Biological analogs. Nature of the binding sites of copper-containing proteins

Amundsen, Alan R.; Whelan, John; Bosnich, B.

doi:10.1021/ja00462a042

Cited by 306 publications

(135 citation statements)

References 8 publications

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“…The 425-nm band in oxyhemocyanin is still present in the lowtemperature absorption spectra of methemocyanin (Fig. 5, dashed line) and thus becomes a likely candidate for a protein ligand-to-copper charge transfer transition; the protein ligand is most likely tyrosine, based on model complex studies (6). Conversely, the lack of any intense bands (e > 1500 M-1 cm-') in the 300-to 400-nm region (see ref.…”

Section: Methodsmentioning

confidence: 90%

“…Conversely, the lack of any intense bands (e > 1500 M-1 cm-') in the 300-to 400-nm region (see ref. 6) of the met hemocyanin spectrum implies that sulfur (cysteine and methionine) is not a copper ligand in hemocyanin and precludes the assignment of the dominant absorption at 345 nm in oxy as a protein ligand-to-copper charge transfer transition. The 345-nm band has also been assigned as a SPE (20): an excitation of two copper centers by one photon at twice the energy of a single center transition.…”

Section: Methodsmentioning

confidence: 99%

“…The dominant absorption at 345 nm has been variously assigned as a simultaneous pair excitation (SPE) (5) or a ligand-to-metal charge transfer transition (LMCT) with the ligand suggested to be S-(cysteine) (6), O22- (7), or N (histidine) (1). The 570-nm band has been assigned as peroxide to copper charge transfer (1) or d-d transitions (6).…”

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confidence: 99%

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Geometric and electronic structure of oxyhemocyanin: spectral and chemical correlations to met apo, half met, met, and dimer active sites.

Eickman¹,

Himmelwright²,

Solomon³

1979

Proc. Natl. Acad. Sci. U.S.A.

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The chemical and spectral properties of a series of hemocyanin derivatives were systematically compared to provide insight into the geometric and electronic structure of the oxyhemocyanin active site. The binuclear copper site is characterized as two tetragonal Cu(II) Oxygen binds as peroxide (1) to the active site in oxyhemocyanin (2) in the ratio of 1 02:2 Cu and it is generally agreed that the two coppers are in the +2 oxidation state, although a Cu(I)Cu(III) active site has recently been proposed (3). The lack of an electron paramagnetic resonance (EPR) signal for oxyhemocyanin, then, requires the existence of antiferromagnetic coupling or a metal-metal bond between the cupric ions. Magnetic susceptibility studies (4) failed to detect any deviation from Curie behavior, placing only a lower limit of 550 cm-1 on any antiferromagnetic etchange interaction. The optical spectrum also exhibits unique spectral features. The dominant absorption at 345 nm has been variously assigned as a simultaneous pair excitation (SPE) (5) or a ligand-to-metal charge transfer transition (LMCT) with the ligand suggested to be S-(cysteine) (6), O22-(7), or N (histidine) (1). The 570-nm band has been assigned as peroxide to copper charge transfer (1) or d-d transitions (6).We have undertaken a systematic study of a series of hemocyanin derivatives in order of increasing complexity to provide insight into the geometric and electronic structure of the active site of oxyhemocyanin (Fig. 1). The resulting spectral perturbations allow a determination of the oxidation state of the copper ions in each derivative, the existence of both exogenous and endogenous bridges between the two coppers, the coordination mode of peroxide in oxy, and a spectral assignment for the unique absorption features exhibited by oxyhemocyanin. MATERIALS AND METHODSBusycon canaliculatum hemocyanin was purified by ultracentrifugation. A Varian E-9 EPR spectrometer (X-band) was used on frozen solution samples. Low-temperature optical spectra were taken of buffered sucrose solutions with a Cary 17 absorption spectrometer and a Spectrim II cryocooler. Difference spectra of the 300-to 500-nm region were taken with the appropriate protein derivative in the reference beam-e.g., met apo-aquo provided the baseline for met apo-N3-. This was necessary to compensate for residual oxyhemocyanin and the steep slope of the protein absorption in the 300-to 500-nm region. RESULTS AND DISCUSSIONMet apo hemocyanin Met apo hemocyanin is prepared (8) The EPR spectrum of met apo-N3-is given in Fig. 2

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Section: Methodsmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

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Geometric and electronic structure of oxyhemocyanin: spectral and chemical correlations to met apo, half met, met, and dimer active sites.

