Description: This article discusses human glutathione synthetase. Abstract: Glutathione synthetase is an enzyme that belongs to the glutathione synthetase ATP-binding domain-like superfamily. It catalyzes the second step in the biosynthesis of glutathione from y-glutamylcysteine and glycine in an ATP-dependent manner. Glutathione synthetase has been purified and sequenced from a variety of biological sources; still, its exact mechanism is not fully understood. A variety of structural alignment methods were applied and four highly conserved residues of human glutathione synthetase (Glu-144, Asn-146, Lys-305, and Lys-364) were identified in the binding site. The function of these was studied by experimental and computational site-directed mutagenesis. The three-dimensional coordinates for several human glutathione synthetase mutant enzymes were obtained using molecular mechanics and molecular dynamics simulation techniques, starting from the reported crystal structure of human glutathione synthetase. Consistent with circular dichroism spectroscopy, the authors' results showed no major changes to overall enzyme structure upon residue mutation. However, semiempirical calculations revealed that ligand binding is affected by these mutations. The key interactions between conserved residues and ligands were detected and found to be essential for enzymatic activity. Particularly, the negatively charged Glu-144 residue plays a major role in catalysis.

Description: This article discusses ligand-field effects for the 3p photoelectron spectra of Cr2O3. A major reason for the departure of core level X-ray photoelectron spectra (XPS) of transition metal cations in oxides from the predictions of atomic models is shown to arise from ligand field splittings in the initial state of photoemission. This splitting often leads to a change in the spatial degeneracy of the initial state but the consequences of this for XPS have not been explicitly identified in prior work. Further changes arise from ligand field splittings in the core-hole final states. Results are reported for non-empirical, cluster model many body wavefunctions for the 3p XPS of Cr2O3. The agreement of the theoretical cluster model XPS with experiment is considerably improved over the pure atomic model. Furthermore, the treatment allows screening of the core hole through changes in the covalent character of the cluster orbitals. This is quite different from the usual description of screening in oxides within the framework of charge transfer configurations and it offers new insights into the role of charge transfer for satellite structure.

Description: This article discusses experimental and computational studies of Ruthenium(II)-Catalyzed addition of arene C-H bonds to olefins. Abstract: Hydroarylation reactions of olefins are catalyzed by the octahedral Ru(II) complex TpRu-(CO)(NCMe)(Ph) (1) (Tp = hydridotris(pyrazolyl)borate). Experimental studies and density functional theory calculations support a reaction pathway that involves initial acetonitrile/olefin ligand exchange and subsequent olefin insertion into the ruthenium-phenyl bond. Metal-mediated C-H activation of arene to form a Ru-aryl bond with release of alkyl arene completes the proposed catalytic cycle. The cyclopentadienyl complex CpRu(PPh3)2(Ph) produces ethylbenzene and styrene from a benzene/ethylene solution at 90 ˚C; however, the transformation is not catalytic. A benzene solution of (PCP)Ru(CO)(Ph) (PCP = 2,6-)CH2Pt-Bu2)2C6H3) and ethylene at 90 ˚C produces styrene in 12% yield without observation of ethylbenzene. Computational studies (DFT) suggest that the C-H activation step does not proceed through the formation of a Ru(IV) oxidative addition intermediate but rather occurs by a concerted pathway.

Description: This article discusses reactions of TpRu(CO)(NCMe)(Me) (Tp = Hydridotris(pyrazolyl)borate) with heteroaromatic substrates. The Ru(II) complex TpRu(CO)(NCMe)(Me) (Tp = hydridotris(pyrazolyl)borate) initiates carbon-hydrogen bond activation at the 2-position of furan and thiophene to produce methane and TpRu(CO)(NCMe)(aryl) (aryl = 2-furyl or 2-thienyl). Solid-state structures have been determined for TpRu(CO)(NCMe)(2-thienyl) and [TpRu(CO)(μ-C,S-thienyl)]2. The complex TpRu(CO)(NCMe)(2-furyl) serves as a catalyst for the formation of 2-ethylfuran from ethylene and furan. DFT calculations of the C-H activation of furan by {(Tab)Ru-(CO)(Me)} (Tab = tris(azo)borate) indicate that the C-H activation sequence does not proceed through a Ru(IV) oxidative addition intermediate.

Description: Article describing how vanadium was "rediscovered" in Sweden and found to be identical to del Rio's sample. Includes tourist information regarding areas relevant to this portion of vanadium's history.