A NUCLEAR MAGNETIC RESONANCE STUDY OF THERMAL EFFECTS UPON BASE STACKING IN OLIGONUCLEOTIDES - APA]P

A proton magnetic resonance study has been made of the effect of temperature upon the spectrum of the dinucleotide ApA>p in aqueous solution at neutral pH. The base-ring proton signals are observed to shift down-field with increasing temperature in the range 5-95°. This down-field shift is attributed to a progressive destacking of the base-rings in the dinucleotide with increasing temperature. A simple analysis of the chemical shift-temperature curves, in terms of a two-state equilibrium, i.e. stacked dinucleotide ai unstacked dinucleotide, yields an enthalpy change of -8.2 ± 1.0 kcal·mole-1 for the stacking process in reasonable agreement with values reported for similar dimers using other techniques. © 1968.