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Coordination Structure (coordination + structure)

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Chemistry100%

Selected Abstracts

The effect of the side chain length of Asp and Glu on coordination structure of Cu2+ in a de novo designed protein

BIOPOLYMERS, Issue 11 2009
Daigo Shiga
Abstract Metal ions in proteins are important not only for the formation of the proper structures but also for various biological activities. For biological functions such as hydrolysis and oxidation, metal ions often adopt unusual coordination structures. We constructed a stable scaffold for metal binding to create distorted metal coordination structures. A stable four stranded ,-helical coiled-coil structure was used as the scaffold, and the metal binding site was in the cavity created at the center of the structure. Two His residues and one Asp or Glu residue were used to coordinate the metal ions, AM2D and AM2E, respectively. Cu2+ bound to AM2D with an equatorial planar coordination structure with two His, one Asp, and H2O as detected by electron spin resonance and UV spectral analyzes. On the other hand, Cu2+ had a slightly distorted square planar structure when it bound two His and Glu in AM2E, due to the longer side-chain of the Glu residue as compared to the Asp residue. Computational analysis also supported the distorted coordination structure of Cu2+ in AM2E. This construct should be useful to create various coordinations of metal ions for catalytic functions. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 907,916, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]

Fourier transform infrared spectroscopic study on the binding of Mg2+ to a mutant Akazara scallop troponin C (E142Q)

BIOPOLYMERS, Issue 1-2 2004
Masayuki Nara
Abstract Troponin C (TnC) is the Ca2+ -binding regulatory protein of the troponin complex in muscle tissue. Vertebrate fast skeletal muscle TnCs bind four Ca2+, while Akazara scallop (Chlamys nipponensis akazara) striated adductor muscle TnC binds only one Ca2+ at site IV, because all the other EF-hand motifs are short of critical residues for the coordination of Ca2+. Fourier transform infrared (FTIR) spectroscopy was applied to study coordination structure of Mg2+ bound in a mutant Akazara scallop TnC (E142Q) in D2O solution. The result showed that the side-chain COO, groups of Asp 131 and Asp 133 in the Ca2+ -binding site of E142Q bind to Mg2+ in the pseudo-bridging mode. Mg2+ titration experiments for E142Q and the wild-type of Akazara scallop TnC were performed by monitoring the band at about 1600 cm,1, which is due to the pseudo-bridging Asp COO, groups. As a result, the binding constants of them for Mg2+ were the same value (about 6 mM). Therefore, it was concluded that the side-chain COO, group of Glu 142 of the wild type has no relation to the Mg2+ ligation. The effect of Mg2+ binding in E142Q was also investigated by CD and fluorescence spectroscopy. The on,off mechanism of the activation of Akazara scallop TnC is discussed on the basis of the coordination structures of Mg2+ as well as Ca2+. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source]

Synthesis, Crystal Structure of Cis -dioxo-catecholatotungsten(VI) Complex and Its NMR Studies on the Interaction with ATP

CHINESE JOURNAL OF CHEMISTRY, Issue 6 2003
Lu Xiao-Ming
Abstract Cis -dioxo-catecholatotungsten(VI) complex anion [W(VI)O2 -(OC6H2O)]2- was obtained with discrete protonated ethylene-diamine (NH2CH2CH2NH3)+ cations by the reaction of tetra-butyl ammonium decatungstate with catechol in the mixed solvent of CH3OH, CH3CN and ethylenediamine, and compared with its molybdenum analogue [Mo(v)O2(OC6H4O)2]3- by crystal structure, UV, EPR. The results of the UV and EPR spectra show that tungsten is less redox active than molybdenum since the molybdenum is reduced from Mo(VI) to Mo(V) but tungsten stays in the original highest oxidized state Mo (VI) when they are crystallized from the solution above. It is worthy to note that [W(VI)O2(OC6H4O2)]2- shows the same coordination structure as its molybdenum analogue in which the metal center exhibits distorted octahedral coordination geometry with two cis -dioxocatecholate ligands and might have the related coordination structure feature with the cofactor of flavoenzyme because [Mo(v)O2(OC6H4O)2]3- presented essentially the same EPR spectra as flavoenzyme. The NMR studies on the interaction of the title complex with ATP reveal that the reduction of W(VI) to W(V) occurs when the title complex is dissolved in D2O and the W (V) is oxidized again when ATP solution is mixed with original solution and the hydrolysis of the catechola-to ligand take places at mean time being monitored by 1H NMR and 13C NMR spectra. [source]

The effect of the side chain length of Asp and Glu on coordination structure of Cu2+ in a de novo designed protein

BIOPOLYMERS, Issue 11 2009
Daigo Shiga
Abstract Metal ions in proteins are important not only for the formation of the proper structures but also for various biological activities. For biological functions such as hydrolysis and oxidation, metal ions often adopt unusual coordination structures. We constructed a stable scaffold for metal binding to create distorted metal coordination structures. A stable four stranded ,-helical coiled-coil structure was used as the scaffold, and the metal binding site was in the cavity created at the center of the structure. Two His residues and one Asp or Glu residue were used to coordinate the metal ions, AM2D and AM2E, respectively. Cu2+ bound to AM2D with an equatorial planar coordination structure with two His, one Asp, and H2O as detected by electron spin resonance and UV spectral analyzes. On the other hand, Cu2+ had a slightly distorted square planar structure when it bound two His and Glu in AM2E, due to the longer side-chain of the Glu residue as compared to the Asp residue. Computational analysis also supported the distorted coordination structure of Cu2+ in AM2E. This construct should be useful to create various coordinations of metal ions for catalytic functions. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 907,916, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]

Fourier transform infrared spectroscopic study on the binding of Mg2+ to a mutant Akazara scallop troponin C (E142Q)

BIOPOLYMERS, Issue 1-2 2004
Masayuki Nara
Abstract Troponin C (TnC) is the Ca2+ -binding regulatory protein of the troponin complex in muscle tissue. Vertebrate fast skeletal muscle TnCs bind four Ca2+, while Akazara scallop (Chlamys nipponensis akazara) striated adductor muscle TnC binds only one Ca2+ at site IV, because all the other EF-hand motifs are short of critical residues for the coordination of Ca2+. Fourier transform infrared (FTIR) spectroscopy was applied to study coordination structure of Mg2+ bound in a mutant Akazara scallop TnC (E142Q) in D2O solution. The result showed that the side-chain COO, groups of Asp 131 and Asp 133 in the Ca2+ -binding site of E142Q bind to Mg2+ in the pseudo-bridging mode. Mg2+ titration experiments for E142Q and the wild-type of Akazara scallop TnC were performed by monitoring the band at about 1600 cm,1, which is due to the pseudo-bridging Asp COO, groups. As a result, the binding constants of them for Mg2+ were the same value (about 6 mM). Therefore, it was concluded that the side-chain COO, group of Glu 142 of the wild type has no relation to the Mg2+ ligation. The effect of Mg2+ binding in E142Q was also investigated by CD and fluorescence spectroscopy. The on,off mechanism of the activation of Akazara scallop TnC is discussed on the basis of the coordination structures of Mg2+ as well as Ca2+. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source]