DETERMINATION OF DISTANCES INVOLVING EXCHANGEABLE PROTONS FROM NOESY SPECTRA OF 2 DNA DODECAMERS

Two-dimensional proton nuclear Overhauser effect (NOESY) spectra were obtained as a function of mixing time for two DNA dodecamers, 5'-CGCGA ATTCGCG-3' and 5'-CGCAAATTTGCG-3', in aqueous solutions. The time evol ution of cross-peak volumes was quantitatively analyzed based on the a pproximate solution of the relaxation/exchange equation over a range o f mixing times from 30 to 150 ms. Inter-proton distances, involving ex changeable protons in key locations of the structures, were calculated and compared to the distances predicted by the crystal structures. Th ese NMR-derived distances enhance the number of constraints, and their accuracy, for determination of solution structures of the two DNA dod ecamers.