Biomedical subjects

E Grelet

Publications and source records attributed to E Grelet.

5 recordsLinked to original sources

PubMed2006

Extension of the resonant scattering technique to liquid crystals without resonant element.

We report X-ray resonant scattering experiments performed on the prototype liquid-crystalline compound MHPOBC doped with a chemical probe containing a resonant atom (selenium). We determined directly for the first time the microscopic 3- and 4-layer structure of the ferrielectric subphases (SmC(FI1)* and SmC(FI2)*) present in MHPOBC. Despite the low fraction of the selenium probe, the resonant signal is strong enough to allow an unambiguous determination of the basic structure of the ferrielectric subphases. These experiments demonstrate that the resonant scattering technique can be extended to liquid crystalline materials without resonant element and may stimulate new studies. A non-resonant Bragg reflection was also found in the SmC(FI1)* phase in pure MHPOBC, consistent with the 3-layer distorted model, but never detected before.

Ferric Compounds↗

PubMed2003

Human Kv1.6 current displays a C-type-like inactivation when re-expressed in cos-7 cells.

The human Kv1.6K(+) channel was functionally re-expressed in COS-7 cells at different levels. Voltage-activated K(+) currents are recorded upon cell membrane depolarization independently of the level of Kv1.6 expression. The current acquires a fast inactivation when Kv1.6 expression is increased. Inactivation was not affected by divalent cations or by extracellular tetraethylammonium. We have characterized the inactivation properties in biophysical terms. The fraction of inactivated current and the kinetics of inactivation are increased as the cell becomes more depolarized. Inactivated current can be reactivated according to a bi-exponential function of time. Additional experiments indicate that Kv1.6 inactivation properties are close to those of a conventional C-type inactivation. This work suggests that the concentration of Kv1.6 channel in the cell membrane strongly modulates the kinetic properties of Kv1.6-induced K(+) current. The physiological implications of these modifications are discussed.

Adaptation, Physiological↗

PubMed2001

Influence of the molecular tilt on the structure of smectic blue phases.

Smectic blue phases (BP(sm)) are original physical systems of thermotropic liquid crystals, displaying a double geometrical frustration: the extension of chirality in the three spatial dimensions, such as classical blue phases, and the competition between smectic order and helical twist, such as twist grain boundary (TGB) phases. We report experimental evidence of the influence of the underlying TGB((A) or (C)) phase on the BP(sm) structure.

Journal Article↗

PubMed2001

Structural investigations on smectic blue phases.

Smectic blue phases ( BP(Sm)) are thermotropic liquid crystalline phases which exhibit both three-dimensional orientational order, such as classical blue phases, and smectic positional order. BP(Sm) appear as the three-dimensional counterpart of twist grain boundary phases. X-ray scattering and optical polarizing microscopy provide information on the hexagonal and cubic symmetries of these new phases.

Journal Article↗

PubMed2000

Hexagonal symmetry for smectic blue phases

Smectic blue phases are liquid crystalline phases which exhibit both three-dimensional-orientational order and smectic positional order. X-ray scattering experiments reveal that at least one of these phases is not cubic, as classical blue phases, but offers a hexagonal symmetry. A comparison of the experimental patterns with the scattering patterns given by smectic double twist tubes sketched by Kamien is proposed.

Journal Article↗