Stefka Kaloyanova

Novel Green Procedure for the Synthesis of 2-Arylbenzothiazoles Under Microwave Irradiation in Peg 200 Or Peg 400

An improved green procedure for the synthesis of 2-aryl- and 2-hetarylbenzothiazoles by condensation of equivalent amounts of 2,2′-diaminodiphenyldisulfides or 2-aminothiophenols and various aromatic aldehydes in PEG 200/400 under microwave irradiation has been developed. This method allows the synthesis of 2-arylbenzothiazoles in high yields and with high purity regardless of the state of the starting compounds (liquid or solid) or the nature of the substituents in the aromatic ring.

Kinetic differentiation between homo- and alternating AT-DNA by sterically restricted phosphonium dyes

By sterically controlled monomer-dimer equilibrium novel dyes kinetically differentiate between homo-AT and alternating AT-AT polynucleotides and finely probe width and sterical occupation of DNA minor groove by induced CD signals.

Synthesis and Photophysical Properties of Yellow-Emitting Iridium Complexes. Effect of the Temperature on the Character of Triplet Emission

The parent study includes synthesis end photophysical characterization of four new phosphorescent cyclometalated iridium (III) complexes. The cyclometaled ligands used here are 2-(4-chlorophenyl)benzo[d]thiazole, 2(4isopropylphenyl)benzo[d] thiazole, 2-(4-methoxyphenyl)benzo[d]thiazole, 4-(benzo[d]thiazol-2-yl)-N,N-dimethylaniline. The auxiliary ligand is acetylacetone (Hacac). The photometric analyses show temperature dependence on phosphorescent spectra and the nature of the emitting state of the synthesized complexes. Using fluorescent and absorption spectroscopy we suggest an explanation of the observed effect points out the transition from ligand centered (LC) to MLCT main character of the emitting state. The quantitative photometric analysis states high phosphorescent quantum yields of the complexes in solution.

New fluorogenic dyes for analysis of cellular processes by flow cytometry and confocal microscopy.

Fluorescent microscopy and fluorescent imaging by flow cytometry are two of the fastest growing areas in the medical and biological research. Innovations in fluorescent chemistry and synthesis of new dye probes are closely related to the development of service equipment such as light sources, and detection techniques. Among compounds known as fluorescent labels, the cyanine-based dyes have become widely used since they have high excitation coefficients, narrow emission bands and high fluorescence upon binding to nucleic acids. The key methods for evaluation of apoptosis and cell cycle allow measuring DNA content by several flow cytometric techniques. We have synthesized new monomethine cyanine dyes and have characterized their applicability for staining of live and/or apoptotic cells. Imaging experiments by flow cytometry and confocal laser scanning microscopy (CLSM) have been also performed. Two of the dyes have shown high-affinity binding to the nuclei at high dilutions, up to 10(-9)M. Flow cytometry and CLSM have confirmed that these dyes labeled selectively non-living, e.g. ethanol-fixed cells that makes them appropriate for estimations of cell viability and apoptosis. The novel structures proved to be appropriate also for analysis of the cell cycle.

Novel cyanine dyes and homodimeric styryl dyes as fluorescent probes for assessment of lactic acid bacteria cell viability

Innovations in labeling techniques and in the design and synthesis of dye structures are closely related to the development of service equipment such as light sources and detection methods. Novel styryl homodimers and monomethine cyanine dyes were synthesized and their staining abilities for discrimination between live and dead lactic acid bacterial cells were investigated. The dyes were combined in pairs based on their excitation and emission maxima and the capacity to penetrate through cell membranes of viable bacterial cells. The absorption maxima in the same region and the large Stocks shifts of the styryl derivatives allowed viability analysis to be done with epifluorescent microscope with a very basic configuration - one light source about 480nm and one filter for the fluorescent emissions. A staining protocol was developed and applied for live/dead analysis of Bulgarian yoghurt starters. The live cells quantification by the fluorescence dyes coincided well with the results of the much more time-consuming tests by plate counting. Thus, the proposed dye combinations are appropriate for rapid viability estimation in small laboratories that may have conventional equipment.

Spectroscopic elucidation of the interaction of native cyclodextrins and their acetylated derivatives with asymmetric monomethyne cyanine dye

Five novel complexes of asymmetric monomethyne cyanine dye (1), with α-, β-, γ-cyclodextrins and the corresponding functionalized derivatives, namely acetyl-β-(Ac-β-CD) and acetyl-γ-(Ac-γ-CD) cyclodextrins were studied by means of UV–VIS, linear-polarized infrared and fluorescence spectroscopy, as well as scanning electron microscopy, powder X-ray diffraction, and thermal methods both in solution and in solid-state. Computational chemistry methods were employed with the purpose of elucidating the electronic structure and vibrational properties of the organic dye.

Synthesis of chloro-substituted analogs of Thiazole orange – Fluorophores for flow cytometric analyses

Synthesis, absorption and fluorescence properties of a series of asymmetrical monomethine cyanine dyes, chloro-containing analogs of Thiazole orange, are reported. Their staining ability was studied by flow cytometry. The saturating concentrations of each dye that gives a stable staining intensity have been determined. The ability of dyes B9, B11, B13 to stain live macrophages and apoptotic splenocytes was investigated. Positive signal in nucleus of adherent macrophages detected by fluorescent microscopy showed good specificity of B9, B11 and B13 dyes for DNA. In apoptotic assay cells positive for Annexin V were stained more brightly with the dyes B9, B11 and B13 than with propidium iodide. Despite that B13 showed high DNA selectivity it induces apoptosis of splenocytes and it is not suitable for detection of dead cells. The other synthesized chloro-containing analogs of Thiazole orange B9 and B11 can be successfully used for flow cytometric analyses of DNA content in live cells and for analyses of cell apoptosis.