Nonspecific prion protein-nucleic acid interactions lead to different aggregates and cytotoxic species.

A misfolded form of the prion protein (PrP) is the primary culprit in mammalian prion diseases. It has been shown that nucleic acids catalyze the misfolding of cellular PrP into a scrapie-like conformer. It has also been observed that the interaction of PrP with nucleic acids is nonspecific and that the complex can be toxic to cultured cells.

Effects of lipid confinement on insulin stability and amyloid formation.

We report on a study of insulin incorporation into cubic phases of mono-olein (MO), using synchrotron small-angle X-ray scattering and FT-IR spectroscopy. We studied the thermal stability and aggregation scenario of insulin as a function of protein concentration in the narrow water channels of the cubic lipid matrix and compared it with data for insulin unfolding and fibrillation in bulk water solutions. The concomitant effect of insulin entrapment on the structure and phase behavior of the lipid matrix itself was also examined.

Fourier transform infrared spectroscopy provides a fingerprint for the tetramer and for the aggregates of transthyretin.

Transthyretin (TTR) is an amyloidogenic protein whose aggregation is responsible for several familial amyloid diseases. Here, we use FTIR to describe the secondary structural changes that take place when wt TTR undergoes heat- or high-pressure-induced denaturation, as well as fibril formation. Upon thermal denaturation, TTR loses part of its intramolecular beta-sheet structure followed by an increase in nonnative, probably antiparallel beta-sheet contacts (bands at 1,616 and 1,686 cm(-1)) and in the light scattering, suggesting its aggregation.

Temperature and pressure effects on structural and conformational properties of POPC/SM/cholesterol model raft mixtures--a FT-IR, SAXS, DSC, PPC and Laurdan fluorescence spectroscopy study.

We report on the effects of temperature and pressure on the structure, conformation and phase behavior of aqueous dispersions of the model lipid "raft" mixture palmitoyloleoylphosphatidylcholine (POPC)/bovine brain sphingomyelin (SM)/cholesterol (Chol) (1:1:1). We investigated interchain interactions, hydrogen bonding, conformational and structural properties as well as phase transformations of this system using Fourier transform-infrared (FT-IR) spectroscopy, small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC) coupled with pressure perturbation calorimetry (PPC), and Laurdan fluorescence spectroscopy. The IR spectral parameters in combination with the scattering patterns from the SAXS measurements were used to detect structural and conformational transformations upon changes of pressure up to 7-9 kbar and temperature in the range from 1 to about 80 degrees C.

Incorporation of alpha-chymotrypsin into the 3D channels of bicontinuous cubic lipid mesophases.

The effects of protein entrapment on the structure and phase behavior of periodically curved lipid mesostructures have been examined by synchrotron small-angle X-ray diffraction and FT-IR spectroscopy. The study was directed towards a better understanding of the effect of confinement in a lipid environment on the stability and unfolding behavior of alpha-chymotrypsin, and, vice versa, the effect of the entrapped protein on the lipid's mesophase structure and temperature- and pressure-dependent phase behavior. We compare the interaction of protein molecules of two different sizes (cytochrome c, 12.

The amino-terminal PrP domain is crucial to modulate prion misfolding and aggregation.

The main hypothesis for prion diseases is that the cellular protein (PrP(C)) can be altered into a misfolded, beta-sheet-rich isoform (PrP(Sc)), which undergoes aggregation and triggers the onset of transmissible spongiform encephalopathies. Here, we investigate the effects of amino-terminal deletion mutations, rPrP(Delta51-90) and rPrP(Delta32-121), on the stability and the packing properties of recombinant murine PrP. The region lacking in rPrP(Delta51-90) is involved physiologically in copper binding and the other construct lacks more amino-terminal residues (from 32 to 121).

Kinetics of lamellar-to-cubic and intercubic phase transitions of pure and cytochrome c containing monoolein dispersions monitored by time-resolved small-angle X-ray diffraction.

We investigated the effect of incorporation of a small aqueous peripheral membrane protein (cyt c) into the three-dimensional periodic nanochannel structures formed by the lipid monoolein (MO) on its rich phase behavior as a function of temperature, pressure, and protein concentration using synchrotron X-ray small-angle diffraction. By simultaneous use of the pressure-jump relaxation technique and time-resolved synchrotron X-ray diffraction, we also studied the kinetics of various lipid mesophase transformations of the system for understanding the mechanistic pathways of their formation influenced by the protein-lipid interactions. Cyt c incorporated into the bicontinuous cubic phase Ia3d of MO has a significant effect on the lipid structure and the pressure stability of the system already at low protein concentrations.

Hydration and packing effects on prion folding and beta-sheet conversion. High pressure spectroscopy and pressure perturbation calorimetry studies.

The main hypothesis for prion diseases proposes that the cellular protein (PrP(C)) can be altered into a misfolded, beta-sheet-rich isoform (PrP(Sc)), which undergoes aggregation and triggers the onset of transmissible spongiform encephalopathies. Here, we compare the stability against pressure and the thermomechanical properties of the alpha-helical and beta-sheet conformations of recombinant murine prion protein, designated as alpha-rPrP and beta-rPrP, respectively. High temperature induces aggregates and a large gain in intermolecular antiparallel beta-sheet (beta-rPrP), a conformation that shares structural similarity with PrP(Sc).