Spore-forming bacteria are a class of microorganisms that possess the ability to survive in extreme environmental conditions. Morphological features of spores assure their resistance to stress factors such as high temperature, radiation, disinfectants, and drying. Consequently, spore elimination in industrial and medical environments is very challenging. Ceragenins are a new class of cationic lipids characterized by a broad spectrum of bactericidal activity resulting from amphipathic nature and membrane-permeabilizing properties. To assess the impact of ceragenin CSA-13 on spores formed by Bacillus subtilis (ATCC 6051), we performed the series of experiments confirming that amphipathic and membrane-permeabilizing properties of CSA-13 are sufficient to disrupt the structure of B. subtilis spores resulting in decreased viability. Raman spectroscopy analysis provided evidence that upon CSA-13 treatment the number of CaDPA-positive spores was clearly diminished. As a consequence, a loss of impermeability of the inner membranes of spores, accompanied by a decrease in spore resistance and killing take place. In addition to their broad antimicrobial spectrum, ceragenins possess great potential for development as new sporicidal agents.
The mechanism of elimination of F -trapped inside the double four-membered ring (D4R) cages of octadecasil has been determined by means of periodic calculations at the B3LYP/VDZP//VTZP level of theory with the CRYSTAL06 program. Finite temperature and entropic effects are taken into account to study the efficiency of the elimination reaction, which is exothermic, requires acid media, and is catalyzed by cationic polar molecules with accessible protons, from which a hydronium ion has been considered in the present study. The mechanism consists of three steps that schematically correspond to hydrolysis of one SiOSi bridge in the D4R cage, extraction of the F -from the unit, and recondensation of the bridge with formation of slightly adsorbed HF · H 2 O in the large cavity that can be easily eliminated by diffusion. The limiting step is the first one and involves a quite low Helmholtz free energy barrier even at 100°C (51.6 kJ mol -1 ) that slowly decreases with increasing temperature.
Understanding the response of cancer cells to ionising radiation is a crucial step in modern radiotherapy. Raman microspectroscopy, together with Partial Least Squares Regression (PLSR) analysis has been shown to be a powerful tool for monitoring biochemical changes of irradiated cells on the subcellular level. However, to date, the majority of Raman studies have been performed using a single spectrum per cell, giving a limited view of the total biochemical response of the cell. In the current study, Raman mapping of the whole cell area was undertaken to ensure a more comprehensive understanding of the changes induced by X-ray radiation. On the basis of the collected Raman spectral maps, PLSR models were constructed to elucidate the time-dependent evolution of chemical changes induced in cells by irradiation, and the performance of PLSR models based on whole cell averages as compared to those based on average Raman spectra of cytoplasm and nuclear region. On the other hand, prediction of X-ray doses for individual cellular components showed that cytoplasmic and nuclear regions should be analysed separately. Finally, the advantage of the mapping technique over single point measurements was verified by a comparison of the corresponding PLSR models.
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