A facile one-pot synthesis of Nα-Z/Boc-protected S-linked 1,3,4-oxadiazole tethered peptidomimetics

A new class of S-linked 1,3,4-oxadiazole-tethered N^α-protected peptidomimetics is designed and synthesized by a reaction of N^α-Z/Boc-protected 1,3,4-oxadiazole-2-thiol with α-bromo ester derived from amino acid. The protocol has also been employed for the synthesis of glycosylated amino acids and N,N′-orthogonally protected dipeptidomimetics bearing S-linked 1,3,4-oxadiazole mimetics as well. The intermediate 5-alkyl amino-1,3,4-oxadiazole-2-thiols have been isolated as stable compounds. Further, the chain extension at both N- and C-termini of N-protected S-linked 1,3,4-oxadiazole tethered dipeptidomimetics was also demonstrated.     

Cobalt(II)–metformin complexes containing α‐diimine/α‐diamine as auxiliary ligand: DNA binding properties

The cobalt(II) complexes [Co(Cl)₂(met)(o‐phen)] ( 1 ), [Co(Cl)₂(en)(met)] ( 2 ) and [Co(Cl)₂(met)(opda)] ( 3 ) (met = metformin, o‐phen = ortho‐phenanthroline, en = ethylenediamine, opda = ortho‐phenylenediamine) were synthesized and characterized using liquid chromatography–mass spectrometry, elemental analysis, molar conductance measurements, thermal analysis, infrared spectroscopy, magnetic moment measurements, electronic spectroscopy and X‐ray diffraction. The metal centre was found to be in an octahedral geometry. UV–visible absorption, fluorescence and viscosity measurements were conducted to assess the interaction of the complexes with calf thymus DNA. The complexes showed absorption hyperchromism in UV–visible spectra with DNA. The binding constants from UV–visible absorption studies were 1.38 × 10⁵, 2.1 × 10⁵ and 3.1 × 10⁵ M^?1 for 1 , 2 and 3 , respectively, and Stern–Volmer quenching constants from fluorescence studies were 0.146, 0.176 and 0.475, respectively. Viscosity measurements revealed that the binding of the complexes with DNA could be surface binding, mainly due to groove binding. The activities of the complexes in DNA cleavage decrease in the order 3 > 2 > 1 . The complexes were docked into DNA topoisomerase II using Discovery Studio 2.1 software.     

Unsteady compressible second-order boundary layers at the stagnation point of two-dimensional and axisymmetric bodies

The unsteady laminar compressible boundary-layer flow over two-dimensional and axisymmetric bodies at the stagnation point with mass transfer has been studied for all second-order boundary layer effects when the basic potential flow admits self-similarity. The solutions for the governing equations are obtained by using an implicit finite-difference scheme. Computations have been carried out for different values of the parameters characterizing the unsteadiness in the free stream velocity, wall temperature, mass transfer rate and variable gas properties. The results are found to be strongly affected by the unsteadiness in the free stream velocity. For large injection rates the second-order boundary layer effects may prevail over the first-order boundary layer, but reverse is true for suction. The wall temperature and the variation of the density-viscosity product across the boundary layer appreciably change the skin-friction and heat-transfer rates due to second-order boundary-layer effects.

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Instationäre kompressible Grenzschichten 2. Ordnung am Staupunkt von zweidimensionalen und achsensymmetrischen Körpern

Zusammenfassung Es wurde die instationäre, laminare, kompressible Grenzschichtströmung über einen zweidimensionalen achsensymmetrischen Körper am Staupunkt mit Stoffübergang für alle Grenzschichteffekte 2. Ordnung studiert, wenn die Potentialströmung in sich selbst ähnlich ist. Die Lösung für die grundlegenden Gleichungen wurden unter Anwendung einer impliziten finiten Differenzenmethode erzielt. Es wurden Rechnungen für verschiedene Werte von Parametern durchgeführt, welche die Unstetigkeit in der Freistrahlgeschwindigkeit, die Wandtemperatur, den Stofftransport und die veränderlichen Zustandsgrößen des Gases charakterisieren. Dabei wurde festgestellt, daß die Ergebnisse stark von der Unstetigkeit in der Geschwindigkeit des Freistrahles beeinflußt werden. Für große Zuströmraten können die Effekte 2. Ordnung in der Grenzschicht über die der 1. Ordnung überwiegen, aber das Gegenteil gilt für Absaugung. Die Wandtemperatur und das Dichte-Viskositätsprodukt über die Grenzschicht ändern die Wandreibung und den Wärmeübergang merklich wegen der Grenzschichteffekte 2. Ordnung.

