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See detailKinetics and energetics of ligand binding determined by microcalorimetry: Insights into active site mobility in a psychrophilic alpha-amylase
D'Amico, Salvino ULg; Sohier, Jean ULg; Feller, Georges ULg

in Journal of Molecular Biology (2006), 358(5), 1296-1304

A new microcalorimetric method for recording the kinetic parameters k(cat)/K-m and K-i of alpha-amylases using polysaccharides and oligosaccharides as substrates is described. This method is based on the ... [more ▼]

A new microcalorimetric method for recording the kinetic parameters k(cat)/K-m and K-i of alpha-amylases using polysaccharides and oligosaccharides as substrates is described. This method is based on the heat released by glycosidic bond hydrolysis. The method has been developed to study the active site properties of the cold-active alpha-amylase produced by an Antarctic psychrophilic bacterium in comparison with its closest structural homolog from pig pancreas. It is shown that the psychrophilic a-amylase is more active on large macromolecular substrates and that the higher rate constants k(cat) are gained at the expense of a lower affinity for the substrate. The active site is able to accommodate larger inhibitory complexes, resulting in a mixed-type inhibition of starch hydrolysis by maltose. A method for recording the binding enthalpies by isothermal titration calorimetry in a low-affinity system has been developed, allowing analysis of the energetics of weak ligand binding using the allosteric activator chloride. It is shown that the low affinity of the psychrophilic a-amylase for chloride is entropically driven. The high enthalpic and entropic contributions of activator binding suggest large structural fluctuations between the free and the bound states of the cold-active enzyme. The kinetic and thermodynamic data for the psychrophilic a-amylase indicate that the strictly conserved side-chains involved in substrate binding and catalysis possess an improved mobility, responsible for activity in the cold, and resulting from the disappearance of stabilizing interactions far from the active site. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailKinetics and mechanism of the exchange reactions catalysed by the oxoglutarate translocator of rat-heart mitochondria.
Sluse, Francis ULg; Goffard, George; lièbecq, Claude

in European Journal of Biochemistry (1973), 32

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See detailKinetics and mechanism of the exchange reactions catalysed by the oxoglutarate translocator of rat-heart mitochondria.
Sluse, Francis ULg; Lièbecq, Claude

in Biochimie (1973), 55(6), 747-754

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See detailKinetics and Thermodynamics of Glucose Isomerase Crystallization
Sleutel, Mike; Willaert, Ronnie; Gillespie, Christopher et al

in Crystal Growth & Design (2009), 9

A quantitative study using laser confocal microscopy combined with differential interference microscopy on the kinetics and thermodynamics of the crystallization of glucose isomerase is presented ... [more ▼]

A quantitative study using laser confocal microscopy combined with differential interference microscopy on the kinetics and thermodynamics of the crystallization of glucose isomerase is presented. Fundamental crystallization parameters are determined from the kinetics of step advancement and rates of two-dimensional (2D) nucleation. The ruling mass transfer pathway and accompanying activation barriers are discussed. In brief, the solubility exhibits normal temperature dependence and the crystallization enthalpy is the thermodynamic driving force. The diminishing entropic cost for higher PEG concentrations is attributed to water structuring and a decrease in water activity. The prominent step generation mechanism is homogeneous 2D nucleation for high supersaturations. At low driving forces 2D nucleation occurs on anomalously hyperactive sites and the step edge free energies for homogeneous and heterogeneous nucleation are determined. The number of nucleation centers for both mechanisms are estimated and from the density of nucleation centers we obtain for the activation barrier of adsorption ∼3.8 kJ mol-1. No step-step interaction is observed for interstep distances >70 nm. Theoretical fits of step velocity data suggest surface diffusion makes a non-negligible contribution to surface kinetics. From the temperature dependence of the step kinetic coefficient the activation barrier for crystallization was determined to be <22.4 kJ mol-1. [less ▲]

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See detailKinetics modelling of convective heat drying of wastewater treatment sludge
Léonard, Angélique ULg; Salmon, Thierry ULg; Janssens et al

in Flamand, G. (Ed.) Récents progrés en génie des procédés vol.13 n.68 : separations. ECCE 2 conference Montpellier 5/7.10.99 (1999, October)

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See detailKinetics of 2-oxoglutarate transport in heart mitochondria
Sluse, Francis ULg; Ranson, Monique; Lièbecq, C.

in Journal de Physiologie (1971), 63

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See detailThe kinetics of a microbial population
Gillet, Marie-Claire ULg; Remacle, Jean

in Loutit, M. W.; Miles, J. A. R. (Eds.) Microbila Ecology (1978)

The study is an attempt to show the relationship between environmental variables such as pH and temperature and the control of some microbial growth characteristics. Two models were used in order to ... [more ▼]

