Validation and application of an LC-ESI-MS method for simultaneous determination of astilbin and its major metabolite 3'-O-methylastilbin in rat plasma.

We herein describe the development of an LC-MS method for simultaneous determination of astilbin and 3'-O-methylastilbin in rat plasma. A simple liquid-liquid extraction procedure was followed by injection of the extracts on to a Shim-pack C(18) column (150 mm x 2.0 mm I.

[Advances in study of novel absorption enhancers based on tight junctions].

Hydrophilic low molecular drugs, peptides and proteins, which are always poor in bioavailability, are mainly absorbed through the paracellular way in which the tight junction is the elementary framework. The tight junctions are a multiple unit structure composed of multiprotein complex that affiliates with the underlying apical actomyosin ring. Tight junction proteins are identified including transmembrane proteins (occludin, claudin and JAM) , cytoplasmic plaque proteins (ZO-1, ZO-2, ZO-3 and cingulin) and cytoskeleton.

Quantum size effect on adatom surface diffusion.

Using scanning tunneling microscopy, we demonstrate that the nucleation density of Fe islands on the surface of nanoscale Pb films oscillates with the film thickness, providing a direct manifestation of the quantum size effect on surface diffusion. The Fe adatom diffusion barriers were derived to be 204+/-5 and 187+/-5 meV on a 21 and 26 monolayer (ML) Pb film, respectively, by matching the kinetic Monte Carlo simulations to the experimental island densities. The effect is further illustrated by the growth of Fe islands on wedged Pb films, where the Fe island density is consistently higher on the odd-layer films than on the even-layer films in the thickness range of 11 to 15 ML.