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
Full Text
Peer Reviewed
See detailThe interactions of apamin and tetraethylammonium are differentially affected by single mutations in the pore mouth of small conductance calcium-activated potassium (SK) channels
Dilly, Sébastien ULg; Philippart, Fabian ULg; Lamy, Cédric et al

in Biochemical Pharmacology (2013), 85

Valine residues in the pore region of SK2 (V366) and SK3 (V520) were replaced by either an alanine or a phenylalanine to evaluate the impact on the interactions with the allosteric blocker apamin. Unlike ... [more ▼]

Valine residues in the pore region of SK2 (V366) and SK3 (V520) were replaced by either an alanine or a phenylalanine to evaluate the impact on the interactions with the allosteric blocker apamin. Unlike TEA which showed high sensitivity to phenylalanine mutated channels, the binding affinity of apamin to the phenylalanine mutants was strongly reduced. In addition, currents from phenylalanine mutants were largely resistant to block by apamin. On the other hand, when the valine residue was replaced by an alanine residue, an increase of the binding affinity and the amount of block by apamin was observed for alanine mutated SK2 channels, but not for mutated SK3 channels. Interestingly, the VA mutation reduced the sensitivity to TEA. In silico data confirmed these experimental results. Therefore, such mutations in the pore region of SK channels show that the three-dimensional structure of the SK tetramers can be disorganized in the outer pore region leading to reduced interaction of apamin with its target. [less ▲]

Detailed reference viewed: 49 (19 ULg)
Full Text
See detailInteractions of apamin with pore mutated SK3 channels
Dilly, Sébastien ULg; Lamy, Cédric; Poncin, Sylvie et al

Poster (2012, March 16)

In the present work, we have tested the impact of the replacement of valine residues in the pore region of SK3 (520) by either an alanine or a phenylalanine residue in terms of the interactions of apamin ... [more ▼]

In the present work, we have tested the impact of the replacement of valine residues in the pore region of SK3 (520) by either an alanine or a phenylalanine residue in terms of the interactions of apamin with these mutants in comparison with the corresponding native channels. Replacing valine residue at position 520 of the SK3 channel by a phenylalanine significantly increased the sensitivity of the channel to be blocked by tetraethylammonium (TEA) as previously reported. Indeed, an aromatic residue, such as a phenylalanine or a tyrosine, is frequently found in the pore region of several potassium channels more sensitive to TEA than SK channels. We measured the affinity (Kd) of apamin in saturation experiments and studied SK currents in transfected cells using patch clamp techniques. In parallel, molecular modelling techniques were used to examine the impact of these local modifications on the interaction of apamin with the corresponding channels. The presence of a phenylalanine in the pore region of potassium channels led to a higher sensitivity for TEA by creating more hydrophobic interactions as found by the docking procedure. In the in vitro binding experiments, the phenylalanine mutant (SK3VF) displayed a very low affinity for apamin. In patch clamp experiments, the SK current was only very partially blocked by apamin in the SK3VF mutant. Furthermore, apamin displayed an affinity and a blocking activity for the alanine mutant close to that for the corresponding native channels. In conclusion, the presence of a bulky and hydrophobic residue at a position near the pore mouth of SK3 channels has a negative impact on their interactions with apamin. [less ▲]

Detailed reference viewed: 52 (3 ULg)
Full Text
Peer Reviewed
See detailInteractions of apomyoglobin with membranes: Mechanisms and effects on heme uptake
Vernier, Gregory; Chenal, Alexandre; Vitrac, Heidi et al

in Protein Science : A Publication of the Protein Society (2007)

Detailed reference viewed: 16 (3 ULg)
Full Text
Peer Reviewed
See detailInteractions of biapenem with active-site serine and metallo-beta-lactamases.
Felici, A.; Perilli, M.; Segatore, B. et al

in Antimicrobial agents and chemotherapy (1995), 39(6), 1300-5

Biapenem, formerly LJC 10,627 or L-627, a carbapenem antibiotic, was studied in its interactions with 12 beta-lactamases belonging to the four molecular classes proposed by R. P. Ambler (Philos. Trans. R ... [more ▼]

