| The enzyme L-aspartase ammonia-lyase (L-aspartase) catalyses the deamination of aspartic acid to yield fumaric acid and ammonia. E. coli L-aspartase shows greatly reduced activity at pH > 7.5 that is be restored by substrate or substrate analog activation and divalent metal binding. These allosteric effectors (activators) bind to an activator site that is different from the active site and indirectly affects the catalytic activity of L-aspartase. The crystal structure of the apo-enzyme has been solved but not the location of the activator site. To identify the location of the activator site and the amino acids involved in binding the activator, we are using solid-state nuclear magnetic resonance (SSNMR) techniques. In addition, the L-aspartase overexpression system in E. coli, purification of L-aspartase, stable isotopic labeling, activator and metal binding and lyophilization conditions have also been explored. These results will aid in better understanding the allosteric interaction between the activator and active site, hence the regulatory control of L-aspartase by activators.; Polyaniline (PANI) is a member of the class of conducting organic. Remarkable progress has been made in developing PANI for use in electronic and optical devices. These PANI based electrochemical devices often suffer from poor environmental stability, slow switching speed and short lifetimes during redox cycling which arise partly due to the poor electrolyte system. It has been shown that room-temperature ionic liquids (RTIL) have the ideal properties to be used as electrolytes in the fabrication of devices based on conducting polymers. SSNMR has been used to obtain a molecular level characterization of PANI/RTIL composites. These studies reveal that the RTIL is dispersed within the polymer matrix, has reduced motion relative to the neat material and only weakly interacts with the polymer. These insights can then be used to aid in the rationale selection of the ideal RTIL for the demands of a specific device. |
