From soft to hard rod behavior in liquid crystalline suspensions of sterically stabilized colloidal filamentous particles.

The liquid crystalline phase behavior of a colloidal system of sterically stabilized rods is reported. Our colloidal suspensions consist of highly monodisperse, semi-flexible filamentous viruses which have been coated with neutral hydrophilic polymers by irreversibly binding poly(ethylene glycol) (PEG) to the surface of the virus particles. Depending on the size of the grafted polymer, up to three different phase transitions are observed (isotropic-to-chiral nematic, chiral nematic-to-smectic, and smectic-to-columnar).

Ring-closing metathesis and glycosylation reactions: synthesis and biophysical studies of polyether-linked carbohydrate-based macrocyclic nucleosides.

Bis-, tris-, and tetrakisuracil-substituted 12-, 13-, 17-, and 21-membered macrocyclic nucleoside analogues with polyether linkages, including C2-symmetric molecules, have been synthesized through coupling of two appropriately allylated sugar derivatives, derived from D-glucose, followed by a sequential ring-closing metathesis reaction using Grubbs catalysts, double-bond reduction, and nucleoside base insertion under Vorbrüggen reaction conditions. Spectroscopic studies on the interaction of these nucleoside analogues with small molecules, such as the alkaloids berberine and palmatine and the DNA intercalator ethidium bromide, revealed a change in the absorbance and fluorescence of the small molecules suggesting the potential use of these nucleoside molecules as a carrier of small molecules in biological systems. Circular dichroism studies indicated that the complexes of the nucleosides with small molecules undergo aggregation/self-organization.