Marina A. Gerasimova

Effect of halogenated fluorescent compounds on bioluminescent reactions

AbstractThe paper investigates an application of luminescent bioassays to monitor the toxicity of organic halides. Effects of xanthene dyes (fluorescein, eosin Y, and erythrosin B), used as model compounds, on bioluminescent reactions of firefly Luciola mingrelica, marine bacteria Photobacterium leiognathi, and hydroid polyp Obelia longissima were studied. Dependence of bioluminescence quenching constants on the atomic weight of halogen substituents in dye molecules was demonstrated. Bacterial bioluminescence was shown to be most sensitive to heavy halogen atoms involved in molecular structure; hence, it is suitable for construction of sensors to monitor toxicity of halogenated compounds. Mechanisms of bioluminescence quenching—energy transfer processes, collisional interactions, and enzyme–dye binding—were considered. Changes of bioluminescence (BL) spectra in the presence of the dyes were analyzed. Interactions of the dyes with enzymes were studied using fluorescence characteristics of the dyes in steady-state and time-resolved experiments. The dependences of fluorescence anisotropy of enzyme-bound dyes, the average fluorescence lifetime, and the number of exponential components in fluorescence decay on the atomic weight of halogen substituents were demonstrated. The results are discussed in terms of “dark effect of heavy halogen atom” in the process of enzyme–dye binding; hydrophobic interactions were assumed to be responsible for the effect. FigureBioluminescent quenching constants vs. atomic weight of substituents in xanthene dyes.

Spectral study of fluorone dyes adsorption on chitosan-based polyelectrolyte complexes.

Polyelectrolyte complexes of the chitosan-chondroitin sulfate and chitosan-hyaluronate polycation-polyanion pairs were synthesized and characterized as potential dye adsorbents at different pH levels. Equilibrium isotherm analysis was applied to investigate the efficiency and the mechanism of the adsorption of fluorone dyes (fluorescein, eosin Y, erythrosin B) on the synthesized complexes. The inefficiency of the fluorescein adsorption was proved by two different quantitative spectroscopic methods. The adsorption isotherm for both eosin Y and erythrosin B was adequately described in terms of the Langmuir-Freundlich model. The observed room-temperature phosphorescence of the adsorbed erythrosin B was attributed to the surface inhomogeneity of the synthesized complexes. The revealed variation in the adsorption properties of fluorone dyes was related to the differences in their ionic forms as well as in their polarity and hydrophobicity.

Laser-induced wavelength-controlled self-assembly of colloidal quasi-resonant quantum dots.

Self-assembly of colloidal semiconductor quantum dots controlled solely by laser-induced interaction is demonstrated for the first time. Pairs of CdTe nanoparticles are formed under irradiation with nanosecond pulses at wavelengths 555 or 560 nm. Formation of pairs is justified by corresponding changes of absorption spectra. Conditions of the experiment are in excellent agreement with those predicted by the theory of laser-induced dipole-dipole interaction of QDs. The fraction of QDs assembled into pairs is up to 47%.

Synthesis and Characterization of Chitosan‐Based Polyelectrolyte Complexes Doped with Xanthene Dyes

Biocompatible chitosan-based polyelectrolyte complexes (PECs) doped with xanthene dyes (fluorescein, eosin Y, erythrosin B, rhodamine 6G) were synthesized and characterized by scanning electron microscopy, dynamic light scattering, zeta potential measurements, and absorption and luminescence (including polarized, time-resolved, and phosphorescence) spectroscopy. The results are discussed in terms of the mechanism and rigidity of dye-PEC binding, the heavy-atom effect in dyes and PEC stability. Eosin Y is found to be the optimal dopant, providing both a high dye content in PECs and a high quantum yield of fluorescence.

Similarity of decay-associated spectra for tryptophan fluorescence of proteins with different structures

Tryptophan fluorescence lifetimes were analyzed for three proteins: human serum albumin, bovine serum albumin, and bacterial luciferase, which contain one, two, and seven tryptophan residues, respectively. For all of the proteins, the fluorescence decays were fitted by three lifetimes: τ1 = 6–7 ns, τ2 = 2.0–2.3 ns, and τ3 ≤ 0.1 ns (the native state), and τ1 = 4.4–4.6 ns, τ2 = 1.7–1.8 ns, and τ3 ≤ 0.1 ns (the denatured state). Corresponding decay-associated spectra had similar peak wavelengths and spectrum half-widths both in the native state (

Spectroscopic behavior of pyrrolanthrone and its derivative in aprotic and protic solvents

\lambda _{\max }^{{\tau _1}} = 324nm

Effect of visible and UV irradiation on the aggregation stability of CdTe quantum dots

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