Biapenem, formerly LJC 10,627 or L-627, a carbapenem antibiotic, was studied in its interactions with 12 beta-lactamases belonging to the four molecular classes proposed by R. P. Ambler (Philos. Trans. R. Soc. Lond. Biol. Sci. 289:321-331, 1980). Kinetic parameters were determined. Biapenem was readily inactivated by metallo-beta-lactamases but behaved as a transient inhibitor of the active-site serine enzymes tested, although with different acylation efficiency values. Class A and class D beta-lactamases were unable to confer in vitro resistance toward this carbapenem antibiotic. Surprisingly, the same situation was found in the case of class B enzymes from Aeromonas hydrophila AE036 and Bacillus cereus 5/B/6 when expressed in Escherichia coli strains. [less ▲]

Detailed reference viewed: 12 (0 ULg)
Full Text
Peer Reviewed
See detailInteractions Of Ciprofloxacin With Dppc And Dppg: Fluorescence Anisotropy, Atr-Ftir And P-31 Nmr Spectroscopies And Conformational Analysis
Bensikaddour, H.; Snoussi, K.; Lins, Laurence ULg et al

in Biochimica et Biophysica Acta-Biomembranes (2008), 1778(11), 2535-43

The interactions between a drug and lipids may be critical for the pharmacological activity. We previously showed that the ability of a fluoroquinolone antibiotic, ciprofloxacin, to induce disorder and ... [more ▼]

The interactions between a drug and lipids may be critical for the pharmacological activity. We previously showed that the ability of a fluoroquinolone antibiotic, ciprofloxacin, to induce disorder and modify the orientation of the acyl chains is related to its propensity to be expelled from a monolayer upon compression [1]. Here, we compared the binding of ciprofloxacin on DPPC and DPPG liposomes (or mixtures of phospholipids [DOPC:DPPC], and [DOPC:DPPG]) using quasi-elastic light scattering and steady-state fluorescence anisotropy. We also investigated ciprofloxacin effects on the transition temperature (T(m)) of lipids and on the mobility of phosphate head groups using Attenuated Total Reflection Fourier Transform Infrared-Red Spectroscopy (ATR-FTIR) and (31)P Nuclear Magnetic Resonance (NMR) respectively. In the presence of ciprofloxacin we observed a dose-dependent increase of the size of the DPPG liposomes whereas no effect was evidenced for DPPC liposomes. The binding constants K(app) were in the order of 10(5) M(-1) and the affinity appeared dependent on the negative charge of liposomes: DPPG>DOPC:DPPG (1:1; M:M)>DPPC>DOPC:DPPC (1:1; M:M). As compared to the control samples, the chemical shift anisotropy (Deltasigma) values determined by (31)P NMR showed an increase of 5 and 9 ppm for DPPC:CIP (1:1; M:M) and DPPG:CIP (1:1; M:M) respectively. ATR-FTIR experiments showed that ciprofloxacin had no effect on the T(m) of DPPC but increased the order of the acyl chains both below and above this temperature. In contrast, with DPPG, ciprofloxacin induced a marked broadening effect on the transition with a decrease of the acyl chain order below its T(m) and an increase above this temperature. Altogether with the results from the conformational analysis, these data demonstrated that the interactions of ciprofloxacin with lipids depend markedly on the nature of their phosphate head groups and that ciprofloxacin interacts preferentially with anionic lipid compounds, like phosphatidylglycerol, present at a high content in these membranes. [less ▲]

Detailed reference viewed: 30 (2 ULg)
Full Text
Peer Reviewed
See detailInteractions of cryptolepine and neocryptolepine with unusual DNA structures
Guittat, Lionel; Alberti, Patrizia; Rosu, Frédéric ULg et al

in Biochimie (2003), 85(5), 535-547

Cryptolepine, the main alkaloid present in the roots of Cryptolepis sanguinolenta, presents a large spectrum of biological properties. It has been reported to behave like a DNA intercalator with a ... [more ▼]

Cryptolepine, the main alkaloid present in the roots of Cryptolepis sanguinolenta, presents a large spectrum of biological properties. It has been reported to behave like a DNA intercalator with a preference for GC-rich sequences. In this study, dialysis competition assay and mass spectrometry experiments were used to determine the affinity of cryptolepine and neocryptolepine for DNA structures among duplexes, triplexes, quadruplexes and single strands. Our data confirm that cryptolepine and neocryptolepine prefer GC over AT-rich duplex sequences, but also recognize triplex and quadruplex structures. These compounds are weak telomerase inhibitors and exhibit a significant preference for triplexes over quadruplexes or duplexes. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Societe francaise de biochimie et biologic moleculaire. All rights reserved. [less ▲]

