Michał Szociński

Inhibition of amyloid fibril formation of hen egg white lysozyme by trimethylamine N-oxide at low pH

In vitro inhibition of the formation of fibrous aggregates of proteins (amyloids) has gained increasing attention due to the number of diseases associated with protein misfolding and fibrillation. An interesting group of compounds for which pronounced activity against this phenomenon can be expected consists of low molecular weight substances (osmolytes) which have the ability to change protein stability. Here we investigate the influence of trimethylamine N-oxide (TMAO) in acidic solution (pH=2) on the fibrillation of hen egg white lysozyme (HEWL). The process was monitored by five techniques: circular dichroism in the UV region, atomic force microscopy, dynamic light scattering, densimetry and gel electrophoresis. The obtained results show that protonated TMAO in a concentration of 400 mM inhibits amyloidogenesis. In the conditions of the experiment the HEWL molecules form clusters about 30 nm in diameter containing a relatively high fraction of covalent-bonded dimers.

Application of impedance imaging to evaluation of organic coating degradation at a local scale

A new approach for evaluating the local electrical properties of organic coatings has been proposed. It was performed with contact mode atomic force microscopy (AFM). A current response signal was measured when a single-frequency voltage perturbation was applied between AFM tip and coated metal. Suitability of the proposed technique has been presented on the representative acrylic coating degraded by two different factors—UV radiation and electrolyte exposure. It was possible to disclose the early stages of the coating deterioration, to spatially localize defective regions, and to observe distinctly different modes of the coating degradation as a result of exposure to various degradation factors.

The Influence of UV Light on Performance of Poly(methyl Methacrylate) in Regard to Dye-Sensitised Solar Cells

Low - cost production and simplicity of the process as well as comparable efficiencies make Dye - Sensitised Solar Cells (DSSC) competitive among commercial solar technologies. Excellent transparency and weatherability make the poly(methyl methacrylate) (PMMA) polymer a possible substitute of transparent, conductive glass commonly used in Dye-Sensitised Solar Cells. In the presented investigation thin PMMA film was applied. UV-C irradiation in range of 200-280nm was used to accelerate polymer degradation. Combination of Electrochemical Impedance Spectroscopy (EIS) and Atomic Force Microscopy (AFM) were used in order to provide information about photodegradation of the polymer coating as well as durability of PMMA film. AFM allowed evaluation of the photodegradation of PMMA coating and indicated possible local defects. The data gained using EIS technique confirmed that the PMMA deteriorated over a period of 141 hours of irradiation with UV-C

Influence of the ionic strength on the amyloid fibrillogenesis of hen egg white lysozyme

The study investigates the role of the electrostatic interactions in the fibrillation of the hen egg white lysozyme (HEWL). In order to achieve this aim the influence of the cations Na+, Mg2+ and Al3+ on the amyloid fibril formation and amorphous aggregation was tested. The amyloids are formed in the solution without added salt but the Thioflavin T fluorescence gives the false-negative result. In these conditions, the HEWL fibrils are long and curvy. If the ionic strength of the solution is sufficiently high, the formed amyloids are shorter and fragmented. Our study shows that the addition of the aluminium salt promotes protein fibrillation. The amorphous aggregation dominates in the high concentration of electrolyte. The in vitro amyloid fibril formation seems to be regulated by universal mechanisms. The theories implemented in the polymer science or for colloidal solutions give the qualitative description of the aggregation phenomena. However, the specific interactions and the additional effects (e.g. fibril fragmentation) modulate the amyloidogenesis.

Corrosivity of environment and the current state of the steel elements at the former Auschwitz concentration camp

The objective of this study was to assess corrosivity of the atmospheric environment in the former Auschwitz I and Auschwitz II-Birkenau concentration and extermination camp, and to identify the protective properties of existing corrosion products in order to estimate the actual corrosion rate of original steel elements located there. The current atmospheric corrosivity of the former Auschwitz camp, specified during one year of exposure of steel samples according to the EN ISO 12944-2 (1998) standard, was determined and it can be described as a boundary between the low C2 and medium C3. The steel corrosion rate in these conditions was in the range of 14–34 µm/year with the average rate of 27 µm/year. A layer of corrosion products formed on uncovered original reinforcement steel rods during ca. 70 years of atmospheric exposure was examined in terms of their protective properties with respect to steel. The microstructure, chemical composition, and elemental chemical state were analyzed by means of scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Potentiodynamic polarization and electrochemical impedance spectroscopy methods were employed to investigate the corrosion resistance of the carbon steel covered with a layer of corrosion products. It has been estimated that this layer slows down the corrosion rate of steel by about five times. Hence, it can be concluded that the corrosion rate of the original steel parts under the layer of corrosion products should not exceed 7 µm/year.

Assessment of copper surface coverage with corrosion inhibitor using AFM-based local electrical measurements

ABSTRACT The paper presents a new method of assessment of metal surface coverage with corrosion inhibitor and thus of inhibitor protective performance. It is based on the atomic force microscopy measurement performed in a contact mode. Apart from topography images the proposed approach allows acquisition of local DC maps and local electrical impedance spectra via application of DC bias voltage or AC perturbation signal between the conductive AFM tip and the substrate. Potentialities of this technique in inhibitor performance monitoring were illustrated on the example of copper/benzotriazole system exposed to elevated humidity environment.

Fatigue Damage Evaluation of Organic Coatings Subjected to Mechanical Stress

A number of structures fail due to the fatigue damage resulting from cyclic mechanical stress. However, as far as coatings are concerned this degradation factor remains underestimated. In the paper the authors compare an impact of repetitive mechanical stress on as-received epoxy coating and on the UV and elevated temperature pre-exposed epoxy film.