Preferential Control of Forward Reaction Kinetics in Hydrogels Crosslinked with Reversible Conjugate Additions

2020 ◽  
Vol 53 (10) ◽  
pp. 3738-3746
Author(s):  
Thomas M. FitzSimons ◽  
Felicia Oentoro ◽  
Tej V. Shanbhag ◽  
Eric V. Anslyn ◽  
Adrianne M. Rosales
Keyword(s):  
Reaction Kinetics ◽  
Forward Reaction ◽  
Conjugate Additions

scholarly journals Elucidating the unusual reaction kinetics of D-glucuronyl C5-epimerase

Glycobiology ◽  
2020 ◽  
Vol 30 (11) ◽  
pp. 847-858 ◽  
Author(s):  
Deepika Vaidyanathan ◽  
Elena Paskaleva ◽  
Troy Vargason ◽  
Xia Ke ◽  
Scott A McCallum ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Enzymatic Reaction ◽  
Chemoenzymatic Synthesis ◽  
Kinetic Behavior ◽  
Forward Reaction ◽  
Steady State Kinetic ◽  
Bioengineered Heparin ◽  
Kinetic Mechanisms ◽  
Anticoagulant Drug ◽  
Kinetics Of

Abstract The chemoenzymatic synthesis of heparin, through a multienzyme process, represents a critical challenge in providing a safe and effective substitute for this animal-sourced anticoagulant drug. D-glucuronyl C5-epimerase (C5-epi) is an enzyme acting on a heparin precursor, N-sulfoheparosan, catalyzing the reversible epimerization of D-glucuronic acid (GlcA) to L-iduronic acid (IdoA). The absence of reliable assays for C5-epi has limited elucidation of the enzymatic reaction and kinetic mechanisms. Real time and offline assays are described that rely on 1D 1H NMR to study the activity of C5-epi. Apparent steady-state kinetic parameters for both the forward and the pseudo-reverse reactions of C5-epi are determined for the first time using polysaccharide substrates directly relevant to the chemoenzymatic synthesis and biosynthesis of heparin. The forward reaction shows unusual sigmoidal kinetic behavior, and the pseudo-reverse reaction displays nonsaturating kinetic behavior. The atypical sigmoidal behavior of the forward reaction was probed using a range of buffer additives. Surprisingly, the addition of 25 mM each of CaCl2 and MgCl2 resulted in a forward reaction exhibiting more conventional Michaelis–Menten kinetics. The addition of 2-O-sulfotransferase, the next enzyme involved in heparin synthesis, in the absence of 3′-phosphoadenosine 5′-phosphosulfate, also resulted in C5-epi exhibiting a more conventional Michaelis–Menten kinetic behavior in the forward reaction accompanied by a significant increase in apparent Vmax. This study provides critical information for understanding the reaction kinetics of C5-epi, which may result in improved methods for the chemoenzymatic synthesis of bioengineered heparin.

Study of C2H5O2 using modulated photolysis: ultra-violet spectrum and self-reaction kinetics in the temperature range 233-363 K

1997 ◽  
Vol 94 ◽  
pp. 484-502
Author(s):  
S Fauvet ◽  
JP Ganne ◽  
J Brion ◽  
D Daumont ◽  
J Malicet ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Ultra Violet ◽  
Temperature Range

SYNTHESIS AND REACTION KINETICS STUDY OF TRI PHENYL PHOSPHITE

2019 ◽  
Vol 2 (2) ◽  
pp. 99-106
Author(s):  
Satish M. Mane ◽  
M. Praharaj Bhatnagar ◽  
M. R. Sawant ◽  
B. N. Thorat
Keyword(s):  
Reaction Kinetics ◽  
Kinetics Study

Impact Of Synthesis Route on the Water Oxidation Kinetics of Hematite Photoanodes

2020 ◽  
Author(s):  
Camilo A. Mesa ◽  
Ludmilla Steier ◽  
Benjamin Moss ◽  
Laia Francàs ◽  
James E. Thorne ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Reaction Kinetics ◽  
Water Oxidation ◽  
Oxidation Kinetics ◽  
Oxidation Reaction ◽  
Charge Accumulation ◽  
Optical Signals ◽  
Current Voltage ◽  
Voltage Performance ◽  
Kinetics Of