Detailed reference viewed: 93 (5 ULg)
See detailInteractions of human breast adenocarcinoma with the extracellular matrix - a new concept to study cancer invasion.
Foidart, Jean-Michel ULg; Verly, M.; Castronovo, Vincenzo ULg et al

in Evaluation du Risque de Cancer Mammaire. Chimiothérapie Première ? (1985)

Detailed reference viewed: 10 (0 ULg)
Peer Reviewed
See detailInteractions of invasive cells with native and modified extracellular matrix in vitro.
Bracke, M.; Castronovo, Vincenzo ULg; De Bruyne, G. et al

in Advances in Experimental Medicine and Biology (1988), 233

Detailed reference viewed: 12 (3 ULg)
See detailInteractions of invasive cells with native and modified extracellular matrix in vitro.
Bracke, M.; Castronovo, Vincenzo ULg; De Bruyne, G. et al

in In Prodi, G.; Liotta, L. A.; Lollini, P. L. (Eds.) et al Cancer Metastasis : Biological and Biochemical Mechanisms and Clinical Aspects. (1988)

Detailed reference viewed: 6 (0 ULg)
Full Text
Peer Reviewed
See detailInteractions of iturinic antibiotics with plasma membrane. Contribution of biomimetic membranes.
Nasir, Mehmet Nail ULg; Besson, Françoise; Deleu, Magali ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013), 17(3), 505-516

Iturinic antibiotics are produced by Bacillus subtilis strains and constitute a family including iturin A, mycosubtilin and bacillomycins D, F and Lc. They are cyclic lipopeptides having -amino fatty ... [more ▼]

Iturinic antibiotics are produced by Bacillus subtilis strains and constitute a family including iturin A, mycosubtilin and bacillomycins D, F and Lc. They are cyclic lipopeptides having -amino fatty acids linked up to a peptide constituted by seven -aminoacids with an invariable LDDLLDL chiral sequence. The first three -aminoacids containing the tyrosyl residue are the same for all members. They are well-known by their strong antifungal activities but they have also antibacterial and hemolytic properties. These biological properties are due to their amphiphilic nature allowing interactions with different membrane components. Sterols found in plasma membranes are the privileged interaction partners of these lipopeptides. Moreover, the tyrosyl residue of the iturinic antibiotics seems to play an important role during their fixation to the plasma membrane, the result of which is often the cellular lysis. Within plasma membranes, there are particular regions with high sterol content. These microdomains have a different composition compared to the rest of the membrane; they are enriched in certain lipids and proteins and they are involved in many key cellular processes. Their perturbation could then have an important impact on the cell. Due to their composition, these microdomains could constitute the preferential target of iturin antibiotics. This review aims to synthetize the works related to the biological activities of iturinic antibiotics and focusses especially to their understanding at the molecular level with a discussion on the key chemical groups of the iturin antibiotics and on the potentiality of microdomains to constitute a target for these molecules [less ▲]

Detailed reference viewed: 51 (14 ULg)
Full Text
Peer Reviewed
See detailInteractions of lipases with milk fat globule membrane monolayers using a Langmuir film balance
Danthine, Sabine ULg; Blecker, Christophe ULg

in International Dairy Journal (2014), 35(1), 81-87

Detailed reference viewed: 22 (2 ULg)
Full Text
Peer Reviewed
See detailInteractions Of Macrolide Antibiotics (Erythromycin A, Roxithromycin, Erythromycylamine [Dirithromycin], And Azithromycin) With Phospholipids: Computer-Aided Conformational Analysis And Studies On Acellular And Cell Culture Models
Montenez, Jp.; Van Bambeke, F.; Piret, J. et al

in Toxicology and Applied Pharmacology (1999), 156(2), 129-40

The potential of 14/15 membered macrolides to cause phospholipidosis has been prospectively assessed, and structure-effects examined, using combined experimental and conformational approaches. Biochemical ... [more ▼]

