Francisco Mendicuti

Intramolecular excimer formation in model compounds for polyesters prepared from 2,6-naphthalene dicarboxylic acid and eight different glycols

Abstract Fluorescence has been measured in dilute solutions of model compounds for polymers of 2,6-naphthalene dicarboxylic acid and eight different glycols. The glycols are HO-(CH 2 ) i -OH, i = 2–6, and H-(OCH 2 CH 2 ) j -OH, j = 1–4. The ratio of excimer to monomer emission depends on the glycol used. Studies as functions of temperature and solvent show that, in contrast with the analogous polyesters in which the naphthalene moiety is replaced with a benzene ring, there can be a substantial dynamic component to the excimer emission. Extrapolation to media of infinite viscosity shows that in the absence of rotational isomerism during the lifetime of the singlet excited state, there is an odd-even effect in the series in which the flexible spacers differ in the number of methylene units, but not in the series in which the flexible spacers differ in the number of oxyethylene units.

A New Class of Pyrazolopyridine Nucleus with Fluorescent Properties, Obtained through Either a Radical or a Pd Arylation Pathway from N-Azinylpyridinium N-Aminides

The synthesis of dipyridopyrazole and pyridopyrazolopyrazine derivatives--both of which incorporate a 3-aryl moiety--can be achieved in moderate yields by intramolecular radical arylation of pyridinium N-aminides using tris(trimethylsilyl)silane and azobisisobutyronitrile. Improved results were obtained on using Pd direct arylation in conjunction with microwave irradiation. A preliminary study into the fluorescent properties of the target compounds is also reported.

Host-Guest-Mediated DNA Templation of Polycationic Supramolecules for Hierarchical Nanocondensation and the Delivery of Gene Material.

Only a few examples of monodisperse molecular entities that can compact exogenous nucleic acids into nanocomplexes, protect the cargo from the biological environment, facilitate cell internalization, and promote safe transfection have been reported up to date. Although these species open new venues for fundamental studies on the structural requirements that govern the intervening processes and their application in nonviral gene-vector design, the synthesis of these moieties generally requires a relatively sophisticated chemistry, which hampers further development in gene therapy. Herein, we report an original strategy for the reversible complexation and delivery of DNA based on the supramolecular preorganization of a β-cyclodextrin-scaffolded polycationic cluster facilitated by bisadamantane guests. The resulting gemini-type, dual-cluster supramolecules can then undergo DNA-templated self-assembly at neutral pH value by bridging parallel DNA oligonucleotide fragments. This hierarchical DNA condensation mechanism affords transfectious nanoparticles with buffering capabilities, thus facilitating endosomal escape following cell internalization. Protonation also destabilizes the supramolecular dimers and consequently the whole supramolecular edifice, thus assisting DNA release. Our advanced hypotheses are supported by isothermal titration calorimetry, NMR and circular dichroism spectroscopic analysis, gel electrophoresis, dynamic light scattering, TEM, molecular mechanics, molecular dynamics, and transfection studies conducted in vitro and in vivo.

Donor-(π-bridge)-azinium as D-π-A+ one-dimensional and D-π-A+-π-D multidimensional V-shaped chromophores

Heteroaromatic cations reacted with N-heteroarylacetylenes under Sonogashira conditions to allow easy access to potential single donor D-π-A(+) and V-shaped D-π-A(+)-π-D chromophores, where the acceptor moiety A is the π-deficient pyridinium cation and the donor moiety is represented by different π-excessive N-heterocycles. The β hyperpolarizabilities were measured using hyper-Rayleigh scattering experiments and the experimental data are supported by a theoretical analysis that combines a variety of computational procedures, including Density Functional Theory (DFT) and correlated Hartree-Fock-based methods (RCIS(D)).

Dynamic Self-Assembly of Polycationic Clusters Based on Cyclodextrins for pH-Sensitive DNA Nanocondensation and Delivery by Component Design

The ability of cyclodextrin-based polycationic cluster to undergo reversible DNA condensation and release in a physiologically useful pH window has been finely tuned by the installation of a capping xylylene moiety at the secondary face of the cyclooligosaccharide. This strategy can be exploited advantageously in the design of self-assembling nonviral gene-delivery systems from molecular entities.

Excimers in dilute solutions of N-vinyl carbazole/styrene copolymers of different molar compositions

Steady-state fluorescence for dilute solutions of poly(N-vinyl carbazole) and N-vinyl carbazole/styrene copolymers of different molar monomer compositions upon excitation of carbazole groups were performed. IE/IM ratios depend on solvent nature, emission wavelength and copolymer composition. Molecular dynamics simulations on pure isotactic and sindiotactic fragments of different monomer compositions were used for identifying the amount and the conformations capable of forming intramolecular excimers. The analysis of theoretical results interprets the variation of the amount of intramolecular excimer with the molar monomer content. Types of complexes by total or partial overlapping between adjacent and non-adjacent carbazole chromophores were also distinguished. q 2002 Elsevier Science Ltd. All rights reserved.

Thermodynamics of the Dimer Formation of 2I,3I-O-(o-Xylylene)-per-O-Me-γ-cyclodextrin: Fluorescence, Molecular Mechanics and Molecular Dynamics

The thermodynamics of the dimer formation of 2I,3I-O-(o-xylylene)-per-O-Me-γ-cyclodextrin (XmγCD) in aqueous solution was studied by fluorescence techniques, Molecular Mechanics and Molecular Dynamics. Lifetime averages

Suppression of the influence of stray light on quantitative measurement of ID/IM for weakly emitting dilute solutions of polymers

\left\langle \tau \right\rangle