Satoshi Nishino

Copper(II) compound with long Cu(II)-phenolic oxygen atom bonding as galactose oxidase model

Abstract A crystal structure determination f Cu(phpyH)ClClO4·CH3OH revealed that the protonated phenolic oxygen atom lies at the apex of a square pyramidal CuN4O arrangement with Cu(II)O(phenolic) distances of 2.46 and 2.57 A; this is a novel copper(II) model compound for galactose oxidase where the Cu(II)-phenolic oxygen (Tyrosine-495) distance is rather long, 2.69 A, and the present results may provide chemical evidence for possible participation of Tyrosine-495 in the oxidation of galactose.

Oxygenation of amyloid beta-peptide (1-40) by copper(II) complex and hydrogen peroxide system

Abstract Electrospray mass-spectrometry (ESI-Mass) has revealed that some copper(II) compounds, but not others, catalyze oxygenation of amyloid β-peptide (1–40), undoubtedly at methionine sulfur atom, in the presence of hydrogen peroxide; this will give an important information to elucidate the role of copper ion in the brain to induce neurodegenerative disorders, such as Alzheimers and Prion diseases.

DNA promotes the activation of oxygen molecules by binuclear cobalt(II) compounds

Abstract We have observed that binuclear cobalt(II) compounds with H(HPTP), Co2(HPTP)(CH3COO)(ClO4)2 and Co2(HPTP)Cl(ClO4)2, react with oxygen molecules when DNA is present in the solution, cleaving the DNA (H(HPTP) denotes N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-diaminopropane-2- ol).

Cleavage of the C-N bond of a peptide group by a copper(II)-peroxide adduct with an η1-coordination mode

Abstract We have obtained clear evidence that a copper(II)-peroxide adduct with an η1-coordination mode can cleave the C–N bond of a peptide group and hydroxylate the alkyl group nearby; this may provide helpful information for elucidation of the reaction mechanism of PAM, peptidylglycine α-amidating monooxygenase.

Interaction between peroxide ion and phenol group which are coordinated to the same iron(III) ion

Abstract We have prepared several new iron(III) complexes with ligands which contain a phenol group; these are tetradentate [(X-phpy)H, X and H(phpy) represent the substituents on the phenol ring and N,N-bis(2-pyridylmethyl)-N-(2-hydroxybenzyl)amine, respectively] and pentadentate ligands [(R-enph-X)H; R=ethyl(Et) or methyl(Me) derivative and H(Me-enph) denotes N,N-bis(2-pyridylmethyl)-N″-methyl-N″-(2″-hydroxyl-benzylamine)ethylenediamine] and have determined the crystal structures of Fe(phpy)Cl2, Fe(5-NO2-phpy)Cl2, and Fe(Me-enph)ClPF6, which are of a mononuclear six-coordinate iron(III) complex with coordination of one or two chloride ion(s). These compounds are highly colored (dark violet) due to the coordination of phenol group to an iron(III) atom. When hydrogen peroxide was added to the solution of the iron(III) complex, a color change occurs with bleaching of the violet color, indicating that oxidative degradation of the phenol moiety occurred in the ligand system. The bleaching of the violet color was also observed by the addition of t-butylhydroperoxide. The rate of the disappearance of the violet color is highly dependent on the substituent on the phenol ring; introduction of an electron-withdrawing group in the phenol ring decreases the rate of bleaching, suggesting that disappearance of the violet band should be due to a chemical reaction between the phenol group and a peroxide adduct of the iron(III) species with an η1-coordination mode and that in this reaction the peroxide adduct acts as an electrophile towards phenol ring. The intramolecular interaction between the phenol moiety and an iron(III)-peroxide adduct may induce activation of the peroxide ion, and this was supported by several facts that the solution containing an iron(III) complex and hydrogen peroxide exhibits high activities for degradation of nucleosides and albumin.

Release of free nucleobases from oligomers by copper(II)–peroxide adduct

Abstract The release of nucleobases from oligonucleotides (12-mer, d(5′-CGCTTTAAAGCG)2, 8-mer, d(5′-AAACGTTT)2, 7-mer, d(TCGCGCG)2, and 6-mer, d(CGCGCG)2) by copper(II) complex and hydrogen peroxide systems was investigated in terms of HPLC. The [Cu(bdpg)Cl]Cl complex gave a large quantity of free nucleobases in the reaction mixture, but the activities of other compounds, such as [Cu(tpa)Cl]ClO4, were much lower than that of the (bdpg)-complex; where (bdpg) and (tpa) represent a N,N-bis(2-pyridylmethyl) derivative of β-alanineamide and 2-aminomethylpyridine, respectively. The above results and the electrospray mass spectral data on the solutions strongly suggest that the remarkable activity of the (bdpg)-compound is due to the high electrophilic nature of the copper(II)–hydroperoxide adduct, whose formation is greatly promoted through hydrogen bonding with the amide-oxygen atom coordinated to the copper(II) atom, and this electrophilic copper(II)–peroxide adduct attacks the sugar ring of nucleoside, to give the corresponding hydroxylated species, and from which free nucleobases are released.

INTERACTION BETWEEN THE PEROXIDE ADDUCT OF BINUCLEAR IRON(III) COMPLEX WITH (HPTP) ANION AND THE SUGAR MOIETY OF NUCLEOSIDES

We have in this study obtained the experimental evidence to suggest that the peroxide adduct of binuclear iron(III) complex with H(HPTP) directly reacts with the sugar moiety of the DNA chain, to cleave it; H(HPTP) denotes N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-diamino- 2 -propanol.

Detection of complex formation between binuclear iron(III)–peroxide adduct and oligonucleotide by electrospray mass spectrometry

Abstract Electrospray mass spectrometry (ESI–Mass) gave clear evidence for complex formation between an iron(III) complex and a DNA chain, and also between a binuclear iron(III)–peroxide adduct and a DNA chain.

Interaction between a copper(II) compound and protein investigated in terms of the capillary electrophoresis method

Abstract The capillary electrophoresis method has revealed that Cu(bdpg)Cl 2 can degrade bovine carbonic anhydrase (BCA) in the presence of hydrogen peroxide, whereas the activity of Cu(tpa)ClClO 4 is much lower than that of the bdpg complex (bdpg and tpa represent N , N -bis(2-pyridylmethyl)-aminomethyl- β -alanineamide and tris(2-pyridylmethyl)amine, respectively). This demonstrates that capillary electrophoresis is a useful method to detect the interaction between protein and a metal complex.

Structure of a new tetranuclear Iron(III) complex with an oxo-bridge; Factors to govern formation and stability of oxo-bridged iron(III) species in the L-subunit of ferritin

Abstract We have investigated the reaction products of several iron(III) compounds with hydrogen peroxide, and have found that hydrogen peroxide promotes the formation of an oxo-bridged iron(III) species in the presence of methanol (electron donor), and carboxyl groups of the ligand systems play a role to give the tetranuclear iron(III) compound containing a bent Fe- O-Fe unit (O: oxo oxygen atom). Based on the present results and the facts that L-chains of human ferritins lack ferroxidase activity, but are richer in carboxyl groups (glutamates) exposed on the cavity surface, it seems reasonable to conclude that (i) the hydrogen peroxide released in the H-subunit may contribute to the formation of a diferric oxo-hydrate in the L-subunit, (ii) the formation of a bent oxo-bridged iron(III) species is essentially important in the L-subunit, and (iii) rich carboxyl groups in L-subunits contribute to facilitate iron nucleation and mineralization through the capture and activation of the peroxide ion, and formation of a stable bent oxo-bridged iron(III) species