Jan Griebel

How Metal Ions Affect Amyloid Formation: Cu2+‐ and Zn2+‐Sensitive Peptides

The common feature of proteins involved in many neurodegenerative diseases is their ability to adopt at least two different stable conformations. The conformational transition that shifts the equilibrium from the functional, mostly partially α‐helical structure, to the β‐sheet rich amyloid can be triggered by numerous factors, such as mutations in the primary structure or changes in the environment. We present a set of model peptides that, without changes in their primary structure, react in a predictable fashion in the presence of transition metal ions by adopting different conformations and aggregate morphologies. These de novo designed peptides strictly follow the characteristic heptad repeat of the α‐helical coiled‐coil structural motif. Furthermore, domains that favor β‐sheet formation have been incorporated to make the system prone to amyloid formation. As a third feature, histidine residues create sensitivity towards the presence of transition metal ions. CD spectroscopy, ThT fluorescence experiments, and transmission electron microscopy were used to characterize peptide conformation and aggregate morphology in the presence of Cu2+ and Zn2+. Furthermore, the binding geometry within peptide–Cu2+ complexes was characterized by electron paramagnetic resonance spectroscopy.

Versatile Reactivity of a Lithium Tris(aryl)plumbate(II) Towards Organolanthanoid Compounds: Stable Lead–Lanthanoid–Metal Bonds or Redox Processes

Redox chemistry: Redox-active europium complexes based on a new tris(2-pyridyl)plumbate ligand are described. Reactions of [LiPb(2-py(R))3(thf)] (py(R) = C5H3-6-OtBu) with tri- or divalent lanthanoid metals resulted in the first stable Pb-Ln-bonded complexes or unprecedented redox reactions, involving, for example, the pentametallic complex depicted.

A Stable and Crystalline Triarylgermyl Radical: Structure and EPR Spectra†

A radical thing: After being obtained unexpectedly in low yields, the synthesis of the first stable triarylgermyl radical (*)Ge[3,5-tBu(2)-2,6-(EtO)(2)C(6)H](3) (1; C gray, O blue) was considerably optimized, and the product was investigated by X-ray analysis and EPR spectroscopy. The results were compared with DFT-MO studies for the model compound (*)Ge[2,6-(MeO)(2)C(6)H(3)].