Browsing by Subject "FLUORESCENT"

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  • Wiktorowicz, Szymon; Damlin, Pia; Salomäki, Mikko; Kvarnström, Carita; Tenhu, Heikki; Aseyev, Vladimir (2019)
    A reductive coupling reaction employing sodium bis(2-methoxyethoxy) aluminum hydride is used to prepare main chain azo-polymers comprising of polycyclic aromatic hydrocarbons (naphthalene, anthraquinone, or fluorenone) from their dinitro-derivatives. The azo-bridges act as effective means of conjugation and all polymers exhibit differences in the ultra-violet-visible light absorption and photoluminescence emission spectra depending on the degree of polymerization. Furthermore, in the case of poly(azofluorenone)s and poly(azoanthraquinone)s, these spectra may be modified by changes in the protonation state of the polymers. The lowest unoccupied molecular orbital and highest occupied molecular orbital energy levels and the band gap of poly(azoanthraquinone) are estimated from cyclic voltammetry data and UV-visible absorption of films.
  • Vus, Kateryna; Girych, Mykhailo; Trusova, Valeriya; Gorbenko, Galyna; Kurutos, Atanas; Vasilev, Aleksey; Gadjev, Nikolai; Deligeorgiev, Todor (2019)
    The potential of novel cyanine dyes to inhibit the insulin amyloid formation was evaluated using thioflavin T fluorescence assay, quantum-chemical calculations, molecular docking and molecular dynamics simulations. According to the ability to suppress the insulin fibrillization under physiological conditions the examined compounds were found to follow the order: trimethines > pentamethines > monomethines > heptamethines. Of these, the trimethines 3-3 and 3-5, and pentamethines 5-3 and 5-9 almost completely prevented the protein aggregation by retarding both nucleation (except 3-3) and elongation processes. The quantum-chemical calculations revealed a complex relationship between the dye structure and its inhibitory effects. The molecular docking studies showed that most cyanines bind specifically to the L17 ladder of the B chain, located at the dry steric zipper of the insulin fibril protofilament, and form the stable complexes with the helices of the insulin monomer. The molecular dynamics simulations provided evidence for the increase of insulin helicity in the presence of cyanines. Collectively, the presented findings highlight two possible mechanisms by which cyanines can inhibit the insulin fibrillization: i) stabilization of the native protein structure followed by the retardation of the protein nucleation (all dyes); and ii) blocking the lateral extension of beta-sheets via the dye-protein stacking interactions (3-3, 3-5, 5-3, 5-9). Overall, the obtained results may prove of importance for the design of small molecules capable of preventing amyloid fibril formation by insulin and other proteins. (C) 2018 Elsevier B.V. All rights reserved.
  • Shakirova, Julia R.; Sadeghi, Amir; Koblova, Alla A.; Chelushkin, Pavel S.; Toropainen, Elisa; Tavakoli, Shirin; Kontturi, Leena-Stiina; Lajunen, Tatu; Tunik, Sergey P.; Urtti, Arto (2020)
    Two iridium [Ir(NC)(2)(NN)](+) complexes with the diimine NN ligand containing a long polymethylene hydrophobic chain were synthesized and characterized by using NMR and ESI mass-spectrometry: NN - 2-(1-hexadecyl-1H-imidazol-2-yl)pyridine, NC - methyl-2-phenylquinoline-4-carboxylate (Ir1) and 2-phenylquinoline-4-carboxylic acid (Ir2). These complexes were used to prepare the luminescent PEGylated DPPC liposomes (DPPC/DSPE-PEG2000/Ir-complex = 95/4.5/1 mol%) using a thin film hydration method. The narrowly dispersed liposomes had diameters of about 110 nm. The photophysics of the complexes and labeled liposomes were carefully studied. Ir1 and Ir2 give red emission (lambda(em) = 667 and 605 nm) with a lifetime in the microsecond domain and quantum yields of 4.8% and 10.0% in degassed solution. Incorporation of the complexes into the liposome lipid bilayer results in shielding of the emitters from interaction with molecular oxygen and partial suppression of excited state nonradiative relaxation due to the effect of the relatively rigid bilayer matrix. Delivery of labeled liposomes to the cultured ARPE-19 cells demonstrated the usefulness of Ir1 and Ir2 in cellular imaging. Labeled liposomes were then injected intravitreally into rat eyes and imaged successfully with optical coherence tomography and funduscopy. In conclusion, iridium complexes enabled the successful labeling and imaging of liposomes in cells and animals.