PubMed Health⌕ Search

Biomedical subjects

Isabelle Rico-Lattes

Publications and source records attributed to Isabelle Rico-Lattes.

12 recordsLinked to original sources
PubMed2005

Monolayers of salen derivatives as catalytic planes for alkene oxidation in water.

Monolayers at the gas/water interface have been used as an adjustable catalytic system in which the molecular density may be modified. Mn(III)-salen complexes bearing perfluoroalkyl substituents have been organized as a Langmuir film on an aqueous subphase containing a urea/hydrogen peroxide adduct (UHP, the oxidant) and cinnamyl alcohol (the substrate). The catalytic activity of the monolayer for the epoxidation of the alkene dissolved in water has been demonstrated and the reaction kinetic investigated. For a constant area per molecule of catalyst, the reaction rate exhibits first-order dependence on oxidant concentration and zero-order dependence on alkene concentration, in agreement with the reaction orders reported for Mn(III)-salen-catalyzed epoxidation reactions carried out in solution. Furthermore, kinetic experiments suggest an enhanced activity of the catalysts assembled in a Langmuir film relative to that observed in bulk reaction. Finally, varying the molecular density of the catalyst at the gas/water interface highlights an important dependence of the catalytic activity of the layer with the mean molecular area. A strong increase of the catalytic properties of the monolayer was observed for a mean molecular area of 140-145 A2, an increase which was supposedly related to a modification of the Mn(III)-salen complex orientation at the interface upon compression. This hypothesis was supported by PM-IRRAS (polarization modulation infrared reflection adsorption spectroscopy) experiments performed in situ on the monolayer. Such results demonstrate that a soft and adjustable molecular system like a Langmuir film can be used to better understand the reactivity in various heterogeneous and/or pseudohomogeneous (such as those based on dendrimers) catalytic systems.

Journal Article↗
PubMed2005

Preparation and characterization of new hybrid organic/inorganic systems derived from calcium (alpha-aminoalkyl)-phosphonates and -phosphonocarboxylates.

We have studied the phenomenon of calcium complexation by lab synthesized amphiphilic (alpha-aminoalkyl)-phosphonocarboxylic or -phosphonic acids. The electrical conductivity of aqueous solutions of sodium salts of all these acids was measured versus the volume of a calcium salt solution added. It appeared that calcium complexes are formed in a Ca/P atomic ratio close to 1. Calcium phosphonocarboxylates and calcium phosphonates were also precipitated by mixing aqueous solutions of disodium salts of phosphorus amphiphiles and calcium nitrate solutions. Before chemical analysis, these complexes were calcined to remove the organic part. In the mineralized products, calcium and phosphate were assayed: the Ca/P atomic ratio was equal to 1. X-ray diffraction and IR spectroscopy showed that they are made entirely of beta pyrophosphate (Ca2P2O7), a result in agreement with previous chemical analysis. The chemical formula of the starting calcium complexes could be written as CaL2H2O (L=ligand). The SEM micrographs of these complexes show plate-like structures. XRD patterns are characteristic of layered structures. These facts suggest that calcium complexes are composed of alternating bimolecular layers of calcium alkylphosphonocarboxylates or calcium alkylphosphonates, the chains being tilted and partially interdigitated.

Journal Article↗
PubMed2005

Dendritic catanionic assemblies: in vitro anti-HIV activity of phosphorus-containing dendrimers bearing galbeta1cer analogues.

Two series of water-soluble dendritic catanionic assemblies, acting as multisite analogues of galactosylceramide (Galbeta1cer), have been prepared with the goal of blocking HIV infection prior to the entry of the virus into human cells. Trifunctional and hexafunctional cinnamic acid-terminated dendrimers have been synthesized from phosphorus-containing dendrimers bearing aldehyde end groups. A classical acid-base reaction performed in water between acid-terminated dendrimers and stoichiometric amounts of N-hexadecylamino-1-deoxylactitol provided the expected catanionic assemblies. Antiviral assays on these supramolecular entities confirmed the crucial roles both of multivalency effects and of lipophilicity on the biological activity of Galbeta1cer analogues. Moreover, correlation between in vitro tests and molecular modeling highlights the specific influence of the assembly shape on the anti-HIV efficiency, with the tri- and hexafunctional cored dendrimers, both decorated with 12 sugar moieties, exhibiting IC50 values of 1.1 and 0.12 microM, respectively.

