Amphotericin B (AmB) is a lifesaving antibiotic used to treat deep-seated mycotic infections. Both the pharmaceutical activity and highly toxic side effects of the drug rely on its interaction with biomembranes, which is governed by the molecular organization of AmB. In the present work, we present a detailed analysis of self-assembly of AmB molecules in different environments, interesting from the physiological standpoint, based on molecular spectroscopy techniques: electronic absorption, circular dichroism, steady state and time-resolved fluorescence and molecular dynamic calculations. The results show that, in the water medium, AmB self-associates to dimeric structures, referred to as "parallel" and "antiparallel". AmB dimers can further assemble into tetramers which can play a role of transmembrane ion channels, affecting electrophysiological homeostasis of a living cell. Understanding structural determinants of self-assembly of AmB opens a way to engineering preparations of the drug which retain pharmaceutical effectiveness under reduced toxicity.

Amphotericin B (AmB) is a lifesaving polyene antibiotic used widely to treat deep-seated mycoses. Both the pharmaceutical effectiveness as well as toxic side effects depend on molecular organization of the drug. In the present study, we analyzed steady-state fluorescence, fluorescence anisotropy spectra, fluorescence lifetimes, and fluorescence anisotropy decays of AmB in the systems believed to ensure monomeric organization of the drug and in model lipid membranes. The results of the analyses show that in all of the systems studied, the drug appears in, at least, two spectral forms, interpreted as monomeric and aggregated. Spectroscopic and fluorescence lifetime characteristics of both forms are provided. Interpretation of the fluorescence anisotropy spectra of AmB incorporated into liposomes formed with dipalmitoylphosphatidylcholine let us conclude that monomers of the drug are more tightly bound to the lipid membranes as compared to the aggregates and that AmB aggregates destabilize the membrane structure. Structural model analysis, compared to the analysis of spectral shifts, leads to the conclusion that basic constituents of AmB aggregated structure is a tetramer composed of two hydrogen-bond-stabilized dimers, each dimer formed by molecules twisted by ca. 170°. The tetramer itself can span lipid bilayers and can act as a transmembrane ion channel. Specific aggregate formation of AmB has been concluded as a universal and ubiquitous form of molecular organization of the drug. This process is discussed in terms of toxic side effects of AmB.

The mode of transmission of signals between plant cells is an important aspect of plant physiology. The main role in generation of long-distance signals is played by changes in the membrane potential and cytoplasm calcium concentration, but the relation between these responses evoked by the same stimuli in the same plant remains unknown. As one of the first plant which colonized lands, the moss Physcomitrella patens is a suitable model organism for studying the evolution of signaling pathways in plants. Here, by application of glutamate as a stimulus, we demonstrated that electrical but not calcium signals can be true carriers of information in long-distance signaling in Physcomitrella. Generation of electrical signals in a form of propagating transient depolarization seems to be dependent on the opening of calcium channels, since the responses were reduced or totally blocked by calcium channel inhibitors. While the microelectrode measurements demonstrated transmission of electric signals between leaf cells and juvenile cells (protonema), the fluorescence imaging of cytoplasmic calcium changes indicated that calcium response occurs only locally - at the site of glutamate application, and only in protonema cells. This study indicates different involvement of glutamate-induced electrical and calcium signals in cell-to-cell communication in these evolutionarily old terrestrial plants.

Enzymes produced by white rot fungi are involved in the synthesis of secondary metabolites with valuable biotechnological properties. One of these metabolites is lactobionic acid (LBA). The aim of this study was to characterize a novel enzyme system consisting of a cellobiose dehydrogenase from Phlebia lindtneri (PlCDH), a laccase from Cerrena unicolor (CuLAC), a redox mediator (ABTS or DCPIP), and lactose as a substrate. We used quantitative (HPLC) and qualitative methods (TLC, FTIR) to characterise the obtained LBA. The free radical scavenging effect of the synthesised LBA was assessed with the DPPH method. Bactericidal properties were tested against Gram-negative and Gram-positive bacteria. We obtained LBA in all the systems tested; however, the study showed that the temperature of 50 °C with the addition of ABTS was the most advantageous condition for the synthesis of lactobionic acid. A mixture with 13 mM LBA synthesised at 50 °C with DCPIP showed the best antioxidant properties (40% higher compared with the commercial reagent). Furthermore, LBA had an inhibitory effect on all the bacteria tested, but the effect was better against Gram-negative bacteria with growth inhibition no lower than 70%. Summarizing the obtained data, lactobionic acid derived in a multienzymatic system is a compound with great biotechnological potential.