References of "Dive, Georges"
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See detailThe Hartree-Fock triplet instability: influence of conformation and substitution
Géron, Christine; Dive, Georges ULg; Dehareng, Dominique ULg

in Journal of Molecular Structure-theochem (2006), 760(1-3), 75-85

The triplet Hartree-Fock (HF) instability is investigated through the examples of substituted ethylenes and the small linear conjugated systems butadiene, hexatriene, octatetraene. A statistical analysis ... [more ▼]

The triplet Hartree-Fock (HF) instability is investigated through the examples of substituted ethylenes and the small linear conjugated systems butadiene, hexatriene, octatetraene. A statistical analysis is performed for several conformations of the latters. The second eigenvalue of the instability matrix appears to be able to discriminate the groups of unsaturated compounds. The HF instability is largely influenced by conjugation and mesomeric effects and thus by the geometry. The number of pi electrons is also an important factor. The electronic correlation related to the HF instability is not quantified by the energy difference between the post-HF and HF levels. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailWave packets in a bifurcating region of an energy landscape: Diels-Alder dimerization of cyclopentadiene
Lasorne, Benjamin; Dive, Georges ULg; Desouter, Michèle ULg

in Journal of Chemical Physics (2005), 122(18), 1843041-10

Quantum dynamics in a valley ridge inflection (VRI) point region is analyzed in the case of the Diels-Alder endo-dimerization of cyclopentadiene pointed out recently by [Caramella , J. Am. Chem. Soc. 124 ... [more ▼]

Quantum dynamics in a valley ridge inflection (VRI) point region is analyzed in the case of the Diels-Alder endo-dimerization of cyclopentadiene pointed out recently by [Caramella , J. Am. Chem. Soc. 124, 1130 (2002)]. The VRI point is located along the reaction path connecting the bispericyclic symmetrical transition structure put in evidence by Caramella and the transition state of the Cope rearrangement. Dynamics is carried out by using constrained Hamiltonian methodology. The active coordinates are the first formed C-C bond length and the difference between the two other C-C bond lengths which achieve the dimerization as 4+2 or 2+4 adducts. A two-dimensional (2D) minimum-energy surface have been computed at the Becke 3 Lee-Yong-Parr/6-31G(*) level. The energy landscape can be classified as an uphill ridge-pitchfork VRI bifurcation according to a recent classification of bifurcation events [W. Quapp, J. Mol. Struct. 695-696, 95 (2004)]. Dynamics does not describe the thermal reaction but concerns wave packets which could be prepared by pulse reagents, i.e., by coherent control. We analyze how the shape and initial location on the ground potential-energy surface are linked to the synchronous or asynchronous mechanism of the final step after the first transition state. We use a one-dimensional model of optimum control theory to check the feasibility of such a coherent preparation. The wave-packet evolution in the VRI domain is well explained by semiclassical predictions even with the negative curvature of the unstable ridge. Finally, a crude model of dissipation has been introduced to test the stability of the 2D predictions. (c) 2005 American Institute of Physics. [less ▲]

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See detailThe Effect of Cyclodextrins on the Aqueous Solubility of a New Mmp Inhibitor: Phase Solubility, 1 H-Nmr Spectroscopy and Molecular Modeling Studies, Preparation and Stability Study of Nebulizable Solutions
Bertholet, Pascal; Guéders, Maud ULg; Dive, Georges ULg et al

in Journal of Pharmacy & Pharmaceutical Sciences : A Publication of the Canadian Society for Pharmaceutical Sciences (2005), 8(2), 164-175

PURPOSE: Ro 28-2653 (RO) is a synthetic inhibitor of matrix metalloproteinases (MMPs), which is potentially effective against bronchial remodeling. Given that this molecule has very poor aqueous ... [more ▼]

