Solid-phase-assisted synthesis of targeting peptide-PEG-oligo(ethane amino)amides for receptor-mediated gene delivery.

In the forthcoming era of cancer gene therapy, efforts will be devoted to the development of new efficient and non-toxic gene delivery vectors. In this regard, the use of Fmoc/Boc-protected oligo(ethane amino)acids as building blocks for solid-phase-supported assembly represents a novel promising approach towards fully controlled syntheses of effective gene vectors. Here we report on the synthesis of defined polymers containing the following: (i) a plasmid DNA (pDNA) binding domain of eight succinoyl-tetraethylenpentamine (Stp) units and two terminal cysteine residues; (ii) a central polyethylene glycol (PEG) chain (with twenty-four oxyethylene units) for shielding; and (iii) specific peptides for targeting towards cancer cells. Peptides B6 and c(RGDfK), which bind transferrin receptor and αvβ3 integrin, respectively, were chosen because of the high expression of these receptors in many tumoral cells. This study shows the feasibility of designing these kinds of fully controlled vectors and their success for targeted pDNA-based gene transfer

The role of antiphase boundaries during ion sputtering and solid phase epitaxy of Si(001)

The Si(001) surface morphology during ion sputtering at elevated temperatures and solid phase epitaxy following ion sputtering at room temperature has been investigated using scanning tunneling microscopy. Two types of antiphase boundaries form on Si(001) surfaces during ion sputtering and solid phase epitaxy. One type of antiphase boundary, the AP2 antiphase boundary, contributes to the surface roughening. AP2 antiphase boundaries are stable up to 973K, and ion sputtering and solid phase epitaxy performed at 973K result in atomically flat Si(001) surfaces.Comment: 16 pages, 4 figures, to be published in Surface Scienc

Hydrodynamic and solid residence time distribution in a circulating fluidized bed: experimental and 3D computational study

Vertical profiles of local pressure, horizontal profiles of net vertical solid mass flux, and residence time distributions (RTD) of the solid phase are experimentally assessed in the riser of a small scale cold Circulating Fluidized Bed of 9 m high having a square cross section of 1111 cm. Air (density 1.2 kg/m3, dynamic viscosity 1.8×10-5 Pa.s) and typical FCC particles (density 1400 kg/m3, mean diameter 70 mm) are used. The superficial gas velocity is kept constant at 7 m/s while the solid mass flux ranges from 46 to 133 kg/m2/s. The axial dispersion of the solid phase is found to decrease when increasing the solid mass flux. Simultaneously, 3D transient CFD simulations are performed to conclude on the usability of the eulerian-eulerian approach for the prediction of the solid phase mixing in the riser. The numerical investigation of the solid mixing is deferred until later since the near-wall region where the solid phase downflow and mixing are predominant is not well predicted in spite of well-predicted vertical profiles of pressure

Superconducting transition of a two-dimensional Josephson junction array in weak magnetic fields

The superconducting transition of a two-dimensional (2D) Josephson junction array exposed to weak magnetic fields has been studied experimentally. Resistance measurements reveal a superconducting-resistive phase boundary in serious disagreement with the theoretical and numerical expectations. Critical scaling analyses of the $IV$ characteristics indicate contrary to the expectations that the superconducting-to-resistive transition in weak magnetic fields is associated with a melting transition of magnetic-field-induced vortices directly from a pinned-solid phase to a liquid phase. The expected depinning transition of vortices from a pinned-solid phase to an intermediate floating-solid phase was not observed. We discuss effects of the disorder-induced random pinning potential on phase transitions of vortices in a 2D Josephson junction array.Comment: 9 pages, 7 figures (EPS+JPG format), RevTeX

Real-time monitoring of solid-phase peptide synthesis using a variable bed flow reactor

On-resin aggregation and incomplete amide bond formation are major challenges for solid-phase peptide synthesis that are difficult to be monitored in real-time. Incorporation of a pressure-based variable bed flow reactor into an automated solid-phase peptide synthesizer permitted real-time monitoring of resin swelling to determine amino acid coupling efficiency and on-resin aggregation

Cross Metathesis Assisted Solid-Phase Synthesis of Glycopeptoids

A solid-phase synthesis of glycopeptoids was explored through olefin cross metathesis (CM). Peptoids and sugar derivatives with appropriate olefin moieties were coupled in the presence of an olefin metathesis catalyst to afford glycopeptoids in good yields. This systematic solid-phase CM study can provide facile access to the molecular sources of glycopeptidomimetics and postchemical modifications on various molecular scaffolds

Novel Fmoc-Polyamino Acids for Solid-Phase Synthesis of Defined Polyamidoamines

A versatile solid-phase approach to sequence-defined polyamidoamines was developed. Four different Fmoc-polyamino acid building blocks were synthesized by selective protection of symmetrical oligoethylenimine precursors followed by introduction of a carboxylic acid handle using cyclic anhydrides and subsequent Fmoc-protection. The novel Fmoc-polyamino acids were used to construct polyamidoamines demonstrating complete compatibility to standard Fmoc reaction conditions. The straightforward synthesis of the building blocks and the high efficiency of the solid-phase coupling reactions allow the versatile synthesis of defined polycations

Charged Particles on Surfaces: Coexistence of Dilute Phases and Periodic Structures on Membranes

We consider a mixture of one neutral and two oppositely charged types of molecules confined to a surface. Using analytical techniques and molecular dynamics simulations, we construct the phase diagram of the system and exhibit the coexistence between a patterned solid phase and a charge-dilute phase. The patterns in the solid phase arise from competition between short-range immiscibility and long-range electrostatic attractions between the charged species. The coexistence between phases leads to observations of stable patterned domains immersed in a neutral matrix background.Comment: 5 pages, 3 figure