Eickman¹,

Himmelwright²,

Solomon³

1979

Proc. Natl. Acad. Sci. U.S.A.

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“…Medidas de condutividade foram efetuadas em soluções 1 x 10 -3 mol.L -1 dos compostos (1), (2), (3) 10 , enquanto que os outros três compostos exibem duas bandas também observadas em outros complexos de Cu(II) descritos na literatura 2,9,10,13 e consistentes com uma geometria piramidal quadrada.…”

Section: Condutivimetriaunclassified

“…Na última década, a estratégia sintética de utilizar grupos imidazólicos ou piridínicos e fenólicos na projeção de novos ligantes tem despertado grande interesse para mimetizar os aminoácidos histidina e tirosina, respectivamente, presentes em um grande número de metaloproteínas. A utilização dessa estratégia na síntese de complexos mononucleares de Cu(II) visa o desenvolvimento de novos compostos que auxiliem na elucidação do papel desempenhado por esse íon em enzimas de cobre tais como a azurina, a plastocianina, a galactose oxidase, a superóxido dismutase, etc [2][3][4] .…”

Section: Introductionunclassified

Síntese e caracterização de novos compostos de coordenação de cobre (II) com ligantes não-simétricos N,O-doadores: contribuições para o sítio ativo da galactose oxidase

Moraes

Neves

2001

Quím. Nova

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2-(4′,4′-Dimethyl-3′,4′-dihydrooxazol-2′-yl)phenol: Some First-Row Transition Metal Complexes of This Naturally Occurring Binding Group

Mugesh

Singh

Butcher

2001

Eur. J. Inorg. Chem.

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The synthesis and characterization of monomeric MnIII, CoII, NiII, CuII, and ZnII phenolates derived from a biologically relevant ligand, 2‐(4′,4′‐dimethyl‐3′,4′‐dihydrooxazol‐2′‐yl)phenol (1), are described. The addition of Mn(OAc)2 · 4 H2O to an ethanolic solution of 1 affords an unexpected 1:3 complex [Mn(OR){O(Ox)}2] (2) [R = C6H4CONHC(Me2)CH2OH, Ox = 2‐(4,4‐dimethyl‐2‐oxazolinyl)phenyl] in which one of the five‐membered oxazoline rings is partially hydrolyzed. The complexes [M{O(Ox)}2] [M = Co (3), Ni (4), Cu (6), or Zn (7)] were prepared in good yield by the reactions of 1 with the corresponding metal acetates. Novel formation of the six‐coordinate NiII complex 5 with neutral acetic acid was observed during the crystallization process. The complexes were characterized by elemental analysis, magnetic susceptibility, as well as EPR, 1H NMR, electronic, and mass spectral techniques. Complexes 2, 3, 5, 6, and 7 were characterized by single crystal X‐ray diffraction studies. Complex 2 is six‐coordinate whereas complexes 3, 6, and 7 are four‐coordinate with two oxazoline bidentate ligands. The geometry around the metal center is found to be distorted tetrahedral for all of the four‐coordinate complexes. Complex 5 is octahedral with four coordination sites occupied by the two bidentate oxazoline ligands and the other two are occupied by two neutral acetic acid molecules. The hydroxy groups of the coordinated acetic acid are hydrogen‐bonded to the phenolate oxygen atoms of the oxazoline ligands. The variable‐temperature 1H NMR spectroscopic studies of complex 7 indicate that the interconversion between the (M) and (P) helix is slow at low temperatures.

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Biological analogs. Nature of the binding sites of copper-containing proteins

Cited by 306 publications

References 8 publications

Geometric and electronic structure of oxyhemocyanin: spectral and chemical correlations to met apo, half met, met, and dimer active sites.

Geometric and electronic structure of oxyhemocyanin: spectral and chemical correlations to met apo, half met, met, and dimer active sites.

Síntese e caracterização de novos compostos de coordenação de cobre (II) com ligantes não-simétricos N,O-doadores: contribuições para o sítio ativo da galactose oxidase

2-(4′,4′-Dimethyl-3′,4′-dihydrooxazol-2′-yl)phenol: Some First-Row Transition Metal Complexes of This Naturally Occurring Binding Group

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