Zinc, cobalt, and cadmium thiolate complexes: models for the zinc (S-cys)2(his)2 centre in transcription factor IIIA (cys = cysteine; his = histidine)

Several structural features frequently characterize the catalytic sites of zinc enzymes. These features comprise a distorted tetrahedral geometry incorporating one or more histidine groups and a coordinated "activated" water molecule oriented out into a cavity or cleft which forms the substrate binding site on the enzyme surface (1, 2). The R-state 1 insulin hexamer represents a well characterized biomolecular analog of this type of coordination unit (3, 4). The metal chelate site in the R-state insulin hexamer comprises a pseudotetrahedral array of three histidines and one exogenous small molecule ligand as shown in Fig. 1. The tris imidazole-Zn(II) motif occurs at the active site of several structurally characterized zinc metalloenzymes, including the carbonic anhydrases (Zn(His) 3 (H 2 O)), ␤-lactamase (Zn(His) 3 S-Cys), astacin (Zn(His) 3 (Tyr)(H 2 O)), DD-carboxypeptidase (Zn(His) 3 (H 2 O)), and the metzincins (5-9). The analysis of spectroscopically congruent transition metal-substituted metalloprotein derivatives has provided revealing insights into the active site structure and mechanistic details of many functionally diverse metalloproteins (1, 10 -12). Despite the importance of such derivatives and their small molecule synthetic analogs, to our knowledge, there are no well characterized examples of small molecule complexes that stabilize pseudotetrahedral tris imidazole coordination with Zn(II) as well as with the chromophoric metal ion probes Co(II) and Cu(II).The R-state insulin hexamer is one system that has been shown to stabilize pseudotetrahedral M(His) 3 L (M ϭ Zn(II), Co(II), Cu(II)) coordination in which the fourth ligand site may be occupied by a wide range of exogenous small molecule ligands (L) (3). This hexamer thus represents a unique and highly pertinent spectrochemical model system for the investigation of the structural and spectroscopic interrelationships of this type of metal center. A major difficulty with biological chromophores is the fact that metalloproteins usually impose low symmetry ligation at the active sites which result in Co(II) derivatives that are difficult to model both theoretically and with small molecule Co(II) complexes. Furthermore, the high spin Co(II) ion in a low symmetry environment gives rise to a particularly complex splitting of the ligand field bands due to the low symmetry geometry in concert with several different electronic effects (13). The difficulty in accounting for the ligand field components observed experimentally has highlighted the importance of Co(II) model systems that incorporate biologically relevant ligands into nonclassical chelate geometries that may be perturbed in a systematic manner. The abbreviations used are: T and R, designate insulin forms, respectively, with extended (T) and ␣-helical (R) conformations for residues 1-8 of the B-chain. The T 6 , T 3 R 3 , and R 6 designations (15) correspond to three crystallographically identified forms of the insulin hexamer. Co(II)-R 6 , the R 6 insulin hexamer with Co(II) substituted for Zn...

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“…complexes with distorted tetrahedral Co(II) centers that exhibit somewhat comparable electronic spectra have been reported (31,32).…”

Section: Effects Of the Exogenousmentioning

confidence: 93%

Ligand Perturbation Effects on a Pseudotetrahedral Co(II)(His)3-Ligand Site

Brader

Kaarsholm

Harnung

et al. 1997

Journal of Biological Chemistry

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“…The bonding of cadmium with amine and thiolate is of keen interest in the context of its solid-state structure and biological activity. Cd(II) complexes with a CdS 2 N 2 core have remained less explored [12]. Our earlier communications include studies on mixed ligand complexes of Ni(II), Cu(II), Zn(II), Cd(II), and Co(II) with 1,1-dicyanoethylene-2,2-dithiolate and some nitrogen bases [13].…”

Section: Introductionmentioning

confidence: 99%

Cd(II) complexation with 1,1-dithiolate and nitrogen donors: synthesis, luminescence, crystal structure, and antifungal activity study

Singh

Sutradhar

Paul

et al. 2015

Journal of Coordination Chemistry

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2015) Cd(II) complexation with 1,1-dithiolate and nitrogen donors: synthesis, luminescence, crystal structure, and antifungal activity studyA new luminescent complex of Cd(II) with 1,1-dicyanoethylene-2,2-dithiolate [i-MNT 2− = {S 2 C:C (CN) 2 } 2− ] has been synthesized and characterized on the basis of spectroscopy and single-crystal X-ray diffraction analysis. Single-crystal X-ray diffraction analysis reveals that the cadmium(II) complex is five coordinate in a 1-D polymer. Biological screening in vitro of the complex has been tested against five fungi Synchytrium endobioticum, Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231), and Trichophyton mentagrophytes by the disk diffusion method. The antifungal activity of the complex of Cd(II) is significant compared to K 2 iMNT on S. endobioticum, P. oryzae, H. oryzae, and T. mentagrophytes and proved to be crucial for the growth-inhibitor effect.A new luminescent complex of Cd(II) with 1,1-dicyanoethylene-2,2-dithiolate [i-MNT 2− = {S 2 C : C (CN) 2 } 2− ] with 1,3-diaminopropane (tn) and 4-methyl pyridine (γ-picoline) as secondary ligands has *Corresponding author. Downloaded by [University of Nebraska, Lincoln] at 03:23 06 April 2015been synthesized and characterized on the basis of spectroscopy and single-crystal X-ray diffraction analysis. Single-crystal X-ray diffraction analysis reveals that cadmium(II) is five coordinate in a 1-D polymer. Biological screening effects in vitro of the synthesized complex has been tested against five fungi Synchytrium endobioticum, Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231), and Trichophyton mentagrophytes by the disk diffusion method. A comparative study of inhibition zone values of K 2 i-MNT·H 2 O and {[Cd(tn)(iMNT)(4-MePy)]·4H 2 O} n (1) indicates that the complex exhibits antifungal activity, whereas K 2 i-MNT·H 2 O became silent on S. endobioticum, P. oryzae, H. oryzae, C. albicans (ATCC10231), and T. mentagrophytes.

