scholarly journals Effects of Single and Double Mutations in Plastocyanin on the Rate Constant and Activation Parameters for the Rearrangement Gating the Electron-Transfer Reaction between the Triplet State of Zinc Cytochromecand Cupriplastocyanin†

Biochemistry ◽  
1998 ◽  
Vol 37 (26) ◽  
pp. 9557-9569 ◽  
Author(s):  
Maja M. Ivković-Jensen ◽  
G. Matthias Ullmann ◽  
Simon Young ◽  
Örjan Hansson ◽  
Milan M. Crnogorac ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Triplet State ◽  
Rate Constant ◽  
Transfer Reaction ◽  
Activation Parameters ◽  
Electron Transfer Reaction

scholarly journals Nonenzymatic NADH-Dependent Reduction of Keggin-Type 12-Tungstocobaltate(III) in Aqueous Medium

2011 ◽  
Vol 8 (3) ◽  
pp. 1152-1157
Author(s):  
Prabla Kumari ◽  
Alaka Das ◽  
Dillip Kumar Baral ◽  
A. K. Pattanaik ◽  
P. Mohanty
Keyword(s):  
Electron Transfer ◽  
Transition State ◽  
Aqueous Medium ◽  
Transfer Reaction ◽  
Activation Parameters ◽  
Electron Transfer Reaction ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
First Order ◽  
Kinetics Of

The kinetics of the electron transfer reaction of NADH with 12-tungstocobaltate(III) has been studied over the range 5.07 ≤ 104[NADH] ≤ 15.22 mol dm-3, 7.0 ≤ pH ≤ 8.0 and 20 ≤ t ≤ 35oC in aqueous medium. The electron transfer reaction showed first-order dependence each in [NADH]Tand [12-tungstocobaltate(III)]T. The products of the reaction were found to be NAD+and 12-tungstocobaltate(II). The activation parameters ΔH#(kJ mol-1) and ΔS#(JK-1mol-1) of the electron transfer reactions were found to be 64.4±1.8 and -48.86±6.0. Negative value of ΔS#is an indicative of an ordered transition state for the electron transfer reaction.

FT-EPR Study of Spin-correlated Radical Pairs Formed by Electron Transfer Quenching of Porphyrin Triplets in Micellar Solution

1998 ◽  
Vol 02 (04) ◽  
pp. 353-361 ◽  
Author(s):  
VOLKER WEIS ◽  
HANS VAN WILLIGEN
Keyword(s):  
Electron Transfer ◽  
Statistical Model ◽  
Rate Constant ◽  
Micellar Solution ◽  
Transfer Reaction ◽  
Electron Transfer Reaction ◽  
Cetyltrimethylammonium Chloride ◽  
Radical Pairs ◽  
Homogeneous Solutions ◽  
Kinetics Of

The spin-correlated radical pairs (SCRPs) formed by photoinduced electron transfer from zinc tetrakis(4-sulfonatophenyl)porphyrin ( ZnTPPS ) to quinones in micelles of the cationic surfactant cetyltrimethylammonium chloride ( CTAC ) were studied by means of Fourier transform EPR (FT-EPR). It is shown that variation of the power of the microwave pulse allows the separation of EPR signals arising from SCRPs and free radicals. The measured kinetics of radical formation can be accounted for in terms of a statistical model taking into account the non-uniform distribution of the solutes over the micelles. The rate constant of electron transfer quenching (kq) of the ZnTPPS triplet state by duroquinone (DQ) is found to be 1.05 × 106 s−1. The FT-EPR measurements gave information also on the kinetics of the homogeneous electron transfer reaction DQ − + DQ → DQ + DQ − in CTAC solution in which the DQ − anion radicals were generated by light-induced electron transfer from ZnTPPS . It is found that the dependence of the rate of this reaction on quinone concentration deviates from the linear relationship found in homogeneous solutions. A statistical model is proposed to account for the data. Based on this model, the rate constant of the self-exchange reaction (k ex ) is 4.1 × 106 s−1. From results obtained with duroquinone and benzoquinone as acceptors, it is concluded that ZnTPPS is located at the micelle/water interface.

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