Analysis of melanosomes from cattle eyes by pyrolysis—gas chromatography

The application of Curie-point pyrolysis—gas chromatography—mass spectrometry to the differentiation of melanosomes isolated from the retinal pigment epithelium, ciliary body and iris of cattle eyes, with special attention to the preparation and the characterization of their melanin part, was investigated. Computer data analysis and evaluation of the pyrograms obtained was used to display variations between the pyrograms of melanosomes and their components represented by sets of peak heights for comparative studies.The mechanisms of formation of the pyrolytic products and the usefulness of the proposed procedure based on pattern recognition in view of biochemical processes in melanosomes are discussed.     

Simulation of the triplet EPR spectra of randomly oriented molecules with an exact method of resonance field calculation

A simple method for the calculation of the resonance fields of the triplet EPR transitions is given, which are the solutions of a cubic equation with coefficients depending on the parameters g, D, and E. This method is very useful for the simulation of EPR powder spectra.     

Electrogenerated Chemiluminescence Ethanol Biosensor Based on Carbon Nanotube‐Titania‐Nafion Composite Film

Mesoporous titania‐Nafion composite doped with carbon nanotube (CNT) has been used for the immobilization of tris(2,2′‐bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) and alcohol dehydrogenase on an electrode surface to yield a highly sensitive and stable electrogenerated chemiluminescence (ECL) ethanol biosensor. The presence of CNT in the composite film increases not only the sensitivity of the ECL biosensor but also the long‐term stability of the biosensor. The present biosensor responds linearly to ethanol in the wide concentration ranges from 1.0×10^?5 M to 1.0×10^?1 M with a detection limit of 5.0×10^?6 M (S/N=3). The present ECL ethanol biosensor exhibited higher ECL response compared to that obtained with the ECL biosensor based on the corresponding composite without CNT. The present CNT‐based ECL biosensor showed good long‐term stability with 75% of its initial activity retained after 2 weeks of storage in 50 mM phosphate buffer at pH 7.0.     

Nonlinear dielectric effect near the critical point of binary mixtures

The nonlinear dielectric effect (NDE) was measured in two binary systems near the critical point. The effect of independent of specific dipole-dipole interactions in contrast with previous conceptions. Its singular part is proportional to (T ? T_c)^{?$\text{1}\text{2}$} in agreement with Snider's theory as applied to NDE.     

Conformation of tert‐butoxy­carbonyl­glycyl‐dehydro­alanyl‐glycine methyl ester in the crystalline state and calculated in the gas phase

tert‐Butoxy­carbonyl­glycyl‐dehydro­alanyl‐glycine methyl ester (systematic name: methyl {2‐[(tert‐butoxycarbonylamino)­acetamido]prop‐2‐enamido}acetate) (Boc⁰‐Gly¹‐ΔAla²‐Gly³‐OMe), C₁₃H₂₁N₃O₆, has been structurally characterized by single‐crystal X‐ray diffraction and by density functional theory (DFT) calculations at the B3LYP/6–311+G** level. The peptide chain in both the solid‐state and calculated structures adopts neither β nor γ turns. All amino acid residues in the tripeptide sequence are linked trans to each other. The bond lengths and valence angles of the amino acid units in the crystal structure and gas phase are comparable. However, the conformation of the third glycyl residue (Gly³) is different in the crystalline state and in the gas phase. It is stabilized in the calculated structure by an additional intra­molecular short contact between Gly³ NH and methyl ester COMe groups.     

Phase relations in the system SbVO5-Sb3V2Mo3O21 in solid-state and in the atmosphere of air

It has been established by XRD, DTA and TG methods that phases of solid solution type of MoO₃ in SbVO₅ are formed in the system V₂O₅-MoO₃-a-Sb₂O₄. The Mo⁶⁺ ions are incorporated into the crystal lattice of SbVO₅ instead of both Sb⁵⁺ and V⁵⁺, while the charge compensation occurs by a formation of cation defects (□) at Sb⁵⁺ and V⁵⁺. The phases Sb_{1-6x □ x}V_{1-6x □ x}Mo_10xO₅ are stable in the solid-state up to 690±10°C and the limit of solubility of MoO₃ in SbVO₅ does not exceed 20.00 mol%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Crystal and molecular structure of di-μ-bromobromopentakis(benzimidazole)dicopper(II) monobromide tetrahydrate [Cu2Br3(C7H6N2)5]Br·4H2O

A new complex compound. [Cu₂Br₃(C₇H₆N₂)₅]Br·4H₂O, has been synthesized and its crystal structure investigated by single-crystal X-ray methods. The crystals are isostructural with those of the [Cu₂Cl₃(C₇H₆N₂)₅]Cl·4H₂O salt. They are orthorombic, space group Pnma with 4 formula units in a cell of dimensions:a+19.923(1),b+17.555(2),c+12.0523(4)Å. The structure was refined by full-matrix least-squares to giveR+0.047 andR _w+0.053 for 3569 intensities above 3σ(I). As in the chloride compound, the complex cation consists of pairs of distorted trigonal bipyramidal Cu(II) centers which share an edge by two equatorial bromide ions. The Cu...Cu nonbonding distance in the complex in 3.4894(7)Å. The two Cu?Br?Cu bridges are not equivalent and their geometry is slightly different from that in the chloride complex. Comparison of the investigated structure to other binulear bis(μ-halide) bridged copper(II) complexes of similar structure has been made.     

Influence of annealing condition on the properties of sputtered hafnium oxide

Hafnium oxide thin films were deposited on p-type (1 0 0) silicon wafers by reactive dc magnetron sputtering. Prior to the deposition of HfO₂ films, a thin Hf film was deposited. Sputtered HfO₂ thin films deposited at room temperature remain amorphous at T<650°C and orthorhombic phases were observed above 650 °C. The monoclinic phase which is a stable HfO₂ polymorphic form appeared after annealing above 800 °C. Capacitance equivalent thickness values decreased and leakage characteristics are improved by the Hf interlayer and O₂ settlement process. The decrease of accumulation capacitance values upon annealing is due to the growth of an interfacial layer upon post-annealing. The flat band voltage (V_FB) shifts negatively due to positive charge generated during post-annealing.     

Highly active MgCl2‐supported CpMCl3 (M = Ti,Zr) catalysts for ethylene polymerization

Monocyclopentadienyl compounds, CpMCl₃ (M = Ti, Zr) supported on activated MgCl₂ were used for the polymerizations of ethylene in the presence of methylaluminoxane (MAO) or a common alkylaluminium as a cocatalyst. By supporting CpMCl₃ on MgCl₂, the catalyst activity was increased drastically to show high activity similar to MgCl₂‐supported TiCl₄ catalysts. The activity of the CpZrCl₃ /MgCl₂ catalyst was higher than that of the CpTiCl₃/MgCl₂ one. Both catalysts gave polymers with high molecular weight (M_w) and broad molecular weight distribution (M_w/M_n) in comparison with the corresponding soluble half‐metallocene catalysts.     

Polymerization kinetics of photocurable acrylic resins

The polymerization kinetics of photocurable compositions based on an epoxyacrylate oligomer and three analogous diacrylate monomers were investigated. The effects of the oligomer-to-monomer ratio, curing conditions, and monomer structure were considered. The polymerization is characterized by a synergistic effect observed in a wide temperature range and occurring for the polymerization rate both in air and Ar and for final conversions in air. The final conversion in Ar is determined by viscosity of a formulation. The presence of a heteroatom (S or O) in the ester group of the reactive diluent is beneficial for the polymerization course, especially in air atmosphere. The best results were obtained for the sulfur-containing monomer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 665–673, 1998