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Edward I. Stiefel

Other affiliations: Kettering University
Bio: Edward I. Stiefel is an academic researcher from ExxonMobil. The author has contributed to research in topics: Molybdenum & Catalysis. The author has an hindex of 45, co-authored 170 publications receiving 5406 citations. Previous affiliations of Edward I. Stiefel include Kettering University.


Papers
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Book ChapterDOI
01 Jan 1980
TL;DR: In this article, a set of structurally defined oxo-molybdenum complexes containing sulfur-donor ligands for comparison with the enzymes by EPR*, EXAFS*, and other spectroscopic probes was provided.
Abstract: The molybdenum enzymes other than nitrogenase have a common molybdenum cofactor1,2 and spectroscopic studies of their molybdenum sites reveal these to be similar although not identical.3 EPR* studies on xanthine oxidase in the Mo(V) oxidation state,4 together with results from model compounds,5 led to the suggestion of sulfur as a donor atom to molybdenum. However, in these original studies and in subsequent investigations, 3,6 the inorganic compounds used in the comparison were not structurally and, at times, not even stoichiometrically defined. In order to provide a comprehensive set of structurally defined oxo-molybdenum complexes containing sulfur-donor ligands for comparison with the enzymes by EPR*, EXAFS* and other spectroscopic probes, we have embarked on an exten sive synthetic and isolation program to obtain relevant compounds in the Mo(IV), Mo(V) and MoiVI) oxidation states. Recently, EXAFS studies on xanthine oxidase and sulfite oxidase8 have confirmed the presence of sulfur and terminal oxo ligands in the coordination sphere of molybdenum and have revealed distinct similarities to some of the model compounds discussed here.9

6 citations

Patent
15 Oct 1985
TL;DR: In this paper, neutral complexes of dithioacid vanadium sulfide dimer were described. But the method of producing the complexes was not described. And the preferred dithiocarbamate was not discussed.
Abstract: This invention relates to neutral complexes of dithioacid vanadium sulfide dimer and to a method of producing the complexes. The 1,1-dithioacid may be a dithiocarbamate, xanthate, dithiophosphate, dithiophosphinate or other similar ligand. The structure is generally of the form ##STR1## where L is a 1,1-dithioacid. The preferred dithioacid is dithiocarbamate. The compositions are suitable for producing hydrotreating catalysts or as a lubricant additive.

6 citations

Patent
30 Jun 1992
TL;DR: In this article, an improved method for preparing compounds of the formula Mo4S4L6 comprising: heating a solution of a compound having the formula, wherein L is a 1,1-dithioacid ligand, at a temperature and for a time sufficient to form the Mo4s4L 6 compound.
Abstract: There is provided an improved method for preparing compounds of the formula Mo4S4L6 comprising: heating a solution of a compound having the formula MoL4, wherein L is a 1,1-dithioacid ligand, at a temperature and for a time sufficient to form the Mo4S4L6 compound. Preferably, the MoL4 compound is dissolved in an organic solvent and the solution is heated at temperatures above 25 DEG C., up to the boiling point of the solvent and, more preferably, at temperatures in the range of from about 50 DEG C. to about 250 DEG C.

6 citations

Book ChapterDOI
01 Jan 1983
TL;DR: Recent results in the areas non-nitrogenase Mo enzymes and the coordination and solid state chemistry of molybdenum are discussed and chemistry reveals some of the structural, spectroscopic and mechanistic possibilities which present themselves when multisulfur metal sites are present.
Abstract: This volume deals with biological nitrogen fixation and chemical systems which may offer analogy with or insight into the biological process. This chapter deals with certain biochemical and chemical systems which have not been studied specifically in the context of the nitrogen fixation problem. Rather, recent results in the areas non-nitrogenase Mo enzymes and the coordination and solid state chemistry of molybdenum are discussed. This chemistry reveals some of the structural, spectroscopic and mechanistic possibilities which present themselves when multisulfur metal sites are present.

6 citations

Book ChapterDOI
TL;DR: Since this initial identification of bacterioferritin its presence has been established in a wide variety of prokaryotic organisms including Escherichia coli, Pseudomonas aeruginosa, Nitrobacter winogradskii, Mycobacterium paratuberculosis, Synechocystis P.C. 6803, Yersinia pestis 9 and Rhodobacter capsulatus.
Abstract: Ferritin has been known in eukaryotic cells for over 50 years1 but only in the last 15 years has a ferritin-like molecule been recognized in bacterial systems. In 1979 2 the hemoprotein originally designated3 as Azotobacter vinelandii cytochrome b557.5 was shown to be ferritin-like in character on the basis of subunit size and composition, electron microscopy of the holoprotein, and physical characterization of the core iron. 2 Since this initial identification of bacterioferritin its presence has been established in a wide variety of prokaryotic organisms including Escherichia coli, 4 Pseudomonas aeruginosa 5 Nitrobacter winogradskii 5 Mycobacterium paratuberculosis, 7 Synechocystis P.C.C. 6803, 8 Yersinia pestis 9 and Rhodobacter capsulatus. 10 In each of the above species heme in the form of extractable protoporphyrin IX is intimately associated with the protein.

