Piotr Piwowar

The use of supramolecular structures as protein ligands

Congo red dye as well as other eagerly self-assembling organic molecules which form rod-like or ribbon-like supramolecular structures in water solutions, appears to represent a new class of protein ligands with possible wide-ranging medical applications. Such molecules associate with proteins as integral clusters and preferentially penetrate into areas of low molecular stability. Abnormal, partly unfolded proteins are the main binding target for such ligands, while well packed molecules are generally inaccessible. Of particular interest is the observation that local susceptibility for binding supramolecular ligands may be promoted in some proteins as a consequence of function-derived structural changes, and that such complexation may alter the activity profile of target proteins. Examples are presented in this paper.

Influence of the electric field on supramolecular structure and properties of amyloid-specific reagent Congo red

Among specific amyloid ligands, Congo red and its analogues are often considered potential therapeutic compounds. However, the results of the studies so far have not been univocal because the properties of this dye, derived mostly from its supramolecular nature, are still poorly understood. The supramolecular structure of Congo red, formed by π–π stacking of dye molecules, is susceptible to the influence of the electric field, which may significantly facilitate electron delocalization. Consequently, the electric field may generate altered physico-chemical properties of the dye. Enhanced electron delocalization, induced by the electric field, alters the total charge of Congo red, making the dye more acidic (negatively charged). This is a consequence of withdrawing electrons from polar substituents of aromatic rings—sulfonic and amino groups—thus increasing their tendency to dissociate protons. The electric field-induced charge alteration observed in electrophoresis depends on dye concentration. This concentration-dependent charge alteration effect disappears when the supramolecular structure disintegrates in DMSO. Dipoles formed from supramolecular fibrillar species in the electric field become ordered in the solution, introducing the modified arrangement to liquid crystalline phase. Experimental results and theoretical studies provide evidence confirming predictions that the supramolecular character of Congo red is the main reason for its specific properties and reactivity.

Intramolecular Immunological Signal Hypothesis Revived - Structural Background of Signalling Revealed by Using Congo Red as a Specific Tool

Micellar structures formed by self-assembling Congo red molecules bind to proteins penetrating into functionrelated unstable packing areas. Here, we have used Congo red - a supramolecular protein ligand to investigate how the intramolecular structural changes that take place in antibodies following antigen binding lead to complement activation. According to our findings, Congo red binding significantly enhances the formation of antigen-antibody complexes. As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade. This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity. These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

Analysis of the temperature influences on the metrological properties of polymer piezoelectric load sensors applied in Weigh-in-Motion systems

This paper describes temperature influence on the uncertainty of weighing results in Weigh in Motion systems (WIM). The analysis bases on the long-term investigation of the WIM site, as well as on simulation tests conducted on sensor and conditioning circuit models. The drawn conclusions suggest, that this uncertainty may be significantly reduced if a proper temperature correction algorithm is applied.

Design and accuracy assessment of the multi-sensor weigh-in-motion system

In every country, road networks are one of the largest and highly expensive investment. Equally expensive are the consequences of not ensuring adequate road safety. This creates the need for an efficient and automatic system for the detection of overloaded vehicles [17]. One of the tools designed to measure the weight and individual axle loads of vehicles are the systems weighing vehicles in motion (WIM). Due to their measurement imprecision, WIM systems composed of two lines of sensors are only used as pre-selection systems. At present, the only viable option for reducing measurement uncertainty in dynamic weighing is to increase number of load sensors (Multi-Sensor systems; MS-WIM). The paper presents the results of research on a MS-WIM system equipped with 16 lines of load sensors. The conceptual objectives, system design, results of experimental evaluation of the systems accuracy, and the final conclusions based on a 6-year operating period, during which the system has been used under normal traffic conditions have been presented.

The use of Titan yellow dye as a metal ion binding marker for studies on the formation of specific complexes by supramolecular Congo red

Abstract Congo red (CR) and other self-assembling compounds creating supramolecular structures of rod- or ribbon-like architecture form specific complexes with cellulose and also with many proteins, including antibodies bound to the antigen and amyloids in particular. The mechanism of complexation and structure of these complexes are still poorly recognized despite the importance of the problem for medicine. This work proposes the progress in electron microscopy studies of amyloid-dye complexes by labeling supramolecular ligand CR with silver ions as a marker. Silver ions are introduced to CR carried by the strongly binding silver dye Titan yellow, which in addition form comicellar structures with CR. Silver carried by self-assembled dye molecules forms in the resulting metal nanoparticles, making the specific amyloid ligand CR perceptible in EM studies.

Formation of amyloid-like aggregates through the attachment of protein molecules to a Congo red scaffolding framework ordered under the influence of an electric field

This study describes a technique which makes it possible to introduce the amyloid-like order to protein aggregates by using the scaffolding framework built from supramolecular, fibrillar Congo red structures arranged in an electric field. The electric field was used not only to obtain a uniform orientation of the charged dye fibrils, but also to make the fibrils long, compact and rigid due to the delocalization of pi electrons, which favors ring stacking and, as a consequence, results in an increased tendency to self-assemble. The protein molecules (immunoglobulin L chain lambda, ferritin) attached to this easily adsorbing dye framework assume its ordered structure. The complex precipitating as plate-like fragments shows birefringence in polarized light. The parallel organization of fibrils can be observed with an electron microscope. The dye framework may be removed via reduction with sodium dithionite, leaving the aggregated protein molecules in the ordered state, as confirmed by X-ray diffraction studies.

Diagnosing Human's Airduct Disease by Negative Pressure Impulse Method

The paper presents a new method applied to quantitative evaluation of the diagnostic parameters of human respiratory system. This method is based on measurement and analysis of the breathing flow during artificially caused transient states. These transient states are caused by short-time negative pulses, which are generated at the outlet patient air ducts. The results of the experiments for the healthy patient and patient with the dysfunction of respiratory system are the topic this paper

Identification of pneumatic parameters of the human respiratory system by negative pressure impulses

This paper presents results of experiments with the identification of pneumatic parameters for the five models of human flow during artificially caused transient states. These transient states are caused by short-time negative pulses, which are generated at the outlet of the patients air-ducts. In this paper is shown the influence of the non-linear character of the model on the respiratory system parameter identification results.

Attempt at a systemic outlook on aging and carcinogenesis

Abstract Two of the key problems plaguing humanity – aging and carcinogenesis – are inexorably linked. While their nature seems different, their mechanisms have a lot in common. Evidence suggests that aging is the result of spontaneous synthesis and accumulation of improperly folded proteins in cells, leading to a variety of pathologies. As for carcinogenesis, it is tied to genetic mutations – permanent, covalent changes in the DNA. Both processes are random in character; however, unlike mutations, the accumulation of malformed proteins is not genetically determined. Instead, control over this process hinges upon regulating the protein exchange rate – a phenomenon that seems a likely candidate for the basic aging control mechanism. Although mutations themselves may be counteracted in a controlled manner, their effects typically cannot. The mechanisms of aging and carcinogenesis, while functionally different, remain correlated: an aging cell is rendered more susceptible to mutational changes. The rapidly growing body of information regarding aging and carcinogenesis enables a systemic approach to both these phenomena – an approach that is attempted in this review.