The NMR structures of the recombinant cellular form of the prion proteins (PrP C ) of the cat (Felis catus), dog (Canis familiaris), and pig (Sus scrofa), and of two polymorphic forms of the prion protein from sheep (Ovis aries) are presented. In all of these species, PrP C consists of an N-terminal flexibly extended tail with Ϸ100 amino acid residues and a C-terminal globular domain of Ϸ100 residues with three ␣-helices and a short antiparallel ␤-sheet. Although this global architecture coincides with the previously reported murine, Syrian hamster, bovine, and human PrP C structures, there are local differences between the globular domains of the different species. Because the five newly determined PrP C structures originate from species with widely different transmissible spongiform encephalopathy records, the present data indicate previously uncharacterized possible correlations between local features in PrP C threedimensional structures and susceptibility of different mammalian species to transmissible spongiform encephalopathies.mammalian species ͉ feline transmissible spongiform encephalopathy ͉ scrapie T he prion protein (PrP) in mammalian organisms has attracted keen interest because of its relation to a group of invariably fatal neurodegenerative diseases, the transmissible spongiform encephalopathies (TSEs) or ''prion diseases,'' which include bovine spongiform encephalopathy (BSE), CreutzfeldtJakob disease in humans, feline spongiform encephalopathy, and scrapie in sheep. It is well established that expression of the host-encoded PrP is essential for TSE propagation (1, 2). In transgenic mice lacking the gene that encodes PrP, TSEs could not be observed, and the susceptibility toward TSE of these mice could only be restored by reestablishing PrP expression (3). High sequence conservation of PrP in mammalian species (4) indicates that this protein is functionally important in the healthy organism (1, 2), but the search for this unknown function is still ongoing.PrP was identified in the context of TSEs in an aggregated ''scrapie'' isoform of PrP (PrP Sc ) (5), which copurifies with the infective agent (6). This osbservation, the apparent stability of the infectious agent under DNA͞RNA denaturing conditions (7), and the unusual progression of the disease (8) led to the ''protein-only hypothesis.'' This hypothesis proposes that the major component, if not the only one, of the infectious particle causing TSE is a protein, i.e., presumably PrP Sc (1,(7)(8)(9)). An early observation in TSE infections has been the species barrier (10). Compared with transmission with infectious material from the same species, the incubation time for onset of TSEs is prolonged if a given species is challenged with infectious brain homogenate originating from another species. The incubation time may be reduced by consecutive passages within the new host, whereby the adaptation to the new host can take several generations for the disease to show clinical signs (11). In vivo and in vitro experiments indicated that the species ba...

NMR structures of recombinant prion proteins from various species expressed in Escherichia coli have been solved during the past years, but the fundamental question of the relevancy of these data relative to the naturally occurring forms of the prion protein has not been directly addressed. Here, we present a comparison of the cellular form of the bovine prion protein isolated and purified from healthy calf brains without use of detergents, so that it contains the two carbohydrate moieties and the part of the GPI anchor that is maintained after enzymatic cleavage of the glycerolipid moiety, with the recombinant bovine prion protein expressed in E. coli. We show by circular dichroism and 1 H-NMR spectroscopy that the three-dimensional structure and the thermal stability of the natural glycoprotein and the recombinant polypeptide are essentially identical. This result indicates possible functional roles of the glycosylation of prion proteins in healthy organisms, and provides a platform and validation for future work on the structural biology of prion proteins, which will have to rely primarily on the use of recombinant polypeptides.

Phenology is a key aspect of plant success. Recent research has demonstrated that herbarium specimens can provide important information on plant phenology. Massive digitization efforts have the potential to greatly expand herbarium-based phenological research, but also pose a serious challenge regarding efficient data collection. Here, we introduce CrowdCurio, a crowdsourcing tool for the collection of phenological data from herbarium specimens. We test its utility by having workers collect phenological data (number of flower buds, open flowers and fruits) from specimens of two common New England (USA) species: Chelidonium majus and Vaccinium angustifolium. We assess the reliability of using nonexpert workers (i.e. Amazon Mechanical Turk) against expert workers. We also use these data to estimate the phenological sensitivity to temperature for both species across multiple phenophases. We found no difference in the data quality of nonexperts and experts. Nonexperts, however, were a more efficient way of collecting more data at lower cost. We also found that phenological sensitivity varied across both species and phenophases. Our study demonstrates the utility of CrowdCurio as a crowdsourcing tool for the collection of phenological data from herbarium specimens. Furthermore, our results highlight the insight gained from collecting large amounts of phenological data to estimate multiple phenophases.

25% annual PV growth is possible over the next decade

A new 2D pulse sequence (BIRD–HMBC) designed for the detection of heteronuclear long‐range connectivities is presented. In contrast to the basic HMBC experiment and its variants, unwanted 1J(C,H) signals are sampled together with nJ(C,H) signals but are cancelled in subsequent scans, taking advantage of a BIRD pulse sequence element. As a result, sensitivities close to the HMBC with only minor losses are measured. Excellent suppression degrees for unwanted 1J(C,H) residual peaks, superior to the state‐of‐the‐art ACCORD–HMBC experiment, are achieved for the whole range of one‐bond couplings. The influence of poorly calibrated pulse angles or off‐resonance effects is marginal and options such as refocusing with additional 13C broadband decoupling or the ACCORDION element, applied for improved sampling of the whole nJ(C,H) coupling range, may easily be implemented. These attractive characteristics, together with the easy set‐up, make this new experiment a valuable alternative to the HMBC experiment and its known variants for standard routine applications. Copyright © 2000 John Wiley & Sons, Ltd.