TxXIIIA, an atypical homodimeric conotoxin found in the Conus textile venom

in Journal of Proteomics (2009), 72(2), 219-226

Venoms of predatory Conus snails are composed of several hundreds of peptide toxins. Many of these peptides display a high selectivity for particular membrane receptors such as ionic channels or G-protein ... [more ▼]

Venoms of predatory Conus snails are composed of several hundreds of peptide toxins. Many of these peptides display a high selectivity for particular membrane receptors such as ionic channels or G-protein coupled receptors. This property makes them very promising tools for the study of receptors and potential new drugs. Conus snails synthesize toxins under various folds, each fold related to particular pharmacological activities. Aiming the discovery of new conotoxins, we looked for toxins with original fold in the Conus textile venom by offline LC-MALDI-TOF/TOF mass spectrometry. Venom fractions were analysed by MALDI-TOF (in 2,5-dihydroxybenzoic acid) before and after the “in-solution” reduction of the disulfide bridges. Comparison of the spectra allows the classification of a large number of conotoxins according to the number of disulfide bridges. We focussed on a component at m/z 2785.7 (non-reduced)/ 1398.4 (reduced), which might represent a novel type of homodimeric toxin. The sequence TSDCCFYHNCCC was determined by De novo sequencing on the reduced species and represent a new fold. This sequence has already been described as the C-terminus part of a conotoxin scaffold IX precursor (expasy: Q9BPH1) but the power of our study resides in the fact that mass spectrometry highlights the right length of the toxin as well as its homodimeric form which could not be determined by the previous cDNA study. TxXIIIA is also the first homodimeric conotoxin with five disulfide bonds and composed of two monomers containing an odd number of cysteins. [less ▲]

Imaging mass spectrometry reveals peptide distributions in MALDI samples

Poster (2009, March)

TxXIIIA, an atypical homodimeric conotoxin found in the Conus textile venom

Poster (2009, March)

Collision induced dissociation of deuterium enriched protonated 2'-deoxyguanosine

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2009), 51(1), 89-96

Collision induced dissociation in mass spectrometry of protonated nucleosides typically yields as charged fragment the protonated nucleobase augmented by one hydrogen transferred from the 2'-deoxyribose ... [more ▼]

Collision induced dissociation in mass spectrometry of protonated nucleosides typically yields as charged fragment the protonated nucleobase augmented by one hydrogen transferred from the 2'-deoxyribose, [ bH(2)]. The origin of the hydrogen transfer for the protonated 2'-deoxyguanosine has been investigated by collision induced dissociation of deuterium enriched molecules. [ 1'-H-2] 2'-deoxyguanosine, [ 2',2aEuro(3)-H-2(2)] 2'-deoxyguanosine, and [ 5',5aEuro(3)-H-2(2)] 2'-deoxyguanosine have been studied and deuterium/hydrogen back exchange has been used following complete or partial exchange of the 2'-deoxyguanosine in solution. Based on the fragmentation of the deuterated molecular ions, the hydrogen transferred from the 2'-deoxyribose to the guanine is found to originate from the O5' atom on the 2'-deoxyribose. A fragmentation mechanism involving a hydrogen shift from the 2' position to the oxygen atom O5' and supported by the kinetic isotope effect on the survival yield curves is proposed. The influence of the 2'-deoxyguanosine conformation on the hydrogen transfer and the fragmentation mechanism is discussed. [less ▲]

DEVELOPMENT OF AN INTEGRATED STRATEGY FOR CONTROLLING THE ALLERGEN ISSUE IN THE BELGIAN FOOD AND CATERING INDUSTRY - ALLERRISK

Report (2009)

Thiaminylated adenine nucleotides — chemical synthesis, structural characterization and natural occurrence

in FEBS Journal (2009), 276(12), 32563268

Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine ... [more ▼]