The study is an attempt to show the relationship between environmental variables such as pH and temperature and the control of some microbial growth characteristics. Two models were used in order to calculate the death rate in continuous cultures. [less ▲]

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See detailKinetics of a specific antibody response after successful treatment in naturally Psoroptes ovis infested cattle
Lonneux, J. F.; Bossaert, K.; Leclipteux, T. et al

Conference (1995)

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See detailKinetics of C-Reactive Protein (CRP) following maintenance infliximab treatment in Crohn's disease identifies profiles of patients with better outcome
Jürgens, M.; Mahachie John, Jestinah ULg; Cleynen, I. et al

in Gastroenterology (2010), 138(5 (Suppl I)), -686

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See detailKinetics of circulating antigens in pigs experimentally infected with Taenia solium eggs
Nguekam, A.; Zoli, A. P.; Vondou, L. et al

in Veterinary Parasitology (2003), 111(4), 323-332

Three groups of four piglets were experimentally infected with different doses (10(3), 10(4) and 10(5)) of Taenia solium eggs whereas a fourth group of two pigs received gravid proglottids. At autopsy 6 ... [more ▼]

Three groups of four piglets were experimentally infected with different doses (10(3), 10(4) and 10(5)) of Taenia solium eggs whereas a fourth group of two pigs received gravid proglottids. At autopsy 6 months post infection, the two latter pigs were heavily infected with more than 3000 living cysts per kg of muscle. Ten of the 12 other pigs harboured light infections, i.e. between 2 and 107 cysticerci, 42.4% of which were degenerated. The two remaining pigs had no detectable cysts at post mortem examination. Circulating antigens (CA) were detected in the sera of all pigs harbouring living cysticerci using a monoclonal antibody based ELISA. CA were first detected between 2 and 6 weeks post infection and remained present generally throughout the entire observation period even in pigs carrying only five to eight living cysts, although strong fluctuations of the level of CA were observed in some pigs. In animals without living cysts at post mortem CA were only detected for a short period and disappeared presumably when the cysticerci became degenerated. The minimum number of living cysts, which could be detected using this ELISA, was 1. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailKinetics of concomitant transfer and hydrolysis reactions catalysed by the exocellular DD-carboxypeptidase-transpeptidase of streptomyces R61
Frère, Jean-Marie ULg; Ghuysen, Jean-Marie ULg; Perkins, Harnold R. et al

in Biochemical Journal (1973), 135(3), 483-492

When Ac(2)-l-Lys-d-Ala-d-Ala and either meso-diaminopimelic acid or Gly-l-Ala are exposed to the exocellular dd-carboxypeptidase-transpeptidase of Streptomyces R61, transpeptidation reactions yielding Ac ... [more ▼]

When Ac(2)-l-Lys-d-Ala-d-Ala and either meso-diaminopimelic acid or Gly-l-Ala are exposed to the exocellular dd-carboxypeptidase-transpeptidase of Streptomyces R61, transpeptidation reactions yielding Ac(2)-l-Lys-d-Ala-(d)-meso- diaminopimelic acid and Ac(2)-l-Lys-d-Ala-Gly-l-Ala occur concomitantly with the hydrolysis of the tripeptide into Ac(2)-l-Lys-d-Ala. The proportion of the enzyme activity which can be channelled in the transpeptidation and the hydrolysis pathways depends upon the pH and the polarity of the environment. Transpeptidation is favoured both by increasing the pH and by decreasing the water content of the reaction mixtures. Kinetics suggest that the reactions proceed through an ordered mechanism in which the acceptor molecule (meso-diaminopimelic acid or Gly-l-Ala) binds first to the enzyme. Both acceptors behave as non-competitive inhibitors of the hydrolysis pathway. Transpeptidation is inhibited by high concentrations of Gly-l-Ala but not by high concentrations of meso-diaminopimelic acid. The occurrence on the enzyme of an additional inhibitory binding site for Gly-l-Ala is suggested. [less ▲]

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See detailKinetics of engraftment following allogeneic hematopoietic cell transplantation with reduced-intensity or nonmyeloablative conditioning.
Baron, Frédéric ULg; Little, Marie-Terese; Storb, Rainer

in Blood Reviews (2005), 19(3), 153-64

Nonmyeloablative or reduced-intensity conditioning regimens have been used to condition elderly or ill patients with hematological malignancies for allogeneic hematopoietic cell transplantation (HCT ... [more ▼]

Nonmyeloablative or reduced-intensity conditioning regimens have been used to condition elderly or ill patients with hematological malignancies for allogeneic hematopoietic cell transplantation (HCT). Initial mixed donor/host chimerism (i.e. the coexistence of hematopoietic cells of host and donor origin) has been observed in most patients after such transplants. Here, we describe both factors affecting engraftment kinetics in patients given a nonmyeloablative or a reduced-intensity conditioning, and associations between peripheral blood cell subset chimerism levels and HCT outcomes. [less ▲]

