title: Free energy of the binding of uridylic acid oligomers with double stranded poly(A) x poly(U).
abstract: The binding parameters (K, omega) and the free energy (DeltaG(0)) of triple helix formation have been estimated for complexes of oligo(U)(n) (n = 5, 7-10) with poly(A) . poly(U) on the basis of hypochromicity measurements. The data were treated according to the formula of McGhee and von Hippel [J. Mol. Biol. 86 (1974) 469] by a computer program ALAU [H. Schütz et al., Stud. Biophys. 104 (1984) 23] which takes absorbancies and total concentrations as input. In 1 mM cacodylate buffer pH 7.0 with 10 mM NaCl and 10 mM MgCl(2) at 5 degrees C the free energy of contiguous binding was found to be a linear function of the oligomer length with a slope of DeltaG(c,U)(0) = -0.72 (+/-0.03) kcal x mol(-1) per nucleotide. The mean cooperativity coefficient (omega) was 24.5 (+/- 5.6), and the corresponding free energy of interaction between the neighbouring oligonucleotides in the third strand was DeltaG(0(omega)) = -1.74 (+/-0.13) kcal x mol(-1).
authors.affiliation: Institute of Experimental Biology of Estonian Academy of Sciences, Harku EE3051, Estonia.
authors.forename: E
authors.initials: E
authors.lastname: Raukas
authors.forename: K
authors.initials: K
authors.lastname: Kooli
authors.forename: V I
authors.initials: VI
authors.lastname: Yamkovoi
authors.forename: H
authors.initials: H
authors.lastname: Schütz