Sequence dependence of hydrogen exchange kinetics in DNA duplexes at the individual base pair level in solution.

Abstract
The kinetics for H exchange at individual base pairs in self-complementary deoxydodecanucleotide duplexes were estimated from NMR saturation recovery measurements on the resolved imino protons as a function of temperature. The imino protons of dA.cntdot.dT base pairs in the center of the fully alternating d(C-G-C-G-T-A-T-A-C-G-C-G) duplex exchange a factor of 2- to 3-fold faster than the corresponding protons at the same positions in the partially alternating d(C-G-C-G-A-A-T-T-C-G-C-G) duplex. These exchange parameters are a direct measure of the rate constants for transient opening of individual dA.cntdot.dT base pairs in the dodecanucleotide duplexes and demonstrate faster opening kinetics for the TATA box region compared to the related AATT segment.