scholarly journals Spectroscopic and Kinetic Studies of Perturbed Trinuclear Copper Clusters:  The Role of Protons in Reductive Cleavage of the O−O Bond in the Multicopper Oxidase Fet3p

2007 ◽  
Vol 129 (43) ◽  
pp. 13118-13126 ◽  
Author(s):  
Anthony J. Augustine ◽  
Liliana Quintanar ◽  
Christopher S. Stoj ◽  
Daniel J. Kosman ◽  
Edward I. Solomon
Keyword(s):  
Kinetic Studies ◽  
Multicopper Oxidase ◽  
Reductive Cleavage ◽  
Copper Clusters

Role of Lys-226 in the Catalytic Mechanism ofBacillus StearothermophilusSerine HydroxymethyltransferaseCrystal Structure and Kinetic Studies†,‡

Biochemistry ◽  
2005 ◽  
Vol 44 (18) ◽  
pp. 6929-6937 ◽  
Author(s):  
Siddegowda Bhavani ◽  
V. Trivedi ◽  
V. R. Jala ◽  
H. S. Subramanya ◽  
Purnima Kaul ◽  
...  
Keyword(s):  
Catalytic Mechanism ◽  
Kinetic Studies

Probing the Role of Tyr 64 ofTreponema denticolaCystalysin by Site-Directed Mutagenesis and Kinetic Studies†

Biochemistry ◽  
2005 ◽  
Vol 44 (42) ◽  
pp. 13970-13980 ◽  
Author(s):  
Barbara Cellini ◽  
Mariarita Bertoldi ◽  
Riccardo Montioli ◽  
Carla Borri Voltattorni
Keyword(s):  
Kinetic Studies ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis

Control of disinfection and halogenated disinfection byproducts by the electrochemical process

2007 ◽  
Vol 55 (12) ◽  
pp. 213-219 ◽  
Author(s):  
Y.J. Jung ◽  
B.S. Oh ◽  
J.W. Kang ◽  
M.A. Page ◽  
M.J. Phillips ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Disinfection Byproducts ◽  
Electrochemical Process ◽  
Free Chlorine ◽  
Haloacetic Acids ◽  
Oh Radicals ◽  
Inactivation Kinetic ◽  
E Coli ◽  
Electrochemical Processes

The aim of this study was to investigate some aspects of the performance of electrochemical process as an alternative disinfection strategy, while minimising DBPs, for water purification. The study of electrochemical processes has shown free chlorine to be produced, but smaller amounts of stronger oxidants, such as ozone, hydrogen peroxide and OH radicals (•OH), were also generated. The formation of mixed oxidants increased with increasing electric conductivity, but was limited at conductivities greater than 0.6 mS/cm. Using several microorganisms, such as E. coli and MS2 bacteriophage, inactivation kinetic studies were performed. With the exception of free chlorine, the role of mixed oxidants, especially OH radicals, was investigated for enhancement of the inactivation rate. Additionally, the formation and reduction of DBPs was studied by monitoring the concentration of haloacetic acids (HAAs) during the process.

From the Understanding of the Reaction Mechanism Towards Optimizing the Deposition Rate and Optoelectronic Properties of a-Si:H

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Veprek ◽  
M. Heintze ◽  
R. Bayer ◽  
N. Jurčik-Rajman
Keyword(s):  
Reaction Mechanism ◽  
Surface Coverage ◽  
Kinetic Studies ◽  
Reactive Intermediates ◽  
Sticking Coefficient ◽  
High Quality ◽  
Rate Determining Step ◽  
Homogeneous Good ◽  
Good Agreement

ABSTRACTWe present new results of kinetic studies of the deposition of high quality a-Si:H which strongly support the reaction mechanism suggested in our earlier papers: 1. SiH4 → SiH2; 2. SiH2 + SiS4 → Si2H6 (SiH2 + Si2H6 → Si3H6); 3. Si2H6 → 2a-Si:H (Si3H8 → 3a-Si:H). The “SiH3 mechanism”, as promoted by several workers, is in contradiction with these experimental facts.The di- and trisilane, which have a much higher reactive sticking coefficient than monosilane, play the role of reactive intermediates which facilitate the heterogeneous decomposition of silicon carrying species at the surface of the growing film. The values of the reactive sticking coefficient of Si2H6 and Si3H8 depend on the surface coverage by chemisorbed hydrogen; they increase with decreasing surface coverage. Under the conditions of the growth of high quality a-Si:H films the reactive sticking coefficient of disilane amounts to 10−4 to 10−2 which is in a good agreement with recent data of other authors.The rate determining step of the growth of high quality a-Si:H films is the desorption of hydrogen from the surface of the growing film. This can be strongly enhanced by ion bombardment at impact energy of <100 eV. In this way, homogeneous, good quality films were deposited at rates up to 1800 Angströms/min, and there is a well justified hope that this rate can be further increased.

