Microalgues: du laboratoire au pilote industriel pour la production de molécules bioactives
Franck, Fabrice ; Gerards, Thomas
Scientific conference (2017, February 01)Detailed reference viewed: 18 (2 ULg)
Isolation and characterization of mutants corresponding to the MENA, MENB, MENC, and MENE enzymatic steps of 5'-monohydroxyphylloquinone biosynthesis in Chlamydomonas reinhardtii.
Emonds-Alt, Barbara ; Coosemans, Nadine ; Gerards, Thomas et al
in Plant Journal (The) (2016)Detailed reference viewed: 23 (8 ULg)
Stereoselective synthesis of lanthionine derivatives in aqueous solution and their incorporation into the peptidoglycan of Escherichia coli.
; Zervosen, Astrid ; Gerards, Thomas et al
in Bioorganic & medicinal chemistry (2014), 22(17), 4621-8
The three diastereoisomers-(R,R), (S,S) and meso-of lanthionine were synthesized in aqueous solution with high diastereoselectivity (>99%). The (S) and (R) enantiomers of two differently protected ... [more ▼]
The three diastereoisomers-(R,R), (S,S) and meso-of lanthionine were synthesized in aqueous solution with high diastereoselectivity (>99%). The (S) and (R) enantiomers of two differently protected sulfamidates were opened by nucleophilic attack of (R) or (S)-cysteine. Acidification and controlled heating liberated the free lanthionines. Using the same chemistry, an alpha-benzyl lanthionine was also prepared. The proposed method, which avoids the need of enrichment by recrystallization, opens the way to the labelling of these compounds with (35)S. Furthermore, in vivo bioincorporation into Escherichia coli W7 was studied. No incorporation of alpha-benzyl lanthionine was observed. In contrast, meso-lanthionine can effectively replace meso-diaminopimelic acid in vivo, while in the presence of (R,R)-lanthionine the initial increase of bacterial growth was followed by cell lysis. In the future, meso-[(35)S]lanthionine could be used to study the biosynthesis of peptidoglycan and its turnover in relation to cell growth and division. [less ▲]Detailed reference viewed: 38 (6 ULg)
New noncovalent inhibitors of penicillin-binding proteins from penicillin-resistant bacteria.
; Verlaine, Olivier ; Gerards, Thomas et al
in PloS one (2011), 6(5), 19418
BACKGROUND: Penicillin-binding proteins (PBPs) are well known and validated targets for antibacterial therapy. The most important clinically used inhibitors of PBPs beta-lactams inhibit transpeptidase ... [more ▼]
BACKGROUND: Penicillin-binding proteins (PBPs) are well known and validated targets for antibacterial therapy. The most important clinically used inhibitors of PBPs beta-lactams inhibit transpeptidase activity of PBPs by forming a covalent penicilloyl-enzyme complex that blocks the normal transpeptidation reaction; this finally results in bacterial death. In some resistant bacteria the resistance is acquired by active-site distortion of PBPs, which lowers their acylation efficiency for beta-lactams. To address this problem we focused our attention to discovery of novel noncovalent inhibitors of PBPs. METHODOLOGY/PRINCIPAL FINDINGS: Our in-house bank of compounds was screened for inhibition of three PBPs from resistant bacteria: PBP2a from Methicillin-resistant Staphylococcus aureus (MRSA), PBP2x from Streptococcus pneumoniae strain 5204, and PBP5fm from Enterococcus faecium strain D63r. Initial hit inhibitor obtained by screening was then used as a starting point for computational similarity searching for structurally related compounds and several new noncovalent inhibitors were discovered. Two compounds had promising inhibitory activities of both PBP2a and PBP2x 5204, and good in-vitro antibacterial activities against a panel of Gram-positive bacterial strains. CONCLUSIONS: We found new noncovalent inhibitors of PBPs which represent important starting points for development of more potent inhibitors of PBPs that can target penicillin-resistant bacteria. [less ▲]Detailed reference viewed: 56 (19 ULg)
Carbon-isotope analysis of fossil wood and dispersed organic matter from the terrestrial Wealden facies of Hautrage (Mons Basin, Belgium).
; Gerards, Thomas ; Gerrienne, Philippe et al
in Palaeogeography, Palaeoclimatology, Palaeoecology (2010), 291Detailed reference viewed: 31 (7 ULg)
Synthesis and Evaluation of 3-(Dihydroxyboryl)benzoic Acids as d,d-Carboxypeptidase R39 Inhibitors.
; Zervosen, Astrid ; et al
in Journal of Medicinal Chemistry (2009)
Penicillin binding proteins (PBPs) catalyze steps in the biosynthesis of bacterial cell walls and are the targets for the beta-lactam antibiotics. Non-beta-lactam based antibiotics that target PBPs are of ... [more ▼]
Penicillin binding proteins (PBPs) catalyze steps in the biosynthesis of bacterial cell walls and are the targets for the beta-lactam antibiotics. Non-beta-lactam based antibiotics that target PBPs are of interest because bacteria have evolved resistance to the beta-lactam antibiotics. Boronic acids have been developed as inhibitors of the mechanistically related serine beta-lactamases and serine proteases; however, they have not been explored extensively as PBP inhibitors. Here we report aromatic boronic acid inhibitors of the d,d-carboxypeptidase R39 from Actinomadura sp. strain. Analogues of an initially identified inhibitor [3-(dihydroxyboryl)benzoic acid 1, IC(50) 400 muM] were prepared via routes involving pinacol boronate esters, which were deprotected via a two-stage procedure involving intermediate trifluorborate salts that were hydrolyzed to provide the free boronic acids. 3-(Dihydroxyboryl)benzoic acid analogues containing an amide substituent in the meta, but not ortho position were up to 17-fold more potent inhibitors of the R39 PBP and displayed some activity against other PBPs. These compounds may be useful for the development of even more potent boronic acid based PBP inhibitors with a broad spectrum of antibacterial activity. [less ▲]Detailed reference viewed: 70 (23 ULg)
Discovery of New Inhibitors of Resistant Streptococcus pneumoniae Penicillin Binding Protein (PBP) 2x by Structure-Based Virtual Screening.
