Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Peer Reviewed
See detailMechanism of action of β-lactamases and DD-peptidases
Frère, Jean-Marie ULg; Joris, Bernard ULg; Jacob, Françoise et al

in Pandit, U.K.; Alderweireldt, F.C. (Eds.) Bioorganic Chemistry in Healthcare and Technology (1991)

Detailed reference viewed: 22 (7 ULg)
Full Text
Peer Reviewed
See detailMechanism of acyl transfer by the class A serine β-lactamase of Streptomyces albus G
Lamotte-Brasseur, Josette; Dive, Georges ULg; Dideberg, Otto et al

in Biochemical Journal (1991), 279(Pt 1), 213-221

Optimization by energy minimization of stable complexes occurring along the pathway of hydrolysis of benzylpenicillin and cephalosporin C by the Streptomyces albus G beta-lactamase has highlighted a ... [more ▼]

Optimization by energy minimization of stable complexes occurring along the pathway of hydrolysis of benzylpenicillin and cephalosporin C by the Streptomyces albus G beta-lactamase has highlighted a proton shuttle that may explain the catalytic mechanism of the beta-lactamases of class A. Five residues, S70, S130, N132, T235 and A237, are involved in ligand binding. The gamma-OH group of T235 and, in the case of benzylpenicillin, the gamma-OH group of S130 interact with the carboxylate group, on one side of the ligand molecule. The side-chain NH2 group of N132 and the carbonyl backbone of A237 interact with the exocyclic CONH amide bond, on the other side of the ligand. The backbone NH groups of S70 and A237 polarize the carbonyl group of the scissile beta-lactam amide bond. Four residues, S70, K73, S130 and E166, and two water molecules, W1 and W2, perform hydrolysis of the bound beta-lactam compound. E166, via W1, abstracts the proton from the gamma-OH group of S70. While losing its proton, the O-gamma atom of S70 attacks the carbonyl carbon atom of the beta-lactam ring and, concomitantly, the proton is delivered back to the adjacent nitrogen atom via W2, K73 and S130, thus achieving formation of the acyl-enzyme. Subsequently, E166 abstracts a proton from W1. While losing its proton, W1 attacks the carbonyl carbon atom of the S70 ester-linked acyl-enzyme and, concomitantly, re-entry of a water molecule W'1 replacing W1 allows E166 to deliver the proton back to the same carbonyl carbon atom, thus achieving hydrolysis of the beta-lactam compound and enzyme recovery. The model well explains the differences found in the kcat. values for hydrolysis of benzylpenicillin and cephalosporin C by the Streptomyces albus G beta-lactamase. It also explains the effects caused by site-directed mutagenesis of the Bacillus cereus beta-lactamase I [Gibson, Christensen [less ▲]

Detailed reference viewed: 19 (2 ULg)
See detailMechanism of amyloid fibril formation by human lysozyme and VHHs
Dumoulin, Mireille ULg; Chavignon, Chloé ULg

Conference (2011, January)

Detailed reference viewed: 19 (9 ULg)
Full Text
Peer Reviewed
See detailMechanism of Collisional Heating in Electrospray Mass Spectrometry: Ion Trajectory Calculations
Hoxha, Antuan; Collette, Caroline ULg; De Pauw, Edwin ULg et al

in Journal of Physical Chemistry A (2001), 105

To simulate the multicollisional heating process taking place in the intermediate pressure region of an electrospray source, ion trajectory calculations have been preformed by introducing in the SIMION ... [more ▼]

To simulate the multicollisional heating process taking place in the intermediate pressure region of an electrospray source, ion trajectory calculations have been preformed by introducing in the SIMION program a subroutine for handling the collision dynamics. The simulated internal energy distributions are compared with already available experimental distributions obtained by the "survival ion yield" method. [less ▲]

Detailed reference viewed: 38 (4 ULg)
Peer Reviewed
See detailMechanism of Colon Cancer Cell Apoptosis Mediated by Pyropheophorbide-a Methylester Photosensitization
Matroule, Jean-Yves; Carthy, Chris M; Granville, David J et al

in Oncogene (2001), 20

Pyropheophorbide-a methylester (PPME) is a second generation of photosensitizers used in photodynamic therapy (PDT). We demonstrated that PPME photosensitization triggered apoptosis of colon cancer cells ... [more ▼]

