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Tetrameric Structure (tetrameric + structure)

Distribution by Scientific Domains

Chemistry	83%

Selected Abstracts

Copper-Azide-Thioarylazoimidazoles , Structure, Spectra, Redox Properties, Magnetism and Theoretical Interpretation

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2010
Prasenjit Bhunia
Abstract Azido-copper(II) and -copper(I) complexes of 1-alkyl-2-[(o -thioalkyl)phenylazo]imidazole (SRaaiNR,) have been prepared and studied. Complex 2 [Cu(SRaaiNR,)(,1,1 -N3)(N3)]2 dimerises via end-to-end (,1,3)-N3 to form a tetrameric structure. Azido-copper(I) complexes of the ligands are obtained as MeOH-bridged dimers, [Cu(SRaaiNR,)(N3)(,-OHMe)]2 (3). The electronic spectra suggest that a small reorganisation energy (0.08 eV) is associated with the change in electronic configuration, structure and oxidation state from CuII to CuI. Redox interconversion, CuII , CuI, [Cu(SMeaaiNMe)(,-N3)(N3)]2 (2a) , [Cu(SMeaaiNMe)(N3)(,-OHCH3)]2 (3a), has been performed in one case. The tetranuclear complex shows ferromagnetic and antiferromagnetic interactions. The spectra, redox chemistry and magnetism are explained by DFT studies. [source]

Crystal structure of highly thermostable glycerol kinase from a hyperthermophilic archaeon in a dimeric form

FEBS JOURNAL, Issue 10 2008
Yuichi Koga
The crystal structure of glycerol kinase from the hyperthermophilic archaeon Thermococcus kodakaraensis (Tk-GK) in a dimeric form was determined at a resolution of 2.4 Å. This is the first crystal structure of a hyperthermophilic glycerol kinase. The overall structure of the Tk-GK dimer is very similar to that of the Escherichia coli glycerol kinase (Ec-GK) dimer. However, two dimers of Ec-GK can associate into a tetramer with a twofold axis, whereas those of Tk-GK cannot. This may be the reason why Tk-GK is not inhibited by fructose 1,6-bisphosphate, because the fructose 1,6-bisphosphate binding site is produced only when a tetrameric structure is formed. Differential scanning calorimetry analyses indicate that Tk-GK is a highly thermostable protein with a melting temperature (Tm) of 105.4 °C for the major transition. This value is higher than that of Ec-GK by 34.1 °C. Comparison of the crystal structures of Tk-GK and Ec-GK indicate that there is a marked difference in the number of ion pairs in the ,16 helix. Four ion pairs, termed IP1,IP4, are formed in this helix in the Tk-GK structure. To examine whether these ion pairs contribute to the stabilization of Tk-GK, four Tk-GK and four Ec-GK derivatives with reciprocal mutations at the IP1,IP4 sites were constructed. The determination of their stabilities indicates that the removal of each ion pair does not affect the stability of Tk-GK significantly, whereas the mutations designed to introduce one of these ion pairs stabilize or destabilize Ec-GK considerably. These results suggest that the ion pairs in the ,16 helix contribute to the stabilization of Tk-GK in a cooperative manner. [source]

Characterization of VR1 within the BMBF-Leitproject: ,Molecular Pain Research'

JOURNAL OF NEUROCHEMISTRY, Issue 2003
R. Jostock
The vanilloid receptor VR1 is a ligand, heat and proton gated ion channel, expressed predominantly by primary sensory neurons. We show the molecular characterization of VR1 and its involvement in nociceptive behavior. Biochemical analysis of VR1 showed glycosylation at N604 and the predicted tetrameric structure. Reduced pH potentiated the gating of the receptor by NADA and anandamide in recombinant VR1. Acidification could sensitize VR1 and lead to hyperalgesia. Therefore, the VR1 antagonist capsazepine was tested in several animal models. Capsazepine reduced formalin induced nocifensive behavior and CFA induced mechanical hyperalgesia, and was antiallodynic and antihyperalgesic in animal models of neuropathic pain. VR1 antisense oligonucleotides inhibited VR1 expression in vitro and reduced tactile allodynia in vivo. In conclusion, we could provide evidence for a role of VR1 in inflammatory and neuropathic pain pathways. [source]

Purification, crystallization and preliminary X-ray analysis of a water-soluble chlorophyll protein from Brassica oleracea L. var. acephala (kale)

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2003
Daisuke Horigome
A water-soluble chlorophyll protein (WSCP) with a chlorophyll a:b ratio of 6:1 from Brassica oleracea L. var. acephala (kale) was purified and crystallized by the hanging-drop vapour-diffusion method using PEG 8000 and zinc acetate as precipitants. The crystal belongs to the hexagonal space group P6422, with unit-cell parameters a = b = 162.2, c = 38.7,Å. A native data set was collected to 2.80,Å resolution at 293,K using Cu,K, radiation from a rotating-anode generator. Preliminary analysis via molecular replacement identified one kale WSCP monomer in the asymmetric unit. The crystal packing showed a tetrameric structure for kale WSCP, as suggested by previous biochemical studies of WSCPs from Brassicaceae plants. [source]

Probing the Subunit-Subunit Interaction of the Tetramer of E. coli KDO8P Synthase by Electrospray Ionization Mass Spectrometry,

CHINESE JOURNAL OF CHEMISTRY, Issue 1 2009
Zhili LI
Abstract Escherichia coli 3-Deoxy- D - manno- octulosonate 8-phosphate (KDO8P) synthase catalyzes the condensation reaction between D -arabinose 5-phosphate (A5P) and phosphoenolpyruvate (PEP) to form KDO8P and inorganic phosphate (Pi). This enzyme exists as a tetramer in solution, which is important for catalysis. Two different states of the enzyme were obtained: i) PEP-bound and ii) PEP-unbound. The effect of the substrates and products on the overall structure of KDO8P synthase in both PEP-bound and unbound states was examined using electrospray ionization mass spectrometry. The analysis of our data showed that the complexes of the PEP-unbound enzyme with PEP (or Pi) favored the formation of monomers, while the complexes with A5P (or KDO8P) mainly favored dimers. The PEP-bound enzyme was found to exist in the monomer and dimer with a small amount of the tetramer, whereas the PEP-unbound form primarily exists in the monomer and dimer, and no tetramer was observed, suggesting that the bound PEP have a role in stabilization of the tetrameric structure. Taken together, the results imply that the addition of the substrates or products to the unbound enzyme may alter the subunit-subunit interactions and/or conformational change of the protein at the active site, and this study also demonstrates that the electrospray ionization mass spectrometric method may be a powerful tool in probing the subunit-subunit interactions and/or conformational change of multi-subunit protein upon binding to ligand. [source]

NMR spectroscopy of organolithium compounds.

MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2004
LiI in diethyl ether, The aggregation behaviour of methyllithium in the presence of LiBr, tetrahydrofuran
Abstract 1H, 6Li and 13C NMR spectroscopy were used to determine the structure of aggregates formed in mixtures of methyllithium, H3CLi, and lithium bromide and iodide in diethyl ether and tetrahydrofuran. From the chemical shifts, the signal intensity distribution and the isotope shifts observed for partially deuterated systems, it was shown that generally tetrameric structures with different halogen contents dominate. For methyllithium,lithium bromide (1:1) in THF a considerable concentration of an H3CLiLiBr dimer was found. For the first time, deuterium-induced 6Li isotope shifts over four bonds were observed. Copyright © 2004 John Wiley & Sons, Ltd. [source]