scholarly journals Determination of the Bridging Ligand in the Active Site of Tyrosinase

Molecules ◽  
2017 ◽  
Vol 22 (11) ◽  
pp. 1836 ◽  
Author(s):  
Congming Zou ◽  
Wei Huang ◽  
Gaokun Zhao ◽  
Xiao Wan ◽  
Xiaodong Hu ◽  
...  
Keyword(s):  
Active Site ◽  
Bridging Ligand

scholarly journals The reaction of nitrite with the haemocyanin of Astacus leptodactylus

1988 ◽  
Vol 249 (3) ◽  
pp. 891-896 ◽  
Author(s):  
J P Tahon ◽  
D Van Hoof ◽  
C Vinckier ◽  
R Witters ◽  
M De Ley ◽  
...  
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Reaction Rate ◽  
Anaerobic Treatment ◽  
Astacus Leptodactylus ◽  
First Order ◽  
Bridging Ligand ◽  
A Value ◽  
Pseudo First Order

The reaction of nitrite at pH 5.7 with deoxyhaemocyanin of Astacus leptodactylus yielded methaemocyanin in two one-electron steps, as nitrite was reduced to NO. This methaemocyanin could be almost fully regenerated by an anaerobic treatment with HONH2, in contrast with the methaemocyanin prepared with H2O2. A destruction of active sites on treating oxyhaemocyanin with HONH2 explains the partial regeneration of methaemocyanin under air, as traces of H2O2 are formed in the autoxidation of HONH2. The reaction rate of nitrite with deoxyhaemocyanin is almost 15 times that with oxyhaemocyanin. The slope of -1.0 for the logarithm of the pseudo-first-order rate constants plotted against pH indicates that HNO2 is the reacting species. Methaemocyanin was e.p.r.-undetectable, but a binuclear signal was observed at g = 2 on binding nitrite to methaemocyanin. This signal disappeared with a pKa of 6.50, suggesting that a mu-aquo bridging ligand, which can be replaced by nitrite, is deprotonated to a mu-hydroxo bridging ligand, which resists substitution by nitrite. The intensity of this triplet e.p.r. signal allowed the determination of the association constant of nitrite to the active site of Astacus methaemocyanin and yielded a value of 237 M-1 at pH 5.7. The interpretation by some authors of nitrosylhaemocyanin as a nitrite derivative of semimethaemocyanin is contradicted by this rapid reaction of nitrite with copper(I) in deoxyhaemocyanin and in semi-methaemocyanin and by the low binding constant of nitrite to the active site of methaemocyanin.

Statistical Description of Isotope Exchange Processes: A Multisite Model for the 18O Exchange

1982 ◽  
Vol 37 (11-12) ◽  
pp. 1161-1169 ◽  
Author(s):  
Paul Rösch
Keyword(s):  
Active Site ◽  
Isotope Exchange ◽  
Analytical Procedure ◽  
Matrix Formalism ◽  
Model Calculations ◽  
Exchange Processes ◽  
Reaction Solution ◽  
Different Types ◽  
Refinement Procedure

Abstract An analytical procedure has been developed for the determination of isotope exchange processes as exemplified by the 18O exchange catalysed by enzyme-nucleotide complexes. The model is able to handle more than one type of active site per reaction solution and is also able to distinguish between different types of inequivalence of the oxygens of enzyme bound Pi. Use of transition matrix formalism and basic statistical considerations lead directly to the simple model. A data refinement procedure is introduced and model calculations are shown.

Nonlinear Vibrations in a 2-Dimensional Protein Cluster Model with Linear Bonds

2000 ◽  
Vol 214 (1) ◽  
Author(s):  
E.G. Shidlovskaya ◽  
L. Schimansky-Geier ◽  
Yu.M. Romanovsky
Keyword(s):  
Active Site ◽  
Internal Resonance ◽  
Cluster Model ◽  
Active Sites ◽  
Nonlinear Vibrations ◽  
Nonlinear Phenomena ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model

A two dimensional model for the substrate inside a pocket of an active site of an enzyme is presented and investigated as a vibrational system. The parameters of the system are evaluated for α-chymotrypsin. In the case of internal resonance it is analytically and numerically shown that the energy concentrated on a certain degree of freedom might be several times larger than in the non-resonant case. Additionally, the system is driven by harmonic excitations and again energy due to nonlinear phenomena is redistributed inhomogeneously. These results may be of importance for the determination of the rates of catalytic events of substrates bound in pockets of active sites.

Potentiometric determination of ionizations at the active site of papain

Biochemistry ◽  
1976 ◽  
Vol 15 (23) ◽  
pp. 5009-5017 ◽  
Author(s):  
Sidney D. Lewis ◽  
Frederick A. Johnson ◽  
Jules A. Shafer
Keyword(s):  
Active Site ◽  
Potentiometric Determination

Spectroscopic studies on plastocyanin single crystals: a detailed electronic structure determination of the blue copper active site

1981 ◽  
Vol 103 (15) ◽  
pp. 4382-4388 ◽  
Author(s):  
K. W. Penfield ◽  
R. R. Gay ◽  
R. S. Himmelwright ◽  
N. C. Eickman ◽  
V. A. Norris ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Single Crystals ◽  
Structure Determination ◽  
Active Site ◽  
Spectroscopic Studies ◽  
Blue Copper
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