Identification of pyrrolo-pyridine derivatives as novel class of antibacterials

Molecular Diversity - A series of 5-oxo-4H-pyrrolo[3,2-b]pyridine derivatives was identified as novel class of highly potent antibacterial agents during an extensive large-scale high-throughput...     

Precipitation of inorganic salts inside hollow micrometer-sized polyelectrolyte shells

Hollow polymer shells formed by layer-by-layer adsorption of oppositely charged polyelectrolytes onto micrometer-sized colloidal particles with subsequent decomposition of the colloidal core were employed as a model system for the study of inorganic crystallization reactions in restricted volumes. The size-selective permeability of shells is used for spatially controlling the precipitation of inorganic salts CaCO3 and BaCO3 into the shell interior. Outside the shells the precipitation was suppressed by the polymers, which are unable to penetrate the shell wall. The precipitates were studied by scanning electron microscopy and atomic force microscopy. The fundamental and applied aspects of research on spatially confined synthesis of inorganic particles are under discussion.     

Model for the distribution of aftershock interoccurrence times

In this work the distribution of interoccurrence times between earthquakes in aftershock sequences is analyzed and a model based on a nonhomogeneous Poisson (NHP) process is proposed to quantify the observed scaling. In this model the generalized Omori's law for the decay of aftershocks is used as a time-dependent rate in the NHP process. The analytically derived distribution of interoccurrence times is applied to several major aftershock sequences in California to confirm the validity of the proposed hypothesis.     

Exactly solvable model of monomer-monomer reactions on a two-dimensional random catalytic substrate

We study the equilibrium properties of a monomer-monomer A+B--> reaction on a two-dimensional substrate containing randomly placed catalytic bonds. Interacting A and B species undergo continuous exchanges with particle reservoirs and react as soon as a pair of unlike particles appears on sites connected by a catalytic bond. For annealed disorder in the placement of catalytic bonds the model is mapped onto a general spin S=1 model and solved exactly for the pressure in a particular case. At equal activities of the two species a second order phase transition is revealed.     

Multicenter bonding and the structure of electron-rich molecules. Model of three-center four-electron bonding reconsidered

The concept of three-center four-electron (3c-4e) bonding, which has often been invoked in attempts to interpret the electronic structure of electron-rich molecules, is scrutinized using various methodologies, including generalized population analysis and the analysis of the so-called domain-averaged Fermi holes. Results for representative examples show clearly how manifestations of the 3c-4e model can depend critically on the quality of the wave function being analyzed. In general, the existence of 3c-4e bonding tends to be most compatible with the analysis of wave functions of lower quality; enhancements to the flexibility of the basis and/or the inclusion of electron correlation can lead to dramatic changes, such that the 3c-4e scheme transforms into a pattern of two more or less normal, albeit often very polar, two-center two-electron bonds.     

Multicenter bonding in organic chemistry. Geometry-sensitive 3c-2e bonding in (C...H...C) fragments of organic cations

This paper reports the application of a new general tool for the study of multicenter bonding, namely the so-called generalized population analysis, to the investigation of interesting geometry dependent variation of 3c-2e bonding in the (C...H...C) fragments of ingeniously designed organic cations I and II. This phenomenon was previously characterized by the correlation between experimental (1)H NMR chemical shifts of the central hydrogen in the (C...H...C) fragment and the changes in the corresponding C-H-C bond angle. The observed values of both chemical shifts and C-H-C angles are shown herein to correlate with the calculated 3-center bond indices but the dependence displays splitting into two separate lines according to the type of corresponding cation.     

Novel structurally characterized o-semiquinonato PCP-pincer nickel complexes

Structural study of dialkyl (PCP)-pincer o-semiquinonato nickel complexes indicated sloped relative positions of bi- and tri-dentate ligands. It became bright confirmation of propositions made on the base of their EPR spectra followed by molecular modelling.     

Methyl methacrylate particles with amino groups on the surface: Colloid stability and sorption of biologically active substances

The present article investigates the influence of dispersion medium on the aggregate stability of cross-linked poly-(methyl methacrylate) particles on the surface layer of which aliphatic amino groups are localized. It is shown that particle size depends on the ionic strength of dispersion medium. The research determines the optimal content of cross-linked agent, ethylene glycol dimetharylate that results in the formation of cationic particles being stable in saline. Particle modification is performed by bovine serum albumin and luminophore fluorescein 5(6)-isothiocyanate. Protein sorption is observed not to influence luminescent properties of the particles. It is also determined that due to the aggregate stability of particles obtained from 5?wt% of ethylene glycol dimethacrylate in saline, the monodispersity and the absence of inversion of zeta potential in wide pH range is retained, such particles may be considered as perspective carriers of biologically active substances.