Die Bestimmung von Verunreinigungen in metallischem Blei

Ohne Zusammenfassung     

Eine einfache und schnelle Trennung von Ni, Mn, Co, Cu und Zn mit Hilfe der Papierchromatographie

Ohne Zusammenfassung     

Die colorimetrische Bestimmung von Fetts?ureestern im Serum

Ohne Zusammenfassung     

Restricted open-shell Kohn-Sham theory: simulation of the pyrrole photodissociation

The authors study the photodissociation reactions of pyrrole and N-methylpyrrole using first-principles molecular dynamics. The first excited state is described with restricted open-shell Kohn-Sham theory. They find a small barrier in the excited state potential energy surface. The possibility of energy redistribution near the Franck-Condon region leads to two different reaction channels in on-the-fly simulations on a single diabatic potential energy surface. The results are discussed in comparison with previous ab initio calculations and with experiments.     

The role of metal ions in dopaminergic neuron degeneration in Parkinsonism and Parkinson’s disease

Abstract  

Parkinson’s disease is characterized by the selective degeneration of neuromelanin-containing dopaminergic neurons in the substantia nigra and locus coeruleus. Although the cause of this disease remains unknown, several transition metals, including manganese and copper, have been associated with the development of the atypical form of Parkinsonism, and iron accumulation has been associated with the development of Parkinson’s disease. Manganese³⁺ is a strong oxidizing agent, which oxidizes dopamine to aminochrome (dopaminochrome), the precursor of neuromelanin. Aminochrome formation in cell culture medium induces acute cell death in cells that uptake aminochrome, explaining the role of manganese in the development of atypical Parkinsonism. Copper accumulation in Wilson’s disease also induces Parkinsonism as one of the main symptoms, and an atypical Parkinsonism has also been observed in young copper miners. Interestingly, copper is able to complex with dopamine, which can be taken up by cells expressing the dopamine transporter, inducing caspase-independent cell death with formation of autophagic vacuoles. Iron is also able to form a complex with dopamine, the neurotoxic action of which also depends on the cellular expression of the dopamine transporter. The neurotoxicities of these transition metals to cells expressing the dopamine transporter all involve dopamine oxidation to quinones and require the inhibition of DT-diaphorase.     

Chirality and Order in Binary Molecular Crystals of Inert Cobalt(III) Complexes

Starting from the enantiomerically pure and racemic chiral Lewis bases 1‐phenylethylamine and 1‐(1‐naphthyl)ethylamine inert cobalt(III) complexes of the general composition Co(Hdmg)₂(lig)X (Hdmg = dimethylglyoximate; lig = Lewis base; X = CN, NCO, NO₂) were synthesized and characterized by single crystal X‐ray diffraction. The enantiopure complexes were used as building blocks for the synthesis of binary crystals. Solid solutions resulted from cocrystallizing isomorphous compounds of equal chirality whereas complexes of opposite chirality formed well‐ordered heterochiral solids with efficient packing. Two binary crystals of the latter type could be studied by X‐ray diffraction: Cocrystallization of two isomorphous phenylethylamine derivatives gave a quasiracemic solid. Starting from two non‐isomorphous naphthylethylamine complexes of opposite chirality cocrystals with an unexpected composition were obtained: Their asymmetric unit comprises four independent complex molecules in a 3:1 ratio between the constituents.