PURPOSE: Ro 28-2653 (RO) is a synthetic inhibitor of matrix metalloproteinases (MMPs), which is potentially effective against bronchial remodeling. Given that this molecule has very poor aqueous solubility, different cyclodextrins (CDs) have been tested to increase its solubility. The aim of this study was to prepare and to characterize inclusion complexes between RO and CDs, in order to develop nebulizable solutions. METHODS: The complex formation was investigated by phase solubility studies. (1)H-NMR spectroscopy and molecular modeling studies were carried out to elucidate the structure of the inclusion complex between RO and dimethyl-beta-CD (DIMEB). Nebulizable solutions of RO were developed with CDs and a stability study was performed over 9 months. RESULTS: The phase solubility studies showed that beta-CD and its derivatives form a 1:2 complex with RO, whereas gamma-CD includes RO with a 1:1 stoichiometry and a weak stability constant. T-ROESY spectra showed that DIMEB is able to complex two RO substituents (nitrophenyl and biphenyl groups) with preferential orientations, while molecular modeling demonstrated that the configurations observed with (1)H-NMR are energetically favorable, especially owing to H-bond formation between RO and DIMEB. Two CDs were selected to develop nebulizable solutions of RO and the stability study demonstrated that RO degradation in solution is strongly dependent on the concentration of the 1:2 inclusion complex. CONCLUSIONS: CDs are able to include RO and to improve its aqueous solubility. The beta-CD derivatives can be used to formulate nebulizable solutions of RO, the stability of which depends on the concentration of the 1:2 complex. [less ▲]

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See detailNovel RGD-like molecules based on the tyrosine template design, synthesis, and biological evaluation on isolated integrins alpha(V)beta/alpha(IIb)beta(3) and in cellular adhesion tests
Biltresse, S.; Attolini, M.; Dive, Georges ULg et al

in Bioorganic & Medicinal Chemistry (2004), 12(20), 5379-5393

RGD (Arg-Gly-Asp) peptidomimetics have been designed for covalent anchorage on biomaterials. The tyrosine template was thus equipped with (i) a basic side chain of various flexibility, (ii) an acidic side ... [more ▼]

RGD (Arg-Gly-Asp) peptidomimetics have been designed for covalent anchorage on biomaterials. The tyrosine template was thus equipped with (i) a basic side chain of various flexibility, (ii) an acidic side chain, which incorporated the XPS fluorine tag, and (iii) a spacer-arm terminated by a primary amine for surface grafting. The most active compounds showed IC50 values in the nanomolar range versus isolated human integrins alpha(v)beta(3) and alpha(IIb)beta(3). Preincubation of CaCo2 cells with soluble peptidomimetics (2 and 19a) prevented cellular adhesion on culture plates coated with vitronectin. On the other hand, peptidomimetics (19a and 19b) immobilized on a poly(ethylene)terephthalate membrane (PET) promoted CaCo2 cells adhesion. A modeling study at the ab initio level in MINI-1' basis allowed to compare the various synthetic ligands of integrins and to propose novel pharmacophore structures. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailThe rational design of modified cinchona alkaloid catalysts. Application to a new asymmetric synthesis of chiral chromanes
Merschaert, Alain; Delbeke, Pieter; Daloze, Désiré et al

in Tetrahedron Letters (2004), 45(24), 4697-4701

A new asymmetric synthesis of 2-substituted chiral chromanes has been achieved. The key step is the intramolecular conjugate addition of a phenolic nucleophile on a alpha,beta-unsaturated ester catalyzed ... [more ▼]

A new asymmetric synthesis of 2-substituted chiral chromanes has been achieved. The key step is the intramolecular conjugate addition of a phenolic nucleophile on a alpha,beta-unsaturated ester catalyzed by Cinchona alkaloids. The high ee's obtained with cinchonine and its derivatives have been rationalized by ab initio quantum chemistry calculations of transition state structures. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailSynthesis and evaluation of N1/C4-substituted beta-lactams as PPE and HLE inhibitors
Gérard, Stéphane; Galleni, Moreno ULg; Dive, Georges ULg et al

in Bioorganic & Medicinal Chemistry (2004), 12(1), 129-138

4-(Alkylamino)carbonyl-1-(alkoxy)carbonyl-2-azetidinones (9-11) have been prepared in five steps from 4-(benzyloxy)carbonyl-1-(t-butyidimethyl)silyl-2-azetidinone (1). The P-lactam reactivity of 9 has ... [more ▼]

4-(Alkylamino)carbonyl-1-(alkoxy)carbonyl-2-azetidinones (9-11) have been prepared in five steps from 4-(benzyloxy)carbonyl-1-(t-butyidimethyl)silyl-2-azetidinone (1). The P-lactam reactivity of 9 has been established by H-1 NMR experiment. Compound 11 was a good reversible inhibitor of PPE and HLE. Based on theoretical design, series of 2-azetidinones (12-17) and 4(alkoxy)carbonyl-2-azetidinones (18-21) bearing various carbonyl (ester, thiolester, amide) and thiocarbonyl (thioamide) functionalities at position N1 were similarly prepared. In the absence of C4-substituent, the compounds were inactive against elastases. On the other hand, 4-(benzyloxy)carbonyl-1-(ethylthioxy)carbonyl-2-azetidinone (19) and 4-(benzyloxy)carbonyl-1-(benzylamino)-thiocarbonyl-2-azetidinone (21) were both good reversible inhibitors, but acting most probably via different mechanisms (enzymic processing of the exocyclic ester function or beta-lactam ring opening). (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailApplication of molecular modeling to the study of cyproterone acetate stability in the presence of cyclodextrin derivatives
Henry de Hassonville, Sandrine; Dive, Georges ULg; Evrard, Brigitte ULg et al

