Wyniki wyszukiwania - Biblioteka Nauki

1

Polska bibliografia Dietricha Bennera

100%

Stepkowski D.

Forum Pedagogiczne

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2011

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nr 2

2

Myślenie transcendentalno-fenomenologiczne Dietricha Bennera (próba zdefiniowania)

100%

Stepkowski D.

Forum Pedagogiczne

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2011

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nr 2

3

Nature of cross-seeding barriers of amyloidogenesis

63%

Stepkowski D. , Bienias J.

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nr 2

EN

The epidemics of bovine spongiform encephalopathy (BSE) several decades ago and present epidemics of chronic wasting disease (CWD) among cervids posed a threat of cross-species infections to humans or other animals. Therefore, the question as to the molecular nature of the species barriers to transmissibility of prion diseases is very important. We approached this problem theoretically, first developing a model of template-monomer interaction based on logical and topological grounds and on experimental data about cross-seeding of PrP 23-144 protein orthologs. Further, we propose that the strength of the cross-seeding barriers is proportional to dissimilarity of key amyloidogenic regions of the proteins. This dissimilarity can be measured by dissimilarity function we propose. Scaled on experimental data, this function predicts if cross-seeding can occur between different variants of PrP23-144. The resemblance of PrP23-144 cross-seeding barriers to the barriers of cross-species transmissibility of prion diseases is discussed. We suggest that a similar theoretical approach could be applied to predicting the occurrence of species barriers of prion diseases at least in part corresponding to the process of multiplication of infectious agent.

4

Motility assay: achievements and perspectives

63%

Makuch R. , Stepkowski D.

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nr 3

5

Order-disorder structural transitions in synthetic filaments of fast and slow skeletal muscle myosins under relaxing and activating conditions

51%

Podlubnaya Z. A. , Malyshev S. L. , Nieznanski K. , Stepkowski D.

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nr 4

EN

In the previous study (Podlubnaya et al., 1999, J. Struc. Biol. 127, 1-15) Ca2+-induced reversible structural transitions in synthetic filaments of pure fast skeletal and cardiac muscle myosins were observed under rigor conditions (-Ca2+/+ Ca2+). In the present work these studies have been extended to new more order-producing conditions (presence of ATP in the absence of Ca2+) aimed at arresting the relaxed structure in synthetic filaments of both fast and slow skeletal muscle myosin. Filaments were formed from column-purified myosins (rabbit fast skeletal muscle and rabbit slow skeletal semimebranosus proprius muscle). In the presence of 0.1 mM free Ca2+, 3 mM Mg2+ and 2 mM ATP (activating conditions) these filaments had a spread structure with a random arrangement of myosin heads and subfragments 2 protruding from the filament backbone. Such a structure is indistinguishable from the filament structures observed previously for fast skeletal, cardiac (see reference cited above) and smooth (Podlubnaya et al., 1999, J. Muscle Res. Cell Motil. 20, 547-554) muscle myosins in the presence of 0.1 mM free Ca2+. In the absence of Ca2+ and in the presence of ATP (relaxing conditions) the filaments of both studied myosins revealed a compact ordered structure. The fast skeletal muscle myosin filaments exhibited an axial periodicity of about 14.5 nm and which was much more pronounced than under rigor conditions in the absence of Ca2+ (see the first reference cited). The slow skeletal muscle myosin filaments differ slightly in their appearance from those of fast muscle as they exhibit mainly an axial repeat of about 43 nm while the 14.5 nm repeat is visible only in some regions. This may be a result of a slightly different structural properties of slow skeletal muscle myosin. We conclude that, like other filaments of vertebrate myosins, slow skeletal muscle myosin filaments also undergo the Ca2+-induced structural order-disorder transitions. It is very likely that all vertebrate muscle myosins possess such a property.

6

The prion peptide forms ion channels in planar lipid bilayers

38%

Berest V. , Rutkowski M. , Rolka K. , Legowska A. , Debska G. , Stepkowski D. , Szewczyk A.

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2003

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tom 08

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nr 2

EN

One of the hypotheses concerning the pathogenic properties of the prion protein, considers its influence on cellular ion homeostasis. Using the lipid bilayer technique, the influence of prion-derived peptides on the lipid bilayer conductance was characterized. To evaluate the physiological significance and possible pathological functions of the peptides, their effect on the membrane potential and respiration rate of hippocampal mitochondria was also studied. We used a peptide bearing the human prion protein sequence YSNQNNF (PrP [169- 175]), and peptide SSQNNF (PrP [170-175]) bearing a naturally-occurring mutation in position 171 [N→S] linked to schizoaffective diseases in humans (Samaia, H.B., Mari, J.J., Vallada, H.P., Moura R.P., Simpson A.J.G., Brentani R.R. A prion-linked psychiatric disorder. Nature 390 (1997) 241). In this report, we show that PrP [170-175] N171S increases the conductance of planar lipid bilayers. Based on the conductance of single channel currents recorded in 500/500 mM KCl (cis/trans), we found a single channel conductance of 8 to 26 pS. The native prion peptide PrP [169-175] does not form ion channels in the lipid bilayer. Neither of the peptides significantly changed the membrane potential or respiration rate of isolated rat hippocampal mitochondria. We propose a possible mechanism for channel formation by aggregation of the prion-derived peptide.