title: Synthesis, structure, and activity of supramolecular mimics for the active site and arg141 residue of copper, zinc-superoxide dismutase.
abstract: Two supramolecular complexes, [Cu(L)(H2O)2(beta-CD)](ClO4)2.10.5H2O.CH3OH (1) and [Cu(L)(H2O)2(beta-GCD)](HClO4)(ClO4)2.10H2O (2) (L = 4-(4'-tert-butyl-benzyl)diethylenetriamine, beta-CD = beta-cyclodextrin, and beta-GCD = mono-6-deoxy-6-guanidinocycloheptaamylose cation), have been synthesized. The structure of 1 has been characterized by X-ray crystallography. The 4-tert-butyl-benzyl of [Cu(L)(H2O)2]2+ moiety in 1 as a guest inserts into the hydrophobic cavity of the beta-CD as a host along the primary hydroxyl side. On the basis of the structure data of 1, complex 2 was modeled, which showed that the distance between the Cu and C atom of the guanidinium is 5.2 A, comparable to the corresponding distance in bovine erythrocyte Cu, Zn-SOD (5.9 A) (SOD = superoxide dismutase). Apparent inclusion stability constants of the host and the guest were measured to be 0.66 (+/-0.01) x 104 and 1.15 (+/-0.03) x 104 M-1 for 1 and 2 respectively. The electronic absorption bands and electronic reflection bands of each complex are almost the same, indicating an identical structure of the complex in aqueous solution and in solid state. The two complexes showed quasi-reversible one-electron Cu(II)/Cu(I) redox waves with redox potentials of -0.345 and -0.338 V for 1 and 2, respectively. Their SOD-like activities (IC50) were measured to be 0.30 +/- 0.01 and 0.17 +/- 0.01 microM by xanthine/xanthine oxidase-NBT assay. The enhanced SOD activity of 2 by approximately 40% compared with 1 suggests that the guanidyl cation in the host of the supramolecular system of 2 can effectively mimic the side chain of Arg141 in the enzyme, which is known to be essential for high SOD activity possibly through steering of the superoxide substrate to and from the active copper ion.
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Ying-Hua
authors.initials: YH
authors.lastname: Zhou
authors.forename: Heng
authors.initials: H
authors.lastname: Fu
authors.forename: Wei-Xi
authors.initials: WX
authors.lastname: Zhao
authors.forename: Wei-Lin
authors.initials: WL
authors.lastname: Chen
authors.forename: Cheng-Yong
authors.initials: CY
authors.lastname: Su
authors.forename: Hongzhe
authors.initials: H
authors.lastname: Sun
authors.forename: Liang-Nian
authors.initials: LN
authors.lastname: Ji
authors.forename: Zong-Wan
authors.initials: ZW
authors.lastname: Mao
mesh_terms: D001120:Arginine; D001665:Binding Sites; D018360:Crystallography, X-Ray; D007700:Kinetics; D018716:Molecular Mimicry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D013482:Superoxide Dismutase / Q000737:chemistry*; D019820:Xanthine / Q000378:metabolism; D047392:beta-Cyclodextrins
chemical_list: D010446:Peptide Fragments; D047392:beta-Cyclodextrins; D019820:Xanthine; D001120:Arginine; D013482:Superoxide Dismutase; C031215:betadex