Proteins are dynamic molecules whose ability to undergo conformational changes and fluctuations can impact their biological function, such as enzyme catalysis and substrate recognition. Mutations or perturbations that do not significantly change protein structure can often have a significant effect on the function by disrupting important internal motions and conformational states. Due to the importance of protein dynamics on function, dynamics have been extensively studied by many different biophysical methods as well as computational means. One of the methods to characterize protein dynamics is by nuclear magnetic resonance (NMR) spectroscopy. NMR spectroscopy is a powerful tool for the characterization of the structure as well as the dynamics of biological molecules. In particular, NMR relaxation experiments have been used to characterize protein motion in a wide range of timescales ranging from sub-nano second (ns) motions up to millisecond (ms) and above. Recent advances in instrumentation, such as the introduction of commercially available cryogenic probes and higher field static magnets (with 1H Larmor frequency of 900 MHz and above), have increased the sensitivity of NMR experiments. However, reevaluation of the methods used in NMR relaxation experiments and the analysis of the data is required to confirm whether the same experimental methods remain valid for the improved instrumentation. In this thesis, the NMR relaxation experiments were evaluated and improvements in the experimental aspects and the analysis of the NMR relaxation data are made for high resolution NMR experiments. In addition, NMR relaxation experiments were used to investigate the dynamics of the Sarcoplasmic Reticulum Ca2+ ATPase and the Human Immunodeficiency Virus Type 1 Protease wild-type (WT) and mutant forms