The potential of 14/15 membered macrolides to cause phospholipidosis has been prospectively assessed, and structure-effects examined, using combined experimental and conformational approaches. Biochemical studies demonstrated drug binding to phosphatidylinositol-containing liposomes and inhibition of the activity of lysosomal phospholipase A1 toward phosphatidylcholine included in the bilayer, in close correlation with the number of cationic groups carried by the drugs (erythromycin A </= roxithromycin < erythromycylamine </= azithromycin). In cultured cells (fibroblasts), phospholipidosis (affecting all major phospholipids except sphingomyelin) was observed after 3 days with the following ranking: erythromycin A </= roxithromycin < erythromycylamine < azithromycin (roxithromycin could, however, not be studied in detail due to intrinsic toxicity). The difference between erythromycylamine and azithromycin was accounted for by the lower cellular accumulation of erythromycylamine. In parallel, based on a methodology developed and validated to study drug-membrane interactions, the conformational analyses revealed that erythromycin A, roxithromycin, erythromycylamine, and azithromycin penetrate into the hydrophobic domain of a phosphatidylinositol monolayer through their desosamine and cladinose moieties, whereas their macrocycle is found close to the interface. This position allows the aminogroups carried by the macrocycle of the diaminated macrolides (erythromycylamine and azithromycin) to come into close contact with the negatively charged phosphogroup of phosphatidylinositol, whereas the amine located on the C-3 of the desosamine, common to all four drugs, is located at a greater distance from this phosphogroup. Our study suggests that all macrolides have the potential to cause phospholipidosis but that this effect is modulated by toxicodynamic and toxicokinetic parameters related to the drug structure and mainly to their cationic character. [less ▲]

Detailed reference viewed: 22 (0 ULg)
Full Text
Peer Reviewed
See detailInteractions of natural rhamnolpids produced by Pseudomonas aeruginosa with plant model membranes
Polo Lozano, Damien ULg; Nasir, Mehmet Nail ULg; Deleu, Magali ULg et al

Poster (2015, January 30)

It is well known that chemical pesticides have harmful effects on human health and environment. In this context, the interest for alternative products such as biopesticides is increasing. Among them ... [more ▼]

It is well known that chemical pesticides have harmful effects on human health and environment. In this context, the interest for alternative products such as biopesticides is increasing. Among them, elicitors act on the plants by inducing systemic resistance against diseases caused by fungal, viral, bacterial agents and insects. Rhamnolipids are surface active molecules produced mainly by various strains of the bacterium Pseudomonas aeruginosa. These secondary metabolites are composed of one to three fatty acids with various chain lengths linked through a glycosidic bond to one or two rhamnose moieties. The fatty acids are linked together through an ester bond. These molecules have shown several biological activities including plant defense stimulation. It has been suggested that this elicitor activity could be related to an interaction of rhamnolipids with the lipid bilayer of the plant plasma membrane (PPM) and lead to its destabilization, which can activate the plant defense signaling pathways. In this context, interactions of two rhamnolipids (Rha-C10-C10 and Rha-Rha-C10-C10) with biomimetic membranes of PPM such as Langmuir monolayers and multilayers were investigated using biophysical and in silico approaches. [less ▲]

Detailed reference viewed: 80 (6 ULg)
Full Text
Peer Reviewed
See detailInteractions of subunits Asa2, Asa4 and Asa7 in the peripheral stalk of the mitochondrial ATP synthase of the chlorophycean alga Polytomella sp.
Miranda-Astudillo, Hector; Cano-Estrada, Araceli; Vazquez-Acevedo, Miriam et al

in Biochimica et Biophysica Acta-Bioenergetics (2014), 1837

Detailed reference viewed: 29 (5 ULg)
Full Text
Peer Reviewed
See detailInteractions of sugar-based bolaamphiphiles with biomimetic systems of plasma membranes
Nasir, Mehmet Nail ULg; Crowet, Jean-Marc ULg; Lins, Laurence ULg et al

in Biochimie (2016), In Press

Glycolipids constitute a class of molecules with various biological activities. Among them, sugar-based bolaamphiphiles characterized by their biocompatibility, biodegradability and lower toxicity, became ... [more ▼]

Glycolipids constitute a class of molecules with various biological activities. Among them, sugar-based bolaamphiphiles characterized by their biocompatibility, biodegradability and lower toxicity, became interesting for the development of efficient and low cost lipid-based drug delivery systems. Their activity seems to be closely related to their interactions with the lipid components of the plasma membrane of target cells. Despite many works devoted to the chemical synthesis and characterization of sugar-based bolaamphiphiles, their interactions with plasma membrane have not been completely elucidated. In this work, two sugar-based bolaamphiphiles differing only at the level of their sugar residues were chemically synthetized. Their interactions with membranes have been investigated using model membranes containing or not sterol and with in silico approaches. Our findings indicate that the nature of sugar residues has no significant influence for their membrane interacting properties, while the presence of sterol attenuates the interactions of both bolaamphiphiles with the membrane systems. The understanding of this distinct behavior of bolaamphiphiles towards sterol-containing membrane systems could be useful for their applications as drug delivery systems. [less ▲]