     

Studies on optical absorption and structural properties of Fe doped CdS quantum dots

Fe doped CdS quantum dots have been prepared using simple precursors by chemical precipitation technique. Fe doped CdS quantum dots have been synthesized by mixing cadmium nitrate, sodium sulfide and adding Fe under suitable conditions. X-ray diffraction analysis reveals that undoped and Fe doped CdS crystallizes in hexagonal structure. The lattice constants of Fe doped CdS nanoparticles decreased slightly with incorporation of Fe and no secondary phase was observed. The average grain size of the nanoparticles is found to lie in the range of 2.8–4.2 nm. HRTEM results show that undoped and 3.75% Fe doped CdS nanoparticles exhibit a uniform size distribution and average size of the nanoparticles is about 2–3 nm. Raman spectra show that 1LO and 2LO peaks of the Fe doped CdS samples are slightly red shifted compared with those of undoped CdS. Optical absorption spectra of Fe doped CdS nanoparticles exhibited red shift.     

Ethyl 2‐form­amido‐2‐(4‐iodo­benzyl)‐3‐(4‐iodo­phenyl)­propionate and ethyl 2‐(3‐bromo­benzyl)‐3‐(3‐bromo­phenyl)‐2‐form­amidopropionate

The title compounds, C₁₉H₁₉I₂NO₃ and C₁₉H₁₉Br₂NO₃, are derivatives of α‐amino­isobutyric acid with halogen substituents at the para and meta positions, respectively. The ethoxycarbonyl and formamide side chains attached to the C_α atom of the mol­ecule adopt extended and folded conformations, respectively. The crystal structures are stabilized by N—H⃛O, C—H⃛O, C—Br⃛O and C—I⃛O interactions.     

Precursors to dodecahedrane

The title compounds, (2R,2′′S,3b′S,4a′R,7b′S,8a′R)‐per­hydro­di­spiro­[furan‐2,3′‐di­cyclo­penta­[a,e]­pentalene‐7′,2′′‐furan]‐5,5′′‐dione, C₂₀H₂₆O₄, and (3aR,3bR,4aR,4bS,5aS,8aR,8bR,9aR,9bS,10aS)‐per­hydro­dipentaleno­[2,1‐a:2′,1′‐e]­pentalene‐1,6‐dione, C₂₀H₂₆O₂, are intermediates identified during the synthesis of dodecahedrane. Crystallographic studies have established the ring‐junction stereochemistry for these important intermediates. All the ring junctions are cis‐fused, and the molecular packing is stabilized by van der Waals interactions.     

A fully vectorial effective index method to analyse the propagation properties of microstructured fiber

Based on numerical simulation, we theoretically study the linear and nonlinear properties of microstructured fiber. Using the fully vectorial effective index method, we calculate the effective refractive index for different air hole size. We show how the linear properties such as spot size, numerical aperture, splice loss and bend loss can be controled by changing the air hole size. We also propose the same method for analysing effective area and self-phase modulation of microstructured fiber for different designing parameters. We compare all our results with other numerical methods.     

X-ray diffraction, spectroscopic and thermal studies on a potential semiorganic NLO material: lithium bis-L-malato borate

A semiorganic nonlinear optical material, lithium bis-L-malato borate (LBMB) (molecular formula C8H8BLiO10), has been synthesized, and single crystals grown from an aqueous solution, by the method of slow evaporation at 30 degrees C. Crystals of size up to 7 mm x 3 mm x 2 mm were harvested and characterized by powder and single crystal X-ray diffraction and Fourier transform infrared techniques to confirm the identity of the compound formed. The TG-DTA results establish the good thermal stability of the material. The UV-Vis-NIR spectral study reveals that the material has a wide transparency window (230-1500 nm) with a lower cutoff at 230 nm. Kurtz powder test with a Nd:YAG laser indicates the production of SHG output.