| Nuclear magnetic resonance (NMR) spectroscopy and microscopy are powerful analytical methods because of their nondestructive nature, intrinsic methods of contrast and breadth of available information. Both techniques, however, suffer from inherently low signal-to-noise ratios (SNR) that become restrictive when interrogating volume-limited samples. Recently, radio frequency microcoils that offer improved sensitivity for small samples have been applied successfully to spectroscopy, examining volumes down to a few nanoliters.; In this presentation, the benefits of microcoils are utilized to investigate single cells, isolated from the influences of a heterogeneous biological system. Rather than improving the spatial resolution of MR microscopy, the goal of this thesis is to examine intracellular regions through methods that are not as restricted by the SNR-dependent voxel size. In particular, localized spectroscopy and diffusion-weighted microimaging were used to analyze single cell models.; Solenoidal microcoils were characterized through electrical and NMR experiments to determine the effects of coil design on spectral linewidth and SNR in both spectroscopy and microimaging. These findings were applied to the construction of optimal microcoils for single cell studies.; With microcoils and high magnetic fields of up to 14 T, proton spectra were acquired from single Xenopus laevis oocytes and Aplysia californica neurons for the first time. These spectra display resonances corresponding to intracellular metabolites, osmolytes and lipids. Voxel volumes down to 10 nanoliters were evaluated, permitting spectra to be acquired from several subcellular regions.; Diffusion-weighted microscopy of these cells displays multi-exponential intracellular self-diffusion, providing evidence of varying degrees of subcellular compartmentalization. These diffusion-based studies indicate the existence of at least four compartments in the single cell model corresponding to extracellular, cytoplasmic (x2) and nuclear regions.; These macroscopic techniques, therefore, have been utilized to investigate microscopic phenomena in single cells through the application of microcoils. As a result, NMR imaging and spatially localized spectroscopy are now capable of interrogating living systems non-invasively from single cells to isolated tissues to humans, further broadening the scope of these versatile analytical techniques. |
