DNA influence on norfloxacin fluorescence

Monitoring of DNA structural changes after incorporation of the phenylpyrazole insecticide fipronil

The use of insecticides presents a risk to the environment because they can accumulate in the water, soil, air, and organisms, endangering human and animal health. It is therefore essential to investigate the effects of different groups of insecticides on individual biomacromolecules such as DNA. We studied fipronil, which belongs to the group of phenylpyrazole insecticides. The interaction of fipronil with calf thymus DNA was investigated using spectroscopic methods (absorption and fluorescence spectroscopy) complemented with infrared spectroscopy and viscosity measurement. Fluorescence emission spectroscopy showed the formation of a fipronil/DNA complex with a combined static and dynamic type of quenching. The binding constant was 4.15 × 103 L/mol. Viscosity changes were recorded to confirm/disconfirm the intercalation mode of interaction. A slight change in DNA viscosity in the presence of fipronil was observed. The phenylpyrazole insecticide does not cause significant conformational changes in DNA structure or increase of its chain length. We hypothesize that fipronil is incorporated into the minor groove of the DNA macromolecule via hydrogen interactions as indicated by FT-IR and CD measurements.

Electrospun nanofiber-based indicatorpaper sensing platform for fluorescence and visualization detection of norfloxacin

Norfloxacin (NOR) residues in water pose a serious threat to human health via the food chain, necessitating the development of a rapid on-site antibiotic detection technique. In this work, we utilize electrostatic spinning technology that combines polyacrylonitrile (PAN) fibers and adenosine triphosphate (ATP)-rare earth metal Tb3+ complexes (ATP/Tb) to construct a new ternary film-based sensor for sensitive, quick, and convenient field testing of NOR in water. The operating mechanism is that the ternary system produces gradually enhanced bright green fluorescence at increasing concentrations of NOR. The unique fluorescence property of the ternary systems is attributed to the use of ATP, rather than the commonly used adenosine monophosphate (AMP), to coordinate with Tb3+, which avoided the possible fluorescence quenching from competitive water binding. Benefiting from the PAN nanofiber's superior stability, acid, and alkali resistance, and flexibility as support, the ternary system exhibited a good linear response to NOR in a wide dynamic range of 0.04-30 μM at the detection limit of 16 nM. Additionally, the combination of a smartphone color recognition app allows for quick on-scene NOR detection. This film sensing strategy is instructive for the development of smart and portable sensing platforms for real-time detection of analytes such as antibiotics, pesticide residues, and hazardous materials in water bodies.

The effect of flanking bases on direct and triplet sensitized cyclobutane pyrimidine dimer formation in DNA depends on the dipyrimidine, wavelength and the photosensitizer

Cyclobutane pyrimidine dimers (CPDs) are the major products of DNA produced by direct absorption of UV light, and result in C to T mutations linked to human skin cancers. Most recently a new pathway to CPDs in melanocytes has been discovered that has been proposed to arise from a chemisensitized pathway involving a triplet sensitizer that increases mutagenesis by increasing the percentage of C-containing CPDs. To investigate how triplet sensitization may differ from direct UV irradiation, CPD formation was quantified in a 129-mer DNA designed to contain all 64 possible NYYN sequences. CPD formation with UVB light varied about 2-fold between dipyrimidines and 12-fold with flanking sequence and was most frequent at YYYR and least frequent for GYYN sites in accord with a charge transfer quenching mechanism. In contrast, photosensitized CPD formation greatly favored TT over C-containing sites, more so for norfloxacin (NFX) than acetone, in accord with their differing triplet energies. While the sequence dependence for photosensitized TT CPD formation was similar to UVB light, there were significant differences, especially between NFX and acetone that could be largely explained by the ability of NFX to intercalate into DNA.

Fluorescence quenching of various indoles by nickel complexes

The interactions between two nickel complexes with the ligand N,N'-bis (2-pyridylmethylene)-1,3-diaminopropyl and the indoles melatonin, serotonin, tryptamine, and tryptophol were characterized using UV-vis and fluorescence spectroscopy. The fluorescence of all the indoles were quenched in the presence of the complex with a hydroxyl group, indicating that hydrogen-bonding is a necessary interaction for quenching to occur. Various quenching parameters were determined using Stern-Volmer analysis and the quenching was determined to be of a mixed nature with high static quenching values (10¹¹-10¹³ M^-1). Additional analysis using the finite sink approximation indicated that the bimolecular reactions were not diffusion-limited and had high activation energies (135-199 kJ mol^-1).

