Electron paramagnetic resonance spectrum and covalency parameters of copper-63(KTS)

Campbell, M.J.M.; Collis, Anthony J.; Grzeskowiak, R.

doi:10.1016/s0006-3061(00)80016-2

Cited by 15 publications

(15 citation statements)

References 15 publications

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“…The numerical results of these fits are summarized in Table 1. (21) to 2.32 A for dithiocarbamates (22). Molecular orbital studies (23,24) as well as electron paramagnetic resonance analysis (24) suggest appreciable ligand-to-metal -r-covalency in copper(II)bis(thiosemicarbazonato) complexes. Thus, if a thiosemicarbazonato sulfur is taken to approximate thiolate, then a Cu(II) bond length of about 2.16 A would be expected for a hypothetical tetrahedral Cu(II)bis(thiosemicarbazonato) complex.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the blue copper site in oxidized azurin by extended x-ray absorption fine structure: Determination of a short Cu—S distance

Tullius

Frank

Hodgson

1978

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

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The primary coordination environment of the "blue" copper ion in oxidized azurin has been elucidated by x-ray absorption spectroscopy. The most striking-feature is the unambiguous presence of a very short copper-sulfur, distance at 2.10 + 0.02 A. Nitrogen ligands, presumed to be from imidazoles, are found at 1.97 A. There is some evidence that the copper coordination sphere may be completed by a second sulfur, the distance of which is determined with much less certainty.Proteins that contain the "blue" (or type 1) copper site (1) have long offered a challenge to chemists to explain their unique spectroscopic and redox properties. Some of the basic aspects of the structure of such blue sites have already become clear, as revealed by interpretation of several types of spectroscopic data. The model for the blue site of bean plastocyanin put forth by Gray and coworkers (2) is probably the best distillation of current spectroscopic and chemical information on blue copper. The ligand field spectrum implies a distorted tetrahedral coordination of the copper, which is also reasonable when the high redox potential of the copper is considered. A thiolate sulfur from cysteine is proposed as one of the metal ligands. Two imidazole nitrogens from histidines are also implicated as ligands, from NMR studies (3-5). The fourth ligand of copper is less certain. A deprotonated peptide nitrogen from the protein has been proposed as this ligand (6), but methionine sulfur now seems to be the most likely possibility. The x-ray protein structure of poplar plastocyanin has recently been solved to 2.7 A resolution (7). The copper in this plastocyanin is coordinated by cysteinate, two imidazoles, and methionine.The availability of even a high-resolution x-ray crystallographic structure of a blue protein would not necessarily explain all of the unusual spectroscopic and redox properties of blue copper. Subtle changes in bond distance and coordination geometry, which the limited accuracy of even a good protein crystal structure might render difficult to resolve, can be expected to have major effects on these properties.A technique that has been recently used to examine the environment of a selected element in a complex macromolecular system is x-ray absorption spectroscopy. The fine structure that occurs at energies above the x-ray absorption edge (called EXAFS) provides a way of determining distances, numbers, and h-ypes of ligands coordinating a metal. Since the EXAFS method does not require crystalline samples, it can be applied to the study of metalloproteins under noncrystalline or physiological conditions (8)(9)(10)(11). In contrast to macromolecular crystallographic results, where it is difficult to obtain high accuracy except in the few cases of very well refined structures, EXAFS can provide accurate metal-to-ligand distances (12). Coupled with the element-selective nature of the measurements, the EXAFS technique is ideal for investigating the environment of a specific metal ion in a protein.In order to further elucidate t...

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Section: Discussionmentioning

confidence: 99%

Characterization of the blue copper site in oxidized azurin by extended x-ray absorption fine structure: Determination of a short Cu—S distance

Tullius

Frank

Hodgson

1978

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

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“…7 (14), so this structure is not involved in the catalysis of oxygen reduction. The structure of CuKTS has been studied by means of ESR because of its established antitumor properties (13,(15)(16)(17)(18). The best-resolved ESR spectrum was obtained from CuKTS doped into the nickel analog, NiKTS (18).…”

Section: Esr Investigations Of Tetradentate Cupric Complexesmentioning

confidence: 99%

“…The structure of CuKTS has been studied by means of ESR because of its established antitumor properties (13,(15)(16)(17)(18). The best-resolved ESR spectrum was obtained from CuKTS doped into the nickel analog, NiKTS (18). The principal values of the ESR parameters were used to determine that the copper-ligand bonds are highly covalent and the Cu-N and Cu-S bonds may be regarded as essentially independent.…”

Section: Esr Investigations Of Tetradentate Cupric Complexesmentioning

confidence: 99%

“…The complex was known to localize in lipophilic parts of cells, presumably membrane (18). Room temperature ESR studies were undertaken to study CuKTSM2 bound in Ehrlich cells (13).…”

Section: Esr Investigations Of Tetradentate Cupric Complexesmentioning

confidence: 99%

“…(ii) direct iron-independent reaction between the adriamycin semiquinone and hydroperoxides; (17) (18) Whereas direct ESR and ESR-spin trapping can be used to verify reactions (15 and (16), one can use oxygenuptake measurements (in the presence of spin trap) to obtain evidence for reaction (18). In fact, evidence for reaction (16) has recently been shown directly by ESR (80).…”

Section: Radical Reaction In Systems Containing Iron Adriamycinmentioning

confidence: 99%

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ESR of Copper and Iron Complexes with Antitumor and Cytotoxic Properties

Antholine¹,

Kalyanaraman²,

Petering³

1985

Environmental Health Perspectives

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The relatively few iron and copper metal complexes which have been examined in cells and tissues for their redox properties, radical generation properties, and antitumor activity are discussed for studies which utilized electron spin resonance spectroscopy (ESR). A common property of a number of metal complexes, which include bleomycin, adriamycin, and thiosemicarbazones described in this review, is that they are readily reduced by thiol compounds and oxidized by oxygen or reduced species of oxygen to produce radicals. Structural features ofthese reactions are identified by ESR spectroscopy in model systems and-often in cells. Furthermore, ESR spectroscopy has been most useful to probe the environment of the complexes in cells and to measure the rate of reduction of their oxidized forms. As a result of these studies, it is anticipated that more attention will be given to the exploration of redox-active metal complexes as drugs.

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The chemistry of chelating agents in medical sciences

Bulman¹

1987

Coordination Compounds: Synthesis and Medical Application

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Electron paramagnetic resonance spectrum and covalency parameters of copper-63(KTS)

Cited by 15 publications

References 15 publications

Characterization of the blue copper site in oxidized azurin by extended x-ray absorption fine structure: Determination of a short Cu—S distance

Characterization of the blue copper site in oxidized azurin by extended x-ray absorption fine structure: Determination of a short Cu—S distance

ESR of Copper and Iron Complexes with Antitumor and Cytotoxic Properties

The chemistry of chelating agents in medical sciences

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