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See detailKinetics of engraftment in patients with hematologic malignancies given allogeneic hematopoietic cell transplantation after nonmyeloablative conditioning.
Baron, Frédéric ULg; Baker, Jennifer E.; Storb, Rainer et al

in Blood (2004), 104(8), 2254-62

We analyzed the kinetics of donor engraftment among various peripheral blood cell subpopulations and their relationship to outcomes among 120 patients with hematologic malignancies given hematopoietic ... [more ▼]

We analyzed the kinetics of donor engraftment among various peripheral blood cell subpopulations and their relationship to outcomes among 120 patients with hematologic malignancies given hematopoietic cell transplantation (HCT) after nonmyeloablative conditioning consisting of 2 Gy total body irradiation (TBI) with or without added fludarabine. While patients rapidly developed high degrees of donor engraftment, most remained mixed donor/host chimeras for up to 180 days after HCT. Patients given preceding chemotherapies and those given granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell (G-PBMC) grafts had the highest degrees of donor chimerism. Low donor T-cell (P = .003) and natural killer (NK) cell (P = .004) chimerism levels on day 14 were associated with increased probabilities of graft rejection. High T-cell chimerism on day 28 was associated with an increased probability of acute graft-versus-host disease (GVHD) (P = .02). Of 93 patients with measurable malignant disease at transplantation, 41 achieved complete remissions a median of 199 days after HCT; 19 of the 41 were mixed T-cell chimeras when complete remissions were achieved. Earlier establishment of donor NK-cell chimerism was associated with improved progression-free survival (P = .02). Measuring the levels of peripheral blood cell subset donor chimerisms provided useful information on HCT outcomes and might allow early therapeutic interventions to prevent graft rejection or disease progression. [less ▲]

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See detailKinetics of Exchange of Alkanethiol Monolayers Self-Assembled on Polycrystalline Gold
Baralia, Gabriel G.; Duwez, Anne-Sophie ULg; Nysten, Bernard et al

in Langmuir (2005), 21

We report on the exchange between a hydrophilic thiol (11-mercapto-1-undecanol) in a liquid or gas phase and a hydrophobic thiol (dodecanethiol) of similar length self-assembled on a polycrystalline gold ... [more ▼]

We report on the exchange between a hydrophilic thiol (11-mercapto-1-undecanol) in a liquid or gas phase and a hydrophobic thiol (dodecanethiol) of similar length self-assembled on a polycrystalline gold surface for a wide range of temperatures and times. The molecular composition of the mixed monolayers is determined by the static water contact angle and X-ray photoelectron spectroscopy measurements. Atomic force microscopy in lateral forcemodeis used to characterize the molecular domains at the nanometer level. The exchange first occurs rapidly at the gold grain boundaries, with an activation energy of about 66 ( 4 kJ/mol. Then, boundaries of ordered thiol domains are progressively replaced, and the exchange is slowed because only regions of increasing perfection are left untouched. Higher temperatures lead to faster kinetics of replacement and the removal of larger amounts of the original thiol. No significant difference could be detected between exchange occurring in an ethanol solution or in the gas phase, and the initial rate of exchange was found to be similar for the displacement of dodecanethiol by 11-mercapto- 1-undecanol molecules and for the converse displacement [less ▲]

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See detailKinetics of IL-7 and IL-15 Levels after Allogeneic Peripheral Blood Stem Cell Transplantation following Nonmyeloablative Conditioning
De Bock, Muriel; Fillet, Marianne ULg; Hannon, Muriel ULg et al

in PLoS ONE (2013), 8(2), 55876

Background: We analysed kinetics of IL-7 and IL-15 levels in 70 patients given peripheral blood stem cells after nonmyeloablative conditioning. Methods: EDTA-anticoagulated plasma and serum samples were ... [more ▼]

Background: We analysed kinetics of IL-7 and IL-15 levels in 70 patients given peripheral blood stem cells after nonmyeloablative conditioning. Methods: EDTA-anticoagulated plasma and serum samples were obtained before conditioning and about once per week after transplantation until day 100. Samples were aliquoted and stored at 280uC within 3 hours after collection until measurement of cytokines. IL-7 and IL-15 levels were measured by ELISAs. Results: Median IL-7 plasma levels remained below 6 pg/L throughout the first 100 days, although IL-7 plasma levels were significantly higher on days 7 (5.1 pg/mL, P = 0.002), 14 (5.2 pg/mL, P,0.001), and 28 (5.1 pg/mL, P = 0.03) (but not thereafter) than before transplantation (median value of 3.8 pg/mL). Median IL-15 serum levels were significantly higher on days 7 (12.5 pg/mL, P,0.001), 14 (10.5 pg/mL, P,0.001), and 28 (6.2 pg/mL, P,0.001) than before transplantation (median value of 2.4 pg/mL). Importantly, IL-7 and IL-15 levels on days 7 or 14 after transplantation did not predict grade II–IV acute GVHD. Conclusions: These data suggest that IL-7 and IL-15 levels remain relatively low after nonmyeloablative transplantation, and that IL-7 and IL-15 levels early after nonmyeloablative transplantation do not predict for acute GVHD. [less ▲]

