Pressure Perturbation Studies of Noncanonical Viral Nucleic Acid Structures

G-quadruplexes are noncanonical structures formed by guanine-rich sequences of the genome. They are found in crucial loci of the human genome, they take part in the regulation of important processes like cell proliferation and cell death. Much less is known about the subjects of this work, the viral G-quadruplexes. We have chosen three potentially G-quadruplex-forming sequences of hepatitis B. We measured the stability and the thermodynamic parameters of these quadruplexes. We also investigated the potential stabilization of these G-quadruplexes by binding a special ligand that was originally developed for cancer therapy. Fluorescence and infrared spectroscopic measurements were performed over wide temperature and pressure ranges. Our experiments indicate the small unfolding volume change of all three oligos. We found a difference between the unfolding of the 2-quartet and the 3-quartet G-quadruplexes. All three G-quadruplexes were stabilized by TMPyP4, which is a cationic porphyrin developed for stabilizing the human telomere.

Photoinactivation Efficiency of Cationic Porphyrin Derivatives Against Multidrug-Resistant Wound Pathogens

The photoinactivation efficiency of antimicrobial photodynamic therapy (aPDT) with cationic porphyrin derivatives (CPDs) against multidrug-resistant (MDR) bacterial strain was assessed. MDR bacterial strains including Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, and Klebsiella pneumoniae were used. The CPDs named PM, PE, PN, and PL were synthesized as a photosensitizer (PS). A diode laser with a wavelength of 655 nm was used as a light source. Photoinactivation efficiency of the combinations formed with different energy density (50, 100, and 150 J/cm²) and PS concentrations (ranging from 3.125 µM and 600 µM) on each bacterial strain were evaluated. Toxicity of the aPDT combinations that showed a strong photoinactivation on the bacterial strains and dark toxicity of PSs and were evaluated on fibroblasts cells. In the aPDT experiments, survival reductions of up to 5.80 log₁₀ on E. coli, 5.90 log₁₀ on P. aeruginosa, 6.11 log₁₀ on K. pneumoniae and 6.78 log₁₀ on A. baumannii were obtained. There was an increase in the photoinactivation efficiency in parallel with increasing the energy density, and the best effect seen at an energy density of 150 J/cm2. PL did not show any toxic effect on fibroblasts. However, other PSs were toxic in fibroblasts at high concentrations. In this research, which reflected the results of in vitro experiments, aPDT provided potent photoinactivation against MDR clinical isolates. The research results lead to an in vivo wound model study of aPDT with CPD infected with an MDR clinical isolate.

Cationic Pyrrolidine/Pyrroline-Substituted Porphyrins as Efficient Photosensitizers against E. coli

New porphyrin–pyrrolidine/pyrroline conjugates were prepared by revisiting 1,3-dipolar cycloaddition reactions between a porphyrinic azomethine ylide and a series of dipolarophiles. Cationic conjugates obtained by alkylation of the pyrrolidine/pyrroline cycloadducts showed ability to generate singlet oxygen and to produce iodine in presence of KI when irradiated with visible light. Some of the cationic derivatives showed photobactericidal properties towards a Gram-negative bioluminescent E. coli. In all cases, these features were significantly improved using KI as coadjutant, allowing, under the tested conditions, the photoinactivation of the bacterium until the detection limit of the method with a drastic reduction of the required photosensitizer concentration and irradiation time. The obtained results showed a high correlation between the ability of the cationic porphyrin derivative to produce singlet oxygen and iodine and its E. coli photoinactivation profile.