Micelles of lipid-oligonucleotide conjugates: implications for membrane anchoring and base pairing

This report examines the organization properties of new fluorescent DNA-lipids, either alone in water or in interaction with 1-octyl-beta-d-glucopyranoside micelles or egg phosphatidylcholine vesicles. We first describe the design and the syntheses of the conjugates. Then, we use UV-Vis absorption, steady-state fluorescence emission, electron microscopy, and fluorescence correlation spectroscopy after two-photon excitation to show that these DNA-lipids form spherical micelles in aqueous solution and incorporate much better in micelles than in vesicles. We also investigate the significance of the lipophilic chains of these DNA-lipids on the melting behavior of the double-stranded hybrids: in water melting curves are broadened whereas in amphiphilic assemblies duplexes melt as the unconjugated controls. This work is expected to be useful for improving the rational design of antisense medicines.     

Synthesis and properties of water-soluble gold colloids covalently derivatized with neutral polymer monolayers

Citrate-capped gold nanoparticles as well as planar gold surfaces can be efficiently grafted with a covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surface with dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shown by UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies. The hydrophilic polymer-coated gold colloids can be freeze-dried and stored as powders that can be subsequently dissolved to yield stable aqueous dispersions, even at very large concentrations. They allow for applying filtrations, gel permeation chromatography, or centrifugation. They do not suffer from undesirable nonspecific adsorption of proteins while allowing the diffusion of small species within the hydrogel surface coating. In addition, specific properties of the original hydrophilic polymers are retained such as a lower critical solution temperature. The latter feature could be useful to enhance optical responses of functionalized gold surfaces toward interaction with various substrates.     

Coumarinylmethyl Caging Groups with Redshifted Absorption

The small and synthetically easily accessible coumarinylmethyl backbone has been modified to generate a family of photolabile protecting groups with redshifted absorption. We relied on introducing electron‐donating groups in the 7 position and electron‐withdrawing groups in the 2‐, and 2‐ and 3 positions. In particular, we showed that the diethylamino‐thiocoumarylmethyl and the diethylamino‐coumarylidenemalononitrilemethyl are relevant for uncaging with cyan light. They both exhibit a significant action cross section for uncaging in the 470–500 nm wavelength range and a low light absorption between 350 and 400 nm. These attractive features are favorable to perform chromatic orthogonal photoactivation with UV and blue‐cyan light sources, respectively.     

Tetrahedral onsager crosses for solubility improvement and crystallization bypass

Pure organic molecules exhibiting a suitable concave rigid shape are expected to give porous glasses in the solid state. Such a feature opens new opportunities to avoid crystallization and to improve molecular solubility in relation to the high internal energy of these solid phases. To quantitatively explore the latter strategy, a series of rigid tetrahedral conjugated molecules nC and the corresponding models nR have been synthesized. Related to the present purpose, several properties have been investigated using UV absorption, steady-state fluorescence emission, differential scanning calorimetry, (1)H NMR translational self-diffusion, magic angle spinning (13)C NMR, and multiple-beam interferometry experiments. The present tetrahedral crosses are up to 8 orders of magnitude more soluble than the corresponding model compounds after normalization to the same molecular length. In addition, they give concentrated monomeric solutions that can be used to cover surfaces with homogeneous films whose thickness goes down to the nanometer range. Such attractive features make cross-like molecular architectures promising for many applications.     

Alcohol uncaging with fluorescence reporting: evaluation of o-acetoxyphenyl methyloxazolone precursors

This paper evaluates a series of photolabile protecting groups with built-in fluorescence reporting. They rely on readily available o-acetoxyphenyl methyloxazolones as activated precursors. Alcohol substrates are easily caged. The resulting photoactivable esters exhibit large one- and two-photon uncaging cross sections. The alcohol substrates are quantitatively released in a 1:1 molar ratio with a strongly fluorescent coumarin coproduct that serves as a reporter to quantify substrate delivery.     

Controlled assembly of covalent and supramolecular chemical modules: from engineering of complex structures to high-performance chromatography

A biological approach to generating complex behaviors in chemistry is described. It is suggested theoretically that the assembly of modules composed of chemical reactions or molecular structures under appropriate external constraints can lead to features typical of the biological world like autocatalysis, kinetic proofreading, or oriented molecular motion. This approach may account for the primitive steps of molecular evolution and, in addition, it can find useful applications in chemistry such as high-performance chromatography.     

"Self-immolative" spacer for uncaging with fluorescence reporting

Dual photoliberation: A caged, branched, self-immolative spacer (see scheme, gray box) was designed to rapidly and simultaneously release a desired compound (green) and a fluorophore?(red) upon photoactivation. Careful kinetic analysis of the disassembly of the spacer shows that it occurs on the shortest time scale reported to date.     

AB5 Derivatives of Cyclotriphosphazene for the Synthesis of Dendrons and Their Applications

AB₅ compounds issued from the reactivity of hexachlorocyclotriphosphazene are relatively easy to obtain using two ways: either first the reaction of one chloride with one reagent, followed by the reaction of the five remaining Cl with another reagent, or first the reaction of five chlorides with one reagent, followed by the reaction of the single remaining Cl with another reagent. This particular property led to the use of such compounds as core for the synthesis of dendrons (dendritic wedges), using the five functions for growing the dendritic branches. The single function can be used for the synthesis of diverse types of dendrimers (onion peel, dumbbell-shape, Janus), for covalent or non-covalent grafting to solid surfaces, providing nanomaterials, for grafting a fluorophore, especially for studying biological mechanisms, or for self-associations to get micelles. All these properties are reviewed in this paper.