Synthesis, spectral, electrochemical and magnetic properties of new symmetrical and unsymmetrical dinuclear copper(II) complexes derived from binucleating ligands with phenol and benzimidazole donors

Amudha, P; Akilan, P.; Kandaswamy, M.

doi:10.1016/s0277-5387(98)00401-x

Cited by 21 publications

(11 citation statements)

References 23 publications

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“…see Refs. [32][33][34][35][36][37][38][39], and it has also been proposed for both met and half-met hemocyanin (11,26,27,60). We note that exchange of the Cu 2 bridging ligand would affect the magnitude of antiferromagnetic coupling (i.e.…”

Section: Discussionsupporting

confidence: 52%

“…We note that exchange of the Cu 2 bridging ligand would affect the magnitude of antiferromagnetic coupling (i.e. Ϫ2J) between both copper ions (33,38,39) and the electron spin distribution over the ligands of both copper ions, thereby affecting the contact coupling constant A for each signal. Because the hyperfine shifts are a function of both Ϫ2J and A (14), it is expected that the shifts for the paramagnetically affected 1 H NMR signals are all dependent on the nature of the Cu 2 bridging ligand.…”

Section: Discussionmentioning

confidence: 98%

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Structural Basis and Mechanism of the Inhibition of the Type-3 Copper Protein Tyrosinase from Streptomyces antibioticusby Halide Ions

Tepper¹,

Bubacco²,

Canters³

2002

Journal of Biological Chemistry

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The inhibition of the type-3 copper enzyme tyrosinase by halide ions was studied by kinetic and paramagnetic 1 H NMR methods. All halides are inhibitors in the conversion of L-3,4-dihydroxyphenylalanine (L-DOPA) with apparent inhibition constants that follow the order I ؊ < F ؊ < < Cl ؊ < Br ؊ at pH 6.80. The results show that the inhibition arises from the interaction of halide with both the oxidized (affinity F ؊ > Cl ؊ > Br ؊ > > I ؊ ) and reduced (affinity I ؊ > Br ؊ > Cl ؊ > > F ؊ ) enzyme. The paramagnetic 1 H NMR of the oxidized enzyme complexed with the halides is consistent with a direct interaction of halide with the type-3 site and shows that the (Cu-His 3 ) 2 coordination occurs in all halide-bound species. It is surmised that halides bridge both of the copper ions in the active site. Fluoride and chloride are shown to bind only to the low pH form of oxidized tyrosinase, explaining the strong pH dependence of the inhibition by these ions. We further show that p-toluic acid and the bidentate transition state analogue, Kojic acid, displace chloride from the oxidized active site, whereas the monodentate substrate analogue, p-nitrophenol, forms a ternary complex with the enzyme and the chloride ion. On the basis of the experimental results, a model is formulated for the inhibitor action and for the reaction of diphenols with the oxidized enzyme.One of the unresolved questions in the enzymology of the type-3 copper-containing tyrosinases (EC 1.14.18.1) is the detailed molecular mechanism of both inhibitor action and substrate conversion. This report focuses on the mechanism of their inhibition by halides. Tyrosinases are monooxygenating enzymes catalyzing the ortho-hydroxylation of monophenols and the subsequent oxidation of the diphenolic products to the corresponding quinones. The reactions take place under concomitant reduction of molecular oxygen to water. The formed quinones are reactive precursors in the synthesis of melanin pigments. In fruits, vegetables, and mushrooms, Ty 1 is a key enzyme in the browning that occurs upon bruising or long-term storage. In mammals, Ty is responsible for skin pigmentation. Defects in the enzyme may lead to some forms of oculocutaneous albinism or vitiligo (1). Furthermore, the enzyme has been linked to Parkinson's and other neurodegenerative diseases (2-6). Consequently, the enzyme poses considerable interest from medical, agricultural, and industrial points of view.The current knowledge of Ty at the biological, mechanistic, and structural levels has recently been reviewed (7-10). Ty harbors a dinuclear so-called type-3 copper center, the occurrence of which has also been established in hemocyanins, which act as oxygen carriers in arthropods and mollusks, and the catechol oxidases, which oxidize o-diphenols to the corresponding quinones. The two closely spaced copper ions in the type-3 active site are coordinated each by 3 histidine residues through the N⑀ nitrogen atoms (9). Although the known type-3 centers are found to be similar both in structure and in their a...

