Doping improves performance: Iron arsenides (Ba1−xKx)Fe2As2 with the ThCr2Si2‐type structure exhibit superconductivity at 3–38 K depending on the potassium doping level. Superconductivity occurs before the structural distortion of the parent compound BaFe2As2 (x=0) is completely suppressed by doping (see phase diagram; • critical temperature, ○ phase‐transition temperature). Doping decreases the bond angles in the iron arsenide layers, suggesting a strong coupling of structural and electronic degrees of freedom.

Superconductors D 8000Superconductivity and Crystal Structures of (Ba1-xKx)Fe2As2 (x = 0-1). -The title compounds are synthesized from stoichiometric mixtures of the elements (Al 2 O 3 crucibles, Ar, 823-1223 K) and characterized by powder XRD and electrical resistance measurements. The XRD patterns at room temperature are indexed with tetragonal body-centered unit cells according to the ThCr2Si2-type (space group I4/mmm) or with orthorhombic face-centered unit cells (space group Fmmm). Superconductivity occurs over the whole doping range with a maximum T C of 38 K at x ≅ 0.4. The superconducting transitions in the orthorhombic compounds (Ba0.9K0.1)Fe2As2 (TC ≅ 3 K) and (Ba0.8K0.2)Fe2As2 (TC ≅ 25 K) give strong evidence for a correlation of superconductivity with the distorted structure and thus, potentially with an antiferromagnetically ordered state. -(ROTTER, M.; PANGERL, M.; TEGEL, M.; JOHRENDT*, D.; Angew. Chem., Int. Ed. 47 (2008) 41, 7949-7952; Fachbereich Chem. Biochem.,

GABAA receptors are the major inhibitory neurotransmitter receptors in the brain. Benzodiazepine exert their action via a high affinity-binding site at the α/γ subunit interface on some of these receptors. Diazepam has sedative, hypnotic, anxiolytic, muscle relaxant, and anticonvulsant effects. It acts by potentiating the current evoked by the agonist GABA. Understanding specific interaction of benzodiazepines in the binding pocket of different GABAA receptor isoforms might help to separate these divergent effects. As a first step, we characterized the interaction between diazepam and the major GABAA receptor isoform α1β2γ2. We mutated several amino acid residues on the γ2-subunit assumed to be located near or in the benzodiazepine binding pocket individually to cysteine and studied the interaction with three ligands that are modified with a cysteine-reactive isothiocyanate group (-NCS). When the reactive NCS group is in apposition to the cysteine residue this leads to a covalent reaction. In this way, three amino acid residues, γ2Tyr58, γ2Asn60, and γ2Val190 were located relative to classical benzodiazepines in their binding pocket on GABAA receptors.

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