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This is a study of five silicates, namely makatite, kanemite, octosilicate, magadiite and kenyaite. The silicates have been analysed using a range of techniques, principally solid-state NMR spectroscopy. High-quality (^29)Si NMR spectra have been obtained for samples of all five layered sodium polysilicate hydrates. Amongst other findings, these have revealed four crystallographically distinct sites in makatite and a Q(^4):Q(^4) site ratio in kenyaite of ca. 5. Proton MAS NMR studies can produce well-resolved spectra, particularly for carefully-dried samples. Distinct water and strongly hydrogen-bonded proton species have been detected. The latter are particularly noteworthy and they are present in kanemite, octosilicate, magadiite and kenyaite, but not in makatite or layered silicic acids. Interactions between the resolved proton species have been investigated with a series of 1- and 2-dimensional experiments resulting in the detection of mixing, via spin-diffusion or chemical exchange. Sodium-23 NMR studies were complicated by second-order effects from strong quadrupolar interactions and the presence of a significant signal from a sodium chloride contamination in many samples. The latter had fooled previous authors. Acidification products of kanemite, octosilicate and magadiite were characterised by (^29)Si CP NMR, thermogravimetric analysis, 1H MAS NMR and powder X-ray diffraction. A single H-kanemite sample proved to be H(_2)Si(_2)O(_5), but two types of H-octosilicate and H-magadiite sample were prepared. These differed in the presence of interlayer water. Several CP experiments were used to investigate the relationship between (^29)Si and (^23)Na nuclei and protons in the silicates. Cross-polarisation mechanisms tended to involve magnetisation transfer from the H-bonded protons only. Their determination was possible with a consideration of the extent of spin-diffusion or chemical exchange over the time-scale of the relevant experiments. Finally, new model structures for kanemite and the interlayer space in kanemite, octosilicate, magadiite and kenyaite have been suggested, while previously- proposed silicate layers have been reconsidered.

19F NMR studies of proteins provide unique insight into biologically relevant phenomena such as conformational fluctuations, folding and unfolding, binding and catalysis. While there are many advantages to the use of 19F NMR, experimental challenges limit its widespread application. The focus of this thesis has been to address some of these limitations, including resonance assignment and perturbations arising from fluorine probes, and to develop more robust methods of studying protein topology by 19F NMR. 19F NMR experiments designed to measure local hydrophobicity and exposure were developed and evaluated in two systems, Fyn SH3 and calmodulin, labeled with 3-fluorotyrosine. Paramagnetic effects from dissolved oxygen, solvent isotope shifts from deuterium oxide, and 1H-19F NOEs were each sufficient in establishing relative solvent exposure, while the combination of effects from oxygen and deuterium oxide were able to delineate local hydrophobicity and solvent accessibility of 19F probes. Two NMR based resonance assignment protocols were developed using 13C, 15N-enriched 3-fluorotyrosine and 3-fluorophenylalanine, separately biosynthetically incorporated into calmodulin. In the first approach, isotopic enrichment facilitated two-dimensional heteronuclear experiments based on INEPT and COSY magnetization transfer schemes to correlate the fluorine nucleus to sidechain and backbone 1H, 13C, and 15N atoms, providing complete spectral assignment. The assignment of 3-fluorophenylalanine resonances was achieved using 19F-, and 15N-edited homonuclear NOE experiments to connect the fluorine nucleus to intraresidue and neighboring 1H and 15N resonances. While both strategies were successful, the NOE-based method was vulnerable to alternate relaxation mechanisms, including chemical shift anisotropy and chemical exchange. Structural perturbations arising from uniform incorporation of 3-fluorophenylalanine in calmodulin was thoroughly investigated using 19F and 1H-15N NMR spectroscopy, 15N spin relaxation and thermal denaturation via circular dichroism spectroscopy. While stability was unaffected, NMR experiments revealed increased protein plasticity, minor conformers and line broadening. The merit of fractional fluorine labeling in reducing such disruptions was demonstrated, and labeling levels of 60-75% provided an optimal balance between native-likeness and the usual advantages of 19F NMR in our system. The 19F NMR techniques developed here are broadly applicable and will expand the utility of 19F NMR in studies of protein systems.

19F NMR studies of proteins provide unique insight into biologically relevant phenomena such as conformational fluctuations, folding and unfolding, binding and catalysis. While there are many advantages to the use of 19F NMR, experimental challenges limit its widespread application. The focus of this thesis has been to address some of these limitations, including resonance assignment and perturbations arising from fluorine probes, and to develop more robust methods of studying protein topology by 19F NMR. 19F NMR experiments designed to measure local hydrophobicity and exposure were developed and evaluated in two systems, Fyn SH3 and calmodulin, labeled with 3-fluorotyrosine. Paramagnetic effects from dissolved oxygen, solvent isotope shifts from deuterium oxide, and 1H-19F NOEs were each sufficient in establishing relative solvent exposure, while the combination of effects from oxygen and deuterium oxide were able to delineate local hydrophobicity and solvent accessibility of 19F probes. Two NMR based resonance assignment protocols were developed using 13C, 15N-enriched 3-fluorotyrosine and 3-fluorophenylalanine, separately biosynthetically incorporated into calmodulin. In the first approach, isotopic enrichment facilitated two-dimensional heteronuclear experiments based on INEPT and COSY magnetization transfer schemes to correlate the fluorine nucleus to sidechain and backbone 1H, 13C, and 15N atoms, providing complete spectral assignment. The assignment of 3-fluorophenylalanine resonances was achieved using 19F-, and 15N-edited homonuclear NOE experiments to connect the fluorine nucleus to intraresidue and neighboring 1H and 15N resonances. While both strategies were successful, the NOE-based method was vulnerable to alternate relaxation mechanisms, including chemical shift anisotropy and chemical exchange. Structural perturbations arising from uniform incorporation of 3-fluorophenylalanine in calmodulin was thoroughly investigated using 19F and 1H-15N NMR spectroscopy, 15N spin relaxation and thermal denaturation via circular dichroism spectroscopy. While stability was unaffected, NMR experiments revealed increased protein plasticity, minor conformers and line broadening. The merit of fractional fluorine labeling in reducing such disruptions was demonstrated, and labeling levels of 60-75% provided an optimal balance between native-likeness and the usual advantages of 19F NMR in our system. The 19F NMR techniques developed here are broadly applicable and will expand the utility of 19F NMR in studies of protein systems.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.