Some physico-chemical parameters that influence proteinase K resistance and the infectivity of PrP Sc after high pressure treatment

Amyloid features and neuronal toxicity of mature prion fibrils are highly sensitive to high pressure

Prion proteins (PrP) can aggregate into toxic and possibly infectious amyloid fibrils. This particular macrostructure confers on them an extreme and still unexplained stability. To provide mechanistic insights into this self-assembly process, we used high pressure as a thermodynamic tool for perturbing the structure of mature amyloid fibrils that were prepared from recombinant full-length mouse PrP. Application of high pressure led to irreversible loss of several specific amyloid features, such as thioflavin T and 8-anilino-1-naphthalene sulfonate binding, alteration of the characteristic proteinase K digestion pattern, and a significant decrease in the β-sheet structure and cytotoxicity of amyloid fibrils. Partial disaggregation of the mature fibrils into monomeric soluble PrP was observed. The remaining amyloid fibrils underwent a change in secondary structure that led to morphologically different fibrils composed of a reduced number of proto-filaments. The kinetics of these reactions was studied by recording the pressure-induced dissociation of thioflavin T from the amyloid fibrils. Analysis of the pressure and temperature dependence of the relaxation rates revealed partly unstructured and hydrated kinetic transition states and highlighted the importance of collapsing and hydrating inter- and intramolecular cavities to overcome the high free energy barrier that stabilizes amyloid fibrils.

High pressure application for food biopolymers

High hydrostatic pressure constitutes an efficient physical tool to modify food biopolymers, such as proteins or starches. This review presents data on the effects of high hydrostatic pressure in combination with temperature on protein stability, enzymatic activity and starch gelatinization. Attention is given to the protein thermodynamics in response to combined pressure and temperature treatments specifically on the pressure-temperature-isokineticity phase diagrams of selected enzymes, prions and starches relevant in food processing and biotechnology.

Protein conformation determines the sensibility to high pressure treatment of infectious scrapie prions

Application of high pressure can be used for gentle pasteurizing of food, minimizing undesirable alterations such as vitamin losses and changes in taste and color. In addition, pressure has become a useful tool for investigating structural changes in proteins. Treatments of proteins with high pressure can reveal conformations that are not obtainable by other physical variables like temperature, since pressure favors structural transitions accompanied with smaller volumes. Here, we discuss both the potential use of high pressure to inactivate infectious TSE material and the application of this thermodynamic parameter for the investigation of prion folding. This review summarizes our findings on the effects of pressure on the structure of native infectious scrapie prions in hamster brain homogenates and on the structure of infectious prion rods isolated from diseased hamsters brains. Native prions were found to be pressure sensitive, whereas isolated prions revealed an extreme pressure-resistant structure. The discussion will be focused on the different pressure behavior of these prion isoforms, which points out differences in the protein structure that have not been taken into consideration before.

Inactivation of transmissible spongiform encephalopathy agents in food products by ultra high pressure-temperature treatment

Bovine spongiform encephalopathy (BSE) contamination of the human food chain most likely resulted from nervous system tissue in mechanically recovered meat used in the manufacture of processed meats. The availability of effective decontamination methods for products considered at risk for BSE or other transmissible spongiform encephalopathies (TSEs) would be an attractive safeguard to human health, but neither of the two proven inactivating methods, autoclaving or exposure to strong alkali or bleach, are applicable to foodstuffs. Ultra high pressure-temperature treatment of foods is an effective decontamination method that can reduce the pathogen load while keeping unaltered the nutritional and organoleptic properties of the product. The application of different combinations of high pressure-temperature pulses to meat products 'spiked' with the agents of TSEs can reduce the level of infectivity by 10(3) to 10(6) mean lethal doses (LD(50)) per gram of tissue. These data indicate that the high pressure-temperature treatment is a ready-to-use and feasible strategy to reduce the risk of TSEs transmission via contaminated meat products.

Highlights of the 3rd International Conference on High Pressure Bioscience and Biotechnology

The 3rd International Conference on High Pressure Bioscience and Biotechnology was held in the city of Rio de Janeiro from September 27 to September 30, 2004. The meeting, promoted by the International Association of High Pressure Bioscience and Biotechnology (IAHPBB), congregated top scientists and researchers from all over the world. In common, they shared the use of hydrostatic pressure for research, technical development, or industrial applications. The meeting consisted of invited lectures, contributed papers and a well-attended poster session. Very exciting discussions were held inside and outside the sessions, and the goals of discussing state-of-the-art data and establishing working collaborations and co-operations were fully attained.