Pyropheophorbide-a methylester (PPME) is a second generation of photosensitizers used in photodynamic therapy (PDT). We demonstrated that PPME photosensitization triggered apoptosis of colon cancer cells as measured by using several classical parameters such as DNA laddering, PARP cleavage, caspase activation and mitochondrial release of cytochrome c. Preincubation of cells with N-acetyl cysteine (NAC) or pyrolidine dithiocarbamate (PDTC) protected against apoptosis mediated by PPME photosensitization showing that reactive oxygen species (ROS) are involved as second messengers. On the other hand, photosensitization carried out in the presence of deuterium oxide (D2O) which enhances singlet oxygen (1O2) lifetime only increases necrosis without affecting apoptosis. Since PPME was localized in the endoplasmic reticulum (ER)/Golgi system and lysosomes, other messengers than ROS were tested such as calcium, Bid, Bap31, phosphorylated Bcl-2 and caspase-12 but none was clearly identified as being involved in triggering cytochrome c release from mitochondria. On the other hand, we demonstrated that the transduction pathways leading to NF-kappaB activation and apoptosis were clearly independent although NF-kappaB was shown to counteract apoptosis mediated by PPME photosensitization. [less ▲]

Detailed reference viewed: 13 (0 ULg)
Full Text
Peer Reviewed
See detailMechanism of improvement in mitral regurgitation after cardiac resynchronization therapy.
Ypenburg, Claudia; Lancellotti, Patrizio ULg; Tops, Laurens F et al

in European Heart Journal (2008), 29(6), 757-65

AIMS: The aim of the current study was to evaluate the relationship between the presence of left ventricular (LV) dyssynchrony at baseline and acute vs. late improvement in mitral regurgitation (MR) after ... [more ▼]

AIMS: The aim of the current study was to evaluate the relationship between the presence of left ventricular (LV) dyssynchrony at baseline and acute vs. late improvement in mitral regurgitation (MR) after cardiac resynchronization therapy (CRT). METHODS AND RESULTS: Sixty eight patients consecutive (LV ejection fraction 23 +/- 8%) with at least moderate MR (>or=grade 2+) were included. Echocardiography was performed at baseline, 1 day after CRT initiation and at 6 months follow-up. Speckle tracking radial strain was used to assess LV dyssynchrony at baseline. The majority of patients improved in MR after CRT, with 43% improving immediately after CRT, and 20% improving late (after 6 months) after CRT. Early and late responders had similar extent of LV dyssynchrony (209 +/- 115 ms vs. 190 +/- 118 ms, P = NS); however, the site of latest activation in early responders was mostly inferior or posterior (adjacent to the posterior papillary muscle), whereas the lateral wall was the latest activated segment in late responders. CONCLUSION: Current data suggest that the presence of baseline LV dyssynchrony is related to improvement in MR after CRT. LV dyssynchrony involving the posterior papillary muscle may lead to an immediate reduction in MR, whereas LV dyssynchrony in the lateral wall resulted in late response to CRT. [less ▲]

Detailed reference viewed: 21 (2 ULg)
Full Text
Peer Reviewed
See detailMechanism of Nicotinic acid-induced Flushing
Hanson, Julien ULg

Conference (2011, June 10)

Detailed reference viewed: 18 (0 ULg)
Full Text
See detailThe mechanism of polymer drag reduction
Terrapon, Vincent ULg

Scientific conference (2004, February)

Detailed reference viewed: 7 (1 ULg)
Full Text
Peer Reviewed
See detailMechanism of reoxygenation after antiangiogenic therapy using SU5416 and its importance for guiding combined antitumor therapy
ANSIAUX, Réginald; BAUDELET, Christine; JORDAN, Bénédicte et al

in Cancer Research (2006), 66(19), 9698704

Emerging preclinical studies support the concept of a transient "normalization" of tumor vasculature during the early stage of antiangiogenic treatment, with possible beneficial effects on associated ... [more ▼]

