A study of the molecular structure of bacterial lysodektose by quantum-chemical calculations and EPR spectroscopy

The standard redox potentials of the sequential oxidation of lysodektose to the corresponding nitrone were estimated by quantum chemistry methods. It follows from these estimates that the experimentally observed accumulation of the intermediate nitroxyl radical in substantial amounts during the oxidation of lysodektose can be explained by high medium reorganization energy in the oxidation of the nitrosyl radical with simultaneous proton abstraction. The EPR spectra of the radical lysodektose form were modeled. Arguments in favor of the suggestion that one nonequivalent proton appeared in the formation of an intramolecular H-bond were presented. Quantum-chemical calculations of the hyperfine structure constants were in satisfactory agreement with experiment.