Transformation Toughening in Sol–Gel-Derived Alumina-Zirconia Composites

The microstructures of α-Al₂O₃ seeded sol–gel-derived alumina-zirconia composites containing 20 wt% unstabilized zirconia (processed from zirconium n-propoxide) were very fine, with submicrometer alumina grains and small, mainly intergranular zirconia particles, the latter having a critical size for the tetragonal-to-monoclinic phase transformation of 0.45 μm. The corresponding ratios of the toughening contribution to the matrix toughness are relatively low (δK_c/K₀<1). This finding is confirmed by an analysis of the tetragonal zirconia particle size dependence of the stress-induced transformation toughening.     

Synthesis and flammability testing of epoxy functionalized phosphorous‐based flame retardants

Several potential new phosphorus‐containing flame retardant molecules were evaluated for heat release reduction potential by incorporation of the molecules into a polyurethane, generated from methylene diphenyl diisocyanate and 1,3‐propane diol. The heat release reduction potential of these substances was evaluated using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods to qualitatively evaluate their potential reactivity into the polyurethane prior to heat release testing. The functionality of the flame retardants was epoxide based that would potentially react with the diol during polyurethane synthesis. Flammability testing via PCFC showed that the heat release reduction potential of each of the flame retardants was structure dependent, with phosphates tending to show more effectiveness than phosphonates in this study, and alkyl functionalized phosphorus groups (phosphate or phosphonate) being more effective at heat release reduction than cyclic functionalized groups. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42296.     

Study of the compositional heterogeneity of ethylene/1–hexene copolymers produced over supported catalysts of different composition

Separation into narrow MWD fractions (liquid–liquid fractionation) and preparative TREF (temperature rising elution fractionation) with subsequent analysis of fractions by GPC, FTIR, and ¹³C NMR spectroscopy were used to study the comonomer distribution of ethylene/1–hexene copolymers produced over highly active supported titanium‐ and vanadium‐magnesium catalysts (TMC and VMC) and a supported zirconocene catalyst. These catalysts produce PE with different MWD: M_w/M_n values vary from 2.9 for zirconocene catalyst, 4.0 for TMC, and 15 for VMC. 1‐Hexene increases polydispersity to 25 for copolymer produced over VMC and hardly affects MWD of the copolymer produced over TMC and zirconocene catalysts. The most broad short chain branching distribution (SCBD) was found for ethylene/1–hexene copolymers produced over TMC. VMC and supported zirconocene catalyst produce copolymers with uniform profile of SCB content vs. molecular weight in spite of great differences in M_w/M_n values (22 and 2.5 respectively). TREF data showed that majority of copolymer produced over supported zirconocene catalyst was eluted at 70–90°C (about 85 wt %). In the case of VMC copolymer's fractions were eluted in the broad temperature interval (40–100°C). Accordingly, TREF data indicate a more homogeneous SCBD in copolymer, produced over supported zirconocene catalyst. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Kinetic study of photoinitiated frontal polymerization

The frontal polymerization of a monomer exposed continuously to UV radiation in the presence of a photobleachable initiator has been studied on the basis of the rate equations. The time dependence of photoinitiator concentration profile and that of monomer conversion within the irradiated sample have been calculated, assuming steady‐state conditions. It is thus possible to visualize how fast the polymerization profile is moving within the sample and how effectively the polymerization of a monomer layer located at a given distance from the surface proceeds upon exposure to UV radiation. © 2001 Society of Chemical Industry     

Structural Analysis of the Minor Cerebrosides from a Glass Sponge Aulosaccus sp.

The minor cerebrosides from a Far‐Eastern glass sponge Aulosaccus sp. were analyzed as constituents of some multi‐component RP‐HPLC fractions. The structures of eighteen new and one known cerebrosides were elucidated on the basis of NMR spectroscopy, mass spectrometry, optical rotation data and chemical transformations. These β‐D‐glucopyranosyl‐(1→1)‐ceramides contain sphingoid bases N‐acylated with straight‐chain (2R)‐2‐hydroxy fatty acids, namely, (2S,3S,4R,11Z)‐2‐aminoeicos‐11‐ene‐1,3,4‐triol, acylated with 15E‐22:1, 16Z‐21:1, 15Z‐21:1, 15Z‐20:1, 15E‐20:1, 19:0, 18:0 acids, (2S,3S,4R)‐2‐amino‐13‐methyltetradecane‐1,3,4‐triol—with 19Z‐26:1, 16Z‐23:1, 23:0, 22:0 acids, (2S,3S,4R)‐2‐amino‐14‐methylpentadecane‐1,3,4‐triol—with 16Z‐23:1, 16E‐23:1, 15Z‐22:1, 22:0 acids, (2S,3S,4R)‐2‐amino‐14‐methylhexadecane‐1,3,4‐triol, linked to 16Z‐23:1, 15Z‐22:1 acids, (2S,3S,4R)‐2‐amino‐9‐methylhexadecane‐1,3,4‐triol—to 16Z‐23:1 acid, and (2S,3S,4R)‐2‐aminohexadecane‐1,3,4‐triol, attached to 15Z‐22:1 acid. The 13‐methyl and 9‐methyl‐branched trihydroxy sphingoid base backbones (C₁₅ and C₁₇, respectively) have not been found previously in sphingolipids. The ceramide parts, containing other backbones, present new variants of N‐acylation of the marine sphingoid bases with the 2‐hydroxy fatty acids. The combination of the instrumental and chemical methods used in this study improved the efficiency of the structural analysis of such complex cerebroside mixtures that gave more detailed information on glycosphingolipid metabolism of the organism.     