; Zervosen, Astrid ; Gerards, Thomas et al
in Journal of Medicinal Chemistry (2009)
Penicillin binding proteins (PBPs) are involved in the biosynthesis of the peptidoglycan layer constitutive of the bacterial envelope. They have been targeted for more than half a century by extensively ... [more ▼]
Penicillin binding proteins (PBPs) are involved in the biosynthesis of the peptidoglycan layer constitutive of the bacterial envelope. They have been targeted for more than half a century by extensively derived molecular scaffolds of penicillins and cephalosporins. Streptococcus pneumoniae resists the antibiotic pressure by inducing highly mutated PBPs that can no longer bind the beta-lactam containing agents. To find inhibitors of PBP2x from Streptococcus pneumoniae (spPBP2x) with novel chemical scaffold so as to circumvent the resistance problems, a hierarchical virtual screening procedure was performed on the NCI database containing approximately 260000 compounds. The calculations involved ligand-based pharmacophore mapping studies and molecular docking simulations in a homology model of spPBP2x from the highly resistant strain 5204. A total of 160 hits were found, and 55 were available for experimental tests. Three compounds harboring two novel chemical scaffolds were identified as inhibitors of the resistant strain 5204-spPBP2x at the micromolar range. [less ▲]Detailed reference viewed: 99 (15 ULg)
Wood remains and sporomorphs from the Wealden facies of Hautrage (Mons Basin, Belgium): palaeoclimatic and palaeoenvironnemental implications.
Gerards, Thomas ; ; et al
in Memoirs of the Geological Survey of Belgium (2008), 55Detailed reference viewed: 30 (6 ULg)
Quelques implications paléoclimatiques de l'observation de bois fossiles du Wealdien du bassin de Mons (Belgique) - Résultats préliminaires.
Gerards, Thomas ; ; Gerrienne, Philippe
in Carnets de Géologie = Notebooks on Geology (2007), 2007(01), 29-34Detailed reference viewed: 30 (6 ULg)
Comparison of cross-field pitting in fresh, dried and charcoalified softwoods
Gerards, Thomas ; Damblon, Freddy ; et al
in Iawa Journal (2007), 28(1), 49-60
Cross-field pitting is one of the most reliable characters for softwood identifi cation. During charcoalification, a range of severe qualitative and quantitative modifications may occur in cross-field ... [more ▼]
Cross-field pitting is one of the most reliable characters for softwood identifi cation. During charcoalification, a range of severe qualitative and quantitative modifications may occur in cross-field pitting. As most fossil or archaeological wood remains are preserved as charcoal (fusain), the question arises whether these modifications hamper the accurate identification of some taxa. This work is a systematic biometric study of a wide range of gymnosperm cross-field pitting after experimental charcoalification. We focused on the window-like, piceoid, taxodioid, cupressoid, araucarioid and podocarpoid cross-field pitting types. Our main results are the following: 1) Cross-field pits of wood specimens dried out before charcoalification are hidden by a thin closing wall; in this case, it is often impossible to discriminate between the various types of cross-field pitting. 2) Piceoid cross-field pitting becomes taxodioid-like after charcoalification. 3) Biometric study of charred softwood cross-field pitting dimensions shows that the ratios between height and width of pit aperture and border allow us to distinguish and characterise four types of pitting (window-like, piceoid, taxodioid, cupressoid + araucarioid + podocarpoid [= CAP]). The discrimination within the CAP type requires further investigation. [less ▲]Detailed reference viewed: 172 (3 ULg)
Premier bilan des analyses récentes du « Pavé de Charlemagne » dans les Hautes-Fagnes à Waimes (Lg.)
Hoffsummer, Patrick ; ; Eeckhout, Jérôme et al
in Archaeologia mediaevalis (2005), 28
This is a presention of different methods of archaeology and archaeometry (palynology, dendrochronology, geomorphology) to date and understand the function of this wooden and stone route infrastructure in ... [more ▼]
This is a presention of different methods of archaeology and archaeometry (palynology, dendrochronology, geomorphology) to date and understand the function of this wooden and stone route infrastructure in a wet deep soil environment. This route is probably from the High Middle Age time with a modification dendrodated at the beginning of the 9th century. the descovery of a old wooden car is also described. [less ▲]Detailed reference viewed: 226 (28 ULg)
Etude comparative au microscope électronique à balayage du xylème secondaire de Gymnospermes et Angiospermes actuelles avant et après carbonisation contrôlée. Résultats préliminaires.
Gerards, Thomas ; Gerrienne, Philippe
Conference (2004)Detailed reference viewed: 31 (3 ULg)