Trehalose-based Janus cyclooligosaccharides: the "Click" synthesis and DNA-directed assembly into pH-sensitive transfectious nanoparticles.

The convergent preparation of Janus molecular nanoparticles by thiourea-"clicking" of α,α'-trehalose halves has been implemented; the strategy allows access to macrocyclic derivatives with seggregated cationic and lipophilic domains that in the presence of DNA undergo pH-dependent self-assembly into lamellar superstructures, as established by electrochemical, structural (SAXS), microscopical (TEM) and computational techniques, that mediate transfection in vitro and in vivo.

Intramolecular energy transfer in compounds with two 1-pyrenoate groups separated by methylene spacers.

Steady-state fluorescence anisotropy (r) and fluorescence lifetime (τ) measurements have been used to study the efficiency of nonradiative singlet energy transfer as a function of alkane size in 1-pyrenecarboxylic acid alkanediyl esters (as a function ofm in Py-COO-(CH2) m -OOC-Py, where Py denotes pyrene substituted in the 1-position, andm=2-6). Experiments were performed in media of different viscosity, η, obtained by changing the temperature (from -20 to 40°C) of dilute solutions in ethylene glycol and by examination of the compounds in a solid matrix of poly(methyl methacrylate) (PMMA) at ambient temperature. The Py-COO-(CH2)m-OOC-Py exhibit intramolecular excimer emission in ethylene glycol at these temperatures, but the intensity of this emission is much lower than when these compounds are placed in common solvents of lower η. The values of τ indicate that excitation hopping or intramolecular energy transfer takes place between the chromophores attached to the ends of the alkane bridges. Values ofr obtained by the extrapolationsT/η→0 orτT/η→0 in ethylene glycol, as well as the values obtained in the rigid matrix of PMMA, show very little dependence onm. A theoretical conformational analysis, using the rotational isomeric state (RIS) model, was also performed. The combination of the experimental results forr in the media of high η with the theoretical (RIS) analysis produces an estimated value of 21 ±2 Å for the Förster radius in Py-COO-(CH2)m-OOC-Py.

Molecular Mechanics Study of the Inclusion Complexes of 2-Methyl Naphthoate with alpha- and beta-Cyclodextrins

Molecular mechanics calculations were employed to study the inclusion of 2-methyl naphthoate in alpha- and beta-cyclodextrin in vacuo and in the presence of water as a solvent. The driving forces for complexation are dominated by nonbonded van der Waals host:guest interactions in both environments. The 2-methyl naphthoate penetrates completely into the cavity of beta-cyclodextrin, but there is only partial penetration by the same molecule into the smaller cavity of alpha-cyclodextrin. Copyright 1997Academic Press