Elektrochemische Untersuchungen an Organothallium(III)-Verbindungen

The electrochemical reduction of dialkylthallium(III) cations in aqueus buffer solutions and dimethylformamide yields by the first electron transfer the instable intermediate {R₂Tl}, which in dependence of the reaction conditions is electrochemical reduced to Tl° or disproportionates to R₃Tl and Tl°. Phenyl-substituted organothallium compounds are reduced to Tl° and (C₆H₅)₂Hg in one step.     

A practical synthesis of gramicidin s and sugar amino Acid containing analogues

A practical gram-scale and high-yielding synthesis of the antimicrobial peptide gramicidin S is presented. An Fmoc-based solid-phase peptide synthesis protocol is employed for the generation of the linear decapeptide precursor, which is cyclized in solution to afford the target compound. The versatility of our method is demonstrated by the construction of eight gramicidin S analogues (15a-h) having nonproteinogenic sugar amino acid residues (4-7) incorporated in the turn regions.     

Active site structure and redox processes of cytochrome c oxidase immobilised in a novel biomimetic lipid membrane on an electrode

Membrane-bound cytochrome c oxidase was attached to an electrode via a His-tag linker and studied by surface enhanced resonance Raman spectroscopy, demonstrating intact redox site structures and electron transfer between the electrode and the immobilized enzyme.     

First Measurement of the Gerasimov-Drell-Hearn Sum Rule for 1H from 0.7 to 1.8 GeV at ELSA

To verify the fundamental Gerasimov-Drell-Hearn (GDH) sum rule for the first time experimentally, we measured the helicity dependent total photoabsorption cross section with circularly polarized real photons and longitudinally polarized nucleons in the photon energy range 0.68-1.82 GeV with the tagged photon facility at ELSA. The experiment was carried out with a 4pi detection system, a circularly polarized tagged photon beam, and a frozen spin polarized proton target. The contribution to the GDH sum rule in this photon energy range is [49.9+/-2.4(stat)+/-2.2(syst)] microb.     

Synthesis of bridged sugar amino acids: a new entry into conformationally locked δ- and ε-amino acids

The synthesis of three methylene bridged sugar amino acids is described. Key transformations in the synthetic strategy are a CO-insertion on fully protected ribose, an aldol condensation with formaldehyde and an oxetane forming cyclisation step. A novel Leu-enkephalin analogue containing the δ-SAA 1 was prepared using standard solution phase peptide chemistry.     

Protein prosthesis: a nonnatural residue accelerates folding and increases stability

Nonnatural residues can endow proteins with desirable properties. Here, replacing a proline residue that has a cis peptide bond in native ribonuclease A with 5,5-dimethyl-l-proline is shown to accelerate protein folding by 6-fold and enhance conformational stability by DeltaTm = 2.8 +/- 0.3 degrees C while having no effect on enzymatic activity. The rational use of this and other prosthetic segments could enable chemotherapeutic proteins to survive longer in vivo or retain activity after oral administration.     

Investigation of X-ray Emission from Plasmas Created by NIXE 6-nsec Nd: Glass Laser System

This paper reports details on the design of the Nd: glass laser facility NIXE at the Central Institute of Optics and Spectroscopy, including the target chamber and the x-ray diagnostics, spatial and temporal behaviour of the 1.06 μm radiation generated are given. Plane, massive targets of aluminium and silicon have been irradiated with 6-nsec FWHM laser pulses. Investigations of laser produced Al- and Si-plasmas have been performed with spectral and spatial high resolution diagnostics, consisting of a 3 channel crystal-spectrometer, 2 crystal-microscopes, and 2 pinhole cameras and the results are presented. Line spectra have been interpreted within the hypothesis of a steady state coronal equilibrium. He-like lines of the Al-plasma indicate temperatures up to 400 eV and densities up to 2 · 10²⁰ cm^?3. Total x-ray photon flux in the He-like resonance line has been calculated giving 10¹³ phot/ster.