ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Equilibrium dialysis measurements and optical melting curve data have been used to study the formation and stability of a number of complexes between polynucleotides and complementary monomers. The cooperativity parameter, (dθ/d ln c)θ = 0.5, where θ is the fraction of U or C residues complexed, and c is the concentration of free monomer has been measured as 1.4 for the 2:1 poly U:d-adenosine-complex, and 2.05 for the 2:1 poly C:d-guanosiue complex at pH 7. The variation of Tm with c for several complexes has been used to calculate their partial molar enthalpies of formation at the midpoint of the transition: in 1.0 MNa + at pH 7, for the 2:1 complex of poly-U with 2-amino-adenine, this is - 18.7 kcal/mole of 2-amino-adenine, for poly-U with adenosine it is - 18.7 kcal/ mole; for poly-C with dG, it is - 16.8 kcal/mole. These results do not agree very well with calorimetric integral heats of reaction reported in the literature.33 Complexes with random copolymers were also studied. The random copolymer, poly-UC, can form a mixed complex with dG and either dA or 2-amino-adenosine; the binding of dG is enhanced by an adenine derivative and vice versa.Similarly, poly AC can form a mixed complex with dG and 3-methyl-xanthine. In each case, it appears that the ideal composition is a 2:1 hydrogen-bonded complex, but the actual stoichiometry is such that each base on the random polynucleotide binds less than one-half of a molecule of its complementary monomer. Poly UG can bind dG and dA, but in a less cooperative and specific way.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360100904
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