In 4H NaCl solutions (dC-dG)n (n=3,4; ̃9mM) exist as a mixture ot B and Z forms. The low and high field components of two 31P NMR resonances originating from internal phosphodiester groups are assigned to the GpC and CpG linkages, respectively. Low temperatures stabilize the Z-forms, which completely disappear above 50°C (n=3) and 65°C (n=4). ΔH=-44 and -17 kJ/mol for B to Z transition in the hexamer and octamer duplexes, respectively. Temperature dependent changes (0-57°C range) in the spin-lattice relaxation times at 145.7 MHz are distinctly different for the 31p nuclei o± GpC and CpG groups. The relaxation data can be explained by assuming that the GpC phosphodiester groups undergo more local internal motion than do the CpG groups.
ASJC Scopus subject areas
- Statistics, Probability and Uncertainty
- Applied Mathematics
- Health, Toxicology and Mutagenesis