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See detailSynthesis and activity of another seleniated auxin: 2,4-dichlorophenylselenoacetic acid
Tadino, Vincent; Faez, Juan Mareque; Christiaens, Léon ULg et al

in Plant Growth Regulation (2003), 40(3), 197-200

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt ... [more ▼]

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt with potassium selenocyanate. 2,4-D-Se has been tested as an auxin in several bioassays including the regeneration of somatic embryos, adventitious root formation and the associated temporary increase of endogenous auxins at the induction phase, and callus formation, and compared with the natural auxin indoleacetic acid (IAA), the classical synthetic auxin(s) naphthaleneacetic acid (NAA) and/or 2,4-dichlorophenoxyacetic acid (2,4-D), and with the synthetic seleniated IAA, 3-(benzo[b] selenienyl) acetic acid, BSAA. These biological assays classified 2,4-D-Se together with BSAA among the most powerful synthetic auxins. The role of selenium is briefly discussed. [less ▲]

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See detailThiolester substrates of DD-peptidases and beta-lactamases
Damblon, Christian ULg; Ledent, P.; Zhao, G. H. et al

in Letters In Peptide Science (1995), 2(3-4), 212-216

With peptide substrates, the penicillin-sensitive DD-peptidases exhibit a strict specificity for D-Ala-D-Xaa C-termini. Only glycine is tolerated as the C-terminal residue, but with a significantly ... [more ▼]

With peptide substrates, the penicillin-sensitive DD-peptidases exhibit a strict specificity for D-Ala-D-Xaa C-termini. Only glycine is tolerated as the C-terminal residue, but with a significantly decreased activity. These enzymes also hydrolyse various ester and thiolester analogues of their natural substrates. Some of the thiolesters whose C-terminal leaving group exhibited an L stereochemistry were significantly hydrolysed by some of the studied enzymes, particularly by the Actinomadura R39 DD-peptidase. By contrast, the strict specificity for a D residue in the penultimate position was fully retained. The same esters and thiolesters also behaved as substrates for beta-lactamases. In this case, thiolesters exhibiting L stereochemistry in the C-terminal position could also be hydrolysed, mainly by the class C and class D enzymes. But, more surprisingly, the class C Enterobacter cloacae P99 beta-lactamase also hydrolysed thiolesters containing an L residue in the penultimate position, sometimes more efficiently than the D isomer. [less ▲]

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See detailBreakdown of the stereospecificity of DD-peptidases and beta-lactamases with thiolester substrates.
Damblon, Christian ULg; Zhao, G. H.; Jamin, M. et al

in Biochemical Journal (1995), 309 ( Pt 2)

With peptide analogues of their natural substrates (the glycopeptide units of nascent peptidoglycan), the DD-peptidases exhibit a strict preference for D-Ala-D-Xaa C-termini. Gly is tolerated as the C ... [more ▼]

With peptide analogues of their natural substrates (the glycopeptide units of nascent peptidoglycan), the DD-peptidases exhibit a strict preference for D-Ala-D-Xaa C-termini. Gly is tolerated as the C-terminal residue, but with a significantly decreased activity. These enzymes were also known to hydrolyse various ester and thiolester analogues of their natural substrates. Some thiolesters with a C-terminal leaving group that exhibited L stereochemistry were significantly hydrolysed by some of the enzymes, particularly the Actinomadura R39 DD-peptidase, but the strict specificity for a D residue in the penultimate position was fully retained. These esters and thiolesters also behave as substrates for beta-lactamases. In this case, thiolesters exhibiting L stereochemistry in the ultimate position could also be hydrolysed, mainly by the class-C and class-D enzymes. However, more surprisingly, the class-C Enterobacter cloacae P99 beta-lactamase also hydrolysed thiolesters containing an L residue in the penultimate position, sometimes with a higher efficiency than the D isomer. [less ▲]

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See detailACCUMULATION OF ACYL-ENZYME IN DD-PEPTIDASE-CATALYZED REACTIONS WITH ANALOGS OF PEPTIDE-SUBSTRATES
JAMIN, M.; Adam, Maggy; Damblon, Christian ULg et al

in Biochemical Journal (1991), 280(Part 2), 499-506

Thioester substrates can be used to study the hydrolysis and transfer reactions catalysed by beta-lactamases and DD-peptidases. With the latter enzymes, accumulation of the acyl-enzyme can be detected ... [more ▼]

Thioester substrates can be used to study the hydrolysis and transfer reactions catalysed by beta-lactamases and DD-peptidases. With the latter enzymes, accumulation of the acyl-enzyme can be detected directly. The efficiency of various amines as acceptor substrates was in excellent agreement with previous results obtained with peptide substrates of the DD-peptidases. The results indicated the presence of a specific binding site for the acceptor substrates, Although most of the results agreed well with a simple partition model, more elaborate hypotheses will be needed to account for all the data presented. [less ▲]

