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The twin-arginine translocase (Tat) carries out the remarkable process of translocating fully folded proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. Tat is required for bacterial pathogenesis and for photosynthesis in plants. TatA, the protein-translocating element of the Tat system, is a small(More)
The enterobacterium Escherichia coli synthesizes two H(2) uptake enzymes, Hyd-1 and Hyd-2. We show using precise electrochemical kinetic measurements that the properties of Hyd-1 and Hyd-2 contrast strikingly, and may be individually optimized to function under distinct environmental conditions. Hyd-2 is well suited for fast and efficient catalysis in more(More)
Methanogenic archaea utilize a specific pathway in their metabolism, converting C1 substrates (i.e., CO2) or acetate to methane and thereby providing energy for the cell. Methyl-coenzyme M reductase (MCR) catalyzes the key step in the process, namely methyl-coenzyme M (CH3-S-CoM) plus coenzyme B (HS-CoB) to methane and CoM-S-S-CoB. The active site of MCR(More)
In oxidative phosphorylation, complex I (NADH:quinone oxidoreductase) couples electron transfer to proton translocation across an energy-transducing membrane. Complex I contains a flavin mononucleotide to oxidize NADH, and an unusually long series of iron-sulfur (FeS) clusters, in several subunits, to transfer the electrons to quinone. Understanding coupled(More)
A continuous wave and pulse electron paramagnetic resonance study of the base-on form of cob(II)alamin diluted in hydroxocob(III)alamin powder is presented. HYSCORE spectroscopy at X-and Q-band was used to study the weakly coupled corrin nitrogens and the remote nitrogen of the axial dimethylbenzimidazole ligand. Simulations of the spectra measured at(More)
The increased blood oxygenation level-dependent contrast-to-noise ratio at ultrahigh field (7 T) has been exploited in a comparison of the spatial location and strength of activation in high-resolution (1.5  mm isotropic) gradient echo (GE) and spin echo (SE), echo planar imaging data acquired during the execution of a simple motor task in five subjects. SE(More)
Palustrisredoxin-B (PuxB) from Rhodopseudomonas palustris (CGA009) is a [2Fe-2S] ferredoxin which is able to accept electrons from NADH via the flavin-dependent palustrisredoxin reductase (PuR); these electrons can then be transferred to the P450 enzyme (CYP199A2). This work reports on the paramagnetic state of the [2Fe-2S](+) cluster in PuxB, both alone(More)
The new tetradentate ligand 1,4-bis(5 H-dibenzo[a,d]cyclohepten-5-yl)-1,4-diazabuta-1,3-diene ((H)tropdad) allows the syntheses of the 16-electron cationic rhodium complexes [M((H)tropdad)](O(3)SCF(3)) (M=Rh, Ir). The structure of the rhodium complex was determined by X-ray analysis and points to a description of these as [M(+1)((H)tropdad)(0)] with short(More)