APPLICATIONS OF TRITIUM NMR TO MACROMOLECULES - A STUDY OF 2 NUCLEIC-ACID MOLECULES

We have tritium labeled two nucleic acid molecules, an 8 kDa DNA oligo mer and a 20 kDa 'hammerhead' RNA for tritium NMR investigations. The DNA sequence studied has been previously used in homonuclear studies o f DNA-bound water molecules and tritium NMR was expected to facilitate these investigations by eliminating the need to suppress the water re sonance in tritium-detected H-3-H-1 NOESY experiments. We observed the anticipated through-space interactions found in B-form DNA in the NOE SY experiments and an unexpected 'antiphase' cross-peak at the water f requency. T-1 measurements on the tritiated DNA molecule indicated tha t relaxation rates were also accelerated for tritium and protons. Trit ium NMR spectra of the hammerhead RNA molecule indicated conformationa l dynamics in the conserved region of the molecule in the absence of M g2+ and spermine, two components necessary for cleavage. The dynamics were also investigated by N-15-correlated H-1 spectroscopy and persist ed after the addition of Mg2+ and spermine.