Aggregation of Dipalmitoylphosphatidylcholine Vesicles Induced by Some Metal Ions with High Activity for Hydrolysis

Langmuir ◽  
1999 ◽  
Vol 15 (20) ◽  
pp. 6643-6651 ◽  
Author(s):  
Hideyuki Minami ◽  
Tohru Inoue
Keyword(s):  
Metal Ions ◽  
High Activity

Effects of Metal Cation on Disposal of CCl4 into Diphenyl Carbonate at Low Temperature

2011 ◽  
Vol 233-235 ◽  
pp. 1423-1426
Author(s):  
Kun Mei Su ◽  
Zhen Huan Li ◽  
Min Ding ◽  
Xiao Long He
Keyword(s):  
Low Temperature ◽  
Metal Ions ◽  
High Activity ◽  
Lewis Acid ◽  
Metal Cation ◽  
Diphenyl Carbonate ◽  
Cation Leaching ◽  
Strong Lewis Acid ◽  
Mcm 41

Zn (II)/SiMCM-41 and Fe (III)/SiMCM-41 showed high activity in disposal of CCl4into diphenyl carbonate (DPC) in presence of CO2at low temperature, due to Zn (II) and Fe (III) have zero Ligands Field Stabblized Energy (LFSE) and strong Lewis acid. Metal ions were immobilized onto the wall of Si-MCM-41, which keep metal cation leaching from catalyst during reaction

SWASV performance toward heavy metal ions based on a high-activity and simple magnetic chitosan sensing nanomaterials

2016 ◽  
Vol 684 ◽  
pp. 1-7 ◽  
Author(s):  
Shao-Feng Zhou ◽  
Xiao-Juan Han ◽  
Ya-Qing Liu
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
High Activity ◽  
Heavy Metal Ions ◽  
Magnetic Chitosan

scholarly journals TM0416, a Hyperthermophilic Promiscuous Nonphosphorylated Sugar Isomerase, Catalyzes Various C5 and C6 Epimerization Reactions

2017 ◽  
Vol 83 (10) ◽  
Author(s):  
Sun-Mi Shin ◽  
Thinh-Phat Cao ◽  
Jin Myung Choi ◽  
Seong-Bo Kim ◽  
Sang-Jae Lee ◽  
...  
Keyword(s):  
Metal Ions ◽  
Binding Site ◽  
High Activity ◽  
Structural Features ◽  
Divalent Metal ◽  
Divalent Metal Ions ◽  
Content Type ◽  
Isomerase Activity ◽  
Hyperthermophilic Bacterium ◽  
Rare Sugars

ABSTRACT There is currently little information on nonphosphorylated sugar epimerases, which are of potential interest for producing rare sugars. We found a gene (the TM0416 gene) encoding a putative d-tagatose-3-epimerase-related protein from the hyperthermophilic bacterium Thermotoga maritima. We overexpressed the TM0416 gene in Escherichia coli and purified the resulting recombinant protein for detailed characterization. Amino acid sequence alignment and a structural similarity search revealed that TM0416 is a putative nonphosphorylated sugar epimerase. The recombinant enzyme exhibited maximal C-3 epimerization of l-ribulose to l-xylulose at ∼80°C and pH 7 in the presence of 1 mM Mn2+. In addition, this enzyme showed unusually high activity for the epimerization of d-tagatose to d-sorbose, with a conversion yield of 20% after 6 h at 80°C. Remarkably, the enzyme catalyzed the isomerization of d-erythrose or d-threose to d-erythrulose significantly, with conversion yields of 71% and 54.5%, respectively, after 6 h at 80°C at pH 7. To further investigate the substrate specificity of TM0416, we determined its crystal structures in complex with divalent metal ions and l-erythrulose at resolutions of 1.5 and 1.6 Å. Detailed inspection of the structural features and biochemical data clearly demonstrated that this metalloenzyme, with a freely accessible substrate-binding site and neighboring hydrophobic residues, exhibits different and promiscuous substrate preferences, compared with its mesophilic counterparts. Therefore, this study suggests that TM0416 can be functionally classified as a novel type of l-ribulose 3-epimerase (R3E) with d-erythrose isomerase activity. IMPORTANCE Rare sugars, which occur naturally in small amounts, have attracted considerable attention in the food and drug industries. However, there is little information on nonphosphorylated sugar epimerases, which might potentially be applied for the production of rare sugars. This study describes the characterization and functional annotation of a putative nonphosphorylated sugar 3-epimerase from a hyperthermophilic bacterium. Furthermore, we determined its crystal structures in complex with divalent metal ions and l-erythrulose, highlighting its metal-dependent, bifunctional, sugar-isomerizing activity. This hyperthermophilic R3E exhibited d-erythrose/d-threose isomerase activity, with structural features near the substrate-binding site distinct from those of its mesophilic counterparts. Moreover, this metalloenzyme showed unusually high activity for the epimerization of d-tagatose to d-sorbose at 70°C. Therefore, TM0416 can be functionally classified as a novel type of promiscuous R3E with a potential for the production of rare sugars for the food and pharmaceutical industries.

