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1.
Chem Commun (Camb) ; 52(38): 6399-402, 2016 May 11.
Article in English | MEDLINE | ID: mdl-27086547

ABSTRACT

How a protein domain motion is coupled to the catalytic cycle is a current subject in enzymology. We render down a complicated domain motion in the 5'-deoxyadenosylcobalamin and pyridoxal-5'-phosphate codependent radical enzyme, lysine 5,6-aminomutase, into dominant contributions from Lys370α and Asp298α to the critical Co-C bond cleavage trigger and open-closed cycle transitions.


Subject(s)
Intramolecular Transferases/chemistry , Binding Sites , Biocatalysis , Clostridium sticklandii/enzymology , Intramolecular Transferases/metabolism , Protein Conformation , Quantum Theory
2.
J Am Chem Soc ; 132(32): 10982-3, 2010 Aug 18.
Article in English | MEDLINE | ID: mdl-20698649

ABSTRACT

Rutile TiO(2) nanoparticles with new sites for effectively trapping photogenerated holes have been prepared by reacting the TiO(2) nanoparticles prepared in hydrogen atmosphere with molecular oxygen at elevated temperatures. The observed g values and the occurrence of (47)Ti and (49)Ti octet hyperfine pattern allowed us to assign this EPR active center to surface oxygen centered anion radical with two coordinating titaniums. The effective trapping of photogenerated holes by these new sites inhibits the electron-hole recombination and results in an enhanced photocatalytic activity under visible light by a factor of 2.5 compared with samples prepared parallel in air. Oxidation of reduced TiO(2) apparently is a simple low-cost and promising route for improving the photoactivity of TiO(2).


Subject(s)
Photochemical Processes , Titanium/chemistry , Catalysis , Electron Spin Resonance Spectroscopy , Light , Surface Properties
3.
J Am Chem Soc ; 130(9): 2760-1, 2008 Mar 05.
Article in English | MEDLINE | ID: mdl-18254632

ABSTRACT

Boron is diamagnetic in B-doped anatase TiO2 nanoparticles which exhibit photocatalytic activities in the visible light range. Using N as a paramagnetic probe for the formal oxidation state of boron in N/B-codoped TiO2, with more than 90% unpaired spin density in the N2p orbital, we infer that boron enters the oxygen vacancy substitutionally in the form of B1-. Combination of spin-Hamiltonian analysis and interpretation of light dependent EPR spectra in terms of a charge compensating mechanism supports a model of [N2-B1-]+1 for the new EPR active center which acts as a trap for electrons liberated from [N1-] centers under blue light irradiation. Definite assignment of the boron oxidation state will contribute to the preparation, characterization, and understanding of B-TiO2 photoactivity under visible light which has been the subject of extensive work in the past few years.

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