Promising gene delivery system based on polyethylenimine-modified silica nanoparticles.

This article reports on the synthesis and full characterization of innovative silica-based nanoparticle composed of fumed silica as a core decorated with polyethylenimine (PEI) with different molecular weights (25, 10 and 1.8 kDa). Wide range of analytical, spectroscopic, and microscopic methods (TEM, DLS, ζ potential, elemental analysis (EA), TNBS and FTIR) were used to characterize the nanoparticles. Furthermore, transfection efficiency of these nanoparticles as non-viral vector was examined. The silica-PEI conjugates retained both the ability of PEI to fully condense plasmid DNA at low N/P ratios and suitable buffering capacity at the endosomal pH range. PEI-functionalized silica remarkably enhanced EGFP-N1 gene expression in murine neuroblastoma (Neuro-2A) cells up to 38 folds compared to PEI 25 kDa. Meanwhile the results of the cytotoxicity assays indicated that these silica-PEI conjugates have acceptable level of viability.

Mechanochemical route to the synthesis of nanostructured Aluminium nitride.

Hexagonal Aluminium nitride (h-AlN) is an important wide-bandgap semiconductor material which is conventionally fabricated by high temperature carbothermal reduction of alumina under toxic ammonia atmosphere. Here we report a simple, low cost and potentially scalable mechanochemical procedure for the green synthesis of nanostructured h-AlN from a powder mixture of Aluminium and melamine precursors. A combination of experimental and theoretical techniques has been employed to provide comprehensive mechanistic insights on the reactivity of melamine, solid state metal-organic interactions and the structural transformation of Al to h-AlN under non-equilibrium ball milling conditions. The results reveal that melamine is adsorbed through the amine groups on the Aluminium surface due to the long-range van der Waals forces. The high energy provided by milling leads to the deammoniation of melamine at the initial stages followed by the polymerization and formation of a carbon nitride network, by the decomposition of the amine groups and, finally, by the subsequent diffusion of nitrogen into the Aluminium structure to form h-AlN.

A mechanistic insight into the effect of piperidine as an organocatalyst on the [3 + 2] cycloaddition reaction of benzalacetone with phenyl azide from a computational study.

Several transition structures (TSs) for catalyst-free [3 + 2] cycloaddition and two plausible mechanistic pathways for the organocatalyzed [3 + 2] cycloaddition (32CA) between benzalacetone and phenyl azide were located by quantum chemistry methods. Calculations were carried out with B3LYP, MPWB1K and M06-2X functionals using 6-31G(d) and 6-311G(d,p) basis sets in gas and solvent phases. The calculated activation barriers imply that the lowest barrier pathway is the catalyzed process producing 3-regioisomers through the iminium intermediate and not through the dienamine route. Electronic displacements along the reaction path have been examined using a topological analysis of the electron-localization function (ELF). ELF topological analyses along the intrinsic reaction coordinates (IRC) of both catalyzed and uncatalyzed 32CA reactions indicated that while the first C1-N1 single bond is formed as a dative bond, the formation of the second C2-N3 bond takes place via a C-to-N coupling between the interacting centers of the reagents. Moreover, the ELF analyses imply that the reaction mechanism is a two-stage one-step process in the presence of a piperidine organocatalyst, while bond formation in an uncatalyzed process is almost synchronous.

Conformational analysis, intramolecular hydrogen bonding, and vibrational assignment of 4,4-dimethyl-1-phenylpentane-1,3-dione.

Molecular structure, conformational stabilities, and intramolecular hydrogen bonding (IHB) of 4,4-dimethyl-1-phenylpentane-1,3-dione (DMPD), have been investigated by means of density functional theory (DFT) calculations and experimental results. The geometries and electronic energies of different cis-enol forms of DMPD have been obtained with the ab initio (MP2 level) and DFT (B3LYP and TPSSh levels) methods, using various basis sets. The energy differences between three stable E1, E2, and E3 chelated enol forms are negligible. According to the theoretical calculations, DMPD has a hydrogen bond strength of about 16.8kcal/mol, calculated at the B3LYP/6-311++G(**) level, which is about 0.7 kcal/mol stronger than that of benzoylacetone (BA). The theoretical and experimental results obtained for stable enol forms of DMPD have been compared with each other and also with those of BA and 5,5-dimethylhexane-2,4-dione (DMHD). The molecular stability and the hydrogen bond strength were investigated by applying the NBO, topological analysis, geometry calculations, and spectroscopic results.

Hydrothermal synthesis, experimental and theoretical characterization of a novel cocrystal compound in the 2:1 stoichiometric ratio containing 6-methyluracil and dipicolinic acid.

This paper reports the hydrothermal synthesis, experimental and theoretical studies of a novel cocrystal compound in the 2:1 stoichiometric ratio of 6-methyluracil (6mu) and dipicolinic acid (pydcH(2)) formulated as [6mu](2)[pydcH(2)] (1), for the first time. DFT calculations were performed to access the most possible geometry of the title cocrystal compound. All calculations were carried out with the B3LYP hybrid density functional level and 6-311+G(d,p) basis sets. The vibrational frequencies together with the (1)H and (13)C NMR chemical shifts have been calculated on the fully optimized geometry of 1. The theoretical results are in good agreement with the experimental and solution data. The theoretical, solution, and experimental (elemental analysis, mass spectrometry, FTIR, (1)H and (13)C NMR spectroscopies) results confirmed our proposed structure for 1 in the 2:1 stoichiometric ratio of 6mu and pydcH(2), respectively. The protonation and equilibrium constants of 6mu and pydcH(2) and constituent systems were determined by potentiometric studies and the corresponding distribution diagrams depicted.

Strontium-selective membrane electrodes based on some recently synthesized benzo-substituted macrocyclic diamides.

Eight different recently synthesized macrocyclic diamides were studied to characterize their abilities as strontium ion carriers in PVC membrane electrodes. The electrode based on 1,13-diaza-2,3;11,12-dibenzo-4,7,10-trioxacyclopentadecane-14,15-dione exhibits a Nernstian response for Sr(2+) ions over a wide concentration range (1.0 × 10(-)(1)-3.2 × 10(-)(5) M) with a limit of detection of 8.0 × 10(-)(6) M (0.7 ppm). The response time of the sensor is ∼10 s, and the membrane can be used for more than three months without observing any deviation. The electrode revealed comparatively good selectivities with respect to many alkali, alkaline earth, and transition metal ions. It was used as an indicator electrode in potentiometric titration of carbonate ions with a strontium ion solution.