Investigation of biological activity of nickel (II) complex with naproxen and 1,10-phenanthroline ligands

After the accidental discovery of cis-platinum, extensive attempts have centralized on the rational design of metallic compounds for cancer treatment. Here a solvent-dependent complex of nickel (II) with 1,10-phenanthroline and naproxen, [Ni(1,10-phenanthroline)(naproxen)₂(solvent)], solvent = 83% H₂O and 17% EtOH in the crystal structure, has been synthesized and specified by the X-ray structure analysis. It's in vitro DNA binding was inspected by the multispectroscopic methods and gel electrophoresis. The data of DNA-viscosity and competition fluorimetric test by methylene blue (MB) and Hoechst 33258 confirm groove binding mode of the complex to CT-DNA. Comparison of the results of this binding study with previous work revealed that the mode of binding of small compounds to DNA is highly influenced by the structure of the compounds. The DNA cleavage potency of the complex was appraised by the agarose gel electrophoretic and it was found that the complex does not have any momentous cleavage potency on the pUC18 plasmid DNA. The cytotoxicity of the complex on HT 29, HepG2 and HEK-293 cell lines by MTT method indicates that %inhibition of the complex on HT 29 is better than HepG2, compared with cisplatin drug. On HEK-293 cells, %inhibition growth of normal cells of the complex is less than cisplatin. Flow cytometry analysis of the complex on the HT 29 cells indicated the apoptosis cell death. RT-PCR studies revealed down-regulation of BCL2 expression, while the expression of BAX, caspase 3 and BAX/BCL2 genes was up-regulated in HT 29 cells by the complex. HighlightsA solvent-dependent nickel (II) with naproxen and 1,10-phenanthroline with aqueous solubility was synthesized and characterized.All experimental results indicate a groove mode of binding of the complex to CT-DNA.Potential biological characteristics confirmed that the complex is a promising candidate as anticancer agent.Communicated by Ramaswamy H. Sarma.

Increasing DNA binding affinity of doxorubicin by loading on Fe3O4 nanoparticles: A multi-spectroscopic study

Magnetic Fe₃O₄ nanoparticles were synthesized successfully by co-precipitation method and characterized using XRD, SEM and EDS analyses. Then doxorubicin (DOX, a known anticancer drug) was loaded onto nanoparticles. In vitro DNA interaction of free DOX and loaded DOX onto Fe₃O₄ nanoparticles (DOX-Fe₃O₄) was investigated by DNA-viscosity measurements, UV-visible and fluorescence spectroscopies. The obtained values for binding constant of DOX and DOX-Fe₃O₄ compounds from UV-visible spectroscopies were 0.04 × 10⁵ and 0.68 × 10⁵ L mol^-1, respectively, which confirms DOX-Fe₃O₄ compound have a stronger interaction with CT-DNA compared to DOX. Considerable changes on viscosity of the compounds recommended that their binding mode with CT-DNA is intercalative binding. Fluorescence intensity of DOX and DOX-Fe₃O₄ was quenched via static process by regular addition of CT-DNA. Thermodynamic parameters suggest that Van der Waals forces and hydrogen bonding for DOX and electrostatic forces for DOX-Fe₃O₄ are predominantly responsible for interaction with CT-DNA. Competition fluorescence studies were done by Hoechst 33258 as a well-known groove binder and ethidium bromide (EtBr) as a known intercalator probe. Percentage of displacement for EtBr-DNA complex with DOX and DOX-Fe₃O₄ was 39% and 61%, and for Hoechst-DNA complex was 9% and 5%, respectively. These results confirmed that both compounds are intercalator binders, although DOX-Fe₃O₄ with a further 22% displacement is a stronger intercalator binder than DOX. The stronger interaction of DOX-Fe₃O₄ compared to DOX suggests that the current system can be used as a new and effective way to targeted therapy of anticancer drugs.

Studies on the interaction of antibiotic drug rifampin with DNA and influence of bivalent metal ions on binding affinity

In this paper, the interaction between rifampin, a known antibiotic used against tuberculosis, and DNA helix is investigated by applying multiple biophysical and molecular modelling approaches in an aqueous solution at pH 7.4 and 5. It was proved that the fluorescence quenching of labeled probe DNA by rifampin is a result of the complex formation of rifampin in groove of DNA. Binding parameters were calculated using the logarithmic Hill equation to provide a quantitative term of the binding affinity between rifampin and DNA sites. The resulting ΔH⁰ = -122.76 ± 0.07 kJ/mol and ΔS⁰ = -308.19 ± 238.78 J/mol K confirms the role of the Van der Waals' forces and hydrogen bonding in the rifampin-DNA complexation. Furthermore, the influence of bivalent metal ions on the binding affinity was resulted in order of Cu(II) > Ca(II) > Co(II) > Zn(II).