Protein docking using continuum electrostatics and geometric fit

The computer program DOT quickly finds low-energy docked structuresfor two proteins by performing a systematic search over sixdegrees of freedom. A novel feature of DOT is its energy function,which is the sum of both a Poisson–Boltzmann electrostaticenergy and a van der Waals energy, each represented as a grid-basedcorrelation function. DOT evaluates the energy of interactionfor many orientations of the moving molecule and maintains separatelists scored by either the electrostatic energy, the van derWaals energy or the composite sum of both. The free energy isobtained by summing the Boltzmann factor over all rotationsat each grid point. Three important findings are presented.First, for a wide variety of protein–protein interactions,the composite-energy function is shown to produce larger clustersof correct answers than found by scoring with either van derWaals energy (geometric fit) or electrostatic energy alone.Second, free-energy clusters are demonstrated to be indicatorsof binding sites. Third, the contributions of electrostaticand attractive van der Waals energies to the total energy termappropriately reflect the nature of the various types of protein–proteininteractions studied.     

N‐Benzyl Substitution of Polyhydroxypyrrolidines: The Way to Selective Inhibitors of Golgi α‐Mannosidase II

Inhibition of the biosynthesis of complex N‐glycans in the Golgi apparatus influences progress of tumor growth and metastasis. Golgi α‐mannosidase II (GMII) has become a therapeutic target for drugs with anticancer activities. One critical task for successful application of GMII drugs in medical treatments is to decrease their unwanted co‐inhibition of lysosomal α‐mannosidase (LMan), a weakness of all known potent GMII inhibitors. A series of novel N‐substituted polyhydroxypyrrolidines was synthesized and tested with modeled GH38 α‐mannosidases from Drosophila melanogaster (GMIIb and LManII). The most potent structures inhibited GMIIb (K_i=50–76 μm , as determined by enzyme assays) with a significant selectivity index of IC₅₀(LManII)/IC₅₀(GMIIb) >100. These compounds also showed inhibitory activities in in vitro assays with cancer cell lines (leukemia, IC₅₀=92–200 μm ) and low cytotoxic activities in normal fibroblast cell lines (IC₅₀>200 μm ). In addition, they did not show any significant inhibitory activity toward GH47 Aspergillus saitoiα1,2‐mannosidase. An appropriate stereo configuration of hydroxymethyl and benzyl functional groups on the pyrrolidine ring of the inhibitor may lead to an inhibitor with the required selectivity for the active site of a target α‐mannosidase.     

Some features of thermophysical properties of γ‐Gd2S3 ceramics based on real structure

The heat capacity C_p, thermal diffusivity χ_T, and lattice thermal conductivity κ_latt of ceramic solid solutions of sesquisulfides Gd_3‐xV_Gd,xS₄ (0 < x < 0.33) in the temperature range 300‐700 K has been studied. Changing the real structure, namely the concentrations of vacancies (N_V) and deformation (N_Dc) centers of polycrystals, significantly decreases κ_latt. A deviation of composition from the stoichiometry 2:3 is accompanied by an increase in the specific area of the crystallite boundaries per unit volume, and, hence, the concentration of deformation centers D_C increases. This observation was confirmed by examining the short‐range order disturbance of the lattice and symmetry environment of the Gd³⁺ and S^2? environment by Raman spectroscopy and the magnetic susceptibility Faraday method. Therefore the thermal diffusivity of gadolinium sesquisulfide is reduced because of the mean free path of phonons decrease. As a result, the thermal conductivity of the polycrystalline samples is reduced by 10%.     

Detection of non-topological motifs in protein structures

We present an efficient technique for the comparison of proteinstructures. The algorithm uses a vector representation of thesecondary structure elements and searches for spatial configurationsof secondary structure elements in proteins. In such recurringprotein folds, the order of the secondary structure elementsin the protein chains is disregarded. The method is based onthe geometric hashing paradigm and implements approaches originatingin computer vision. It represents and matches the secondarystructure element vectors in a 3-D translation and rotationinvariant manner. The matching of a pair of proteins takes onaverage under 3 s on a Silicon Graphics Indigo2 workstation,allowing extensive all-against-all comparisons of the data setof non-redundant protein structures. Here we have carried outsuch a comparison for a data set of over 500 protein molecules.The detection of recurring topological and non-topological,secondary structure element order-independent protein foldsmay provide further insight into evolution. Moreover, as theserecurring folding units are likely to be conformationalHy favourable,the availability of a data set of such topological motifs canserve as a rich input for threading routines. Below, we describethis rapid technique and the results it has obtained. Whilesome of the obtained matches conserve the order of the secondarystructure elements, others are entirely order independent. Asan example, we focus on the results obtained for Che Y, a signaltransduction protein, and on the profilin-ß-actincomplex. The Che Y molecule is composed of a five-stranded,parallel ß-sheet flanked by five helices. Here weshow its similarity with the Escherichia coli elongation factor,with L-arabinose binding protein, with haloalkane dehalogenaseand with adenylate kinase. The profilin–ß-actincontains an antiparallel ß-pleated sheet with -helicaltermini. Its similarities to lipase, fructose disphosphataseand ß-lactamase are displayed.