Structural and ecofunctional biodiversity of the amphipod crustacean benthic taxocoenoses in the Southern Ocean

in Belgian Scientific Research Programme on the Antarctic-Phase 4. Vol 1. Marine Biota and Global Change (2003)

Structural and electrical properties of tellurovanadate glasses containing Li2O

Conference (2006)

Structural and electrochemical characterization of mesoporous thin films of Nb2xV2-2xO5 upon lithium intercalation

in Solid State Ionics (2009), 180(11-13), 848-852

Nb2xV2 - 2xO5 (0 <= x <= 1) powders were prepared by a synthetic route based on the inorganic polymerization of alkoxy-choride precursors and characterized by a combination of X-ray diffraction V-51 and ... [more ▼]

Nb2xV2 - 2xO5 (0 <= x <= 1) powders were prepared by a synthetic route based on the inorganic polymerization of alkoxy-choride precursors and characterized by a combination of X-ray diffraction V-51 and Nb-93 NMR and Raman spectroscopy. Amorphous mesoporous thin films of similar compositions were successfully prepared by a modified Evaporation Induced Self Assembly method using polystyrene-b-polyethyleneoxide diblock copolymer as structuring agent. The electrochemical properties of the mesoporous films upon lithium insertion-deinsertion are investigated by cyclic voltammetry. This study highlights the advantages of such nanoarchitecture in terms of increased capacity to insert lithium. (C) 2009 Elsevier B.V. All rights reserved. [less ▲]

Structural and electronic properties of high-temperature fluid selenium

in Computational Materials Science (2000), 17(2-4), 239-242242

A semi-empirical tight-binding energy model is developed for selenium. It includes s and p electrons as well as an empirical description of the dispersion forces. The band structure parameters are ... [more ▼]

A semi-empirical tight-binding energy model is developed for selenium. It includes s and p electrons as well as an empirical description of the dispersion forces. The band structure parameters are obtained by fitting ab initio calculations. The simulated liquid structures are in very good agreement with the most recent X-ray scattering and EXAFS measurements. The Monte Carlo simulations performed show that the complex liquid structures observed result from the breaking and branching of the selenium chains. The total coordination number is shown to result from the balance between one-, two- and three-fold coordinated atoms. The role of these defects is discussed in relationship with the electrical conductivity of the liquid, i.e. the semiconductor-metal and metal-non-metal transitions observed at high pressure and temperature [less ▲]

Structural and functional adaptations to extreme temperatures in psychrophilic, mesophilic, and thermophilic DNA ligases

in Journal of Biological Chemistry (2003), 278(39), 37015-37023

Psychrophiles, host of permanently cold habitats, display metabolic fluxes comparable to those exhibited by mesophilic organisms at moderate temperatures. These organisms have evolved by producing, among ... [more ▼]

Psychrophiles, host of permanently cold habitats, display metabolic fluxes comparable to those exhibited by mesophilic organisms at moderate temperatures. These organisms have evolved by producing, among other peculiarities, cold-active enzymes that have the properties to cope with the reduction of chemical reaction rates induced by low temperatures. The emerging picture suggests that these enzymes display a high catalytic efficiency at low temperatures through an improved flexibility of the structural components involved in the catalytic cycle, whereas other protein regions, if not implicated in catalysis, may be even more rigid than their mesophilic counterparts. In return, the increased flexibility leads to a decreased stability of psychrophilic enzymes. In order to gain further advances in the analysis of the activity/flexibility/stability concept, psychrophilic, mesophilic, and thermophilic DNA ligases have been compared by three-dimensional-modeling studies, as well as regards their activity, surface hydrophobicity, structural permeability, conformational stabilities, and irreversible thermal unfolding. These data show that the cold-adapted DNA ligase is characterized by an increased activity at low and moderate temperatures, an overall destabilization of the molecular edifice, especially at the active site, and a high conformational flexibility. The opposite trend is observed in the mesophilic and thermophilic counterparts, the latter being characterized by a reduced low temperature activity, high stability and reduced flexibility. These results strongly suggest a complex relationship between activity, flexibility and stability. In addition, they also indicate that in cold-adapted enzymes, the driving force for denaturation is a large entropy change. [less ▲]

Structural and Functional Aspects of Chloride Binding to Alteromonas Haloplanctis Alpha-Amylase

in Journal of Biological Chemistry (1996), 271(39), 23836-41

Chloride is the allosteric effector of vertebrate pancreatic and salivary alpha-amylases and of the bacterial alpha-amylase from Alteromonas haloplanctis. Activation experiments of A. haloplanctis alpha ... [more ▼]