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See detailKinetics of interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and beta-lactam antibiotics. A choice of models
Frère, Jean-Marie ULg; Ghuysen, Jean-Marie ULg; Iwatsubo, Motohiro

in European Journal of Biochemistry (1975), 57(2), 343-351

The simplest model for the interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and beta-lactam antibiotics involves the three following steps: (a) the formation of ... [more ▼]

The simplest model for the interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61 and beta-lactam antibiotics involves the three following steps: (a) the formation of a reversible equimolar enzyme - antibiotic complex; (b) the irreversible transformation of this complex into a modified enzyme - antibiotic complex; and (c) the breakdown of this latter complex and the concomitant release of a regenerated enzyme and a modified antibiotic molecule. The dissociation constant for step 1 and the rate constants for steps 2 and 3 were measured with various beta-lactam antibiotics. With antibiotic such as benzylpenicillin, which behaves as a good 'substrate', steps 1 and 2 occur at enzymic velocities, whereas step 3 occurs at a very low velocity and hence is responsible for the low efficiency of the overall process. [less ▲]

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See detailKinetics of light emission and oxygen consumption by bioluminescent bacteria.
Bourgeois, J. J.; Sluse, Francis ULg; Baguet, F. et al

in Journal of Bioenergetics & Biomembranes (2001), 33

Oxygen plays a key role in bacterial bioluminescence. The simultaneous and continuous kinetics of oxygen consumption and light emission during a complete exhaustion of the exogenous oxygen present in a ... [more ▼]

Oxygen plays a key role in bacterial bioluminescence. The simultaneous and continuous kinetics of oxygen consumption and light emission during a complete exhaustion of the exogenous oxygen present in a closed system has been investigated. The kinetics are performed with Vibrio fischeri, V. harveyi, and Photobacterium phosphoreum incubated on respiratory substrates chosen for their different reducing power. The general patterns of the luminescence time courses are different among species but not among substrates. During steady-state conditions, substrates, which are less reduced than glycerol, have, paradoxally, a better luminescence efficiency. Oxygen consumption by luciferase has been evaluated to be approximately 17% of the total respiration. Luciferase is a regulatory enzyme presenting a positive cooperative effect with oxygen and its affinity for this final electron acceptor is about 4-5 times higher than the one of cytochrome oxidase. The apparent Michaelis constant for luciferase has been evaluated to be in the range of 20 to 65 nM O2. When O2 concentrations are as low as 10 nM, luminescence can still be detected; this means that above this concentration, strict anaerobiosis does not exist. By n-butyl malonate titration, it was clearly shown that electrons enter the luciferase pathway only when the cytochrome pathway is saturated. It is suggested that, in bioluminescent bacteria, luciferase acts as a free-energy dissipating valve when anabolic processes (biomass production) are impaired. [less ▲]

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See detailKinetics of Microsporum canis adherence using an in vitro model of reconstituted feline epidermis
Baldo, Aline ULg; Tabart, J.; Vermout, S. et al

Conference (2006)

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See detailKinetics of moisturizing and firming effects of cosmetic formulations.
Xhauflaire, Emmanuelle ULg; Fontaine, K.; Pierard, Gérald ULg

in International Journal of Cosmetic Science (2008), 30(2), 131-8

The assessment of cosmetic efficacy is rarely performed in studies comparing different concentrations of active compounds. The aim of the present study was to determine the skin hydrating and the skin ... [more ▼]

The assessment of cosmetic efficacy is rarely performed in studies comparing different concentrations of active compounds. The aim of the present study was to determine the skin hydrating and the skin firming dose-response effects of cosmetic formulations enriched in compounds derived from algae and fish collagen. A series of factors were studied including the type of formulation (cream or serum), the concentration in active ingredients, the effect of repetitive applications, as well as any residual effect of the formulations after stopping their applications. The serum enriched in marine compounds showed a better moisturizing effect in short term. The cream appeared more active later, particularly following repeat applications. A sustained tensor (firming) effect was observed during treatment with both the lotion and the cream. However, no remnant firming effect was perceived after stopping treatment. [less ▲]

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