Papers by Michel Laguerre
Langmuir, Sep 4, 2008
The colloidal behavior of eight synthetic procyanidins (three monomers, four dimers, and a trimer... more The colloidal behavior of eight synthetic procyanidins (three monomers, four dimers, and a trimer) has been investigated in water or in a winelike medium using DOSY NMR spectroscopy and molecular dynamics simulations. Different behavior was observed for monomers and oligomers. Monomers self-associate with a high affinity constant (37-53 M(-1)) to form micelles at low cmc (critical micelle concentration) values (1-5 g.L(-1)). These micelles undergo a time-dependent coalescence process to form hazes and precipitates. As for dimers and the trimer, self-association also occurs but with a lower affinity (approximately 6 M(-1)) and at higher cmc values (10-20 g.L(-1)) to form small micelles (<5 nm) that remain stable throughout the experiment. The presence of 10% ethanol does not significantly affect the self-association constant for monomers and oligomers but increases their cmc values by approximately 50% and decreases the micelle size by a factor 2. However, the presence of 20 mM NaCl appears to negate the effect of ethanol. This study helps to clarify the role of procyanidin monomers versus oligomers in wine turbidity and demonstrates that procyanidin oligomers are fully available to interact with saliva proteins.
![Research paper thumbnail of Synthesis and Solution Structure Analysis of a Bispyrenyl Bishydroxamate Calix[4]arene-Based Receptor, a Fluorescent Chemosensor for Cu<sup>2+</sup> and Ni<sup>2+</sup> Metal Ions](https://attachments.academia-assets.com/106506060/thumbnails/1.jpg)
Journal of Organic Chemistry, Aug 25, 1999
A bispyrenyl calix[4]arene-based receptor, 1, incorporating two hydroxamic acid functionalities h... more A bispyrenyl calix[4]arene-based receptor, 1, incorporating two hydroxamic acid functionalities has been designed for the optical detection of Cu 2+ and Ni 2+ metal ions in solution. The synthetic route is based on the utilization of pyrene-labeled, O-protected hydroxylamines that represent versatile building blocks for the generation of fluorescent siderophore-based chelators. Compound 1 is shown to exist in CDCl 3 solution at room temperature as a mixture of mainly two conformers, namely, the cone and partial-cone species (partial-cone/cone ratio ca. 57/43). The full assignment of the proton and carbon resonances of the calix[4]arene core for both conformers is described. Ligand 1 exhibited in solution a dual fluorescence emission spectrum composed of monomer and excimer contributions, the latter resulting from intramolecular interactions between pyrene nuclei in the excited state. In methanol/water (80/20 v/v), the fluorescence intensity was shown to be sensitive to proton concentration and to the presence of transition-metal ions. Addition of Cu 2+ and Ni 2+ metal cations induced a dramatic quenching of fluorescence of 1 depending on the value of-log[H + ]. The excimer-forming photoresponsive ligand 1 belongs to a new class of sensitive chemosensors for the selective detection of transition-metal species in aqueous media.
Chemischer Informationsdienst, Oct 23, 1984
Journal of Agricultural and Food Chemistry, Jan 27, 1998
The kinetics of decomposition of the following flavan-3-ol derivatives isolated from grape seeds ... more The kinetics of decomposition of the following flavan-3-ol derivatives isolated from grape seeds under oxidative conditions by airing and using metal ion catalysis (iron and copper) are determined: (+)catechin and (-)-epicatechin; seven natural procyanidin dimers, B1 [(-)-epicatechin-(4f8)-(+)catechin], B2 [(-)-epicatechin-(4f8)-(-)-epicatechin], B3 [(+)-catechin-(4f8)-(+)-catechin], B4 [(+)catechin-(4f8)-(-)-epicatechin], B6 [(+)-catechin-(4f6)-(+)-catechin], B7 [(-)-epicatechin-(4f6)-(+)-catechin], and B8 [(-)-epicatechin-(4f6)-(-)-epicatechin]; trimers, C1 [(-)-epicatechin-(4f8)-(-)-epicatechin-(4f8)-(-)-epicatechin], (+)-catechin-(4f8)-(+)-catechin-(4f8)-(-)-epicatechin, and (+)-catechin-(4f8)-(-)-epicatechin-(4f6)-(+)-catechin, monogallate esters of B2 and B4 and digallate of B2, which were isolated from grape seeds. Kinetic decomposition comparisons were monitored by HPLC. The following order was found for oxidative decomposition for procyanidin dimers: B3 ≈ B4 > B7 ≈ B6 > B1 ≈ B2 > B8. In the conditions of this study, the gallate ester of (-)-epicatechin is more unstable than (-)-epicatechin; inversely, kinetic decompositions of dimeric procyanidins B2 and B4 are much more important than those of their gallate esters. Molecular mechanics (MM2*) and 1 H NMR studies of dimeric 3-O-gallate structures show a π-π stacking arrangement between the aromatic gallate and catechol rings, absent in analogous dimeric procyanidins, which reduces the total surface accessible to oxidizing agents.