in Journal of Drug Delivery Science and Technology (2004), 14(5, SEP-OCT), 357-362

The ability of cyclodextrins (CDs) to increase the solubility of cyproterone acetate (CPA) was previously shown by phase-solubility and NMR studies [1]. In the present work, the influence of various CDs ... [more ▼]

The ability of cyclodextrins (CDs) to increase the solubility of cyproterone acetate (CPA) was previously shown by phase-solubility and NMR studies [1]. In the present work, the influence of various CDs on the stability of CPA was studied in pH 6 and pH 8 aqueous solutions at 25degreesC. Different CDs were tested: hydroxypropyl-beta-cyclodextrin (HPbetaCD), randomly methylated beta-cyclodextrin (RAMEB), hydroxypropyl-gamma-cyclodextrin (HPgammaCD) and gamma-cyclodextrin (gammaCD). At pH 6, the presence of these CDs reduces the degradation of CPA. Nevertheless, at pH 8, the gamma-CD derivatives are ineffective against the degradation of CPA, whereas the beta-CD derivatives (HPbetaCD and RAMEB) allow decreasing CPA hydrolysis. Molecular modeling was performed to theoretically calculate some of the most energetically favorable conformations for gamma-CD and RAMEB complexes with CPA. The position of the ester group in the CD caivity seems to be the most important factor influencing the hydrolysis of CPA. Other factors, such as the size of the cavity, the substitution of the CD hydroxyls and the stability constant also have a strong incidence on CPA stability. [less ▲]

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See detailVertical ionization energies of alpha-L-amino acids as a function of their conformation: an ab initio study
Dehareng, Dominique ULg; Dive, Georges ULg

in International Journal of Molecular Sciences (2004), 5(11-12, NOV-DEC), 301-332

Vertical ionization energies (IE) as a function of the conformation are determined at the quantum chemistry level for eighteen alpha-L-amino acids. Geometry optimization of the neutrals are performed ... [more ▼]

Vertical ionization energies (IE) as a function of the conformation are determined at the quantum chemistry level for eighteen alpha-L-amino acids. Geometry optimization of the neutrals are performed within the Density Functional Theory (DFT) framework using the hybrid method B3LYP and the 6-31G**(5d) basis set. Few comparisons are made with wave-function-based ab initio correlated methods like MP2, QCISD or CCSD. For each amino acid, several conformations are considered that lie in the range 10-15 kJ/mol by reference to the more stable one. Their IE are calculated using the Outer-Valence-Green's-Functions (OVGF) method at the neutrals' geometry. Few comparisons are made with MP2 and QCISD IE. It turns out that the OVGF results are satisfactory but an uncertainty relative to the most stable conformer at the B3LYP level persists. Moreover, the value of the IE can largely depend on the conformation due to the fact that the ionized molecular orbitals (MO) can change a lot as a function of the nuclear structure. [less ▲]

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See detailRelationship between structure and biological properties of different lipopeptides produced by B. Subtilis.
Jacques, Ph.; Hbid, Ch.; Razafindralambo, Hary ULg et al

Poster (2003, August)

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See detailInfluence of cyclodextrins on the solubility and the stability of cyproterone acetate
Henry de Hassonville, Sandrine; Dive, Georges ULg; Prosperi, Christelle ULg et al

Conference (2003, May)

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See detailWave packet dynamics along bifurcating reaction paths
Lasorne, Benjamin; Dive, Georges ULg; Lauvergnat, David et al

in Journal of Chemical Physics (2003), 118(13), 5831-5840

The problem of bifurcating reaction paths is revisited by wave packet (WP) dynamics. The pitchfork model connecting five stationary points-a reactive, two transition structures and two enantiomeric ... [more ▼]

