Non-viral transfection vectors: are hybrid materials the way forward?

Transfection is a process by which oligonucleotides (DNA or RNA) are delivered into living cells. This allows the synthesis of target proteins as well as their inhibition (gene silencing). However, oligonucleotides cannot cross the plasma membrane by themselves; therefore, efficient carriers are needed for successful gene delivery. Recombinant viruses are among the earliest described vectors. Unfortunately, they have severe drawbacks such as toxicity and immunogenicity. In this regard, the development of non-viral transfection vectors has attracted increasing interests, and has become an important field of research. In the first part of this review we start with a tutorial introduction into the biological backgrounds of gene transfection followed by the classical non-viral vectors (cationic organic carriers and inorganic nanoparticles). In the second part we highlight selected recent reports, which demonstrate that hybrid vectors that combine key features of classical carriers are a remarkable strategy to address the current challenges in gene delivery.

A new class of supramolecular ligands stabilizes 14-3-3 protein-protein interactions by up to two orders of magnitude.

We report the first supramolecular stabilizers of the interaction between 14-3-3ζ and two of its effectors, Tau and C-Raf, which are involved in neurodegenerative diseases and proliferative signal transduction, respectively. These supramolecular ligands open up an opportunity to modulate functions of 14-3-3 with these effectors.

Molecular recognition of carboxylates in the protein leucine zipper by a multivalent supramolecular ligand: residue-specific, sensitive and label-free probing by UV resonance Raman spectroscopy.

Ultraviolet resonance Raman (UVRR) spectroscopy is a selective, sensitive and label-free vibrational spectroscopic technique. Here, we demonstrate as proof of concept that UVRR can be used for probing the recognition between a multivalent supramolecular ligand and acidic residues in leucine zipper, an α-helical structural motif of many proteins.

Two-component self-assembly of a tetra-guanidiniocarbonyl pyrrole cation and Na4EDTA: formation of pH switchable supramolecular networks.

A guanidiniocarbonyl pyrrole (GCP) cation forms stable H-bond assisted ion pairs with carboxylates even in aqueous solutions. A tetra GCP cation 1 undergoes efficient two-component self-assembly with Na4EDTA, a tetra-carboxylate, leading to 3D supramolecular networks. These networks show dual pH responsiveness and reversibly dissociate back into monomers upon addition of either acid or base.

Transforming polyethylenimine into a pH-switchable hydrogel by additional supramolecular interactions.

Attaching a self-complementary zwitterionic supramolecular binding site to the amino groups of polyethyleneimine leads to a pH switchable hydrogel as dimerization of the zwitterions introduces additional crosslinks between the polymer chains. This gel responds to both the addition of either acid or base, as only the zwitterion can self-assemble but neither the protonated or deprotonated form.

Water soluble SERS labels comprising a SAM with dual spacers for controlled bioconjugation.

Self-assembled monolayers (SAMs) of Raman reporter molecules adsorbed to the surface of metal nanoparticles are labelling agents for the selective detection of biomolecules by surface-enhanced Raman scattering (SERS). Advantages of SAM-based SERS labels include maximum coverage with Raman reporter molecules combined with their uniform molecular orientation within the SAM as well as minimal co-adsorption of other molecules from the surrounding. Water solubility and stability together with the option for controlled bioconjugation are desired properties of SERS labels. We present an approach to synthesize hydrophilic SERS labels in which the colloidal particle is stabilized by two different ethylene glycols attached to the SAM. This guarantees water solubility, independent of the type of a particular Raman reporter molecule and its properties at the SAM/solvent interface. Our dual SAM design is based on two different ethylene glycol spacers covalently bound to the same type of reporter molecule: a short monoethylene glycol (MEG-OH) and a longer triethylene glycol (TEG-COOH) moiety. The terminal carboxy group of the TEG spacer allows subsequent conjugation to biomolecules such as antibodies. Controlled bioconjugation is possible by varying the stoichiometric ratio of both spacers. Finally, dual SAM SERS labels are used in immuno-SERS microscopy for selective imaging of prostate-specific antigen in the epithelium of biopsies from patients with prostate cancer.

Characterization of guanidiniocarbonyl pyrroles in water by pH-dependent UV Raman spectroscopy and component analysis.

Guanidiniocarbonyl pyrroles are artificial receptors for the efficient complexation of carboxylates even in polar solvents such as water. Their carboxylate binding site (CBS) exhibits an electronic absorption maximum at approximately 298 nm and can be probed selectively by ultraviolet resonance Raman (UV RR) scattering. We present a pH-dependent UV RR spectroscopic investigation of two guanidiniocarbonyl pyrroles in water: the model receptor CBS-NH2 and the peptide receptor CBS-Lys-Lys-Phe-NH2. UV RR spectra of 1 mM aqueous solutions with 275 nm laser excitation were recorded between pH 6 and 7. Within this small pH range near the pKa of 6.4, protonated and neutral CBS species are simultaneously present at similar concentrations (acid/base equilibrium). Using non-negative matrix factorization (NMF), the individual UV RR component spectra of these distinct CBS species were determined without any a priori knowledge. The pH-dependent UV RR spectra of the small model receptor CBS-NH2 and the larger peptide receptor CBS-Lys-Lys-Phe-NH2 can both be described as linear combinations of only two components. Control experiments at pH 2 and pH 10 show an excellent agreement with the derived NMF component spectra and confirm their assignment to the protonated and neutral CBS species, respectively.

A self-threaded "molecular 8".