Thiamine and its three phosphorylated derivatives (mono-, di- and triphosphate) occur naturally in most cells. Recently, we reported the presence of a fourth thiamine derivative, adenosine thiamine triphosphate (AThTP), produced in E. coli in response to carbon starvation. Here, we show that the chemical synthesis of AThTP leads to another new compound, adenosine thiamine diphosphate (thiaminylated ADP, AThDP), as a side product. The structure of both compounds was confirmed by mass spectrometry and 1H-, 13C- and 31P-NMR and some of their chemical properties were determined. Our results show an upfield shifting of the C-2 proton of the thiazolium ring in adenosine thiamine derivatives compared to the conventional thiamine phosphate derivatives. This modification of the electronic environment of the C-2 proton might be explained by a through-space interaction with the adenosine moiety, suggesting an U-shaped folding of adenosine thiamine derivatives. Such a structure where the C-2 proton is embedded in a closed conformation can be located using molecular modeling as an energy minimum. In E. coli, AThTP may account for 15% of total thiamine under energy stress. It is less abundant in eukaryotic organisms, but is consistently found in mammalian tissues and in some cell lines. Using a HPLC method, we show for the first time that AThDP may also occur in small amounts in E. coli and in vertebrate liver. The discovery of two natural thiamine adenine compounds further highlights the complexity and diversity of thiamine biochemistry, which is not restricted to the cofactor role of thiamine diphosphate. [less ▲]

Le ciblage thérapeutique : vers une guerre propre et efficace contre le cancer

in Revue Médicale de Liège (2009), 64

One promising avenue towards the development of more selective, better anticancer drugs consists in the targeted delivery of bioactive compounds to the tumor environment by means of binding molecules ... [more ▼]

One promising avenue towards the development of more selective, better anticancer drugs consists in the targeted delivery of bioactive compounds to the tumor environment by means of binding molecules specific for tumor-associated biomarkers. Eligibility of such markers for therapeutic use implies ideally three criteria : (i) accessibility from the bloodstream, (ii) expression at sufficient level and (iii) no (or much lower) expression in normal tissues. Most current discovery strategies (such as biomarker searching into body fluids) provide no clue as to whether proteins of interest are accessible, in human tissues, to suitable high-affinity ligands, such as systemically delivered monoclonal antibodies. Innovative proteomic technologies are able to identify such accessible biomarkers and represent a key step in the clinical development of such target therapies. [less ▲]

Occurrence of furan in foodstuffs from the Belgian market

Poster (2009)

Electron detachment dissociation (EDD) pathways in oligonucleotides

in International Journal of Mass Spectrometry (2009), 283

Electron detachment dissociation (EDD) and electron photodetachment dissociation (EPD) are two novel fragmentation methods yielding radicals from negatively charged ions. With the goal of comparing EDD ... [more ▼]

Electron detachment dissociation (EDD) and electron photodetachment dissociation (EPD) are two novel fragmentation methods yielding radicals from negatively charged ions. With the goal of comparing EDD, EPD and the more traditional Collision-Induced Dissociation (CID) and Infrared Multiphoton Disscociation (IRMPD) fragmentation processes in oligonucleotides, we studied here the EDD fragmentation pathways of oligonucleotides of varying length. We chose polythymine oligonucleotides because these are the least prone to secondary structure formation, and found complete sequence coverage by EDD for up to dT20. We also found that the fragmentation pathways change with oligonucleotide length: electron detachment is a mandatory step in the fragmentation of larger sequences, while shorter oligonucleotides can also fragment via direct electronic or vibrational excitation by the electrons. This is supported by (1) the fact that continuous ejection of the charge reduced species does not totally prevent fragmentation of short oligonucleotides dT5 and dT6, (2) the fact that CID and EDD fragments are more similar for small oligonucleotides (although double resonance experiments show that they are not all issued from the same mechanisms), and (3) the fact that electron-induced dissociation (EID) of singly charged dT3 and dT4 gives similar fragments as EDD of doubly charged dT5 and dT6. Finally, the detachment efficiency as a function of the nature of the nucleobase was studied. The effect of base on electron detachment in EDD (G > T > A > C) is different than in EPD (G > A > C > T), indicating different electron loss mechanisms. [less ▲]

A new method for the determination of the relative affinity of a ligand against various DNA sequences by electrospray ionization mass spectrometry. Application to a polyamide minor groove binder

in Journal of Mass Spectrometry [=JMS] (2009), 44

A new method for the determination of the relative affinity of a ligand against various dsDNA sequences is presented by using electrospray ionization time-of-flight mass spectrometry (ESI-QTOF) mass ... [more ▼]

A new method for the determination of the relative affinity of a ligand against various dsDNA sequences is presented by using electrospray ionization time-of-flight mass spectrometry (ESI-QTOF) mass spectrometry. Thismethod does not require knowing the ligand concentration accurately. It allows determination of the relative affinity of a ligand against various dsDNA sequences for 1 : 1 complex stoichiometries in a quick manner without labeling. [less ▲]