| The subject of this Ph.D. thesis is to demonstrate the utilities of nuclear magnetic resonance (NMR), in both solution and solid-state, to study metal ions in biologically relevant molecules. We have used one- and two-dimensional solid-state 23Na NMR spectroscopy to determine accurate 23Na NMR parameters for Na+ sites in 10 nucleotides. Quantum mechanical calculation of 23Na NMR parameters was performed to unambiguously assign the observed 23Na parameters to individual Na+ sites. We have identified for the first time 23 Na, 39K and 15N NMR spectral signatures (or spectral features) for Na+, K+ and NH 4+ cations bound to a four stranded nucleic acid structure known as G-quadruplex. We have introduced a novel solid-state NMR titration experiment to measure thermodynamic data for cation binding affinity in a G-quadruplex formed by guanosine-5'-monophosphate (5 '-GMP). On the basis of these data, the binding affinity of monovalent cations was determined to be Li+ > NH4 + > Na+ > Cs+ > Rb+ > K+ at the surface site and K+ > NH4 + > Rb+ > Na+ > Cs+ > Li+ at the channel site. We have used 23Na NMR to measure the rate of Na+ ions travelling through a 5 '-GMP quadruplex channel in aqueous solution. We have performed 1H diffusion experiments to measure the translational diffusion coefficients, from which the molecular size of 5'GMP quadruplex was determined. On the basis of Na+ dynamics and quadruplex size, an 'ion-pushing mechanism' is proposed for the movement of Na + ions along the 5'-GMP quadruplex channel. We have also discovered that the 5'-GMP channel can be turned on and off by controlling the presence of channel blockers. We have determined 23Na and 39K NMR parameters for two cation-pi compounds, Na[BPh4] and K[BPh4]. The isotropic chemical shifts are found to be highly shielded. Such chemical shifts could be the key to localize the binding sites with cation-pi interactions in proteins. We have determined the crystal structure and solid-state 25Mg NMR parameters for Mg(Pc)·H2O·Py and Mg(TPP)·Py2 . These compounds are used as models for the Mg2+ binding site in Chlorophyll a. |