Emerging preclinical studies support the concept of a transient "normalization" of tumor vasculature during the early stage of antiangiogenic treatment, with possible beneficial effects on associated radiotherapy or chemotherapy. One key issue in this area of research is to determine whether this feature is common to all antiangiogenic drugs and whether the phenomenon occurs in all types of tumors. In the present study, we characterized the evolution of the tumor oxygenation (in transplantable liver tumor and FSAII tumor models) after administration of SU5416, an antagonist of the vascular endothelial growth factor receptor. SU5416 induced an early increase in tumor oxygenation [measured by electronic paramagnetic resonance (EPR)], which did not correlate with remodeling of the tumor vasculature (assessed by CD31 labeling using immunohistochemistry) or with tumor perfusion (measured by dynamic contrast enhanced-magnetic resonance imaging). Inhibition of mitochondrial respiration (measured by EPR) was responsible for this early reoxygenation. Consistent with these unique findings in the tumor microenvironment, we found that SU5416 potentiated tumor response to radiotherapy but not to chemotherapy. In addition to the fact that the characterization of the tumor oxygenation is essential to enable correct application of combined therapies, our results show that the long-term inhibition of oxygen consumption is a potential novel target in this class of compounds. [less ▲]

Detailed reference viewed: 31 (9 ULg)
Peer Reviewed
See detailMechanism of Single-Electron Capture by the Dichlorocarbene Dication.
Leyh, Bernard ULg; Hautot, D.

in Journal of the American Society for Mass Spectrometry (1996), 7

The single-electron capture (SEC) by dichlorocarbene with eight different atomic and molecular target gases, (CCl2)2++G->(CCl2)++G+, has been studied by product ion spectroscopy and ion kinetic energy ... [more ▼]

The single-electron capture (SEC) by dichlorocarbene with eight different atomic and molecular target gases, (CCl2)2++G->(CCl2)++G+, has been studied by product ion spectroscopy and ion kinetic energy spectroscopy. The experimental data have been interpreted in the framework of a theoretical model that describes the charge exchange process. Exothermic charge exchange is handled within the Landau-Zener model, whereas endothermic charge exchange is described by the Demkov model. The calculated data reproduce qualitatively the essential features of the experimental results: (1) the appearance of a reaction window centered at an exothermicity in the 4-4.5 eV range, (2) the lower SEC cross sections for endothermic charge exchange, (3) the wider internal energy distributions obtained for CCl2+ in the endothermic regime than in the exothermic one, which results in larger dissociation yields, (4) the excitation of molecular targets that accompany their ionization in the SEC process, and (5) the kinetic energy released on the CCl++Cl fragments in dissociative SEC. [less ▲]

Detailed reference viewed: 2 (0 ULg)
Peer Reviewed
See detailMechanism of sound production in Oreochromis niloticus
Longrie, Nicolas; Herrel, Anthony; Mauguit, Quentin et al

Poster (2007)

Detailed reference viewed: 11 (0 ULg)
Peer Reviewed
See detailMechanism of sound production in Oreochromis niloticus
longrie, Nicolas; van Wassemberg, Sam; Mauguit, Quentin et al

Poster (2008)

Detailed reference viewed: 4 (0 ULg)
Full Text
Peer Reviewed
See detailMechanism of the exchanges catalysed by the oxoglutarate translocator of rat-heart mitochondria. Kinetics of the external-product inhibition.
Sluse, Francis ULg; goffart, george; lièbecq, claude

in Archives Internationales de Physiologie et de Biochimie (1973), 81

Detailed reference viewed: 3 (1 ULg)
Full Text
Peer Reviewed
See detailMechanism of the medium-duration afterhyperpolarization in rat serotonergic neurons
Alix, Philippe ULg; Venkatesan, Kumar; Scuvée-Moreau, Jacqueline et al

in European Journal of Neuroscience (2014), 39(2), 186-196

Most serotonergic neurons display a prominent medium-duration afterhyperpolarization (mAHP), which is mediated by small conductance Ca2+-activated K+ (SK) channels. Recent ex vivo and in vivo experiments ... [more ▼]

Most serotonergic neurons display a prominent medium-duration afterhyperpolarization (mAHP), which is mediated by small conductance Ca2+-activated K+ (SK) channels. Recent ex vivo and in vivo experiments have suggested that SK channel blockade increases the firing rate and/or bursting in these neurons. The purpose of this study was therefore to characterize the source of Ca2+ which activates the mAHP channels in serotonergic neurons. In voltage clamp experiments, an outward current was recorded at -60 mV after a depolarizing pulse to + 100 mV. A supra-maximal concentration of the SK channel blockers apamin or (-)- bicuculline methiodide blocked this outward current. This current was also sensitive to the broad Ca2+ channel blocker Co2+ and was partially blocked by both ω-conotoxin and mibefradil, which are blockers of N-type and T-type Ca2+ channels, respectively. Neither blockers of other voltage-gated Ca2+ channels nor DBHQ, an inhibitor of Ca2+-induced Ca2+ release, had any effect on the SK current. [less ▲]

