The interaction of the divalent metal ions Mg2+, Cd2+, and Ni2+ with liquid crystalline NaDNA solutions (molar ratios Me2+/DNA-phosphate less than or equal to0.050) was investigated by polarized light microscopy and multinuclear P-31, H-2, and Na-23 NMR. Our findings show that the state of the cholesteric NaDNA phase at equal MgCl2, CdCl2, or NiCl2 concentration is affected in a different way and to a different extent by the nature of the divalent cation. Indeed, we found that the occurrence of an isotropic phase is markedly favored by Mg2+, and to a lower extent by Cd2+, and that the pitch of the cholesteric phase decreases in the presence of Cd2+ or Ni2+. Na-23 NMR spectroscopy also shows differences between the binding behavior of Mg2+ and the transition metal ions in the counterion atmosphere around DNA. The results are discussed in terms of different binding modes of the metal ions.
Binding of Mg2+, Cd2+, and Ni2+ to liquid crystalline NaDNA: Polarized light microscopy and NMR investigations
CATTE, ANDREA;CESARE MARINCOLA, FLAMINIA;
2004-01-01
Abstract
The interaction of the divalent metal ions Mg2+, Cd2+, and Ni2+ with liquid crystalline NaDNA solutions (molar ratios Me2+/DNA-phosphate less than or equal to0.050) was investigated by polarized light microscopy and multinuclear P-31, H-2, and Na-23 NMR. Our findings show that the state of the cholesteric NaDNA phase at equal MgCl2, CdCl2, or NiCl2 concentration is affected in a different way and to a different extent by the nature of the divalent cation. Indeed, we found that the occurrence of an isotropic phase is markedly favored by Mg2+, and to a lower extent by Cd2+, and that the pitch of the cholesteric phase decreases in the presence of Cd2+ or Ni2+. Na-23 NMR spectroscopy also shows differences between the binding behavior of Mg2+ and the transition metal ions in the counterion atmosphere around DNA. The results are discussed in terms of different binding modes of the metal ions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.