Designing conditions for in vitro formation of amyloid protofilaments and fibrils

We have been able to convert a small α/β protein, acylphosphatase, from its soluble and native form into insoluble amyloid fibrils of the type observed in a range of pathological conditions. This was achieved by allowing slow growth in a solution containing moderate concentrations of trifluoroethanol. When analyzed with electron microscopy, the protein aggregate present in the sample after long incubation times consisted of extended, unbranched filaments of 30–50 Å in width that assemble subsequently into higher order structures. This fibrillar material possesses extensive β-sheet structure as revealed by far-UV CD and IR spectroscopy. Furthermore, the fibrils exhibit Congo red birefringence, increased fluorescence with thioflavine T and cause a red-shift of the Congo red absorption spectrum. All of these characteristics are typical of amyloid fibrils. The results indicate that formation of amyloid occurs when the native fold of a protein is destabilized under conditions in which noncovalent interactions, and in particular hydrogen bonding, within the polypeptide chain remain favorable. We suggest that amyloid formation is not restricted to a small number of protein sequences but is a property common to many, if not all, natural polypeptide chains under appropriate conditions.

Mapping the universe in three dimensions

The determination of the three-dimensional layout of galaxies is critical to our understanding of the evolution of galaxies and the structures in which they lie, to our determination of the fundamental parameters of cosmology, and to our understanding of both the past and future histories of the universe at large. The mapping of the large scale structure in the universe via the determination of galaxy red shifts (Doppler shifts) is a rapidly growing industry thanks to technological developments in detectors and spectrometers at radio and optical wavelengths. First-order application of the red shift-distance relation (Hubble’s law) allows the analysis of the large-scale distribution of galaxies on scales of hundreds of megaparsecs. Locally, the large-scale structure is very complex but the overall topology is not yet clear. Comparison of the observed red shifts with ones expected on the basis of other distance estimates allows mapping of the gravitational field and the underlying total density distribution. The next decade holds great promise for our understanding of the character of large-scale structure and its origin.