Computer Physics Communications, Aug 1, 2006
A general method to derive effective force fields for the simulation of coarse-grained versions o... more A general method to derive effective force fields for the simulation of coarse-grained versions of phospholipids is presented. The specific case of the dimyristoylphosphatidylcholine (DMPC) bilayers is considered in detail. It is shown that key structural properties are fairly well reproduced, improving the results obtained with other methods. In particular, we obtain rather accurate descriptions of the water-lipid interactions that mimic important hydration properties.
FIGURES 59‒62. Eucereon vestalis (Schaus, 1892a), habitus male (59, 60), dorsal (left) and ventra... more FIGURES 59‒62. Eucereon vestalis (Schaus, 1892a), habitus male (59, 60), dorsal (left) and ventral (right) view; male genitalia; dorsal (61), ventral (62), lateral (63), phallus (64). Scale bars: 0.5 / 1 mm.
ZooKeys, Feb 6, 2013
Four new species of Lophocampa Harris, are described and illustrated: Lophocampa flavodorsata sp.... more Four new species of Lophocampa Harris, are described and illustrated: Lophocampa flavodorsata sp. n., Lophocampa griseidorsata sp. n., Lophocampa herbini sp. n. and Lophocampa sullivani sp. n. Lophocampa atriceps (Hampson) is redescribed, illustrated and compared to the new species. Résumé Quatre nouvelles espèces de Lophocampa Harris sont décrites et illustrées, Lophocampa flavodorsata sp. n., Lophocampa griseidorsata sp. n., Lophocampa herbini sp. n. et Lophocampa sullivani sp. n. Lophocampa atriceps Hampson, est redécrite illustrée, et compareé aveć les especies nouvelles.
Archiv Der Pharmazie, 1994
A series of 5-(1-aryl-4-piperazino)methyl-2-amino-2-oxazolines has been prepared and screened for... more A series of 5-(1-aryl-4-piperazino)methyl-2-amino-2-oxazolines has been prepared and screened for antidepressant activity. Their lipophilic behaviour has been discussed in relation to the nature and the position of substituents on the aromatic ring. The influence of steric effects on the pharmacological activity has been investigated using experimental methods (X-ray diffraction, NMR) and theoretical calculations (semi-empirical quantum mechanics). The ortho-substitution on the phenyl ring or the C-alpha substitution on the piperazine ring by a methyl group results in the same effects i.e. an increase of the angle between the two rings up to 64 degrees (X-ray and calculation) and a loss of the antidepressant activity. Using NMR, only the influence of the ortho-substitution has been observed.
Heterocycles, 1993
... INIST-CNRS. 2, Allée du Parc de Brabois CS 10310 F-54519 Vandoeuvre-lès-Nancy Cedex France Ph... more ... INIST-CNRS. 2, Allée du Parc de Brabois CS 10310 F-54519 Vandoeuvre-lès-Nancy Cedex France Phone: +33 (0)3 83 50 46 64 Fax: +33 (0)3 83 50 46 66. ... Auteur(s) / Author(s). JARRY C. (1) ; FORFAR I. (1) ; THOMAS J. (1) ; LEGER J.-M. ; LAGUERRE M. ; ...
