Thermodynamics of polymolecular duplexes between phosphate-methylated DNA and natural DNA.
Phosphate-methylated (P.M.) DNA possesses a very high affinity for complementary natural DNA, as a result of the absence of interstrand electrostatic repulsions. In this study, a model system phosphate-methylated d[Cn] with natural d(Gk) (n less than k) is chosen for an investigation of the thermodynamic properties that determine duplex stability. The enthalpy change of a melting transition is shown to be considerably larger than is observed for corresponding natural DNA duplexes. It is found that delta Hn0 of GG/CC nearest neighbor pairwise interaction equals -15.6 kcal/mol, compared to -11.0 kcal/mol for the natural analog. The entropy change is strongly dependent on the length of the natural DNA strand and the number of phosphate-methylated DNA oligomers hybridized. The results are explained by means of a model in which a cooperative effect for subsequent hybridizations of phosphate-methylated DNA oligomers is assumed, thus giving additional stability.
Moody
M R
MR
Department of Organic Chemistry, Eindhoven University of Technology, The Netherlands.
van Genderen
M H
MH
Buck
H M
HM
D004247:DNA / Q000737:chemistry*; D008745:Methylation; D009690:Nucleic Acid Conformation; D009693:Nucleic Acid Hybridization; D010710:Phosphates / Q000737:chemistry; D013816:Thermodynamics
D010710:Phosphates; D004247:DNA