scholarly journals Studies on the Ruthenium Complexes. IX. Kinetic Studies on the Deaquation-anation Reaction of Aquapentaammineruthenium(III) Complexes

1975 ◽  
Vol 48 (1) ◽  
pp. 262-265 ◽  
Author(s):  
Akira Ohyoshi ◽  
Shun-ichi Hiraki ◽  
Tomio Odate ◽  
Susumu Kohata ◽  
Junko Oda
Keyword(s):  
Ruthenium Complexes ◽  
Kinetic Studies ◽  
Anation Reaction

scholarly journals Studies of the Ruthenium Complexes. XIII. Kinetic Studies of Electrontransfer Reactions between Aquapentaammineruthenium(II) and Halopentaammineruthenium(III) Comlexes

1977 ◽  
Vol 50 (3) ◽  
pp. 666-669 ◽  
Author(s):  
Akira Ohyoshi ◽  
Kenichiro Yoshikuni ◽  
Hidetoshi Ohtsuyama ◽  
Tomohisa Yamashita ◽  
Shigeyoshi Sakaki
Keyword(s):  
Ruthenium Complexes ◽  
Kinetic Studies

Phosphato complexes of cobalt(III). V. The anation of diaquobis(ethylenediamine) cobalt(III) by orthophosphates

1968 ◽  
Vol 21 (7) ◽  
pp. 1745 ◽  
Author(s):  
SF Lincoln ◽  
DR Stranks
Keyword(s):  
Water Exchange ◽  
Ion Pairs ◽  
Kinetic Studies ◽  
Ion Pair ◽  
Significant Shift ◽  
Kcal Mole ◽  
Sharp Maximum ◽  
Anation Reaction ◽  
High Phosphate ◽  
Anation Rate

The anation reaction of [Co en2(OH2)2]3+ by PO43-, and their protonic analogues, is shown to proceed in two kinetic steps. The first is the rapid equilibrium formation of ion-pairs, followed by a slow substitution step. Ion-pair formation causes a significant shift in the cis-trans equilibrium position at pH 7. The anation rate exhibits a sharp maximum around pH 7, and kinetic studies demonstrate that the anation proceeds predominantly via the trans-[Co en2OH.OH2]2+.HPO2-4ion-pair. The rate of inner-sphere substitution from this ion-pair (k = 0.255 min-1 at 47.9�, ΔH? = 30.0 � 0.6 kcal mole-1 =, ΔS? = +(19 � 3) e.u.) is 10-20 times slower than the estimated rate of water exchange with trans-[Co en2OH.OH2I2+. Specific structures are assigned to the ion-pairs and these structures influence rates of substitution. At high phosphate concentrations, there is spectral evidence for the slower formation of diphosphate complexes. The relevance of these kinetic observations to the generation and preparation of phosphato complexes is discussed.

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.

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