Proton and phosphorus magnetic relaxation studies on the dynamic structure of single-stranded polyriboadenylic acid
✍ Scribed by Kazuyuki Akasaka
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1974
- Tongue
- English
- Weight
- 450 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Proton and phosphorus-31 nuclear spin-lattice relaxation times ( T I ) have been measured with the Fourier-transform method at 100 and 40.5 MHz, respectively, on single-stranded polyriboadenylic acid (poly(A)) in a neutral D20 solution in the temperature range of 14432°C. TI minimum is observed around 3545°C for H(8), H(l'), and phosphorus resonances. Rotational correlation times have been deduced from the TI data, which indicate that the sugar-phosphate backbone as well as the basesugar segment is undergoing rapid internal motion of 10*-lO-lo sec range. The molecular motion of the sugar-phosphate baokbone as deduced from the phosphorus relaxation is well-characterized by a single activation enthalpy of 8.1 kal/mole for the whole temperature range of 14-82°C. Activation enthalpies of similar magnitude have been obt.ained for the motion of the adenine-ribose moiety from H(8) and H(1') relaxation. The relative magnitude of TI for H(8) and H(1') infers that the poly(A) nucleotide exists on the average as anti in the single-stranded form. The phosphorus T I value is consistent with a conformation such that both C(4')-C(5') and C(4')-C(3') bonds are nearly trans to their connected 0-P bonds.