HREM Study of electron-induced surface radiation damage in ReO3

1991 ◽  
Vol 49 ◽  
pp. 636-637
Author(s):  
R. Ai ◽  
H.-J. Fan ◽  
L. D. Marks
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Metal Oxides ◽  
Electron Irradiation ◽  
Transition Metal Oxides ◽  
Carbon Film ◽  
Transition Metal Ions ◽  
Surface Radiation ◽  
Valence Transition ◽  
Electron Microscopes

It has been known for a long time that electron irradiation induces damage in maximal valence transition metal oxides such as TiO2, V2O5, and WO3, of which transition metal ions have an empty d-shell. This type of damage is excited by electronic transition and can be explained by the Knoteck-Feibelman mechanism (K-F mechanism). Although the K-F mechanism predicts that no damage should occur in transition metal oxides of which the transition metal ions have a partially filled d-shell, namely submaximal valence transition metal oxides, our recent study on ReO3 shows that submaximal valence transition metal oxides undergo damage during electron irradiation.ReO3 has a nearly cubic structure and contains a single unit in its cell: a = 3.73 Å, and α = 89°34'. TEM specimens were prepared by depositing dry powders onto a holey carbon film supported on a copper grid. Specimens were examined in Hitachi H-9000 and UHV H-9000 electron microscopes both operated at 300 keV accelerating voltage. The electron beam flux was maintained at about 10 A/cm2 during the observation.

ELNES of Iron Compounds

1990 ◽  
Vol 48 (2) ◽  
pp. 28-29
Author(s):  
Hiroki Kurata ◽  
Kazuhiro Nagai ◽  
Seiji Isoda ◽  
Takashi Kobayashi
Keyword(s):  
Energy Loss ◽  
Metal Ions ◽  
Energy Resolution ◽  
Transition Metal Oxides ◽  
Local Symmetry ◽  
Iron Compounds ◽  
Fine Structures ◽  
Electron Energy Loss ◽  
Fe Ions ◽  
Electron Energy Loss Spectra

Electron energy loss spectra of transition metal oxides, which show various fine structures in inner shell edges, have been extensively studied. These structures and their positions are related to the oxidation state of metal ions. In this sence an influence of anions coordinated with the metal ions is very interesting. In the present work, we have investigated the energy loss near-edge structures (ELNES) of some iron compounds, i.e. oxides, chlorides, fluorides and potassium cyanides. In these compounds, Fe ions (Fe2+ or Fe3+) are octahedrally surrounded by six ligand anions and this means that the local symmetry around each iron is almost isotropic.EELS spectra were obtained using a JEM-2000FX with a Gatan Model-666 PEELS. The energy resolution was about leV which was mainly due to the energy spread of LaB6 -filament. The threshole energies of each edges were measured using a voltage scan module which was calibrated by setting the Ni L3 peak in NiO to an energy value of 853 eV.

Metal Ions in Life Sciences

2011 ◽  
Keyword(s):  
Metal Ions ◽  
Life Sciences

Solvent Exchange on Metal Ions

2003 ◽  
Keyword(s):  
Metal Ions ◽  
Solvent Exchange
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