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“…Strong absorbtion just below 1020 cm ±1 suggested that in 1 either oxygen atoms from some Si±O±C bonds interact with the metal or take part in hydrogen bond formation. [13].…”

Section: Synthesis and Propertiesmentioning

confidence: 99%

Cobalt(II) and Cobalt(III) Tri-tert-butoxysilanethiolates. Synthesis, Properties, Crystal and Molecular Structures of [Co{μ-SSi(OBut)3}{SSi(OBut)3}(NH3)]2 and [Co{SSi(OBut)3}2(NH3)4][SSi(OBut)3] Complexes

Becker

Zalewska

Konitz

et al. 2001

Z. anorg. allg. Chem.

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The heteroleptic neutral tri-tert-butoxysilanethiolate of cobalt(II) incorporating ammonia as additional ligand (1) has been prepared by the reaction of a cobalt(II) ammine complex with tri-tert-butoxysilanethiol in water. Complex 1, dissolved in hexane, undergoes oxidation in an ammonia saturated atmosphere to the ionic cobalt(III) compound 2. Molecular and crystal structures of 1 and 2 have been determined by single crystal X-ray structural analysis. 1 forms a dimeric molecule [Co{l-SSi(OBu t ) 3 }{SSi(OBu t ) 3 }(NH 3 )] 2 with a folded central Co 2 S 2 ring and distorted tetrahedral ligand arrangement at both Co II atoms (CoNS 3 core). The product 2 is composed of the octahedral Co III complex cation [Co{SSi(OBu t ) 3 } 2 (NH 3 ) 4 ] + and the tri-tertbutoxysilanethiolate anion. Within the crystal two pairs of ions interact by hydrogen bonds forming well separated entities. 1 and 2 are the first structurally characterized cobalt thiolates where metal is also bonded to ammonia and 2 is the first cobalt(III) silanethiolate.Beitra È ge zur Chemie der Silicium-Schwefel Verbindungen. 74. Cobalt(II) und Cobalt(III) Tri-tert-butoxysilanthiolate. Darstellung, Eigenschaften, Kristall-und Moleku È lstrukturen von [Co{l-SSi(OBu t ) 3 }{SSi(OBu t ) 3 }(NH 3 )] 2 und [Co{SSi(OBu t ) 3 } 2 (NH 3 ) 4 ][SSi(OBu t ) 3 ]Inhaltsu È bersicht. Das heteroleptische, neutrale, als zusa Ètz-lichen Liganden Ammoniak enthaltende Cobalt(II)-tri-tertbutoxysilanthiolat (1) wurde bei der Umsetzung von Tri-tertbutoxysilanthiol mit einem Cobalt±Ammin-Komplex in wa È sseriger Lo È sung erhalten. Verbindung 1, aufgelo È st in Hexan, oxidiert sich in einer mit Ammoniak gesa È ttigen Atmospha È re zum ionischen Cobalt(III)-Komplex 2. Die Moleku È lund Kristallstrukturen von 1 und 2 wurden ro È ntgenographisch bestimmt. 1 bildet ein dimeres Moleku È l [Co{l-SSi(OBu t ) 3 }{SSi(OBu t ) 3 }(NH 3 )] 2 mit einen gefaltenen Co 2 S 2 Ring und einer fast tetraedrischen Anordnung der Liganden an beiden Co II -Atomen (CoNS 3 Rumpf). 2 ist ionisch aufgebaut mit einem oktaedrischen Co III -Kation [Co{SSi(OBu t ) 3 } 2 (NH 3 ) 4 ] + und einem Tri-tert-butoxysilanthiolat-Anion. Im Kristall sind zwei Paare dieser Ionen durch Wasserstoffbru È cken zu isolierten Einheiten gebunden.

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Zinc, cobalt, and cadmium thiolate complexes: models for the zinc (S-cys)2(his)2 centre in transcription factor IIIA (cys = cysteine; his = histidine)

Abstract: complexes of Zn", Coil, and Cd" have been synthesized and characterized as models for the postulated metal centre in the nucleic acid binding protein, transcription factor IIIA.

Cited by 48 publications

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Ligand Perturbation Effects on a Pseudotetrahedral Co(II)(His)3-Ligand Site

Ligand Perturbation Effects on a Pseudotetrahedral Co(II)(His)3-Ligand Site

Cd(II) complexation with 1,1-dithiolate and nitrogen donors: synthesis, luminescence, crystal structure, and antifungal activity study

Cobalt(II) and Cobalt(III) Tri-tert-butoxysilanethiolates. Synthesis, Properties, Crystal and Molecular Structures of [Co{μ-SSi(OBut)3}{SSi(OBut)3}(NH3)]2 and [Co{SSi(OBut)3}2(NH3)4][SSi(OBut)3] Complexes

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