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See detailColard Mansion, passeur de textes
Adam, Renaud ULg

Conference (2013, October 14)

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See detailColchiques dans les prés
Angenot, Luc ULg; Lambert, Philippe

Article for general public (1990)

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See detailCold adaptation of a phosphoglycerate kinase affects the stability of only one domain
Zecchinon, Laurent; Bentahir, M.; Feller, Georges ULg et al

Poster (2000)

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See detailCold adaptation of a psychrophilic chitinase: a mutagenesis study
Mavromatis, K.; Feller, Georges ULg; Kokkinidis, M. et al

in Protein Engineering (2003), 16(7), 497-503

The gene encoding chitinase ArChiB from the Antarctic Arthrobacter sp. TAD20 has been expressed in Escherichia coli and the recombinant enzyme purified to homogeneity. In an effort to engineer cold ... [more ▼]

The gene encoding chitinase ArChiB from the Antarctic Arthrobacter sp. TAD20 has been expressed in Escherichia coli and the recombinant enzyme purified to homogeneity. In an effort to engineer cold-adapted biocatalysts through rational redesign to operate at elevated temperatures, we performed several mutations aiming to increase the rigidity of the molecular edifice of the selected psychrophilic chitinase. The mutations were designed on the basis of a homology-based three-dimensional model of the enzyme, and included an attempt to introduce a salt bridge (mutant N198K) and replacements of selected Gly residues by either Pro (mutants G93P, G254P) or Gln (G406Q). Mutant N198K resulted in a more stable protein (DeltaT(m)=0.6degreesC). Mutant G93P exhibited a DeltaT(m) of 1.2degreesC, while mutants G254P and G406Q exhibited decreased stability. We conclude that the effect of mutating Gly residues on enzyme stability is rather complex and can only be understood in the context of the structural environment. Kinetic and spectroscopic analysis of these enzyme variants revealed that the kinetic parameters k(cat) and K-m have been significantly modified. [less ▲]

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See detailCold adaptation of enzymes: structural, kinetic and microcalorimetric characterizations of an aminopeptidase from the Arctic psychrophile Colwellia psychrerythraea and of human leukotriene A(4) hydrolase
Huston, A. L.; Haeggstrom, J. Z.; Feller, Georges ULg

in Biochimica et Biophysica Acta (2008), 1784(11), 1865-72

The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a ... [more ▼]

The relationships between structure, activity, stability and flexibility of a cold-adapted aminopeptidase produced by a psychrophilic marine bacterium have been investigated in comparison with a mesophilic structural and functional human homolog. Differential scanning calorimetry, fluorescence monitoring of thermal- and guanidine hydrochloride-induced unfolding and fluorescence quenching were used to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a low structural stability versus thermal and chemical denaturants and a greater structural permeability to a quenching agent relative to the mesophilic homolog. These findings support the hypothesis that cold-adapted enzymes maintain their activity at low temperatures as a result of increased global or local structural flexibility, which results in low stability. Analysis of the thermodynamic parameters of irreversible thermal unfolding suggests that entropy-driven factors are responsible for the fast unfolding rate of the cold-adapted aminopeptidase. A reduced number of proline residues, a lower degree of hydrophobic residue burial and a decreased surface accessibility of charged residues may be responsible for this effect. On the other hand, the reduction in enthalpy-driven interactions is the primary determinant of the weak conformational stability. [less ▲]

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See detailCold Adaptation of Proteins. Purification, Characterization, and Sequence of the Heat-Labile Subtilisin from the Antarctic Psychrophile Bacillus Ta41
Davail, S.; Feller, Georges ULg; Narinx, E. et al

in Journal of Biological Chemistry (1994), 269(26), 17448-53

The gene of subtilisin S41, an alkaline protease secreted by the psychrophile Bacillus TA41, encodes for a preproenzyme of 419 amino acids residues. The nucleotide sequence and NH2- and COOH-terminal ... [more ▼]

The gene of subtilisin S41, an alkaline protease secreted by the psychrophile Bacillus TA41, encodes for a preproenzyme of 419 amino acids residues. The nucleotide sequence and NH2- and COOH-terminal amino acid sequencing of the purified enzyme indicate that the mature subtilisin S41 is composed of 309 residues with a predicted M(r) = 31,224. Subtilisin S41 shares most of its properties with mesophilic subtilisins (structure of the precursor, 52% amino acid sequence identity, alkaline pH optimum, broad specificity, Ca2+ binding) but is characterized by a higher specific activity on macromolecular substrate, by a shift of the optimum of activity toward low temperatures, and by a low thermal stability. The enzyme also differs by an acidic pI (5.3) and the presence of one disulfide bond. It is proposed that the psychrophilic enzyme possesses a more flexible molecular structure when compared to mesophilic and thermophilic subtilases in order to compensate for the reduction of reaction rates at low temperatures. The model of subtilisin S41 indeed reveals several features able to induce a more flexible, heat-labile conformation: the occurrence of four extended surface loops, a very hydrophilic surface through 11 extra Asp residues, and the lack of several salt bridges and aromatic-aromatic interactions. The low affinity of the Ca1 calcium binding site (Kd(app) = 10(-6) M), resulting possibly from one chelating side chain substitution and the stacking of Gly residues, also reflect a less compact conformation. The difference of free energy of stabilization between subtilisin S41 and a mesophilic subtilisin suggests that the balance of exo- and endothermically formed weak bonds is critical for the enzyme flexibility. [less ▲]

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See detailCold adaptation of proteins: a biophysical study of a psychrophilic alpha-amylase and its stabilized mutants
Cipolla, Alexandre ULg; D'Amico, Salvino ULg; Feller, Georges ULg

