The temperature dependence to the 31P NMR spectra of poly[d(GC)]·poly[d(GC)], d(GC)4, phenylalanine tRNA (yeast) and mixtures of poly(A) + oligo(U) is presented. The 31P NMR spectra of mixtures of complementary RNA and of the poly d(GC) self-complementary DNA provide torsional information on the phosphate ester conformation in the double, triple, and "Z" helix. The increasing downfield shift with temperature for the single-strand nucleic acids provides a measure of the change in the phosphate ester conformation in the single helix to coil conversion. A separate upfield peak (20-26% of the total phosphates) is observed at lower temperatures in the oligo(U)·poly(A) mixtures which is assigned to the double helix/triple helix. Proton NMR and UV spectra confirm the presence of the multistrand forms. The 31P chemical shift for the double helix/triple helix is 0.2-0.5 ppm upfield from the chemical shift for the single helix which in turn is 1.0 ppm upfield from the chemical shift for the random coil conformation.
|Original language||English (US)|
|Number of pages||10|
|State||Published - 1982|
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