Quasi-SMILES: quantitative structure–activity relationships to predict anticancer activity

Molecular Diversity - Reliable prediction of anticancer potential of different substances for different cells using unambiguous algorithms is attractive alternative of experimental investigation of...     

Periodic subgroups of projective linear groups in positive characteristic

We classify the maximal irreducible periodic subgroups of PGL(q, ), where is a field of positive characteristic p transcendental over its prime subfield, q = p is prime, and ^× has an element of order q. That is, we construct a list of irreducible subgroups G of GL(q, ) containing the centre ^×1 _q of GL(q, ), such that G/ ^×1 _q is a maximal periodic subgroup of PGL(q, ), and if H is another group of this kind then H is GL(q, )-conjugate to a group in the list. We give criteria for determining when two listed groups are conjugate, and show that a maximal irreducible periodic subgroup of PGL(q, ) is self-normalising.      

Influence of arm length and number on star-shaped poly(2-isopropyl-2-oxazoline) aggregation in aqueous solutions near cloud point

Four-arm star-shaped poly(2-isopropyl-2-oxazolines) (PiPrOx₄) are synthesized by cationic polymerization on t-butylcalix[4]arene macroinitiator. The obtained samples differ by polymerization degree of arms N_PiPrOx = 9 and 25 and are characterized in chloroform. The behavior in aqueous solutions is studied by light scattering methods and compared with the results of investigation of eight-arm star with similar structure. Three types of particles are observed in solution of short-arm PiPrOx₄ at room temperature, whereas only two particle types are present in long-arm star solution. Arm shortening leads to widening of the phase transition interval. The arm number decreasing reduces the phase transition temperature by 1°C.     

Formation of mesoscopic water networks in aqueous systems

Formation of the macroscopically-infinite hydrogen-bonded water network in various aqueous systems occurs via 3D percolation transition when the probability of finding a spanning water cluster exceeds 95%. As a result, in a wide interval of water content below the percolation threshold, rarefied quasi-2D water networks span over the mesoscopic length scale. Formation and topology of spanning water networks, which affect various properties of aqueous systems, can be described within the framework of the percolation theory.     

A practical one-pot synthesis of vinylstannanes from ketones

Treatment of ketones with Bu3SnLi followed by addition of MsCl/Et3N to the resulting alkoxide provides vinylstannanes. Cyclic vinylstannanes are particularly amenable to this procedure and isolated yields of 81-83% could be consistently attained. Traces of Bu3SnH in crude reaction products could be removed by stirring in CHCl3 with a catalytic amount of AIBN followed by filtration through silica gel.     

Simple and fast method for the fabrication of switchable bicomponent micropatterned polymer surfaces

We report on the fabrication of micropatterned polymer surfaces that allow the reversible inversion of surface topography, charge, and wettability. Micropatterned surfaces were prepared by grafting two oppositely charged polyelectrolytes (poly(acrylic acid) and poly(2-vinylpyridine)) using a combination of photolithography, "lift off", and "grafting to" techniques. The switchable surfaces are of interest in microprinting and for the design of microfluidic devices and programmed protein adsorption.     

Water-soluble magnetic nanoparticles with biologically active stabilizers

We present the results of the interaction of iron oxide nanoparticles with some biologically active surfactants, namely, oleic acid and cytotoxic alkanolamine derivatives. Physico-chemical properties, as magnetization, magnetite concentration and particle diameter, of the prepared magnetic samples were studied. The nanoparticle size of 11 nm for toluene magnetic fluid determined by TEM is in good agreement with the data obtained by the method of magnetogranulometry. In vitro cytotoxic effect of water-soluble nanoparticles with different iron oxide:oleic acid molar ratio were revealed against human fibrosarcoma and mouse hepatoma cells. In vivo results using a sarcoma mouse model showed observable antitumor action.     

Chemistry of vinylidene complexes. XVIII. Synthesis and molecular structure of the novel trinuclear μ3-vinylidene complex CpReFePt(μ3-CCHPh)(CO)6(PPh3)

The interaction between Cp(CO)₂RePt(μ-CCHPh)(PPh₃)₂ (1) and Fe₂(CO)₉ afforded the new heterometallic μ₃-vinylidene cluster CpReFePt(μ₃-CCHPh)(CO)₆(PPh₃) (2). An X-ray diffraction study shows the complex 2 possesses a trimetallic Re-Fe-Pt chain core. The bond lengths are Re-Fe 2.8221(8), Fe-Pt 2.5813(8) Å; the Re?Pt distance is 3.3523(7) Å; the bond angle Re-Fe-Pt is 76.55(3)°. The μ₃-CCHPh ligand is η¹-bound to the Re and Pt atoms and η²-coordinated to the Fe atom. The CC bond length is 1.412(4) Å. The Pt atom is coordinated by the PPh₃ and CO groups. Complex 2 is characterized by the IR and ¹H, ¹³C and ³¹P NMR spectra.     

Why are ionic liquids liquid? A simple explanation based on lattice and solvation energies

We have developed a simple and quantitative explanation for the relatively low melting temperatures of ionic liquids (ILs). The basic concept was to assess the Gibbs free energy of fusion (Delta(fus)G) for the process IL(s) --> IL(l), which relates to the melting point of the IL. This was done using a suitable Born-Fajans-Haber cycle that was closed by the lattice (i.e., IL(s) --> IL(g)) Gibbs energy and the solvation (i.e., IL(g) --> IL(l)) Gibbs energies of the constituent ions in the molten salt. As part of this project we synthesized and determined accurate melting points (by DSC) and dielectric constants (by dielectric spectroscopy) for 14 ionic liquids based on four common anions and nine common cations. Lattice free energies (Delta(latt)G) were estimated using a combination of Volume Based Thermodynamics (VBT) and quantum chemical calculations. Free energies of solvation (Delta(solv)G) of each ion in the bulk molten salt were calculated using the COSMO solvation model and the experimental dielectric constants. Under standard ambient conditions (298.15 K and 10(5) Pa) Delta(fus)G degrees was found to be negative for all the ILs studied, as expected for liquid samples. Thus, these ILs are liquid under standard ambient conditions because the liquid state is thermodynamically favorable, due to the large size and conformational flexibility of the ions involved, which leads to small lattice enthalpies and large entropy changes that favor melting. This model can be used to predict the melting temperatures and dielectric constants of ILs with good accuracy. A comparison of the predicted vs experimental melting points for nine of the ILs (excluding those where no melting transition was observed and two outliers that were not well described by the model) gave a standard error of the estimate (s(est)) of 8 degrees C. A similar comparison for dielectric constant predictions gave s(est) as 2.5 units. Thus, from very little experimental and computational data it is possible to predict fundamental properties such as melting points and dielectric constants of ionic liquids.