title: Spectral-fluorescent study of the interaction of the polymethine dye probe Cyan 2 with chondroitin-4-sulfate.
abstract: The noncovalent interaction of the polymethine dye probe 3,3',9-trimethylthiacarbocyanine iodide (Cyan 2) with chondroitin-4-sulfate (C4S) in buffer solutions with different pH and in water in the absence of buffers has been studied by spectral-fluorescent methods. It has been shown that in all media studied, at relatively high concentrations, the dye is bound to C4S mainly as a monomer, which is accompanied by a steep rise of fluorescence (the intermediate formation of dye aggregates on the biopolymer is also observed). From the dependence of the fluorescence quantum yield on the concentration of C4S, the parameters of binding of the dye monomer to C4S were obtained: the effective binding constant K, the number of the monomeric C4S units n per one dye monomer bound to C4S, and the fluorescence quantum yield of the bound dye monomer Φfb. The dependence of Φfb(and K) on рН of the medium is not monotonic: it has a minimum in the region of neutral pH and a growth in the regions of acid and basic pH. This can be explained by changing the charge of a C4S macromolecule as a function of pH and related conformational alterations in the biopolymer, which can affect the rigidity of a dye molecule and the energy of its interaction with the biopolymer.
authors.affiliation: N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119334, Russia. Electronic address: tatikolov@mail.ru.
authors.forename: Аlexander S
authors.initials: АS
authors.lastname: Tatikolov
authors.affiliation: N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin St. 4, Moscow 119334, Russia.
authors.forename: Timofey M
authors.initials: TM
authors.lastname: Akimkin
authors.affiliation: N.K. Koltsov Institute of Developmental Biology, Russian Academy of Sciences, Vavilov St. 26, Moscow 119334, Russia.
authors.forename: Ina G
authors.initials: IG
authors.lastname: Panova
authors.affiliation: Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, ul. Zabolotnogo 150, Kiev 252143, Ukraine.
authors.forename: Sergiy M
authors.initials: SM
authors.lastname: Yarmoluk
mesh_terms: D002232:Carbocyanines / Q000737:chemistry*; D002809:Chondroitin Sulfates / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence
chemical_list: D002232:Carbocyanines; D004396:Coloring Agents; D005456:Fluorescent Dyes; D007211:Indoles; C120934:cyan 2; C098209:VPM chloride; D002809:Chondroitin Sulfates
keywords: Chondroitin-4-sulfate; Fluorescence growth; Noncovalent binding; Polymethine (cyanine) dye; pH dependence