Anti-HIV Agents↗
PubMed2004

Polynorbornene polycationic polymers as gene transfer agents. Influence of the counterion for in vitro transfection.

Polycationic derivatives of polynorbornene with different non-cytotoxic counterions, have been prepared by organometallic polymerization of methyleneammonium norbornene and subsequent exchange of the counterion. In this paper the effect of the counterion on the polycationic polymer binding onto plasmid DNA was studied via different ethidium bromide assays, heparin displacement and protection against degradation by DNAse. According to the nature of the counterions and consequently the size of the polymer particles, their complexation with the DNA led to aggregates with variable binding affinity for the plasmid. The relative transfection efficiency of each polyplex was compared, on the basis of reporter gene expression, in cells in culture. The nature of the counterion was seen to affect gene delivery. The order of transfection efficiency of the counterions studied at equivalent charge ratios (NH3+/PO4-) is lactobionate, acetate, chloride. The results obtained with the polynorbornene methyleneammonium lactobionate and acetate are particularly encouraging.

Action Potentials↗
PubMed2004

Langmuir films of (alpha-amino) phosphorus amphiphiles on various ion-containing subphases.

Monolayers of amphiphilic (alpha-amino)phosphonocarboxylic and (alpha-amino)phosphonic acids have been formed by adsorption at the air/water interface. The influence of both the ionic strength and the pH of the subphase on the stability and compactness of the monolayers have been studied. The stability and the compactness of the Langmuir films are enhanced by introduction of metallic ions such as Ca(2+) or Mg(2+) in the subphases. These effects are more pronounced with Ca(2+). These metal ions can form dimeric complexes with the phosphorus moieties of the surfactant polar heads and therefore bring the amphiphiles closer. For the less hydrophobic derivative, complexation with Ca(2+) or Mg(2+) is required to ensure the formation of a stable monomolecular film. For both phosphonocarboxylic and phosphonic compounds, models have been proposed to represent the complexation phenomenon at the air/water interface.

Journal Article↗
PubMed2003

Crystal structure of the dimeric beta-cyclodextrin complex with 1,12-dodecanediol.

The structure of the complex of beta-cyclodextrin (beta-CD) with 1,12-dodecanediol has been determined at 173 K and refined to a final R=0.0615 based on 22,386 independent reflections. The complex crystallizes in the triclinic space group P1; with a=17.926(4), b=15.399(3), c=15.416(3) A, alpha=103.425(4), beta=113.404(4), gamma=98.858(4) degrees, D(c)=1.362 Mg cm(-3) and V=3651.4(13) A(3) for Z=1. One molecule of the diol is located as a guest in the hydrophobic cavity of a beta-CD-dimer, forming a [3]pseudorotaxane. The guest molecule shows a disorder over two positions. The hydroxyl groups of the diol emerge from the primary faces of the beta-CD dimer and form several hydrogen bonds with water molecules lying in the interstitial space, similarly to dimeric complexes of beta-CD with other alpha,omega-bifunctional guests.

Alcohols↗
PubMedDate not supplied

Photochemical behavior of a new long-chain UV absorber derived from 4-tert-butyl-4'-methoxydibenzoylmethane.

A new UV filter, the 1-(4-tert-butylphenyl)-2-decanyl-3-(4'-methoxyphenyl)-propane-1,3-dione, called C10-DBM, was prepared by grafting a 10-carbon aliphatic chain to the alpha-carbonyl position of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM), a well-known and often used UV filter. The UV-A absorption efficiency of organic solutions containing the new filter was tested and compared with identical solutions containing BM-DBM with or without irradiation (xenon lamp). The originality of this new filter is that its UV-A absorbance appeared during irradiation of the molecule. Although the molar absorption coefficient of C10-DBM in the UV-A domain was lower than that of BM-DBM, the solutions absorption exhibited a much more photostable behavior under irradiation. In this study, we first demonstrated that C10-DBM was a precursor of BM-DBM (enol isomer) by means of high-performance liquid chromatography followed by mass spectrometry. Indeed, we showed that the UV-A absorption of C10-DBM solutions appearing during the irradiation of the molecule was due to a Norrish-II reaction (beta-cleavage), which induced the release of the BM-DBM enol form and 1-decene. Then, we established a kinetic model for the photochemistry of C10-DBM and fitted the variation of UV absorption spectra to confirm the proposed mechanism.

Journal Article↗