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Section: Discussionsupporting

confidence: 52%

Section: Discussionmentioning

confidence: 98%

Structural Basis and Mechanism of the Inhibition of the Type-3 Copper Protein Tyrosinase from Streptomyces antibioticusby Halide Ions

Tepper¹,

Bubacco²,

Canters³

2002

Journal of Biological Chemistry

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“…33,34 The absence of aminophenyl ring absorption at 3350 cm -1 and appearance of a strong intensity band in the IR spectra of compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) in the range of 1610-1650 cm -1 attributable to nC=N provides a strong evidence for the condensation and also confirms the formation of the azomethines 1-10. 35 The oxidative cyclisation of compounds 1-10 to 11-20 were accompanied by the disappearance of the absorption maxima at 3150-3300 cm -1 , which are ascribed to the vibrations of NH group of the benzimidazole ring; at the same time the appearance of a new maximum at 1360-1388 cm --1 , which is characteristic for benzimidazoquinazoline ring with a tertiary nitrogen atom, appears. 23,36 The 1 H NMR spectra of the compound A as well as its derivatives have been recorded in CDCl 3 /DMSO-d 6 using TMS as internal standard.…”

Section: Chemistrymentioning

confidence: 97%

“…In the spectra of 2-(o-aminophenyl) benzimidazole (A), signals at d 6.4 and d 8.25 ppm were appeared corresponding to free amino and imidazolyl protons respectively. 33,35 The aromatic protons of various environments present in all compounds appeared as multiplets in the range of d 6.84-8.81 ppm.…”

Section: Chemistrymentioning

confidence: 99%

Synthesis and antimicrobial activities of a new class of 6-arylbenzimidazo[1,2-c]quinazolines

Rohini¹,

Shanker²,

Reddy³

et al. 2010

J. Braz. Chem. Soc.

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Uma série de compostos 6-arilbenzimidazo[1,2-c]quinazolina (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) foram sintetizados pela condensação do 2-(o-aminofenil)benzimidazol com diferentes arilaldeídos seguida pela ciclização oxidativa dos 2-o-arilidenoaminofenilbenzimidazol (1-10). Todos os produtos foram caracterizados por espectroscopia no infravermelho (IR), ressonância magnética nuclear de prótons e de carbono, (RMN 1 H e RNN

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“…In all the azomethines (Ia -Ij, 2-o-arylidineaminophenylindoles) the characteristic IR peaks for the -CHO and -NH 2 groups at 1680 -1695 cm -1 and 3380 -3440 cm -1 are absent and the characteristic peak for the CH=N around 1610 -1635 cm -1 is observed, which indicates the effective condensation of the aldehyde group with the amino group of the key indole derivative (2-o-aminophenylindole) [36]. The formation of the final 6-substituted indolo[1,2-c]quinazolines was identified by disappearance of m (NH-) absorption band at 3400 -3330 cm -1 present in 2-o-aminophenylindole, and the appearance of the absorption band at 1360 -1380 cm -1 characteristic for the indoloquinazoline ring with a tertiary nitrogen atom (C-N) [37].…”

Section: Chemistrymentioning

confidence: 98%

6‐Substituted Indolo[1,2‐c]quinazolines as New Antimicrobial Agents

Rohini

Shanker

Reddy

et al. 2009

Archiv der Pharmazie

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A series of 2-o-arylidineaminophenylindoles and their cyclic derivatives (indolo[1,2-c]quinazolines) were synthesized. The reactions occurred under relatively mild conditions and afforded the desired product in good yields. Molecular structures of the synthesized compounds were confirmed by IR, (1)H-NMR,( 13)C-NMR, MS spectra, and elemental analyses. Furthermore, all the final products were screened for in-vitro antibacterial activity against three Gram-positive and three Gram-negative bacteria and also tested for their inhibitory action against three strains of fungi. Compound IIc showed potent activity against all the bacterial (except S. typhimurium) and fungal strains. Especially, compounds IIi and IIj which have isoquinolyl and pyridyl substituents displayed potent antibacterial as well as antifungal activities compared to those of the respective standard drugs Ampicillin and Ketoconazole.

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Synthesis, spectral, electrochemical and magnetic properties of new symmetrical and unsymmetrical dinuclear copper(II) complexes derived from binucleating ligands with phenol and benzimidazole donors

Cited by 21 publications

References 23 publications

Structural Basis and Mechanism of the Inhibition of the Type-3 Copper Protein Tyrosinase from Streptomyces antibioticusby Halide Ions

Structural Basis and Mechanism of the Inhibition of the Type-3 Copper Protein Tyrosinase from Streptomyces antibioticusby Halide Ions

Synthesis and antimicrobial activities of a new class of 6-arylbenzimidazo[1,2-c]quinazolines

6‐Substituted Indolo[1,2‐c]quinazolines as New Antimicrobial Agents

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