Non-thiolate ligation of nickel by nucleotide-free UreG of Klebsiella aerogenes.

Nickel-dependent ureases are activated by a multiprotein complex that includes the GTPase UreG. Prior studies showed that nucleotide-free UreG from Klebsiella aerogenes is monomeric and binds one nickel or zinc ion with near-equivalent affinity using an undefined binding site, whereas nucleotide-free UreG from Helicobacter pylori selectively binds one zinc ion per dimer via a universally conserved Cys-Pro-His motif in each protomer. Iodoacetamide-treated K.

Unique effect of Cu(II) in the metal-induced amyloid formation of β-2-microglobulin.

β-2-Microglobulin (β2m) forms amyloid fibrils in the joints of patients undergoing hemodialysis treatment as a result of kidney failure. In the presence of stoichiometric amounts of Cu(II), β2m self-associates into discrete oligomeric species, including dimers, tetramers, and hexamers, before ultimately forming amyloid fibrils that contain no copper. To improve our understanding of whether Cu(II) is unique in its ability to induce β2m amyloid formation and to delineate the coordinative interactions that allow Cu(II) to exert its effect, we have examined the binding of Ni(II) and Zn(II) to β2m and the resulting influence that these metals have on β2m aggregation.

Direct evidence of active-site reduction and photodriven catalysis in sensitized hydrogenase assemblies.

We report photocatalytic H(2) production by hydrogenase (H(2)ase)-quantum dot (QD) hybrid assemblies. Quenching of the CdTe exciton emission was observed, consistent with electron transfer from the quantum dot to H(2)ase. GC analysis showed light-driven H(2) production in the presence of a sacrificial electron donor with an efficiency of 4%, which is likely a lower limit for these hybrid systems.

Cysteine dioxygenase: structure and mechanism.

Cysteine dioxygenase (CDO) catalyzes the oxidation of cysteine to cysteine sulfinic acid, which is the first major step in cysteine catabolism in mammalian tissues. Crystal structures of mouse, rat, human and bacterial CDO have recently become available and provide significant mechanistic insights. Unlike most non-heme Fe(II) dioxygenases, coordination of the Fe in CDO deviates from the 2-His-1-carboxylate facial triad archetype and instead adopts a His3 facial triad.

Substituent effects on nitrosyl iron corrole complexes Fe(Ar3C)(NO).

A series of nitrosyl tris(5,10,15-aryl)corrolate complexes of iron(III) Fe(Ar3C)(NO) with different substituents on the aryl groups have been prepared, and certain spectroscopic and reaction properties were compared. The cyclic voltammetric analysis of the various Fe(Ar3C)(NO) complexes demonstrated that both the one-electron oxidation and one-electron reduction potentials respond in systematic and nearly identical trends relative to the electron-donor properties of the substituents. A similar pattern was seen in the nitrosyl stretching frequency, nu(NO), which modestly decreased with the stronger donor substituents.

The remarkable axial lability of iron(III) corrole complexes.

Flash photolysis of nitrosyl tris(aryl)corrolate complexes of iron(III), Fe(Ar(3)C)(NO) (Ar(3)C(3-) = 5,10,15-tris(4-nitro-phenyl)corrolate (TNPC(3-)), 5,10,15-tris(phenyl)corrolate (TPC(3-)) or 5,10,15-tris(4-tolyl)corrolate (H(3)TTC(3-))) leads to NO labilization. This is followed by the rapid reaction of NO with Fe(III)(C) to regenerate the starting complex. The second-order rate constants for the back reactions (k(NO)) were determined to be many orders of magnitude faster than the corresponding reactions of ferric porphyrin complexes and indeed are reminiscent of the very large values seen for those of the corresponding ferrous porphyrin analogues.