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See detailNo-Carrier-Added Regioselective Preparation of 6-[18f]Fluoro-L-Dopa
Bozet, Claire ULg; Guillaume, Marcel; Cantineau, R. et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (1990), 31(7), 1247-51

This paper describes the preparation of 6-[18F]fluoro-L-dopa by a no-carrier-added method based on the nucleophilic displacement of nitro groups of two commercially available substrates, 3,4-dimethoxy-2 ... [more ▼]

This paper describes the preparation of 6-[18F]fluoro-L-dopa by a no-carrier-added method based on the nucleophilic displacement of nitro groups of two commercially available substrates, 3,4-dimethoxy-2-nitrobenzaldehyde (nitroveratraldehyde) and 6-nitropiperonal. Fluorination was conducted in DMSO with fluorine-18 (18F) in the presence of the aminopolyether Kryptofix 222 and potassium carbonate. The condensation of the fluorinated aldehydes with phenyloxazolone and the subsequent hydrolysis with HI/P yield, after purification by HPLC, only the 6-(D, L) isomers. The racemic mixture (50/50) was resolved on an analytical scale chiral column. The method, which requires 100 min (EOB) to complete, produces 6-[18F]fluoro-L-dopa with a decay-corrected radiochemical yield of 10%, an enantiomeric purity greater than 99%, and a specific activity of 1.2 Ci/mumole. [less ▲]

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See detailNo-carrier-added regioselective preparation of 6-[18F]fluoro-L-dopa
Lemaire, Christian ULg; Guillaume, Marcel ULg; Cantineau, Robert et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (1990), 31(7), 1247-1251

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See detailCHROMOGENIC DEPSIPEPTIDE SUBSTRATES FOR BETA-LACTAMASES AND PENICILLIN-SENSITIVE DD-PEPTIDASES
Adam, M.; Damblon, Christian ULg; PLAITIN, B. et al

in Biochemical Journal (1990), 270(2), 525-529

Various ester and thioester derivatives of hippuric acid have been prepared which were substrates of both beta-lactamases and DD-peptidases. The thioesters were more rapidly hydrolysed by nearly all the ... [more ▼]

Various ester and thioester derivatives of hippuric acid have been prepared which were substrates of both beta-lactamases and DD-peptidases. The thioesters were more rapidly hydrolysed by nearly all the enzymes. Surprisingly, the enzymes acted rather efficiently on substrates which did not contain any chiral centre. [less ▲]

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See detailA New Route for the Synthesis of [18f]Fluoroaromatic Substituted Amino Acids: No Carrier Added L-P-[18f]Fluorophenylalanine
Lemaire, Christian ULg; Guillaume, M.; Christiaens, Léon ULg et al

in International Journal of Radiation Applications and Instrumentation. Part A : Applied Radiation and Isotopes (1987), 38(12), 1033-8

L-p-[18F]fluorophenylalanine was designed as a potential marker for probing protein synthesis in the human brain by positron emission tomography. This radiotracer has been synthesized using nucleophilic ... [more ▼]

L-p-[18F]fluorophenylalanine was designed as a potential marker for probing protein synthesis in the human brain by positron emission tomography. This radiotracer has been synthesized using nucleophilic displacement of the activated nitro group of p-nitrobenzaldehyde by NCA 18F- obtained from the 18O (p, n) reaction on enriched water. The L-form of the [18F]fluoroamino acid can be separated on an analytical scale chiral column. A typical production run of 22.2 GBq (600 mCi) of 18F obtained after a 10 microA.h bombardment of 18 MeV protons on 99.8% 18O-enriched water leads to a batch of 1.11 GBq (30 mCi) of NCA L-p-[18F]fluorophenylalanine after a total synthesis time of 120 min. [less ▲]

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See detailSynthesis of chalcogeno lactones. II. 3, 4-dihydro-1 H-2-benzothiin-3-one, 3,4-dihydro-1H-2-benzoselenin-3-one and 3,4-dihydro-1H-2-benzotellurin-3-one
Lemaire, Christian ULg; Luxen, André ULg; Christiaens, Léon ULg et al

in Journal of Heterocyclic Chemistry (1983), 20(3), 811-812

The synthesis of 3, 4-dihydro-1H-benzothiin-3-one and its selenium and tellurium analogs is reported from o-bromomethylphenylacetyl chloride and sodium hydrogen chalcogenates, via phase-transfer catalysis.

Detailed reference viewed: 15 (1 ULg)