Biomedical subjects

Sophie Brasselet

Publications and source records attributed to Sophie Brasselet.

6 recordsLinked to original sources

PubMed2006

Electro-optical microscopy: mapping nonlinear polymer films with micrometric resolution.

The first demonstration, to the best of our knowledge, of electro-optical microscopy is presented and applied to a polymer-based optical device. A confocal transmission microscope with interferometric homodyne detection is implemented to measure Pockels phase shifts with micrometric spatial resolution and an accuracy level down to 4 x 10(-7) rad. This technique is applied to poled polymer films in which noncentrosymmetric molecular orientation is preliminarily achieved in the sample plane between transverse planar electrodes. The electro-optic mapping of this structure exhibits nonuniform and asymmetric patterns of the nonlinear response that are characteristic of the poling spatial inhomogeneity as confirmed by second-harmonic generation microscopy.

Journal Article↗

PubMed2004

All-optical orientation of photoisomerizable octupolar zinc(II) complexes in polymer films.

A new type of 4,4'-bis(styryl)-2,2'-bipyridine functionalized by a dialkylamino-azobenzene group has been prepared. This ligand has allowed the preparation of photoisomerizable octupolar tris(bipyridyl)zinc(II) complexes and the corresponding star-shaped polymer by atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). The photoisomerization properties of such new metallo-chromophores have been studied. The macroscopic molecular orientation of the corresponding doped and grafted NLO-polymer films is reported for the first time.

Journal Article↗

PubMed2004

Coherent control of the optical nonlinear and luminescence anisotropies in molecular thin films by multiphoton excitations.

Photoinduced orientational distributions are implemented with one- and two-photon absorption interference in polymer films containing chromophores that exhibit luminescent and nonlinear properties. The odd- and even-order parameters of the final distribution are probed by simultaneous measurement of second-harmonic generation (SHG) and two-photon fluorescence (TPF). We show the possibility of engineering local SHG and TPF anisotropies by controlling the polarization states and intensities of the writing optical fields. Complex multipolar orders are modeled with an irreducible spherical tensor-based formalism jointly applied to the molecular polarizabilities and field tensors.

Journal Article↗

PubMed2004

In situ diagnostics of the crystalline nature of single organic nanocrystals by nonlinear microscopy.

We elucidate the crystalline nature and the three-dimensional orientation of isolated organic nanocrystals embedded in a sol-gel matrix, using a polarized nonlinear microscopy technique that combines two-photon fluorescence and second harmonic generation. This technique allows the distinction between monocrystalline structures and nanoscale polycrystalline aggregates responsible for incoherent second harmonic signals.

Acetonitriles↗

PubMed2004

Enhanced second-harmonic generation by metal surfaces with nanoscale roughness: nanoscale dephasing, depolarization, and correlations.

On the basis of spectral-expansion Green's function theory, we theoretically describe the topography, polarization, and spatial-coherence properties of the second-harmonic (SH) local fields at rough metal surfaces. The spatial distributions of the fundamental frequency and SH local fields are very different, with highly enhanced hot spots of the SH. The spatial correlation functions of the amplitude, phase, and direction of the SH polarization all show spatial decay on the nanoscale in the wide range of the metal fill factors. This implies that SH radiation collected from even nanometer-scale areas is strongly depolarized and dephased, i.e., has the nature of hyper-Rayleigh scattering, in agreement with recent experiments. The present theory is applicable to nanometer-scale nonlinear-optical illumination, probing, and modification.

Journal Article↗

PubMed2002

Translational diffusion of individual class II MHC membrane proteins in cells.

Single-molecule epifluorescence microscopy was used to observe the translational motion of GPI-linked and native I-E(k) class II MHC membrane proteins in the plasma membrane of CHO cells. The purpose of the study was to look for deviations from Brownian diffusion that might arise from barriers to this motion. Detergent extraction had suggested that these proteins may be confined to lipid microdomains in the plasma membrane. The individual I-E(k) proteins were visualized with a Cy5-labeled peptide that binds to a specific extracytoplasmic site common to both proteins. Single-molecule trajectories were used to compute a radial distribution of displacements, yielding average diffusion coefficients equal to 0.22 (GPI-linked I-E(k)) and 0.18 microm(2)/s (native I-E(k)). The relative diffusion of pairs of proteins was also studied for intermolecular separations in the range 0.3-1.0 microm, to distinguish between free diffusion of a protein molecule and diffusion of proteins restricted to a rapidly diffusing small domain. Both analyses show that motion is predominantly Brownian. This study finds no strong evidence for significant confinement of either GPI-linked or native I-E(k) in the plasma membrane of CHO cells.

Actins↗