Discourse on synthesis and characterization of bimetallic complexes of oxygen/nitrogen donor ligands as structural and functional models of the active site of xylose/glucose isomerase

This research presents and discusses the synthesis and characterization of structural and functional model complexes of Xylose/Glucose Isomerases (XGI). The XGI enzyme is a metal-ion activated bacterial enzyme that catalyzes the stereospecific interconversion of D-xylose to D-xylulose and D-glucose to D-fructose. However, very little is known about the mode of substrate binding or mechanism of action. This project focuses on an original systematic design, synthesis, and characterization of models which mimic the structural and functional nature of XGI. Several structural bimetallic model ligands of XGI were synthesized using organic reactions. These ligands were then reacted with metal ions of interest to produce bimetallic model complexes. Binding of the carbohydrate substrates in a specific stereochemistry to the bimetallic modeled complex was demonstrated using UV-vis spectroscopic technique at different reaction conditions. The specific mode of binding to the complexes has been elucidated using NMR spectroscopy. Additionally, molecular calculations were performed to reaffirm suspected modes of substrate binding to the model complexes. The data indicated that both D-glucose and D-xylose to interact through 1,2-binding to the bimetallic complexes.