Sofia University

About: Sofia University is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Large Hadron Collider & Standard Model. The organization has 8533 authors who have published 15730 publications receiving 306320 citations. The organization is also known as: University of Sofia & BFUS.

Non-aggregated Ga(III)-phthalocyanines in the photodynamic inactivation of planktonic and biofilm cultures of pathogenic microorganisms

Abstract: Visible light-absorbing cationic water-soluble gallium(III) phthalocyanines (GaPcs) peripherally substituted with four and eight methylpyridyloxy groups were synthesized and investigated as antimicrobial photodynamic sensitizers The inserted large gallium ion in the phthalocyanine ligand is axially substituted by one hydroxyl group which prevents aggregation of the complexes in aqueous solution The cellular uptake and the photodynamic activity for the representative strains of the Gram positive bacteria methicillin-resistant Staphylococcus aureus(MRSA) and Enterococcus faecalis, of the Gram negative bacterium Pseudomonas aeruginosa and of the fungus Candida albicans in planktonic phase were studied The tetra-methylpyridyloxy substituted GaPc1 showed lower cellular uptake compared to the octa-methylpyridyloxy substituted GaPc2 The photodynamic activity of the GaPcs was studied in comparison to methylene blue (MB) and a photodynamically active Zn(II)-phthalocyanine with the same substitution (ZnPcMe) Photodynamic treatment with 30 μM GaPc1 at mild light conditions (50 J cm−2, 60 mW cm−2) resulted in a high photoinactivation of the microorganisms in the planktonic phase nevertheless the dark toxicity of GaPc1 towards MRSA and E faecalis GaPcs against fungal biofilm grown on polymethylmethacrylate (PMMC) resin showed a complete inactivation at a higher concentration of GaPc2 (60 μM) and of the referent sensitizer ZnPcMe However, the bacterial biofilms were not susceptible to treatment of GaPcs with only 1–2 log reduction of the biofilm The bacterial biofilm E faecalis was effectively inactivated only with MB The water-soluble octa-methylpyridyloxy substituted GaPc2 has a potential value for photodynamic treatment of C albicans biofilms formed on denture acrylic resin

Prompt chlorophyll a fluorescence as a rapid tool for diagnostic changes in PSII structure inhibited by salt stress in Perennial ryegrass.

Abstract: Perennial ryegrass (Lolium perenne L.) is one of the most popular grass species in Europe. It is commonly used for establishing the lawns in urban areas, where the salt stress is one of the major environmental conditions limiting its growth. The basic aim of this study was the detailed in vivo analysis of the changes in photosynthetic efficiency, induced by salt stress, of two lawn varieties of Perennial ryegrass and to find out the variety of better properties to create lawn on the soils contaminated with salt. Two lawn varieties of L. perenne L. were used: Nira and Roadrunner. The salinization was applied 8 weeks after sowing by adding NaCl in water solution (0, 0.15, and 0.30 M). The measurements were carried out 8 times: 0, 24, 48, 96, 144, 192, 240 and 288 h after salinization. Our results revealed that the disturbance of PSII function could easily be estimated by measuring chlorophyll a fluorescence and analyzing that signal by JIP-test. Our work allowed to identify various limiting parameters of photosynthetic efficiency of perennial ryegrass lawn varieties grown under salt stress conditions. This knowledge can allow for selection of plants with a higher potential photosynthetic efficiency (vitality) during salt stress conditions, that can be used successfully neighboring roads, where salt is applied.

Role of Jahn-Teller disorder in Raman scattering of mixed-valence manganites

Abstract: The mixed-valence perovskitelike manganites are characterized by the unique interrelation of Jahn-Teller distortions, electric and magnetic properties. The Jahn-Teller distortion follows the ${\mathrm{Mn}}^{3+}\ensuremath{\rightarrow}{\mathrm{Mn}}^{4+}$ charge transfer with some delay. Its development depends on the lifetime of Mn in the $3+$ state, governed by the ${\mathrm{Mn}}^{4+}/{\mathrm{Mn}}^{3+}$ ratio and magnetic correlations. The noncoherence of Jahn-Teller distortions in orthorhombic mixed-valence manganites and rhombohedral $R{\mathrm{MnO}}_{3}$ $(R=\mathrm{rare}$ earth) results in oxygen disorder. We demonstrate that the Raman spectra in this case are dominated by disorder-induced bands, reflecting the oxygen partial phonon density of states (PDOS). The PDOS origin of the main Raman bands in insulating phases of such compounds is evidenced by the similar line shape of experimental spectra and calculated smeared PDOS and disappearance of the PDOS bands in the ordered ferromagnetic metallic phase.