Chloride is the allosteric effector of vertebrate pancreatic and salivary alpha-amylases and of the bacterial alpha-amylase from Alteromonas haloplanctis. Activation experiments of A. haloplanctis alpha-amylase by several monovalent anions show that a negative charge, not restricted to that of Cl-, is essential for the amylolytic reaction. Engineering of the chloride binding site reveals that a basic residue is an essential component of the site. The mutation K337R alters the Cl--binding properties, whereas the mutation K337Q produces an active, chloride-independent enzyme. Comparison of the Kd values for Cl- in three homologous alpha-amylases also indicates that the binding affinity is dependent on the chloride coordination mode by this basic residue. Analysis of substrate and chloride binding according to the allosteric kinetic model shows that the chloride effector is not involved in substrate binding. By contrast, the pH dependence of activity and experiments of chemical modifications and Ca2+ inhibition show that the chloride ion is responsible for the pKa shift of catalytic groups and interacts with active site carboxyl groups. [less ▲]

Structural and functional characterization of the Arabidopsis halleri HMA4 N-terminal domain

Poster (2013, February 26)

The Structural And Functional Organization Of H-Ns-Like Proteins Is Evolutionarily Conserved In Gram-Negative Bacteria

in Molecular Microbiology (1999), 31(1), 319-29

The structural gene of the H-NS protein, a global regulator of bacterial metabolism, has been identified in the group of enterobacteria as well as in closely related bacteria, such as Erwinia chrysanthemi ... [more ▼]

The structural gene of the H-NS protein, a global regulator of bacterial metabolism, has been identified in the group of enterobacteria as well as in closely related bacteria, such as Erwinia chrysanthemi and Haemophilus influenzae. Isolated outside these groups, the BpH3 protein of Bordetella pertussis exhibits a low amino acid conservation with H-NS, particularly in the N-terminal domain. To obtain information on the structure, function and/or evolution of H-NS, we searched for other H-NS-related proteins in the latest databases. We found that HvrA, a trans-activator protein in Rhodobacter capsulatus, has a low but significant similarity with H-NS and H-NS-like proteins. This Gram-negative bacterium is phylogenetically distant from Escherichia coli. Using theoretical analysis (e.g. secondary structure prediction and DNA binding domain modelling) of the amino acid sequence of H-NS, StpA (an H-NS-like protein in E. coli), BpH3 and HvrA and by in vivo and in vitro experiments (e.g. complementation of various H-NS-related phenotypes and competitive gel shift assay), we present evidence that these proteins belong to the same class of DNA binding proteins. In silico analysis suggests that this family also includes SPB in R. sphaeroides, XrvA in Xanthomonas oryzae and VicH in Vibrio cholerae. These results demonstrate that proteins structurally and functionally related to H-NS are widespread in Gram-negative bacteria. [less ▲]

Structural and functional organization of the fengycin synthetase multienzyme system from Bacillus subtilis b213 and A1/3

in Chemistry & Biology (1999), 6(31-41),

Structural and functional properties of apolipoprotein B in chemically modified low density lipoproteins.

in Atherosclerosis (1992), 97(2-3), 187-99

The structural and compositional changes occurring during in vitro chemical modification of apolipoprotein B-100 (apo B), the apolipoprotein component of low density lipoproteins (LDL), were investigated ... [more ▼]

The structural and compositional changes occurring during in vitro chemical modification of apolipoprotein B-100 (apo B), the apolipoprotein component of low density lipoproteins (LDL), were investigated in this study. The functional properties of chemically modified apo B and especially its potential to induce accumulation of cholesterol esters in macrophages were related to the structural changes of apo B. Acetylation, maleylation or malondialdehyde conjugation did not significantly affect the lipid composition of LDL. However, the unsaturated cholesteryl esters content, especially that of cholesteryl arachidonate was significantly decreased through Cu-oxidation. The number of reactive lysine residues in apo B was decreased by Cu-catalyzed LDL oxidation, acetylation, maleylation and by malondialdehyde conjugation. The number of free cysteines decreased from six in native apo B-100 to three in Cu-oxidized LDL. The tryptophan fluorescence intensity decreased most in malondialdehyde-conjugated LDL and in Cu-oxidized LDL, compared with acetylated and maleylated LDL. The secondary structure of native and chemically modified LDL was measured by attenuated total reflection infrared spectroscopy and by circular dichroism. No significant changes were observed in the secondary structure of any of the modified LDL. These data suggest that neither acetylation, malondialdehyde treatment or even Cu-oxidation substantially altered the secondary structure of apo B, in spite of significant modifications in the primary structure. Incubation of chemically modified LDL with J774 macrophages induced an accumulation of cellular cholesteryl esters and foam cell formation. The highest cholesterol accumulation was induced after malondialdehyde treatment of LDL. These data suggest that the cellular uptake and accumulation of modified LDL is not modulated by changes in the apo B structure. Rather it seems dependent upon the net charge of the apo B protein and probably involves the modification of critical lysine residues. [less ▲]