References of "Gabelica, Valérie"
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See detailOn the specificity of cyclodextrin complexes detected by electrospray mass spectrometry
Gabelica, Valérie ULg; Galic, Nives; De Pauw, Edwin ULg

in Journal of the American Society for Mass Spectrometry (2002), 13(8), 946-953

alpha-cyclodextrin complexes with linear alpha,omega-dicarboxylic acids were investigated by electrospray mass spectrometry. These hydrophobic complexes are known to have an equilibrium binding constant ... [more ▼]

alpha-cyclodextrin complexes with linear alpha,omega-dicarboxylic acids were investigated by electrospray mass spectrometry. These hydrophobic complexes are known to have an equilibrium binding constant that increases with the diacid chain length. However, the electrospray mass spectrometry (ES-MS) spectra showed that the relative intensity of the complex did not vary significantly with chain length. This contradiction is caused by a contribution of nonspecific adducts to the signal of the complex in ES-MS. In order to estimate the contribution of nonspecific adducts to the total intensity of the complexes with alpha-cyclodextrin, the comparison was made between alpha-cyclodextrin and maltohexaose, the latter being incapable of making inclusion complexes in solution. The signal observed for complexes between diacids and maltohexaose can only result from nonspecific electrostatic aggregation, and is found to be more favorable with the shorter diacids. This is also supported by MS/MS experiments. A procedure is described which allows estimation of the contribution of the nonspecific complex in the spectra of the complexes with alpha-cyclodextrin by using the relative intensity of the complex with maltohexaose. The contribution of the specific complex to the total signal intensity is found to increase with the diacid chain length, which is in agreement with solution behavior. [less ▲]

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See detailComparison of the collision-induced dissociation of duplex DNA at different collision regimes: Evidence for a multistep dissociation mechanism
Gabelica, Valérie ULg; De Pauw, Edwin ULg

in Journal of the American Society for Mass Spectrometry (2002), 13(1), 91-98

The dissociation mechanism of duplex DNA has been investigated in detail by collision-induced dissociation experiments at different collision regimes. MS/MS experiments were performed either in a ... [more ▼]

The dissociation mechanism of duplex DNA has been investigated in detail by collision-induced dissociation experiments at different collision regimes. MS/MS experiments were performed either in a quadrupole collision cell (hybrid quadrupole-TOF instrument) or in a quadrupole ion trap with different activation times and energies. In addition to the noncovalent dissociation of the duplex into the single strands, other covalent bond fragmentation channels were observed. Neutral base loss from the duplex is favored by slow activation. In fast activation conditions, however, the major reaction channel is the noncovalent dissociation into single strands, which is highly entropy-favored. Fast activation regimes can favor the entropy-driven noncovalent dissociation, while in slow heating conditions the competition with enthalpy-driven covalent fragmentation can completely hinder the dissociation of the complex. We also evidence that the noncovalent dissociation of DNA duplex is a multistep process involving a progressive unzipping, preferentially at terminal positions. This is proposed to be a general feature for complexes containing a high number of contributing interactions organized at the interface of the ligands. The overall (observed) dissociation kinetics of noncovalent complexes can therefore depend on a complicated mechanism for which a single transition state description of the kinetics is too simplistic. [less ▲]

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See detailCollision-induced dissociation of 16-mer DNA duplexes with various sequences: evidence for conservation of the double helix conformation in the gas phase
Gabelica, Valérie ULg; De Pauw, Edwin ULg

in International Journal of Mass Spectrometry (2002), 219(1), 151-159

The MS/MS of 11 different 16-mer non-self-complementary DNA duplexes with various sequences has been under-taken with a quadrupole-TOF hybrid instrument, The comparison of the dissociation yields for ... [more ▼]

The MS/MS of 11 different 16-mer non-self-complementary DNA duplexes with various sequences has been under-taken with a quadrupole-TOF hybrid instrument, The comparison of the dissociation yields for complexes having different amounts of GC base pairs, though complicated by side-reactions like single-strand fragmentation, confirms the effect of the number of GC base pairs. More importantly, for complexes containing the same fraction of GC and different base sequences, the fragmentation yield remarkably parallels the DeltaH(diss) in solution calculated by a nearest-neighbor model for B-DNA. In addition to specific hydrogen bonding interactions, base stacking interactions also seem to survive in the gas phase and the conformation is conserved in the gas phase. Moreover, we have studied the uneven partition of the negative charges between the single strands, which was found to be directed by the nature of the terminal bases exclusively, and correlated with the gas-phase acidities of the (sugar-phosphate-sugar-base) species. [less ▲]

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See detailFirst synthesis of a '1,2-diquinone-calix[4]arene'. Interaction of its reduced form with Ag+
Vataj, Rame; Ridaoui, Hassan; Louati, Alain et al

in Journal of Electroanalytical Chemistry (2002), 519(1-2), 123129

Electrochemical oxidation of 5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinoylmethoxy)-27,28-dihydroxycalix[4]arene (3), a calixarene with two phosphoryl units appended on proximal positions ... [more ▼]

Electrochemical oxidation of 5,11,17,23-tetra-tert-butyl-25,26-bis(diphenylphosphinoylmethoxy)-27,28-dihydroxycalix[4]arene (3), a calixarene with two phosphoryl units appended on proximal positions, affords the corresponding '1,2-diquinonecalix[4]arene' (4). The formation of 4 results from nucleophilic attack of residual water on anodically generated diphenoxylium. cations. Preliminary voltammetric experiments in CH3CN on a platinum electrode showed that 4 is suitable for electrochemical detection of the silver metal cation. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailKinetics of solvent addition on electrosprayed ions in an electrospray source and in a quadrupole ion trap
Gabelica, Valérie ULg; Lemaire, David; Laprévote, Olivier et al

in International Journal of Mass Spectrometry (2001), 210/211

Benzylpyridinium cations readily fragment in the electrospray source by loss of pyridine to give benzyl cations (M-79). The full-scan spectra obtained with some instruments also show, in addition, an m/z ... [more ▼]

