1H NMR study on the inclusion complex of glutathione with a glutathione peroxidase mimic, 2,2′-ditelluro-bridged β-cyclodextrins

The complex formation of 2, 2'-ditelluro-bis(beta-cyclodextrin) (2-TeCD) with glutathione (GSH) was investigated in D2O at room temperature by H-1 nuclear magnetic resonance (H-1 NMR) technique. The association constant and stoichiometry between GSH and 2-TeCD was determined from the chemical shifts dependence of the H5 proton in GSH on the concentration of 2-TeCD. The stoichiometry of the inclusion complex was determined by the molar method to be of 2:1 host-to-guest. 2-TeCD showed higher affinity toward GSH than beta-cyclodextrin (beta-CD). This may be attributed the reason that 2-TeCD which possesses dual hydrophobic cavities in a close vicinity enhances GSH binding ability through the cooperative binding of two cavities. The formation of the (2-TeCD)(2)/GSH complex was one of the reason that 2-TeCD showed higher glutathione peroxidase (GPX) activity than Ebselen.