Cationic Graft Copolymers as Carriers for Delivery of Antisense‐Oligonucleotides

Self‐assembling systems based on ionic complexes of DNA fragments (36 base pairs), bcl‐2 antisense oligonucleotides (octadecamer), oligophosphates (25 phosphate groups) or acrylic oligomers (18 groups of phosphonic acid) with poly(L ‐lysine) (PLL) ( = 130 000 and 88 000) grafted with short poly[N‐(2‐hydroxypropyl)methacrylamide] (PHPMA) chains ( = 4 300 or 8 600) were studied by static and dynamic light scattering methods as systems suitable for gene therapy applications. The graft copolymers (GPLLs) with shorter PHPMA grafts ( = 4 300) provide polyelectrolyte complexes (PECs) with smaller and R_H than the corresponding GPLLs with longer grafts ( = 8 600) and the same content of PLL. The lowest aggregation number of 2 was observed for PECs prepared from the GPLL with short grafts and 40 wt.‐% of PLL. The complexes of oligonucleotides and DNA fragments with GPLLs showed quite similar behavior to that with oligophosphates and acrylic oligomer. The complexes prepared from GPLLs containing 40 wt.‐% of PLL and at excess of oligophosphate were stable for at least 48 h under physiological conditions (0.15 M NaCl) and in bovine serum albumin solutions (1 mg · mL^?1). Additionally, polyanion exchange reactions of the PECs in contact with poly(styrenesulfonate) and DNA were studied in 0.15 M NaCl solutions. The oligophosphates in complexes were at least partially substituted with high‐molecular‐weight polyanions. The structure of the initial PECs dominated the PEC structure after the exchange reaction.

The dependence of the molecular weight (a) and the hydrodynamic radius R_H (b) of complexes of the oligophosphate (OPP) and four graft copolymers (GPLLi, i = 0–3) on the mixing ratio X.     

Interaction of DNA/polycation complexes with phospholipids: stabilizing strategy for gene delivery

The interaction between negatively charged lipid vesicles and positively charged DNA/polylysine complexes was studied. The interaction does not lead to release of DNA from the initial complexes. The particles formed are easy to prepare, they have slight negative charge, small dimensions and show good stability in physiological NaCl solution. Such properties might indicate that stabilization of the particles by lipid coating might be a potent strategy, alternative to PEGylation of DNA/polycation complexes. Interaction of DNA/polycation complex particles with lipid vesicles.     

Oxygen and hydrogen profiles and electrical properties of unintentionally doped gallium nitride grown by hydride vapor phase epitaxy

Commercially available hydride vapor phase epitaxy gallium nitride (GaN) is characterized with the aim to correlate the oxygen and hydrogen secondary ion mass spectrometry profiles of a GaN wafer with the electrical properties of the sample. A GaN layer model, including doping profile and mobility, is derived, utilizing electrical (capacitance–voltage, Hall), structural (high resolution X‐ray diffraction) and optical (polarized infrared spectroscopy) methods. Oxygen and hydrogen are easily incorporated during hydride vapor phase epitaxy growth of GaN. Oxygen is an n‐type dopant in GaN, whereas hydrogen may passivate some of the donors. Electrical and optical properties correlate with a low defect concentration top GaN layer and a high defect concentration GaN interlayer.     

Large-scale semidefinite programming via a saddle point Mirror-Prox algorithm

In this paper, we first demonstrate that positive semidefiniteness of a large well-structured sparse symmetric matrix can be represented via positive semidefiniteness of a bunch of smaller matrices linked, in a linear fashion, to the matrix. We derive also the “dual counterpart” of the outlined representation, which expresses the possibility of positive semidefinite completion of a well-structured partially defined symmetric matrix in terms of positive semidefiniteness of a specific bunch of fully defined submatrices of the matrix. Using the representations, we then reformulate well-structured large-scale semidefinite problems into smooth convex–concave saddle point problems, which can be solved by a Prox-method developed in [6] with efficiency . Implementations and some numerical results for large-scale Lovász capacity and MAXCUT problems are finally presented.      

On verifiable sufficient conditions for sparse signal recovery via <Emphasis Type="Italic">ℓ</Emphasis><Subscript>1</Subscript> minimization

We discuss necessary and sufficient conditions for a sensing matrix to be “s-good”—to allow for exact ℓ ₁-recovery of sparse signals with s nonzero entries when no measurement noise is present. Then we express the error bounds for imperfect ℓ ₁-recovery (nonzero measurement noise, nearly s-sparse signal, near-optimal solution of the optimization problem yielding the ℓ ₁-recovery) in terms of the characteristics underlying these conditions. Further, we demonstrate (and this is the principal result of the paper) that these characteristics, although difficult to evaluate, lead to verifiable sufficient conditions for exact sparse ℓ ₁-recovery and to efficiently computable upper bounds on those s for which a given sensing matrix is s-good. We establish also instructive links between our approach and the basic concepts of the Compressed Sensing theory, like Restricted Isometry or Restricted Eigenvalue properties.     

Tubular conjugated polymer for chemosensory applications

In this paper, we present the concept of a soluble tubular conjugated polymer (TCP). We report on a fluorescent 5,5'-Bicalixarene-based polymer where the calixarene units are seamlessly incorporated in the conjugated polymeric chain that can respond to a small molecule complexation inside the hydrophobic cavity. In particular, our system demonstrated a reversible rapid fluorescence quenching upon interaction of gaseous nitric oxide with the calixarene moiety.     

Fluorescent Calixarene Scaffolds for NO Detection in Protic Media

We present the first fluorescent water‐soluble conjugated calixarene scaffolds that are capable of NO gas detection. Two different scaffolds, one based on a 5,5′‐bicalixarene structure and its isomer bearing two distantly conjugated calixarene moieties, were synthesized. While the fluorescence of both isomers is quenched upon either passing of NO gas or generating it in situ from diethylamine NONOate, the bicalixarene‐based scaffold showed a significantly stronger response. We also present an example of a dye encapsulation strategy to achieve the detection of NO at longer wavelengths than in the parent calixarene host. Finally, a conjugated polymer bearing a 5,5′‐bicalixarene scaffold has also been prepared and demonstrated enhanced sensitivity compared to the monomer due to the molecular wire effect.     

An automatic sampling device for capillary zone electrophoresis

An automatic sampling device has been developed for capillary zone electrophoresis. The sample is introduced to the column electrokinetically by rapidly exchanging buffer for sample in a narrow channel drilled in a plexiglass block. The autosampler is capable, under computer control, of performing multiple sample injections from a large volume sample source (such as a reaction vessel) as the sample concentration changes, and thus presents the possibility of analyzing time-varying processes by CZE. Peak area reproducibility in electropherograms obtained after use of the sampler is less than 1% and efficiency is more than 2.2 × 10⁵ theoretical plates.     

Metal-mediated formation of carbon-halogen bonds

Organic halides represent basic starting materials for numerous metal-catalyzed organic transformations. Generally, the carbon-halogen is broken in the first step, that is, an oxidative addition reaction, of the catalytic cycle. On the other hand, very little is known about the reverse reaction, carbon-halogen reductive elimination from a transition-metal center. In this Concept article, we describe the examples of C(sp(3))-halide and C(sp(2))-halide reductive-elimination reactions which demonstrate that this type of reactivity can be quite common in organometallic chemistry. Although the thermodynamic driving force for the formation of carbon-halogen bonds is relatively small, the kinetic barrier for these reactions can also be low. Thus, C-halide reductive elimination can compete favorably with the more established organic transformations, such as C-C reductive elimination.