A new type of [1]rotaxanes containing two aliphatic bridges between axle and wheel is obtained in 39% yield in a one-step synthesis starting from a [2]rotaxane which contained one sulfonamide group each in both the wheel and the axle. Temperature controlled chemoselective substitution reactions first at these sulfonamide nitrogens and then subsequently at the various other carboxamide nitrogens in the wheel and axle give rise to the formation of an isomeric mixture of three double-bridged [1]rotaxanes which could be separated by HPLC. Structure determination of the main product 3a was possible by NMR experiments supported by molecular modeling calculations. Using different reaction conditions, a double-substituted but not yet bridged [2]rotaxane 4 could be isolated as an intermediate giving further evidence for the assigned structure of 3a and the way of its formation. The shape of this double-bridged [1]rotaxane 3a reminds of a self-intertwining chiral "molecular 8", in which any possible racemization due to deslipping is hindered by the two stoppers originating from the former rotaxane axle. Hence, to the best of our knowledge this is the first example of a molecule in which both concepts, cycloenantiomerism and helical chirality, are realised in one structure. Enantiomer separation of the main product was possible by further HPLC using chiral stationary phases. The Cotton effects of the circular dichrograms are different to those of the already synthesized [1]rotaxanes bearing just one aliphatic bridge between axle and wheel.

Anion-dependent dimerization of a guanidiniocarbonyl pyrrole cation in DMSO.

With spherical counteranions such as chloride or hexafluorophosphate, the glycine-derived guanidiniocarbonyl pyrrole cation 1 self-assembles into discrete dimers in DMSO, as can be seen by NMR and ESI mass spectral analysis. According to concentration- and temperature-dependent NMR studies, the dimerization is endothermic and therefore entropy driven. Molecular modeling suggests that the dimers are held together by hydrogen bonding in combination with pi-pi interactions. In the presence of picrate anions, dimerization of cation 1 does not occur, probably due to the formation of pi-stacked ion pairs.

Self-folding molecules: a well defined, stable loop formed by a carboxylate-guanidinium zwitterion in DMSO

Two zwitterions 1a,b have been synthesized, in which a carboxylate group is attached via a flexible alkyl chain of different length (butylene and ethylene, respectively) to a guanidiniocarbonyl pyrrole cation moiety. For 1b, no signs for either an intra- or intermolecular association between these two groups in polar solution (DMSO) could be found. In contrast to this, the 1H NMR spectrum of 1a shows clear evidence for a strong interaction between the carboxylate and the guanidiniocarbonyl pyrrole cation. According to variable-temperature and concentration-dependent concentration-dependent NMR studies, this interaction stems from an intramolecular complexation. It was shown by ROESY and H/D-solvent exchange experiments that 1a, even in DMSO, folds into a well-defined intramolecular loop conformation held together by multiple weak interactions.

Carboxylate binding by 2-(guanidiniocarbonyl)pyrrole receptors in aqueous solvents: improving the binding properties of guanidinium cations through additional hydrogen bonds.

A series of guanidiniocarbonyl pyrrole receptors has been synthesized which bind carboxylates by ion pairing in combination with multiple hydrogen bonds. Their binding properties with various carboxylates have been investigated using NMR titration studies in 40% water/DMSO (v/v). The best receptor has association constants which are in the order of K approximately/= 10(3) mol(-1) and hence some 30 times larger than with the simple acetyl guanidinium cation. Through a systematic variation of the receptor structure, semiquantitative estimates for the energetic contributions of the individual binding interactions could be derived. These data show that the various hydrogen bonds are not equally important for the binding but differ significantly in their energetic contribution to the overall complexation process. Furthermore, the receptor can be made chiral and shows selectivity upon binding of enantiomeric amino acid carboxylates. Molecular modeling was used to obtain structural information for the various receptor carboxylate complexes and served as a basis to explain the observed differences in binding constants.

Broadcasts for a billion: the growth of commercial television in China.

PIP: At present, Chinese television reaches 35% of the population (80-90% in urban areas) and is used by the government as a source of education and information. In recognition of the potential market represented by 1.1 billions consumers, Western advertisers have commissioned elaborate market research studies. Drama, sports, news, and movies are consistently identified as the favorite type of programming among Chinese television viewers. About 75% of Beijing adults watch television daily, making the medium both an important target for advertising campaigns and a way for Westerners to influence Chinese business and government leaders. Western advertisers have tended to concentrate their investments in the more urban, affluent regions where products have the greatest likelihood of being sold. There has been a recent trend, however, toward industrial commercials, with British and French companies buying television time to promote their image as partners in China's modernization. Key to the future of commercial advertising on Chinese Television. In many provinces, local television stations have developed a unique character and portray different sociocultural values than the national channel. Outside advertisers have sometimes experienced problems with local networks that substitute local advertising without informing the network. To correct this situation, the government is enacting pro-sponsor regulations that forbid the preemption of the national channel and its advertisements. At the same time, efforts are being made to improve relationships with local television stations by either paying them a fee or airing local commercials on the national network.^ieng

Photosynthetic Carbon Metabolism in the Palisade Parenchyma and Spongy Parenchyma of Vicia faba L.

Palisade parenchyma cells and spongy parenchyma cells were isolated separately from Vicia faba L. leaflets. Extracts of the cell isolates were assayed for several enzymes involved in CO(2) fixation and photorespiration. When compared on a chlorophyll basis, the levels of enzyme activities either were equal in the different cell types or were greater in the spongy parenchyma; this difference is a reflection, perhaps, of the higher protein-chlorophyll ratio in the latter tissue. The distribution of radioactivity in the products of photosynthesis by each cell type was the same at various times after exposure to NaH(14)CO(3), and the kinetics of (14)C incorporation into these compounds was similar. However, a larger percentage of radioactivity was incorporated by the cell isolates into the 80% ethanol-insoluble fraction and correspondingly less into the neutral fraction as compared to whole leaf. It was concluded that photosynthetic CO(2) fixation is similar in the different mesophyll tissues from which these cells were derived.