Characterization of the active site for the selective oxidation of methanol to formaldehyde on polycrystalline silver catalyst

1994 ◽  
pp. 1717 ◽  
Author(s):  
Graeme J. Millar ◽  
James B. Metson ◽  
Graham A. Bowmaker ◽  
Ralph P. Cooney
Keyword(s):  
Selective Oxidation ◽  
Active Site ◽  
Silver Catalyst ◽  
Oxidation Of Methanol ◽  
Polycrystalline Silver

scholarly journals Characterization of a novel methanol dehydrogenase containing a Ba2+ ion at the active site

1996 ◽  
Vol 318 (2) ◽  
pp. 673-679 ◽  
Author(s):  
Matthew G GOODWIN ◽  
Christopher ANTHONY
Keyword(s):  
Activation Energy ◽  
Active Site ◽  
Pyrroloquinoline Quinone ◽  
Methanol Dehydrogenase ◽  
Reduction Step ◽  
Deuterium Isotope Effect ◽  
Quinone Reduction ◽  
Oxidation Of Methanol ◽  
Substrate Addition

The quinoprotein methanol dehydrogenase (MDH) contains a Ca2+ ion at the active site. Ca2+-free enzyme (from a processing mutant) was used to obtain enzyme containing Sr2+ or Ba2+, the Ba2+-MDH being the first enzyme to be described in which a Ba2+ ion functions at the active site. The activation energy for oxidation of methanol by Ba2+-MDH is less than half that of the reaction catalysed by Ca2+-MDH (a difference of 21.4 kJ/mol), and the Vmax value is 2-fold higher. The affinities of Ba2+-MDH for substrate and activator are very much less than those of Ca2+-MDH; the Km for methanol is 3.5 mM (compared with 3 µM) and the KA for ammonia is 52 mM (compared with 2 mM). The different activity of Ba2+-MDH is probably due to a change in the conformation of the active site, leading to a decrease in the free energy of substrate binding and hence a decrease in activation energy. The kinetic model for Ba2+-MDH with respect to substrate and activator is consistent with previous models for Ca2+-MDH. The pronounced deuterium isotope effect (6.0–7.6) is influenced by ammonia, and is consistent with activation of the pyrroloquinoline quinone reduction step by ammonia. Because of its low affinity for substrates, it is possible to prepare the oxidized form of Ba2+-MDH. No spectral intermediates could be detected during reduction by added substrate, and so it is not possible to distinguish between those mechanisms involving covalent substrate addition and those involving only hydride transfer.

Performance and Characterization of a New Crystalline SbRe2O6 Catalyst for Selective Oxidation of Methanol to Methylal

2000 ◽  
Vol 195 (1) ◽  
pp. 51-61 ◽  
Author(s):  
Youzhu Yuan ◽  
Haichao Liu ◽  
Hideo Imoto ◽  
Takafumi Shido ◽  
Yasuhiro Iwasawa
Keyword(s):  
Selective Oxidation ◽  
Oxidation Of Methanol

Characterization of an Abnormal Antithrombin (Milano 2) with Defective Thrombin Binding

1986 ◽  
Vol 56 (03) ◽  
pp. 349-352 ◽  
Author(s):  
A Tripodi ◽  
A Krachmalnicoff ◽  
P M Mannucci
Keyword(s):  
Venous Thromboembolism ◽  
Active Site ◽  
Inhibitory Activity ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Molecular Defect ◽  
Affinity Adsorption ◽  
Italian Family ◽  
Crossed Immunoelectrophoresis

SummaryFour members of an Italian family (two with histories of venous thromboembolism) had a qualitative defect of antithrombin III reflected by normal antigen concentrations and halfnormal antithrombin activity with or without heparin. Anti-factor Xa activities were consistently borderline low (about 70% of normal). For the propositus’ plasma and serum the patterns of antithrombin III in crossed-immunoelectrophoresis with or without heparin were indistinguishable from those of normal plasma or serum. A normal affinity of antithrombin III for heparin was documented by heparin-sepharose chromatography. Affinity adsorption of the propositus’ plasma to human α-thrombin immobilized on sepharose beads revealed defective binding of the anti thrombin III to thrombin-sepharose. Hence the molecular defect of this variant appears to be at the active site responsible for binding and neutralizing thrombin, thus accounting for the low thrombin inhibitory activity.

scholarly journals Structural Characterization of Two CO Molecules Bound to the Nitrogenase Active Site

2020 ◽  
Author(s):  
Trixia M. Buscagan ◽  
Kathryn A. Perez ◽  
Ailiena O. Maggiolo ◽  
Douglas C. Rees ◽  
Thomas Spatzal
Keyword(s):  
Structural Characterization ◽  
Active Site

scholarly journals Characterization of Light-Induced, Short-Lived Interacting Radicals in the Active Site of Flavoprotein Ferredoxin-NADP+ Oxidoreductase

2021 ◽  
Vol 143 (7) ◽  
pp. 2757-2768
Author(s):  
Bo Zhuang ◽  
Daisuke Seo ◽  
Alexey Aleksandrov ◽  
Marten H. Vos
Keyword(s):  
Active Site
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