6 citations


Cited by
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Journal ArticleDOI
TL;DR: A great deal of research effort is now concentrated on two aspects of ferritin: its functional mechanisms and its regulation and the apparent links between iron and citrate metabolism through a single molecule with dual function are described.

2,486 citations

Journal ArticleDOI
TL;DR: The geometries of 131 SBUs, their connectivity and composition of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal-organic frameworks (MOFs).
Abstract: This critical review presents a comprehensive study of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) towards construction and synthesis of metal–organic frameworks (MOFs). We describe the geometries of 131 SBUs, their connectivity and composition. This contribution presents a comprehensive list of the wide variety of transition-metal carboxylate clusters which may serve as secondary building units (SBUs) in the construction and synthesis of metal–organic frameworks. The SBUs discussed here were obtained from a search of molecules and extended structures archived in the Cambridge Structure Database (CSD, version 5.28, January 2007) which included only crystals containing metal carboxylate linkages (241 references).

2,145 citations

Journal ArticleDOI
TL;DR: It is now well-established that all molybdenum-containing enzymes other than nitrogenase fall into three large and mutually exclusive families, as exemplified by the enzymes xanthine oxidation, sulfite oxidase, and DMSO reductase; these enzymes represent the focus of the present account.
Abstract: Molybdenum is the only second-row transition metal required by most living organisms, and is nearly universally distributed in biology. Enzymes containing molybdenum in their active sites have long been recognized,1 and at present over 50 molybdenum-containing enzymes have been purified and biochemically characterized; a great many more gene products have been annotated as putative molybdenum-containing proteins on the basis of genomic and bioinformatic analysis.2 In certain cases, our understanding of the relationship between enzyme structure and function is such that we can speak with confidence as to the detailed nature of the reaction mechanism and, with the availability of high-resolution X-ray crystal structures, the specific means by which transition states are stabilized and reaction rate is accelerated within the friendly confines of the active site. At the same time, our understanding of the biosynthesis of the organic cofactor that accompanies molybdenum (variously called molybdopterin or pyranopterin), the manner in which molybdenum is incorporated into it, and then further modified as necessary prior to insertion into apoprotein has also (in at least some cases) become increasingly well understood. It is now well-established that all molybdenum-containing enzymes other than nitrogenase (in which molybdenum is incorporated into a [MoFe7S9] cluster of the active site) fall into three large and mutually exclusive families, as exemplified by the enzymes xanthine oxidase, sulfite oxidase, and DMSO reductase; these enzymes represent the focus of the present account.3 The structures of the three canonical molybdenum centers in their oxidized Mo(VI) states are shown in Figure 1, along with that for the pyranopterin cofactor. The active sites of members of the xanthine oxidase family have an LMoVIOS-(OH) structure with a square-pyramidal coordination geometry. The apical ligand is a Mo=O ligand, and the equatorial plane has two sulfurs from the enedithiolate side chain of the pyranopterin cofactor, a catalytically labile Mo–OH group, and most frequently a Mo=S. Nonfunctional forms of these enzymes exist in which the equatorial Mo=S is replaced with a second Mo=O; in at least one member of the family the Mo=S is replaced by a Mo=Se, and in others it is replaced by a more complex –S–Cu–S–Cys to give a binuclear center. Members of the sulfite oxidase family have a related LMoVIO2(S–Cys) active site, again square-pyramidal with an apical Mo=O and a bidentate enedithiolate Ligand (L) in the equatorial plane but with a second equatorial Mo=O (rather than Mo–OH) and a cysteine ligand contributed by the protein (rather than a Mo=S) completing the molybdenum coordination sphere. The final family is the most diverse structurally, although all members possess two (rather than just one) equiv of the pyranopterin cofactor and have an L2MoVIY(X) trigonal prismatic coordination geometry. DMSO reductase itself has a catalytically labile Mo=O as Y and a serinate ligand as X completing the metal coordination sphere of oxidized enzyme. Other family members have cysteine (the bacterial Nap periplasmic nitrate reductases), selenocysteine (formate dehydrogenase H), –OH (arsenite oxidase), or aspartate (the NarGHI dissimilatory nitrate reductases) in place of the serine. Some enzymes have S or even Se in place of the Mo=O group. Members of the DMSO reductase family exhibit a general structural homology to members of the aldehyde:ferredoxin oxidoreductase family of tungsten-containing enzymes;4 indeed, the first pyranopterin-containing enzyme to be crystallographically characterized was the tungsten-containing aldehyde:ferredoxin oxidoreductase from Pyrococcus furiosus,5 a fact accounting for why many workers in the field prefer “pyranopterin” (or, perhaps waggishly, “tungstopterin”) to “molybdopterin”. The term pyranopterin will generally be used in the present account. Open in a separate window Figure 1 Active site structures for the three families of mononuclear molybdenum enzymes. The structures shown are, from left to right, for xanthine oxidase, sulfite oxidase, and DMSO reductase. The structure of the pyranopterin cofactor common to all of these enzymes (as well as the tungsten-containing enzymes) is given at the bottom.

1,541 citations