Ethidium Binding to Salmonella enterica ser. Typhimurium Cells and Salmon Sperm DNA

Bacterial resistance to antibiotics due to increased efficiency of the efflux is a serious problem in clinics of infectious diseases. Knowledge of the factors affecting the activity of efflux pumps would help to find the solution. For this, fast and trustful methods for efflux analysis are needed. Here, we analyzed how the assay conditions affect the accumulation of efflux indicators ethidium (Et+) and tetraphenylphosphonium in Salmonella enterica ser. Typhimurium cells. An inhibitor phenylalanyl-arginyl-β-naphtylamide was applied to evaluate the input of RND family pumps into the total efflux. In parallel to spectrofluorimetric analysis, we used an electrochemical assessment of Et+ concentration. The results of our experiments indicated that Et+ fluorescence increases immediately after the penetration of this indicator into the cells. However, when cells bind a high amount of Et+, the intensity of the fluorescence reaches the saturation level and stops reacting to the accumulated amount of this indicator. For this reason, electrochemical measurements provide more trustful information about the efficiency of efflux when cells accumulate high amounts of Et+. Measurements of Et+ interaction with the purified DNA demonstrated that the affinity of this lipophilic cation to DNA depends on the medium composition. The capacity of DNA to bind Et+ considerably decreases in the presence of Mg2+, Polymyxin B or when DNA is incubated in high ionic strength media.

Ethidium binding to Salmonella enterica ser. Typhimurium Cells and Salmon sperm DNA

Bacterial resistance to antibiotics due to an increased efficiency of the efflux is a serious problem in clinics of infectious diseases. Knowledge of the factors affecting the activity of efflux pumps would help to find the solution. For this, fast and trustful methods for the efflux analysis are needed. Here we analyzed how the assay conditions affect the accumulation of efflux indicators ethidium (Et+) and tetraphenylphosphonium in Salmonella enterica ser. Typhimurium cells. An inhibitor phenyl-alanyl-arginyl-β-naphtylamide was applied to evaluate the input of RND family pumps into the total efflux. In parallel to spectrofluorimetric analysis, we used an electrochemical assessment of Et+ concentration. Results of our experiments indicated that Et+ fluorescence increases immediately after the penetration of this indicator into the cells. However, when cells bind a high amount of Et+, intensity of the fluorescence reaches the saturation level and stops reacting to the accumulated amount of this indicator. For this reason, electrochemical measurements provide more trustful information about the efficiency of efflux when cells accumulate high amounts of Et+. Measure-ments of Et+ interaction with the purified DNA demonstrated that affinity of this lipophilic cation to DNA depends on the medium composition. The capacity of DNA to bind Et+ considerably de-creases in presence of Mg2+, Polymyxin B or when DNA is incubated in high ionic strength media.

The influence of posttranscription silensing protein-suppressor P19 on the transient gfp gene expression level in aztec tobacco plants (Nicotiana rustica L.)

Aim. Genetic constructs creation for studying the influence effect of the viral posttranscriptional silencing protein suppressor p19 on transient reporter green fluorescent protein (GFP) expression and accumulation. Methods. The Golden Gate molecular cloning method was used to create the genetic constructs; the leafy tissues of the Aztec tobacco plants (Nicotiana rustica L.) were infiltrated with a suspension of Agrobacterium tumefaciens L.; the gfp gene expression level was determined by spectrofluorometric and quantitative protein (Bradford method) assays. Results. As a result of the work, the pSPV2324 genetic construct was created, which contained the reporter gene for the green fluorescent protein gfp and the gene for the synthesis of the viral posttranscriptional silencing protein suppressor p19 and its effect on the accumulation of the recombinant GFP protein was determined. A comparative analysis of the gfp gene expression level without and with the suppressor protein synthesis gene in the genetic vector showed that the fluorescence level of GFP protein in Aztec tobacco tissues was 1.3 times higher during spectrofluorimetric analysis using the p19 suppressor gene construct. Conclusions. The positive effect of the viral suppressor silencing P19 gene on the accumulation of recombinant GFP protein in tissues plants of N. rustica L. was shown for the first time. The increase in GFP protein fluorescence when using the p19 suppressor protein construct in spectrofluorimetric analysis coincides with an increase in the total concentration of total water-soluble proteins and the level fluorescence of GFP protein in their native electrophoretic separation. Keywords: cloning, genetic constructs, transient expression, silencing protein suppressor p19, green fluorescent protein (GFP).

In Search of a Phosphorus Dendrimer-Based Carrier of Rose Bengal: Tyramine Linker Limits Fluorescent and Phototoxic Properties of a Photosensitizer

Photodynamic therapy (PDT) is a skin cancer treatment alternative to chemotherapy and radiotherapy. This method exploits three elements: a phototoxic compound (photosensitizer), light source and oxygen. Upon irradiation by light of a specific wavelength, the photosensitizer generates reactive oxygen species triggering the cascade of reactions leading to cell death. The positive therapeutic effect of PDT may be limited due to low solubility, low tumor specificity and inefficient cellular uptake of photosensitizers. A promising approach to overcome these obstacles involves the use of nanocarrier systems. The aim of this initial study was to determine the potential of the application of phosphorus dendrimers as carriers of a photosensitizer—rose bengal (RB). The primary goal involved the synthesis and in vitro studies of covalent drug–dendrimer conjugates. Our approach allowed us to obtain RB–dendrimer conjugates with the use of tyramine as an aromatic linker between the carrier and the drug. The compounds were characterized by FT-IR, 1H NMR, 13C NMR, 31P NMR, size and zeta potential measurements and spectrofluorimetric analysis. The dialysis to check the drug release from the conjugate, flow cytometry to specify intracellular uptake, and singlet oxygen generation assay were also applied. Finally, we used MTT assay to determine the biological activity of the tested compounds. The results of our experiments indicate that the conjugation of RB to phosphorus dendrimers via the tyramine linker decreases photodynamic activity of RB.