First evaluation of acyloxymethyl or acylthiomethyl groups as biolabile 2'-O-protections of RNA

[reaction: see text] Short oligo-U sequences containing 2'-O-acyloxymethyl or acylthiomethyl groups as biolabile 2'-O-protections of RNA have been synthesized. These modified homouridylates are deprotected upon cellular esterase activation to release the parent RNA. They exhibit exceptional resistance to nuclease degradation, and the evaluation of their pairing properties shows that the 2'-acyloxymethyl groups do not prevent the duplex dsRNA formation. These biolabile 2'-modifications overcome the first hurdle to turn oligoribonucleotides into candidates for RNA interference drugs.     

Selective immunoclean-up followed by liquid chromatography for the monitoring of a biomarker of exposure to polycyclic aromatic hydrocarbons in urine at the ng l-1 level

A selective clean-up procedure using an immunosorbent (IS) was developed for the trace-level determination, in water and urine samples, of 3-benzo(a)pyrene-glucuronide (3-BP-G), a biomarker of exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs). First, three sorbents used for the immobilization of antibodies were evaluated for their ability to limit the risk of non-specific interactions and to provide a high bonding density. The best sorbent, i.e. sepharose, was used for the immobilization of two different monoclonal antibodies. The most specific antibody for 3-BP-G was applied to the selective extraction from urine providing a clean extract, an easy and reliable quantification by comparison with a classical SPE process. The sensitivity of the fluorescence associated with the selectivity of the IS provides a limit of detection up to 1.2 ng l(-1) in urine for 3-BP-G.     

Structural changes in poly(ethyleneimine) modified microemulsion

The influence of branched poly(ethyleneimine) on the phase behavior of the system sodium dodecylsulfate/toluene-pentanol (1:1)/water has been studied. The isotropic microemulsions still exist when water is replaced with aqueous solutions of PEI (up to 30% in weight), but their stability is significantly influenced. From a polymer concentration of 20 wt%, the polymer enhances the solubilization of water in oil, changes the sign of the spontaneous curvature of the surfactant film, and induces an inversion of the microemulsion type from water-in-oil (L(2)) to oil-in-water (L(1)), by the formation of a bicontinuous channel. Further investigations show that the addition of polymer in the L(2) phase changes the droplet-droplet interactions as the conductivity drops and the percolation disappears. In the bicontinuous channel, higher viscosities can be detected, as well as a weak percolation followed by a steep increase of the conductivity, which can be related to evident structural changes in the system. DSC measurements allow then to follow the changes of the water properties in the system, from interfacial-water in the L(2) phase to free-water in the sponge-like phase. Finally, all the measurements performed permit to characterize the structural transitions in the system and to understand the role of the added polymer.     

Fullerene Derivatives Functionalized with Diethylamino‐Substituted Conjugated Oligomers: Synthesis and Photoinduced Electron Transfer

Diethylamino‐substituted oligophenylenevinylene (OPV) building blocks have been prepared and used for the synthesis of two [60]fullerene–OPV dyads, F‐D1 and F‐D2 , which exhibit different conjugation length of the OPV fragments. The electrochemical properties of these acceptor–donor dyads have been studied by cyclic voltammetry. The first reduction is always assigned to the fullerene moiety and the first oxidation centered on the diethylaniline groups of the OPV rods, thus making these systems suitable candidates for photoinduced electron transfer. Both the OPV and the fullerene‐centered fluorescence bands are quenched in toluene and benzonitrile, which suggests the occurrence of photoinduced electron transfer from the amino‐substituted OPVs to the carbon sphere in the dyads in both solvents. By means of bimolecular quenching experiments, transient absorption spectral fingerprints of the radical cationic species are detected in the visible (670 nm) and near‐IR (1300–1500 nm) regions, along with the much weaker fullerene anion band at λ_max=1030 nm. Definitive evidence for photoinduced electron transfer in F‐D1 and F‐D2 comes from transient absorption measurements. A charge‐separated state is formed within 100 ps and decays in less than 5 ns.     

Combining phosphinidene units with malonate anion: Synthesis of highly functional phosphine complexes

Malonate anion traps the [RP-W(CO)₅] bridge of 7-phosphanorbornadiene complexes 1–3 to give functional secondary phosphine complexes [RP(H)-CH(CO₂Et)₂]W(CO)₅ ( 7–9 ). Metalation of these complexes by NaH in THF occurs at the malonic CH group, but the alkylation of the resulting carbanions preferentially takes place at phosphorus. When R stands for β-chloroethyl, the corresponding carbanion cyclizes to give the functional phosphirane complex 11 . © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:258–262, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20014