Amphotericin B (AmB) is a polyene antibiotic used to treat deep-seated mycoses. Both the therapeutic action and the toxic side effects of this drug are dependent on its molecular organization. AmB appears as a zwitterion at neutral pH owing to -NH 3 + and -COO -groups.The results obtained with electronic absorption, fluorescence, resonance light scattering and infrared absorption spectroscopic analyses show that in the aqueous medium at pH above 10 AmB appears in the monomeric form owing to the negative net electric charge of the molecule. On the contrary, anomalously high aggregation level has been observed at pH below 2, despite the positive net electric charge. The effect is interpreted in terms of the permanent polarization of the polyene chain at low pH, associated with relative rotational freedom of the charged mycosamine fragment of the molecule. The pH-dependent aggregation of AmB is discussed in aspect of pharmacological action of the drug.

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The aim of this research is to investigate amphotericin B (AmB)-Cu(2+) complexes in aqueous solution at different pH values. Electronic absorption, circular dichroism (CD), Raman and FTIR spectroscopies were used in this study. We found that different concentrations of AmB and Cu(2+) ions in solution leads to formation of complexes with stoichiometry of 2:1 and 1:1. The formation of AmB-Cu(2+) complexes at physiological pH values is accompanied by changes of the molecular organization of AmB especially disaggregation. These observed effects might be significant from a medical point of view.

The article presents the results of spectroscopic studies focused on a selected compound from the 1,3,4-thiadiazole group—2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thia-diazole (FABT)—in a micellar system formed by Triton X-100, a non-ionic detergent. Fluorescence measurements revealed the phenomenon of dual fluorescence whose emergence is related to the particular molecular organisation of the compound, which depends both on the concentration of the detergent and, most of all, the concentration of the compound itself. Dual fluorescence of FABT in a micellar system was observed for the compound dissolved in a methanol aqueous system, i.e., an environment wherein the dual fluorescence of the compound had never been reported before. Based on the interpretation of UV-Vis electronic absorption, resonance light scattering (RLS), emission and excitation fluorescence spectra, as well as measurements of dynamic light scattering (DLS) and Principal Component Analysis (PCA), we were able to relate the occurrence of this effect to the process of molecular aggregation taking place between FABT molecules in the micellar system in question. Results of fluorescence spectra measurements and time-correlated single photon counting (TCSPC) indicate that dual fluorescence occurs at detergent concentrations necessary to form micellar systems, which in turn facilitate the process of aggregation of FABT molecules. The correlation between the observed fluorescence effects and the previous measurements performed for analogues from this group suggests the possibility of charge transfer (CT) within the range of detergent concentrations wherein the aforementioned fluorescence effects are observed. It ought to be emphasised that this type of fluorescence effects are relatively easy to induce, which predisposes this groups of fluorophores as ideal fluorescence probes in the context of biological samples.

It acts through membrane receptors (MT1 and MT2), nuclear receptors (ROR/RZR -retinoid orphan receptors/ retinoid Z receptors), and nonreceptor-mediated mechanisms (Slominski et al., 2012). Melatonin, through its antioxidant properties, protects against damage of cellular components including DNA, cytosolic proteins, and cell membrane lipids (Yürüker et al., 2015). Studies on the antioxidant properties of melatonin are most commonly associated with agents that induce free radicals in cells (Nazıroğlu et al., 2013). Antibiotics also induce the generation of free radicals. One of them, amphotericin B (AmB), causes lipid peroxidation through generation of reactive oxygen species (ROS). AmB belongs to the group of polyene antibiotics and is an effective antifungal drug commonly used to treat systemic mycoses. It is believed that the fungicidal activity is due to the binding of AmB with the ergosterol present in the cell membrane of fungi, resulting in membrane permeabilization and osmotic imbalance (Brajtburg et al., 1990;Paulo et al., 2013). One of the mechanisms leading to fungal cell death is leakage of potassium ions caused by formation of ion channels in the cell membrane as a consequence of AmB binding with ergosterol (Chudzik et al., 2015). This situation leads to the generation of ROS and lipid peroxidation (Mesa-Arango et al., 2012). Unfortunately, AmB, besides its affinity to ergosterol, also shows an affinity to cholesterol present in human cell membranes, causing nephrotoxic and hepatotoxic side effects (Antonowicz-Juchniewicz et al.