<p><i>Operando</i> spectroelectrochemical analysis is used to determine the water oxidation reaction kinetics for hematite photoanodes prepared using four different synthetic procedures. Whilst these photoanodes exhibit very different current / voltage performance, their underlying water oxidation kinetics are found to be almost invariant. Lower photoanode performance was found to correlate with the observation of optical signals indicative of charge accumulation in mid-gap oxygen vacancy states, indicating these states do not contribute directly to water oxidation.</p>

Kinetic Solvent Effects in Organic Reactions

2017 ◽  
Author(s):  
Belinda Slakman ◽  
Richard West
Keyword(s):  
Solvent Effect ◽  
Reaction Kinetics ◽  
Computational Methods ◽  
High Throughput ◽  
Kinetic Modeling ◽  
Solvent Effects ◽  
Reaction Rates ◽  
Prior Work ◽  
Solvent Phase ◽  
High Throughput Manner

<div> <div> <div> <p>This article reviews prior work studying reaction kinetics in solution, with the goal of using this information to improve detailed kinetic modeling in the solvent phase. Both experimental and computational methods for calculating reaction rates in liquids are reviewed. Previous studies, which used such methods to determine solvent effects, are then analyzed based on reaction family. Many of these studies correlate kinetic solvent effect with one or more solvent parameters or properties of reacting species, but it is not always possible, and investigations are usually done on too few reactions and solvents to truly generalize. From these studies, we present suggestions on how best to use data to generalize solvent effects for many different reaction types in a high throughput manner. </p> </div> </div> </div>

An All-Photonic Molecular Amplifier and Binary Flip-flop

2020 ◽  
Author(s):  
Thomas MacDonald ◽  
Timothy Schmidt ◽  
Jonathon Beves
Keyword(s):  
Numerical Modeling ◽  
Visible Light ◽  
Reaction Kinetics ◽  
Memory Storage ◽  
Chemical System ◽  
Initial Composition ◽  
Flip Flop ◽  
Sequential Logic ◽  
Behavior Based

A chemical system is proposed that is capable of amplifying small optical inputs into large changes in internal composition, based on a feedback interaction between switchable fluorescence and visible-light photoswitching. This system would demonstrate bifurcating reaction kinetics under irradiation and reach one of two stable photostationary states depending on the initial composition of the system. This behavior would allow the system to act as a chemical realization of the flip-flop circuit, the fundamental element in sequential logic and binary memory storage. We use detailed numerical modeling to demonstrate the feasibility of the proposed behavior based on known molecular phenomena, and comment on some of the conditions required to realize this system.

Highly Electron-Deficient Pyridinium-Nitrones for Rapid and Tunable Inverse-Electron-Demand Strain-Promoted Alkyne-Nitrone Cycloaddition to Bicyclo[6.1.0]nonyne

2019 ◽  
Author(s):  
Praveen Gunawardene ◽  
Wilson Luo ◽  
Alexander M. Polgar ◽  
John F. Corrigan ◽  
Mark Workentin
Keyword(s):  
Density Functional Theory ◽  
Reaction Kinetics ◽  
Density Functional ◽  
Functional Theory ◽  
X Ray ◽  
Inverse Electron Demand ◽  
X Ray Crystallography ◽  
Electron Demand

<div> <div> <p>Highly accelerated inverse-electron-demand strain-promoted alkyne-nitrone cycloaddition (IED SPANC) between a sta- ble cyclooctyne (bicyclo[6.1.0]nonyne (BCN)) and nitrones delocalized into a Cα-pyridinium functionality is reported, with the most electron-deficient “pyridinium-nitrone” displaying among the most rapid cycloadditions to BCN that is currently reported. Density functional theory (DFT) and X-ray crystallography are explored to rationalize the effects of N- and Cα-substituent modifications at the nitrone on IED SPANC reaction kinetics and the overall rapid reactivity of pyridinium-delocalized nitrones.</p> </div> </div>

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