Kinetics of Plasmon-Driven Hydrosilylation of Silicon Surfaces: Photogenerated Charges Drive Silicon- Carbon Bond Formation

2021 ◽  
Author(s):  
Chengcheng Rao ◽  
Brian Olsen ◽  
Erik Luber ◽  
Jillian Buriak
Keyword(s):  
Green Light ◽  
Kinetic Studies ◽  
Silicon Surfaces ◽  
Moderate Intensity ◽  
Carbon Bond ◽  
Silicon Carbon ◽  
Set Up ◽  
Kinetics Of ◽  
Insight Into

Optically transparent PDMS stamps coated with a layer of gold nanoparticles were employed as plasmonic stamps to drive surface chemistry on silicon surfaces. Illumination of a sandwich of plasmonic stamps, an alkene ink, and hydride-terminated silicon with green light of moderate intensity drives hydrosilylation on the surface. The key to the mechanism of the hydrosilylation is the presence of holes at the Si-H-terminated interface, which is followed by attack by a proximal alkene and formation of the silicon-carbon bond. In this work, detailed kinetic studies of the hydrosilylation on silicon with different doping levels, n++, p++, n, p, and intrinsic were carried out to provide further insight into the role of the metal-insulator-semiconductor (MIS) junction that is set up during the stamping.

scholarly journals Enhanced biosorption of Cr(VI) using cotton fibers coated with chitosan – role of ester bonds

2018 ◽  
Vol 78 (3) ◽  
pp. 476-486 ◽  
Author(s):  
Sergio I. Rojas ◽  
Diana C. Duarte ◽  
Sergio D. Mosquera ◽  
Felipe Salcedo ◽  
Juan P. Hinestroza ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Freundlich Isotherm ◽  
Kinetic Studies ◽  
Chitosan Solution ◽  
Cotton Fibers ◽  
Isotherm Models ◽  
Order Kinetic ◽  
Amino Groups ◽  
Removal Capacity

Abstract We report on the role of ester bonds in the enhanced removal of hexavalent chromium from water using cotton fibers coated with chitosan. Adsorption capacities up to five times higher than those of the unmodified fibers were observed when the cotton fibers were exposed to an NaOH, followed by citric acid (0.97 M), and a chitosan solution (2%). We found that the use of NaOH favors the formation of ester bonds over amide bonds on the surface of the cotton fibers. This increase in the surface density of ester bonds generates an increase in the amount of exposed amino groups from the chitosan, hence increasing the removal capacity of the modified fibers. Experimental results also reveal that the adsorption is induced by the electrostatic attraction between the protonated amino groups on the surface and the negatively charged chromium ions in the water. Adsorption isotherms and kinetic studies indicated that the adsorption process fits the Langmuir and the Freundlich isotherm models as well as the pseudo-first and pseudo-second order kinetic models. These results can open a new avenue for the manufacturing of fibers with enhanced removal capacities for hexavalent chromium.

Role of the (H2O)n (n = 1–3) cluster in the HO2 + HO → 3O2 + H2O reaction: mechanistic and kinetic studies

2018 ◽  
Vol 20 (12) ◽  
pp. 8152-8165 ◽  
Author(s):  
Tianlei Zhang ◽  
Xinguang Lan ◽  
Zhangyu Qiao ◽  
Rui Wang ◽  
Xiaohu Yu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Single Molecule ◽  
Kinetic Studies ◽  
Water Dimer ◽  
Water Trimer ◽  
Catalytic Effects

Upon incorporation of the catalyst (H2O)n (n = 1–3) into the reaction HO2 + HO → H2O + 3O2, the catalytic effects of water, water dimer, and water trimer mainly arise from the contribution of a single molecule of water vapor.

Stimulation of P(i) transport in opossum kidney cells by hyposmotic media

1993 ◽  
Vol 264 (4) ◽  
pp. F585-F592
Author(s):  
M. Loghman-Adham ◽  
G. T. Motock
Keyword(s):  
Fluid Phase ◽  
Kinetic Studies ◽  
Uptake Kinetic ◽  
Opossum Kidney ◽  
Pi Transport ◽  
Opossum Kidney Cells ◽  
Fluid Phase Endocytosis ◽  
Peroxidase Uptake ◽  
Stimulation Of

Exposure of various cells to hyposmotic media (Hypo) results in a rapid inhibition of both receptor-mediated and fluid-phase endocytosis. We used this maneuver to investigate the role of endocytosis in regulation of Pi transport in opossum kidney (OK) cells. Following exposure to Hypo, Na(+)-dependent Pi uptake increased rapidly, reaching a maximum within 5 min, and remained elevated up to 30 min. This was associated with a simultaneous reduction of horseradish peroxidase uptake. Kinetic studies showed increased apparent Vmax for Pi (9.38 +/- 0.93 vs. 13.08 +/- 1.04 nmol.mg-1.5 min-1 for control and Hypo, respectively; P < 0.05, n = 6) with no change in apparent Km. The effect was specific for Pi with no change in the Na(+)-dependent or -independent uptake of L-proline, L-glutamine, or methyl-alpha-D-glucopyranoside. Stimulation of Pi transport persisted when control and Hypo had identical ionic compositions. Stimulation of Pi transport was rapidly reversed when cells were returned to an isosmotic medium. Preincubation with Hypo at 4 degrees C had no effect on Pi transport. Addition of cycloheximide or actinomycin D did not prevent the increased Pi uptake after exposure to Hypo. The effect also persisted after protein kinase C downregulation. Stimulation of Pi transport by Hypo is consistent with reduced endocytic retrieval of Na(+)-Pi cotransporters from brush-border membrane (BBM), resulting in an increase in their number on the BBM.

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