Cover Picture (Angew. Chem. Int. Ed. Engl. 16/1997)

The cover picture shows a thin section of a brain from a patient who died of Creutzfeldt–Jakob disease. The severe perforation of the cortex is clearly seen. A class of neurodegenerative diseases, the transmissible spongiform encephalopathies, was named after these spongelike alterations in the tissue. Among them are also scrapie in sheep and bovine spongiform encephalopathy (BSE, the “Mad Cow Disease”). The biochemical mechanism discussed as the cause of this kind of disorder is shown in the foreground: the conversion of α‐helices of the prion protein into β‐sheet domains. The β‐sheet‐rich pathogenic form of the prion protein aggregates in the brain of the affected organisms and triggers the pathological changes. The pathogenic form of the prion protein seems to be intrinsically infectious—it might therefore represent a novel class of pathogens that replicate in the absence of a nucleic acid. The latest results on this topic are reported by E.‐L. Winnacker, M. Famulok et al. on pp. 1674 ff.