title: Complexation, structure, and superoxide dismutase activity of the imidazolate-bridged dinuclear copper moiety with beta-cyclodextrin and its guanidinium-containing derivative.
abstract: An imidazolate-bridged homodinuclear complex, {[Cu(L)(H2O)]2(im)}(ClO4)3 (1), assembled with beta-cyclodextrin (betaCD) and its guanidinium-containing derivative (betaGCD), and thus a helical inclusion complex, {[Cu(L)(H2O)(betaCD)]2(im)}(ClO4)3 (2), were successfully isolated and structurally characterized. Structural analysis showed that each Cu(II) ion has a distorted square pyramidal N4Ow coordination sphere and forms a chiral chain through hydrogen-bonding and hydrophobic interactions. The UV-vis data showed that such a chain can provide the imidazolate bridge additional stability and results in the dissociation equilibrium taking place at the physiological pH. The obtained IC50 value for 2 (0.23 muM) showed a high superoxide dismutase (SOD) activity, which corresponds to a highly stable imidazolate bridge. Interestingly, the guanidinium-containing 1/betaGCD system showed higher SOD activity (IC50 = 0.16 muM), which is enhanced at least by 30% in comparison with that of guanidinium-lacking 2. This result supports that the positive guanidinium plays a role in the catalytic mechanism of Cu,Zn-SOD by ensuring that superoxide enters and peroxide leaves rapidly from the coordination sphere of the copper ion.
authors.affiliation: School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Heng
authors.initials: H
authors.lastname: Fu
authors.forename: Ying-Hua
authors.initials: YH
authors.lastname: Zhou
authors.forename: Wei-Lin
authors.initials: WL
authors.lastname: Chen
authors.forename: Zhuo-Ga
authors.initials: ZG
authors.lastname: Deqing
authors.forename: Ming-Liang
authors.initials: ML
authors.lastname: Tong
authors.forename: Liang-Nian
authors.initials: LN
authors.lastname: Ji
authors.forename: Zong-Wan
authors.initials: ZW
authors.lastname: Mao
mesh_terms: D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D019791:Guanidine / Q000737:chemistry* / Q000378:metabolism; D007093:Imidazoles / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism; D047392:beta-Cyclodextrins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D007093:Imidazoles; D009942:Organometallic Compounds; D047392:beta-Cyclodextrins; D003300:Copper; D013482:Superoxide Dismutase; D019791:Guanidine; C031215:betadex