Poster (2010, September 28)

Habitats of permanently cold temperature, like polar regions for example, have been colonized by a great variety of psychrophilic organisms producing enzymes adapted to function efficiently in these cold ... [more ▼]

Habitats of permanently cold temperature, like polar regions for example, have been colonized by a great variety of psychrophilic organisms producing enzymes adapted to function efficiently in these cold environments. According to the hypothesis developed in our laboratory, the adaptation to cold temperature involves relationships between activity, flexibility and stability. Even if activity and stability are not physically linked in proteins 1, the consensus for the adaptive strategy is to take advantage of the lack of selective pressure for stable proteins to lose stability, therefore increasing the flexibility or mobility of the enzyme at low temperatures that restrict molecular motions. 2 Working on alpha-amylase, we have investigated the role of weak interactions in thermal adaptation of proteins by site-directed mutagenesis. We have built two multiple-mutants (Mut5 and Mut5CC) of the psychrophilc alpha-amylase (AHA) from the Antarctic bacterium, Pseudoalteromonas haloplanktis. The single mutations were selected by comparison of the presence of weak interactions in a mesophilic chloride-dependant homolog from pig pancreas, PPA. The study of selected single mutations prompt us to construct two multiple-mutants, Mut5 and Mut5CC, carrying 5 and 6 additional weak interactions found in PPA, that showed an increased stability and a lower activity at 25 °C.3 We have compared AHA, Mut5 and Mut5CC with additional methods like differential scanning calorimetry, thermal and chemical unfolding in order to determine the gain in stability. We also studied the flexibility or breathing of the enzymes by acrylamide-induced fluorescence quenching and we determined the optimum activity temperature for the three amylases. In order to investigate the kinetic origin of the gain in stability 4 for the two multiple-mutants, we studied in a first step the kinetic unfolding and refolding by GdmCl of the three amylases by manual methods following fluorescence signal at 15°C. The newly introduced weak interactions stabilized the proteins, protected them against heat and chemical unfolding and also induced an effective loss of flexibility. In addition, the two multiple-mutants exhibit a different optimum activity temperature than AHA. The first result in manual kinetic studies seems to show a similar refolding phase but a difference between the three amylases in the unfolding phase. This is in correlation with results of Dieter, P et al 4. These results and those of the previous work 3, unambiguously support the capital role of weak interactions in the balance between activity, flexibility and stability and provide a better knowledge of the adaptation of enzymes to cold temperatures. [less ▲]

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See detailCold Adaptations in Proteins from Psychrophiles
Feller, Georges ULg

Scientific conference (2013)

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See detailCold adapted endoglucanase from Antarctic bacteria
Sonan, Guillaume; Feller, Georges ULg; Gerday, Charles ULg

Poster (2002)

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See detailThe cold atom micromaser in a vertical configuration
Martin, John ULg; Bastin, Thierry ULg

Poster (2003)

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See detailThe cold atom micromaser in a vertical configuration
Martin, John ULg; Bastin, Thierry ULg

Poster (2003)

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See detailThe cold atom micromaser in a vertical configuration
Bastin, Thierry ULg; Martin, John ULg

Poster (2003)

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See detailCold DUst around NEarby Stars (DUNES). First results. A resolved exo-Kuiper belt around the solar-like star ζ2 Ret
Eiroa, C.; Fedele, D.; Maldonado, J. et al

in Astronomy and Astrophysics (2010), 518

We present the first far-IR observations of the solar-type stars δ Pav, HR 8501, 51 Peg and ζ2 Ret, taken within the context of the DUNES Herschel open time key programme (OTKP). This project uses the ... [more ▼]

We present the first far-IR observations of the solar-type stars δ Pav, HR 8501, 51 Peg and ζ2 Ret, taken within the context of the DUNES Herschel open time key programme (OTKP). This project uses the PACS and SPIRE instruments with the objective of studying infrared excesses due to exo-Kuiper belts around nearby solar-type stars. The observed 100 μm fluxes from δ Pav, HR 8501, and 51 Peg agree with the predicted photospheric fluxes, excluding debris disks brighter than Ldust/ ~ 5 × 10-7 (1σ level) around those stars. A flattened, disk-like structure with a semi-major axis of ~100 AU in size is detected around ζ2 Ret. The resolved structure suggests the presence of an eccentric dust ring, which we interpret as an exo-Kuiper belt with Ldust/ ≈ 10-5. [less ▲]

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See detailCold enzymes : a hot topic
Gerday, Charles ULg; Aittaleb, M.; Arpigny, J. L. et al

in Margesin, R.; Schinner, F. (Eds.) Cold-adapted Organisms : Ecology, Physiology, Enzymology and Molecular Biology (1999)

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See detailCold injuries.
PIERARD, Gérald ULg; QUATRESOOZ, Pascale ULg; FRANCHIMONT, Claudine ULg

in Goldsmith, L.; Gilchrest, B; Katz, S (Eds.) et al Fitzpatrick's Dermatology in General Medicine (2012)

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See detailA cold love story
Feller, Georges ULg

Conference (1997)

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See detailCold Roll Forming and Metal Cutting Simulation using a 3D Arbitrary Lagrangian Eulerian Formulation
Boman, Romain ULg; Papeleux, Luc ULg; Ponthot, Jean-Philippe ULg

in de Saxcé, Géry; Moës, Nicolas (Eds.) Modeling in Mechanical and Civil Engineering : Collection of Papers from Prof. Nguyen Dang Hung's former students (2006)

Detailed reference viewed: 48 (9 ULg)