NMR studies of myoglobin translational diffusion in perfused myocardium and conformational analysis on the poly-gamma-D-glutamic acid capsule of Bacillus licheniformis: Implication on the regulation of oxygen transport and a virulence factor in anthrax

NMR has become one of the most important techniques to study dynamic and static protein structures as well as physiological and clinical researches. In this dissertation the main focuses have been to investigate the translational diffusion behavior of myoglobin (Mb) in myocardium and to explore the conformation of the capsular poly-gamma-D-glutamate (gamma-D-PGA) by means of NMR spectroscopy.; Due to the capability of observing the distinct Val E11 gamma-methyl group signal of oxymyoglobin in vivo, the pulsed-field gradient NMR methods have been applied to determine the endogenous Mb translational diffusivity in perfused rat myocardium for the first half of the dissertation. The results demonstrate that the averaged translational diffusion coefficient of the endogenous Mb has a value of 4.24 x 10-7 cm 2/s at 22°C and it rises up to 8.37 x 10-7 cm2/s at 40°C. No orientation preference of Mb diffusivity has been observed within this temperature range, corresponding to a mean displacement of 2.5--3.5 mum. Given the resting PO2 in respiring muscle in vivo of around 10 mmHg, Mb has no general role in facilitated O2 transport under basal physiological condition.; The conformational change of the gamma-D-PGA synthesized by Bacillus licheniformis ATTC 9945A has been investigated by 1H NMR under various conditions for the second part of this dissertation. The experimental data present that the gamma-D-PGA endures a mixed secondary structure of the coil and helix forms. In particular, the results in this study do not reveal obvious conformational change of the purified gamma-D-PGA induced by pH because only do the minor differences in the chemical shifts show on 1H NMR spectra. Owning to small quantities of paramagnetic ion contamination in this biopolymer aqueous solution, the formation of a H2O-ion-gamma-D-PGA complex is affected by different pH and ion-strength environments, performing on the 1H NMR spectra and relaxation times.; In summary, the Mb translational diffusion determined in this study has then helped to clarify the role of Mb in facilitating O2 transport in vivo; it also reveals the effect of paramagnetic ions on the conformation of gamma-D-PGA.