title: [Interaction of ethidium bromide with synthetic double-stranded polyribonucleotides].
abstract: The interaction of ethidium bromide (EtBr) with double helical synthetic polyribonucleotides poly(G).poly(C), poly(A).poly(U) and poly(I).poly(C) has been investigated by the method of isothermal microcalorimetry and according to the character of changes on the spectra of circular dichroism, absorption and fluorescence at binding. The calculations showed that at binding of EtBr with poly(A).poly(U) the saturation stechiometry was one EtBr molecule per 2 base pairs with binding constant (2.5 +/- 0.5).10(6) M-1 at 30 degrees C and 0.1 M. NaCl. In the case of binding of EtBr with poly(G).poly(C) and poly(I).poly(C) the saturation stechiometry was not less than 0.2 EtBr molecule per 1 base pair with binding constant (4 +/- 1).10(3) M-1 and (1.5 +/- 0.3).10(4) M-1 respectively, at 25 degrees C and 0.1 M NaCl. The binding enthalpies of EtBr with poly(A).poly(U) and poly(G).poly(C) have been determined to be (-7.5 +/- 0.5) Kcal per 1 mol of bound EtBr in average for both polymers. It has been shown that the observed strong selectivity of EtBr binding with polyribonucleotides is of entropic origin.
authors.forename: Iu S
authors.initials: IuS
authors.lastname: Babaian
authors.forename: G
authors.initials: G
authors.lastname: Mnzini
authors.forename: F
authors.initials: F
authors.lastname: Quadrifoglio
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D004996:Ethidium / Q000378:metabolism*; D011063:Poly A-U / Q000378:metabolism; D011066:Poly C / Q000378:metabolism; D011068:Poly G / Q000378:metabolism; D011070:Poly I-C / Q000378:metabolism; D011131:Polyribonucleotides / Q000138:chemical synthesis / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D011131:Polyribonucleotides; D011063:Poly A-U; D011068:Poly G; C008961:poly G-poly C; D011066:Poly C; D004247:DNA; D004996:Ethidium; D011070:Poly I-C
vernacular_title: Vzaimodeĭstvie bromistogo étidiia s sinteticheskimi dvuspiral'nymi poliribonukleotidami.