Detailed reference viewed: 43 (15 ULg)
Full Text
Peer Reviewed
See detailMechanism of Thiamine Transport in Neuroblastoma Cells. Inhibition of a High Affinity Carrier by Sodium Channel Activators and Dependence of Thiamine Uptake on Membrane Potential and Intracellular Atp
Bettendorff, Lucien ULg; Wins, Pierre

in Journal of Biological Chemistry (1994), 269(20), 14379-14385

Nerve cells are particularly sensitive to thiamine deficiency. We studied thiamine transport in mouse neuroblastoma (Neuro 2a) cells. At low external concentration, [14C]thiamine was taken up through a ... [more ▼]

Nerve cells are particularly sensitive to thiamine deficiency. We studied thiamine transport in mouse neuroblastoma (Neuro 2a) cells. At low external concentration, [14C]thiamine was taken up through a saturable high affinity mechanism (Km = 35 nM). This was blocked by low concentrations of the Na+ channel activators veratridine (IC50 = 7 +/- 4 microM) and batrachotoxin (IC50 = 0.9 microM). These effects were not antagonized by tetrodotoxin and were also observed in cell lines devoid of Na+ channels, suggesting that these channels are not involved in the mechanism of inhibition. At high extracellular concentrations, thiamine uptake proceeds essentially via a low affinity carrier (Km = 0.8 mM), insensitive to veratridine but blocked by divalent cations. In both cases, the uptake was independent on external sodium, partially inhibited (10-35%) by depolarization and sensitive to metabolic inhibitors. A linear relationship between the rate of thiamine transport and intracellular ATP concentration was found. When cells grown in a medium of low thiamine concentration (6 nM) were exposed to 100 nM extracellular thiamine, a 3-fold increase in intracellular thiamine diphosphate was observed after 2 h while the concomitant increase in intracellular free thiamine was barely significant. These data suggest a secondary active transport of thiamine, the main driving force being thiamine phosphorylation rather than the sodium gradient. [less ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
Peer Reviewed
See detailMechanism of Trypanosoma brucei gambiense resistance to human serum.
Uzureau, Pierrick; Uzureau, Sophie; Lecordier, Laurence et al

in Nature (2013), 501(7467), 430-4

The African parasite Trypanosoma brucei gambiense accounts for 97% of human sleeping sickness cases. T. b. gambiense resists the specific human innate immunity acting against several other tsetse-fly ... [more ▼]

The African parasite Trypanosoma brucei gambiense accounts for 97% of human sleeping sickness cases. T. b. gambiense resists the specific human innate immunity acting against several other tsetse-fly-transmitted trypanosome species such as T. b. brucei, the causative agent of nagana disease in cattle. Human immunity to some African trypanosomes is due to two serum complexes designated trypanolytic factors (TLF-1 and -2), which both contain haptoglobin-related protein (HPR) and apolipoprotein LI (APOL1). Whereas HPR association with haemoglobin (Hb) allows TLF-1 binding and uptake via the trypanosome receptor TbHpHbR (ref. 5), TLF-2 enters trypanosomes independently of TbHpHbR (refs 4, 5). APOL1 kills trypanosomes after insertion into endosomal/lysosomal membranes. Here we report that T. b. gambiense resists TLFs via a hydrophobic beta-sheet of the T. b. gambiense-specific glycoprotein (TgsGP), which prevents APOL1 toxicity and induces stiffening of membranes upon interaction with lipids. Two additional features contribute to resistance to TLFs: reduction of sensitivity to APOL1 requiring cysteine protease activity, and TbHpHbR inactivation due to a L210S substitution. According to such a multifactorial defence mechanism, transgenic expression of T. b. brucei TbHpHbR in T. b. gambiense did not cause parasite lysis in normal human serum. However, these transgenic parasites were killed in hypohaptoglobinaemic serum, after high TLF-1 uptake in the absence of haptoglobin (Hp) that competes for Hb and receptor binding. TbHpHbR inactivation preventing high APOL1 loading in hypohaptoglobinaemic serum may have evolved because of the overlapping endemic area of T. b. gambiense infection and malaria, the main cause of haemolysis-induced hypohaptoglobinaemia in western and central Africa. [less ▲]

Detailed reference viewed: 18 (4 ULg)