The molecular mechanism of the open-closed protein conformational cycle transitions and coupled substrate binding, activation and product release events in lysine 5,6-aminomutase.

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.

A potential site for trapping photogenerated holes on rutile TiO(2) surface as revealed by EPR spectroscopy: an avenue for enhancing photocatalytic activity.

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).

Chemical state and environment of boron dopant in B,N-codoped anatase TiO2 nanoparticles: an avenue for probing diamagnetic dopants in TiO2 by electron paramagnetic resonance spectroscopy.

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.