β-hairpin-mediated formation of structurally distinct multimers of neurotoxic prion peptides

Protein misfolding disorders are associated with conformational changes in specific proteins, leading to the formation of potentially neurotoxic amyloid fibrils. During pathogenesis of prion disease, the prion protein misfolds into β-sheet rich, protease-resistant isoforms. A key, hydrophobic domain within the prion protein, comprising residues 109–122, recapitulates many properties of the full protein, such as helix-to-sheet structural transition, formation of fibrils and cytotoxicity of the misfolded isoform. Using all-atom, molecular simulations, it is demonstrated that the monomeric 109–122 peptide has a preference for α-helical conformations, but that this peptide can also form β-hairpin structures resulting from turns around specific glycine residues of the peptide. Altering a single amino acid within the 109–122 peptide (A117V, associated with familial prion disease) increases the prevalence of β-hairpin formation and these observations are replicated in a longer peptide, comprising residues 106–126. Multi-molecule simulations of aggregation yield different assemblies of peptide molecules composed of conformationally-distinct monomer units. Small molecular assemblies, consistent with oligomers, comprise peptide monomers in a β-hairpin-like conformation and in many simulations appear to exist only transiently. Conversely, larger assemblies are comprised of extended peptides in predominately antiparallel β-sheets and are stable relative to the length of the simulations. These larger assemblies are consistent with amyloid fibrils, show cross-β structure and can form through elongation of monomer units within pre-existing oligomers. In some simulations, assemblies containing both β-hairpin and linear peptides are evident. Thus, in this work oligomers are on pathway to fibril formation and a preference for β-hairpin structure should enhance oligomer formation whilst inhibiting maturation into fibrils. These simulations provide an important new atomic-level model for the formation of oligomers and fibrils of the prion protein and suggest that stabilization of β-hairpin structure may enhance cellular toxicity by altering the balance between oligomeric and fibrillar protein assemblies

Open data, trials and new ethics of using others\u27 work.

Data and ideas are the capital of research productivity. Is it ethical to preempt the publication of another researcher\u27s unpublished data or preliminary analysis, perhaps without citation? The long-established answer is \u27certainly not\u27-but recent \u27open data\u27 use suggests otherwise. A research competition was held using data from The Systolic Blood Pressure Intervention Trial (SPRINT). This SPRINT Data Analysis Challenge created a novel environment for using open data as data became open early. This allowed third-party researchers the opportunity to assess some of the trial\u27s outcomes before trialists. Could this infringe on trialists\u27 right to analyse their data? Simultaneously, trialists had access to analyses from submissions to the competition that were not formally \u27published\u27 with a typical author credit or citation. Therefore, trialists had the opportunity to view the competition submissions and published on those ideas first without a typical way to cite the source of that idea. Could this infringe on researchers\u27 right to be credited for their ideas? This is not intended as a criticism of open data, the SPRINT Data Analysis Challenge, or similar systems/ventures, but is an effort to objectively note what may be remediable flaws in the worthwhile, growing and dynamic uses of open data. We offer preliminary analytics to shed more light and provide fodder for additional discussion