Detailed reference viewed: 18 (4 ULg)
Full Text
Peer Reviewed
See detailInteractions of the antifungal mycosubtilin with ergosterol-containing interfacial monolayers
Nasir, Mehmet Nail ULg; Besson, Françoise

in Biochimica et Biophysica Acta - Biomembranes (2012), 1818(5), 1302-1318

Mycosubtilin, an antimicrobial lipopeptide produced by Bacillus subtilis, is characterized by strong antifungal activities. The molecular mechanisms of its biological activities on the membranes of the ... [more ▼]

Mycosubtilin, an antimicrobial lipopeptide produced by Bacillus subtilis, is characterized by strong antifungal activities. The molecular mechanisms of its biological activities on the membranes of the sensitive yeasts or fungi have not yet been clearly elucidated. Our purpose was to mimic the mycosubtilin interactions with these membranes using various Langmuir monolayers. Since the major sterol of yeasts or fungi is ergosterol, the interactions of mycosubtilin with monolayers constituted by ergosterol, DPPC/ergosterol or DPPC/sphingomyelin/ergosterol were examined at different initial surface pressures (Πi). Plotting the mycosubtilin-induced surface pressure increases versus Πi allowed to determine that the exclusion pressures of mycosubtilin from these different monolayers is higher than the surface prevailing within the biological membranes. However, this behavior was lost when mycosubtilin was interacting with ergosteryl acetate-containing monolayers. This suggests the involvement of the sterol alcohol group in the mycosubtilin interactions within membranes. Furthermore, the behavior of mycosubtilin with stigmasterol, similar to that observed with ergosterol, differs from that previously observed with cholesterol, suggesting a role of the alkyl side chain of the sterols. The adsorption of mycosubtilin to ergosterol monolayers induced changes in the lipopeptide orientation at the air-water interface as revealed by polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). Moreover, imaging the air-water interface by Brewster angle microscopy (BAM) indicates that mycosubtilin induced changes in the organization and morphology of monolayers containing pure ergosterol with the appearance of small condensed dots, suggesting again that the target of mycosubtilin might be the ergosterol present in the membranes of the sensitive yeasts or fungi. [less ▲]

Detailed reference viewed: 28 (4 ULg)
Full Text
Peer Reviewed
See detailInteractions of the natural antimicrobial mycosubtilin with phospholipid membrane models
Nasir, Mehmet Nail ULg; Thawani, Ankita; Kouzayha, Achraf et al

in Colloids and Surfaces B: Biointerfaces (2010), 78

Among the secondary metabolite lipopeptides produced by Bacillus subtilis, mycosubtilin is characterized by its strong antifungal activities. Even though its structure and its cellular target, the ... [more ▼]

Among the secondary metabolite lipopeptides produced by Bacillus subtilis, mycosubtilin is characterized by its strong antifungal activities. Even though its structure and its cellular target, the cytoplasmic membrane, have been determined, the molecular mechanisms of the biological activity of mycosubtilin have not been completely elucidated. In this work, the interactions between mycosubtilin and cytoplasmic membranes were modelled by using biomimetic systems such as Langmuir monolayers at the air-water interface and lipid multilamellar vesicles. The interactions of mycosubtilin with these biomimetic systems were examined, for the first time, by using specific techniques such as polarization modulation infrared reflection absorption spectroscopy, Brewster angle microscopy and high-resolution magic angle spinning NMR. Our findings indicate that mycosubtilin alone, at the air-water interface, forms a monolayer film and keeps its turn conformation. In the presence of DMPC, mycosubtilin binds to phospholipid monolayers, in a surface pressure-dependent manner. This binding results in the appearance of condensed domains which can be due to the formation of mycosubtilin clusters and/or to the lipopeptide aggregation with some phospholipid molecules and/or the formation of liquid-condensed domains of DMPC. Furthermore, in multilamellar vesicles, the mycosubtilin-DMPC interactions take place at the level of the aliphatic chains of the phospholipid because the phase transition temperature of DMPC decreased in the presence of mycosubtilin. [less ▲]

Detailed reference viewed: 33 (3 ULg)