Benzylpyridinium cations readily fragment in the electrospray source by loss of pyridine to give benzyl cations (M-79). The full-scan spectra obtained with some instruments also show, in addition, an m/z (M-38) peak corresponding to the addition of acetonitrile, being present in the solvent mixture, on the benzyl cations. Here we report that the addition reaction can occur in the source region of electrospray mass spectrometry instruments, and in a quadrupole ion trap. The kinetics of acetonitrile addition was monitored in an ion trap, acetonitrile being provided by leakage from the source, through the heated capillary. For benzyl ions with different substituents, the addition kinetics has been found positively correlated with the Brown parameter sigma+ of the benzyl radical, and therefore with the effective charge density on the alpha-carbon atom of the benzyl ion. This is consistent with the Langevin or average-dipole-orientation (ADO) theory of ion–molecule reaction kinetics. [less ▲]

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See detailComparison between Solution-Phase Stability and Gas-Phase Kinetic Stability of Oligodeoxynucleotide Duplexes
Gabelica, Valérie ULg; De Pauw, Edwin ULg

in Journal of Mass Spectrometry [=JMS] (2001), 36(4), 397-402

The relative kinetic stabilities of different 16-mer oligonucleotide duplexes were investigated by source collision-induced dissociation (CID) in a heated capillary electrospray ion source. They were ... [more ▼]

The relative kinetic stabilities of different 16-mer oligonucleotide duplexes were investigated by source collision-induced dissociation (CID) in a heated capillary electrospray ion source. They were compared with the relative stabilities in solution obtained by thermal denaturation monitored by UV spectrophotometry. The results clearly show that both hydrogen bonding and base stacking interactions that are present in solution are maintained in the gas phase. This suggests that the electrospray process preserves the double-helix structure of DNA. A step by step opening of the double helix structure is proposed for the gas-phase dissociation, competing with the covalent bond cleavage of bases. We also draw attention to the fact that by source CID, it is the kinetic stability of the complexes that is probed. In particular, this implies that only complexes of the same size can be compared. [less ▲]

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See detailGas Phase Thermal Denaturation of an Oligonucleotide Duplex and Its Complexes with Minor Groove Binders
Gabelica, Valérie ULg; Rosu, Frédéric ULg; Houssier, Claude ULg et al

in Rapid Communications in Mass Spectrometry : RCM (2000), 14(6), 464-467

Electrospray ionization with in-source collisionally induced dissociation has been used to probe the gas phase stability of an oligonucleotide duplex and its complexes with some minor groove binding drugs ... [more ▼]

Electrospray ionization with in-source collisionally induced dissociation has been used to probe the gas phase stability of an oligonucleotide duplex and its complexes with some minor groove binding drugs. On the basis of the arguments developed in detail by Drahos et al. (J. Mass Spectrom. 1999; 34:1373), this type of experiment can also be described as 'thermal denaturation in the gas phase'. We found that the gas phase denaturation curves were very similar to the solution phase denaturation curves determined by the traditional UV spectrophotometric method and, by analogy with the melting temperature T(m) which characterizes the stability in solution, we define a melting voltage V(m) to characterize the stability in the gas phase. A comparison of the T(m) and V(m) relative values suggests that the structure of the complexes is conserved during the electrospray process which transfers the ions from the solution to the gas phase. [less ▲]

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See detailInteraction between Antitumor Drugs and a Double-Stranded Oligonucleotide Studied by Electrospray Ionization Mass Spectrometry
Gabelica, Valérie ULg; De Pauw, Edwin ULg; Rosu, Frédéric ULg

in Journal of Mass Spectrometry [=JMS] (1999), 34(12), 1328-1337

Electrospray ionization mass spectrometry was used to investigate the complex formation between a double-stranded oligonucleotide and various antitumor drugs belonging to two categories: intercalators ... [more ▼]

Electrospray ionization mass spectrometry was used to investigate the complex formation between a double-stranded oligonucleotide and various antitumor drugs belonging to two categories: intercalators (ethidium bromide, amsacrine and ascididemin) and minor groove binders (Hoechst 33258, netropsin, distamycin A, berenil and DAPI). The goal of this study was to determine whether the relative intensities in the mass spectra reflect the relative abundances of the species in the solution phase. The full-scan mass spectra suggest non-specific binding for the intercalators and specific binding for the minor groove binders. The preferential stoichiometries adopted by each minor groove binder were determined by studying the influence of the drug concentration on the spectra. We obtained 2:1 > 1:1 for distamycin, 1:1 > 2:1 for Hoechst 33258 and DAPI and only the 1 : 1 complex for netropsin and berenil. These features reflect their known behavior in solution. The compared tandem mass spectra of the 1 : 1 complexes with Hoechst 33258 and netropsin, when correlated with published crystallographic data, suggest the possibility of inferring some structural information. The relative binding affinities of the drug for the considered duplex were deduced with two by two competition experiments, assuming that the relative intensities reflect the composition of the solution phase. The obtained affinity scale is netropsin > distamycin A > DAPI > Hoechst 33258 > berenil. These examples show some of the potential uses of mass spectrometry as a useful tool for the characterization of specific drug binding to DNA, and possibly a rapid drug screening method requiring small amounts of materials. [less ▲]

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