S. Henry
Keyword(s):  
Human Serum ◽  
Human Plasma ◽  
Kinetic Data ◽  
Human Factor ◽  
Kinetic Studies ◽  
Partial Purification ◽  
Factor V ◽  
Two Stage ◽  
Plasma Factor ◽  
Tissue Thromboplastin

SummaryA method is described for the partial purification of a human plasma factor which accelerates the conversion of prothrombin to thrombin in the presence of tissue thromboplastin. This factor may be dried from the frozen state, and may be kept in stable dry form for long periods of time. The quantitative assay of this activity is done in a classical two-stage prothrombin system using tissue thromboplastin and calcium. From its properties, it is concluded that this activity corresponds to factor V, labile factor and plasma Ac-globulin.Chemical and kinetic studies reveal that human factor V is active in plasma and is destroyed by thrombin. Human serum has little or no factor V activity.These results thus fail to support the postulated activation of factor V during clotting. All of the kinetic data are consistent with an enzymatic role for factor V in the formation of tissue prothrombin activator (thromboplastin).

Preparation of a Viable Population of Indium-111- Labelled Human Blood Platelets

1979 ◽  
Vol 42 (05) ◽  
pp. 1473-1482 ◽  
Author(s):  
A Dup Heyns ◽  
P N Badenhorst ◽  
H Pieters ◽  
M G Lötter ◽  
P C Minnaar ◽  
...  
Keyword(s):  
Platelet Rich Plasma ◽  
Blood Platelets ◽  
Kinetic Studies ◽  
Physiological Saline ◽  
Human Platelets ◽  
Autologous Plasma ◽  
Platelet Suspension ◽  
Viable Population ◽  
Indium 111

SummaryFactors influencing labelling of human platelets with 111Indium-8-hydroxyquinoline ([111In]-oxine) in a physiological saline medium were investigated. The efficiency of labelling is influenced by time of incubation, concentration of oxine, and pH of the incubating medium. It was found that a viable platelet population could be labelled under the following conditions: (1) centrifugation of platelet rich plasma in polystyrene conical tubes at 800 g for 15 min; (2) resuspension of the platelet pellet in saline, pH 5.5; (3) incubating for 30 min at 22°C with [111In]-oxine at a concentration of 6.25 mg oxine/litre platelet suspension; (4) washing once with platelet poor autologous plasma (PPP); and (5) finally resuspending the platelets in PPP. The labelled platelets aggregated normally with collagen and ADP. Electron microscopy, done immediately after labelling, showed internal organelle reorganization characteristic of activated platelets. These ultrastructural features were reversible on incubation in PPP at 37°C for 30 min. The 111In is not released from aggregated platelets and the label does not elute from incubated platelets for at least five hr. We conclude that human platelets thus labelled are suitable for in vivo kinetic studies.

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