Tetrahedron Letters, 1981
ABSTRACT
Journal of Organometallic Chemistry, Jul 1, 1975
ABSTRACT
Journal of the American Society for Mass Spectrometry, May 1, 2003
Journal of Agricultural and Food Chemistry, Mar 16, 2004
Tonnellerie Demptos seconded to the CESAMO (Centre d'Etudes Structurales et d'Analyses des
Phytochemistry, Sep 1, 1997
Dimers resulting from acetaldehyde-flavanol condensation were studied in an acidic hydroalcc, hol... more Dimers resulting from acetaldehyde-flavanol condensation were studied in an acidic hydroalcc, holic medium (12% ethanol pH 3.2) in order to simulate the conditions of wine tannin-transformation during the wine-ageing process. One of the dimers was isolated after hemisynthesis and studied by mass spectrometry, NMR and molecular mechanics. Mass spectrometric analysis was in accordance with a dimeric structure with a CH CH3 linkage. NMR showed the presence of a 6-8 (ethane-l,l-diyl)di(+)-catechin. The carbon aloms, C-6 and C-8, involved in the linkage, have an asymmetric conformation, with the two catechols in an equa~;orial position. ~, 12~ 1997 Elsevier Science Ltd
The FASEB Journal, Jul 6, 2010
In organoleptic science, the association of tannins to saliva proteins leads to the poorly unders... more In organoleptic science, the association of tannins to saliva proteins leads to the poorly understood phenomenon of astringency. To decipher this interaction at molecular and colloidal levels, the binding of 4 procyanidin dimers (B1-4) and 1 trimer (C2) to a human saliva proline-rich peptide, IB7(14), was studied. Interactions have been characterized by measuring dissociation constants, sizes of complexes, number, and nature of binding sites using NMR (chemical shift variations, diffusion-ordered spectroscopy, and saturation transfer diffusion). The binding sites were identified using molecular mechanics, and the hydrophilic/hydrophobic nature of the interactions was resolved by calculating the molecular lipophilicity potential within the complexes. The following comprehensive scheme can be proposed: 1) below the tannin critical micelle concentration (CMC), interaction is specific, and the procyanidin anchorage always occurs on the same three IB7(14) sites. The tannin 3-dimensional structure plays a key role in the binding force and in the tannin&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s ability to act as a bidentate ligand: tannins adopting an extended conformation exhibit higher affinity toward protein and initiate the formation of a network. 2) Above the CMC, after the first specific hydrophilic interaction has taken place, a random hydrophobic stacking occurs between tannins and proteins. The whole process is discussed in the general frame of wine tannins eliciting astringency.
HAL (Le Centre pour la Communication Scientifique Directe), Sep 4, 2007
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Zootaxa, Nov 23, 2021
In preparation for a general account of the Trinidad and Tobago Arctiini, the following taxonomic... more In preparation for a general account of the Trinidad and Tobago Arctiini, the following taxonomic changes are made and justification provided. A lectotype is designated for Castrica sordidior Rothschild, 1909. Castrica oweni Schaus, 1896, stat rev. is returned to species rank. The following new synonyms are established: Castrica sordidior Rothschild, 1909 syn. nov. of Castrica oweni Schaus, 1896; Automolis nigroapicalis Gaede, 1923, Automolis semicostalis Rothschild, 1909, Automolis alboatra Rothschild, 1909, Automolis alboatra borussica Seitz, 1922, Sallaea unifascia Druce, 1899, Automolis hamifera Dognin, 1907, and Automolis apicata Schaus, 1905 syn. nov. of Pryteria costata Möschler, 1883; and Sphinx Adfeit. psamas Cramer, [1779] syn. nov. of Phalaena Noctua onytes Cramer, [1777]. Virbia birchi Druce, 1911 is confirmed to be a synonym of Phalaena medarda Stoll, [1781]. Pryteria tenuis (Rothschild, 1935) stat. nov. and P. intensa (Rothschild, 1935) stat. nov. are raised to species level pending clarification of the genus Pryteria in Central America.
Chemischer Informationsdienst, Jul 18, 1978
ChemInform Abstract In einfacher Weise wird aus Dimethyldichlorsilan das Cyclohexasilan (II) herg... more ChemInform Abstract In einfacher Weise wird aus Dimethyldichlorsilan das Cyclohexasilan (II) hergestellt.
Tropical Lepidoptera Research, Jan 3, 2018
We describe a new genus, Leocephaluncus Espinoza & Laguerre n. gen., with three new species of Ar... more We describe a new genus, Leocephaluncus Espinoza & Laguerre n. gen., with three new species of Arctiinae (Erebidae), Leocephaluncus elianahenrichae Espinoza n. sp., Leocephaluncus rafaelangelespinozai Espinoza n. sp. and Leocephaluncus boliviensis Laguerre n. sp., from Central and South America, and clarify their identification with respect to Pseudapistosia Möschler, 1878 (Arctiinae). Leocephaluncus leucocorypha (Dognin, 1914) new comb. is transferred to the new genus from Pseudapistosia. Pseudapistosia chimaera Druce, 1893 new comb. is transferred from the genus Elysius, and Pseudapistosia gigas (Dognin, 1890) rev. stat. is restored to species status. A lectotype is designated for Phalaena umber Cramer, [1776]. For the new genus Leocephaluncus, we include images of the adult males and their genitalia, data from DNA barcodes and notes on the species' geographical distribution. In addition, we discuss the phylogenetic placement of the new genus.
Bulletin de la Société entomologique de France, 2008
Illice intacta decrite a l'origine par Rothschild comme sous-espece de I. citrina Druce est c... more Illice intacta decrite a l'origine par Rothschild comme sous-espece de I. citrina Druce est consideree de rang specifique. Les deux especes sont redecrites et figurees, et leurs genitalia mâles et femelles sont illustres.
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Papers by Michel Laguerre