The problem of bifurcating reaction paths is revisited by wave packet (WP) dynamics. The pitchfork model connecting five stationary points-a reactive, two transition structures and two enantiomeric products-is characterized by a Valley Ridge inflection point (VRI) where WP could leave the standard intrinsic reaction path. We question the role of such a VRI point to determine whether the mechanism is sequential or concerted. WP simulations on two-dimensional minimum energy surfaces are carried out in the benchmark case of the methoxy radical isomerization H3CO-->H2COH. The ab initio potential energy surface (PES) is fitted to an analytical model which is bent to analyze the incidence of geometrical parameters on the WP behavior. For each of these generated PES, the WP width in the entrance valley is the main factor which conditions the behavior on the unstable ridge. The WP evolution is also analyzed in terms of nonadiabatic transitions among adiabatic channels along the reaction coordinate. Finally, the location of VRI points according to an invariant definition is discussed. (C) 2003 American Institute of Physics. [less ▲]

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See detailCumulative reaction probability by constrained dynamics: H transfer in HCN, H2CO, and H3CO
Baloitcha, Ezinvi; Lasorne, Benjamin; Lauvergnat, David et al

in Journal of Chemical Physics (2002), 117(2), 727-739

A strategy to obtain quantum corrections to the cumulative reaction probability from a subspace of active coordinates is analyzed. The kinetic energy operator exactly takes into account the constraints ... [more ▼]

A strategy to obtain quantum corrections to the cumulative reaction probability from a subspace of active coordinates is analyzed. The kinetic energy operator exactly takes into account the constraints due to inactive coordinates. The geometry of the inactive skeleton is adiabatically adjusted to the dynamical variables or simply frozen according to the coupling to the active space. Dynamics is carried out using the curvilinear coordinates of the Z-matrix so that computation of the potential energy surface and dynamics are coupled. The cumulative reaction probability N(E) is obtained directly in a large range of energy by a time independent formulation of the Zhang and Light transition state wave packet method. N-nD(E) is first computed in the active n-dimensional space and then convoluted with a bath. The efficiency of the Chebyshev expansion of the microcanonical projection operator delta(E-(H) over cap (nD)) appearing in the quantum expression of N-nD(E) is checked. The method is implemented for the study of tunneling effect in H transfer. The coordinates are three spherical coordinates referred to the frozen or adiabatic skeleton. We compare the quantum corrections brought about by different 2D groups of internal coordinates. (C) 2002 American Institute of Physics. [less ▲]

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See detailSynthesis, hydrolysis, biochemical and theoretical evaluation of 1,4-bis(alkoxycarbonyl)azetidin-2-ones as potential elastase inhibitors
Gérard, Stéphane; Dive, Georges ULg; Clamot, Brigitte et al

in Tetrahedron (2002), 58(12), 2423-2433

A series of 1,4-bis(alkoxycarbonyl)azetidin-2-ones, designed as potential suicide-inhibitors of serine proteases, has been synthesized and evaluated against porcine pancreatic elastase (PPE). The most ... [more ▼]

A series of 1,4-bis(alkoxycarbonyl)azetidin-2-ones, designed as potential suicide-inhibitors of serine proteases, has been synthesized and evaluated against porcine pancreatic elastase (PPE). The most active compound (K(i)similar to10 muM; reversible inhibitor) was equipped with phenethyloxycarbonyl and benzyloxycarbonyl side-chains at positions N1 and C4, respectively, with the (S)-configuration. H-1 NMR spectroscopic analysis of the reaction mixtures showed that the ester function is preferentially hydrolyzed, in both chemical and enzyme-catalyzed reactions, with regard to the azetidinone and urethane functions. Considering the three potentially sensitive carbonyl functions and the two stereoisomers, ab initio calculations were performed to determine the energetic barriers required to reach the transition state structures of hydrolysis in a model of the enzyme pocket. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailCrystal structures of the Bacillus licheniformis BS3 class A beta-lactamase and of the acyl-enzyme adduct formed with cefoxitin
Fonzé, Evelyne; Vanhove, Mac; Dive, Georges ULg et al

in Biochemistry (2002), 41(6), 1877-1885

The Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common ... [more ▼]

The Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common and thoroughly studied cause of antibiotic resistance. Although they escape the hydrolytic activity of the prototypical Staphylococcus aureus beta-lactamase, many cephems are good substrates for a large number of beta-lactamases. However, the introduction of a 7alpha-methoxy substituent, as in cefoxitin, extends their antibacterial spectrum to many cephalosporin-resistant Gram-negative bacteria. The 7alphamethoxy group selectively reduces the hydrolytic action of many beta-lactamases without having a significant effect on the affinity for the target enzymes, the membrane penicillin-binding proteins. We report here the crystallographic structures of the BS3 enzyme and its acyl-enzyme adduct with cefoxitin at 1.7 Angstrom resolution. The comparison of the two structures reveals a covalent acyl-enzyme adduct with perturbed active site geometry, involving a different conformation of the Omega-loop that bears the essential catalytic Glu166 residue. This deformation is induced by the cefoxitin side chain whose position is constrained by the presence of the alpha-methoxy group. The hydrolytic water molecule is also removed from the active site by the 7beta-carbonyl of the acyl intermediate. In light of the interactions and steric hindrances in the active site of the structure of the BS3-cefoxitin acyl-enzyme adduct, the crucial role of the conserved Asn132 residue is confirmed and a better understanding of the kinetic results emerges. [less ▲]

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See detailRetrosynthetic analysis of fullerene C-60: structure, stereochemistry and calculated stability of C-30 fragments
Geneste, Florence; Moradpour, Alec; Dive, Georges ULg et al

in Journal of Organic Chemistry (2002), 67(2), 605-607

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See detailHartree-Fock instabilities: Relation between an artifact and some properties.
Dehareng, Dominique ULg; Dive, Georges ULg; Geron, Christine

in Recent Research Development in Chemical Physics (2002), 3

The Hartree-Fock instability problem is reviewed and some of the instabilities are put in relation with particular properties of the system.

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See detailMolecular Modeling Study of Beta- and Gamma-Cyclodextrin Complexes with Miconazole
Piel, Géraldine ULg; Dive, Georges ULg; Evrard, Brigitte ULg et al

in European Journal of Pharmaceutical Sciences (2001), 13(3), 271-9

Different authors have demonstrated the inclusion of miconazole in cyclodextrins (CD). Miconazole can be included in the CD cavity both in the neutral and in the ionized form. The present study tries to ... [more ▼]

Different authors have demonstrated the inclusion of miconazole in cyclodextrins (CD). Miconazole can be included in the CD cavity both in the neutral and in the ionized form. The present study tries to understand which fragment of the miconazole molecule is involved in the inclusion. Austin Model 1 approximate molecular orbital calculations have been performed on several complexes between beta-cyclodextrin (betaCD) or gamma-cyclodextrin (gammaCD) and miconazole in the ionized and the non-ionized forms of the two R and S enantiomers in three different orientations. We observed that betaCD is a good vehicle to transport miconazole which can be very easily released. The complexation energy between miconazole and betaCD is not very high but the entropic factor has a great incidence on the stability of the formed complex. The inclusion of the dichlorobenzene-CH(2)-O- and of the imidazole part of the S isomer gives rise to the most probable complex in acidic conditions (ionized miconazole). Nevertheless, the inclusion should be considered as a dynamic process in which different parts of the molecule could be alternatively included in betaCD. The present work demonstrates the high capability of deformation of betaCD which could easily accommodate several types of ligand. By opposite, the cycle extension in gammaCD leads to a more rigid vehicle with regards to miconazole. [less ▲]

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See detailQualitative Comparison between the Quantum Calculations and Electrospray Mass Spectra of Complexes of Polyammonium Macrotricyclic Ligands with Dicarboxylic Acids
Collette, Caroline ULg; Dehareng, Dominique ULg; De Pauw, Edwin ULg et al

in Journal of the American Society for Mass Spectrometry (2001), 12(3), 304-16

The host-guest interactions play a very important role in chemical and biological processes. It is therefore important to be able to characterize these complexes. Electrospray mass spectrometry can be ... [more ▼]

The host-guest interactions play a very important role in chemical and biological processes. It is therefore important to be able to characterize these complexes. Electrospray mass spectrometry can be used to characterize the complex formation. It provides information on the mass and the charge of these ionic complexes. In this article, we show that the use of ab initio and semiempirical calculations, in addition to the results obtained by electrospray mass spectrometry, reveal to be a promising tool for the study of these noncovalent complexes. In this article, host-guest complexes formed by macropolycyclic polyammonium host molecules and dicarboxylic acids are studied. [less ▲]

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See detailImidazolopyrazinones as potential antioxydants
Devillers, Ingrid; Dive, Georges ULg; De Tollenaere, Catherine et al

in Bioorganic & Medicinal Chemistry Letters (2001), 11(17), 2305-2309

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