G-type Halohydrin Dehalogenases Catalyze Ring Opening Reactions of Cyclic Epoxides with Diverse Anionic Nucleophiles**

Halohydrin dehalogenases are promiscuous biocatalysts, which enable asymmetric ring opening reactions of epoxides with various anionic nucleophiles. However, despite the increasing interest in such asymmetric transformations, the substrate scope of G-type halohydrin dehalogenases toward cyclic epoxides has remained largely unexplored, even though this subfamily is the only one known to display activity with these sterically demanding substrates. Herein, we report on the exploration of the substrate scope of the two G-type halohydrin dehalogenases HheG and HheG2 and a newly identified, more thermostable member of the family, HheG3, with a variety of sterically demanding cyclic epoxides and anionic nucleophiles. This work shows that, in addition to azide and cyanide, these enzymes facilitate ring-opening reactions with cyanate, thiocyanate, formate, and nitrite, significantly expanding the known repertoire of accessible transformations.     

Reactions of chelated η-pentadienyl iron complexes with nucleophiles

Ferracyclic (1-3-η³)pentadienyl complexes with electronically decoupled allyl and vinyl moieties were reacted with various heteroatom and carbon nucleophiles. Primary amines selectively attacked neutral (4-6-η³-pentadienyl)ferralactones 2 on the end of the allyl ligand to give 3-(endo-vinyl)-(4-6-η³-allyl)ferralactams 4 and by a similar reaction of the latter eventually 6-(exo-vinyl)-(4-6-η³-allyl)ferralactams 5. -like attack on the conjugated coplanar vinyl residue of 2 was not observed. The cationic η³-allyl complex 3 was attacked by nucleophiles either on the allylic terminus furnishing free (1Z, 3E)-dienes 8, or on the vinyl residue which is part of an activated Michael system to give η⁴-1,3-diene complexes 9. η⁴-1,3,5-Triene complex 10 was obtained with basic nucleophiles.     

Surface characterization of standard cotton fibres and determination of adsorption isotherms of fragrances by IGC

The surface characterizations of the WFK16000 standard cotton by dispersive, specific and total surface energy heterogeneity profiles with surface energy distributions and acid–base properties determined by surface energy analyser are presented in this work. The Dorris–Gray and Schultz methods for the determination of the dispersive surface energy component are compared, and their critical analysis is given. It is concluded that the Dorris–Gray method is more applicable at elevated temperature. Furthermore, Henry's coefficient, standard free enthalpy, enthalpy and entropy data at infinite dilution and adsorption isotherms for some fragrances (benzyl acetate, Cyclal C, diphenyl oxide, eucalyptol, linalool and viridine) measured on dry cotton fibres by inverse gas chromatography at various temperatures are given. The temperature‐dependent form of the Langmuir equation has been fitted to the multiple temperature adsorption isotherms with good agreement. Copyright © 2015 John Wiley & Sons, Ltd.     

Dielektrische und akustische Eigenschaften von Ag5SbS4

Measurements of the temperature dependences of the real and imaginary part of the complex dielectric permittivity at microwave frequencies together with the damping constant and the velocity of ultrasonic waves in Ag₅SbS₄ crystals have been made. The Peculiarities of the crystals grown and the nature of the phase transition in Ag₅SbS₄ are discussed.     

Auto-orientation of G-wire DNA on mica

Scanning probe microscopy was used to examine the orientation of Tet1.5 quadruplex DNA polymers, a.k.a. “G-wires”, after adsorption onto freshly cleaved Phyllosilicate micas. The G-wires appear to have a preferential orientation at 60° intervals after thorough rinsing and slow drying. The angles the G-wires made with the fast scan direction of the SPM probe were measured and the frequency-angle information was quantitatively characterized by an empirical correlation coefficient. Careful measurements indicate the Tet1.5 G-wires orient along the b lattice vector of mica, the next nearest neighbor potassium vacancy. A model is proposed to explain this auto-orientation affect due to alignment of the G-wires’ phosphate backbone through magnesium tether cations. Pairs of adjacent, parallel phosphate groups of the G-wires (0.95 nm apart) appear to align with the next nearest neighbor potassium vacancy sites of mica (0.90 nm apart). This behavior is not observed in solution. The potential for using the auto-orientation phenomena in the development of high-density biomolecular nano-electronic devices is explored.     

Numerical algorithm for waveguide and leaky modes determination in multilayer optical waveguides

A new algorithm for waveguide and leaky modes spectrum calculation in multilayer planar waveguides is proposed. The method is of high computational efficiency due to the preliminary search for propagation constants approximation. Numerical efficiency of this algorithm is demonstrated for several waveguide structures. Waveguide and leaky modes propagation constants calculated for these structures using proposed method are in good agreement with previously published results.     

Dynamical model of silicon evanescent laser

Numerical self-consisted dynamical model of silicon evanescent laser is developed. P-I characteristics and mode composition of laser radiation are obtained. Dynamical processes are investigated, self-modulation mode is observed.