Highly activated thioesters formed by the rapid reaction of C‐terminal thioacids derived from protected amino acids and peptides with the Sanger reagent and other electron‐deficient aryl halides in the presence of a free amine immediately form a peptide bond with the amine. This essentially epimerization‐free method was used for the 4+4 block synthesis of a hindered octapeptide (see scheme; Boc, Pbf, and Trt are protecting groups).
Switching characteristics: The 633 nm wavelength of an He–Ne laser is used to fabricate holographic transmission gratings in polymer‐dispersed liquid‐crystal cells. The microstructure and diffraction efficiency (η) both improve with increasing functionality (see figure). For functionalities of 2.5 or more, η approaches 34 % and can be switched off with electric fields of about 20 MV m?1.
The proposed L ‐histidine sensing system composed of a molecularly imprinted solid‐phase microextraction component combined with a molecularly imprinted polymer sensor was used to determine critical levels of test analyte in a complex matrix of highly diluted human blood serum without any non‐specific sorption and false‐positive contributions. The molecularly imprinted polymer was a zwitterionic polymer brush derived from the disodium salt of EDTA and chloranil, grafted to solid‐phase microextraction material. The hyphenated approach was able to detect L ‐histidine quantitatively with a limit of detection as low as 0.0435 ng/mL (RSD = 0.2%, S/N = 3). 相似文献
The degradation efficiency of Th-doped TiO2 / TiO2 photocatalysts were investigated under UV and solar light illumination. The model compound chosen for the study was Oryzalin
(OZ). Doping of inner transition metal ion Th was intended to modify the electronic properties of TiO2. The Th-doped TiO2 were synthesized by incorporating 0.02, 0.04, 0.06, and 0.1 atom percentage of Th into the TiO2 lattice by solid-state reaction. The stochiometry of the prepared samples is Ti1−xThxO2, where ‘x’ is the percentage of Th. The samples were characterized by UV-Visible absorption, UV-Visible -Diffused reflectance
spectra, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and X-ray Diffraction (XRD). The pore
size and surface area of these samples were studied by Brunauer, Emmett and Teller (BET) adsorption method. It was found that
metal ion doping at various percentage compositions enables a large shift in the absorption band of the TiO2 towards visible light region. This is due to the formation of various mid band gaps at 2.84 eV, 2.804 eV, 2.66 eV, and 2.55
eV. The extent of degradation of the pesticide was followed by UV-Visible spectroscopy and GC-MS methods. Based on the spectral
analysis, the probable degradation reaction mechanism for OZ is proposed. These results indicate that Th-doped TiO2 with the modified electronic properties is a good catalyst under solar light irradiation. But these particles show marginal
variation in rates under UV-illumination. All the photodegradation reactions follow the first order kinetics.
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Potentiodynamic polarization studies were carried out on nanocrystalline I, nanocrystalline II and nanocrystalline III states having crystallite size 35 ± 5 nm, 18 ± 2 nm and 10 ± 2 nm of the alloy Ti60Ni40 in 1 M H2SO4 aqueous medium. It was observed that the nanocrystalline III state exhibits superior corrosion resistance as compared to the nanocrystalline II and nanocrystalline I states of the alloy Ti60Ni40. XPS studies were also performed after corrosion test and it was observed that nanocrystalline III state contains only Ti2+ and Ti4+ species whereas nanocrystalline I and nanocrystalline II state contains Ti2+, Ti3+and Ti4+ along with some unoxidized metallic Ti0 in the case of nanocrystalline I state. Thus the small crystallite size and the presence of only Ti2+ and Ti4+ species in the form of TiO and TiO2 leads to the formation of a protective oxide film which is adherent, stable and improves the corrosion resistance of the nanocrystalline III state of the alloy Ti60Ni40. 相似文献
Thiosemicarbazides and their derivatives are well known for their use in biological activity and many applications in pharmaceutical
and industrial fields. The cyclization of 1-benzoyl-4-(2-nitrophenyl)-3-thiosemicarbazide (BNPTSC) in dimethylformamide (DMF)
medium furnished N-(2-nitrophenyl)-5-phenyl-1,3,4-oxadiazole-2-amine (NPPOA). The chemical structure of the above substituted 1,3,4-oxadiazole
has been assigned by IR, mass and X-ray diffraction studies. The XRD studies reveal the presence of four types of hydrogen
bonds (N–H···O, N–H···N, C–H···O, C–H···N) in the crystal packing. The crystal system was found to be orthorhombic with a
space group Pca2(1) and the unit cell dimensions are: a = 26.873(3) ?, b = 6.0827(7) ?, c = 7.8502(10) ?, α = 90°, β = 90°, γ = 90° and Z = 4. 相似文献
The 4-(2-bromo-4-methyl-phenoxymethyl)-6-methylcoumarin (1) have been synthesized from bromination of corresponding 4-aryloxymethyl coumarin, which is a regioisomer of 4-(2-bromo-4-methyl-phenoxymethyl)-7-methylcoumarin
(2) (CCDC-695895). The compound 1 crystallizes with triclinic space group P-1, a = 8.0943(3) ?, b = 9.3502(3) ?, c = 10.1476(4) ?, α = 90.234(2)°, β = 94.065(2)°, γ = 95.106(2)°, Z = 2 and compound 2 crystallizes with monoclinic space group P21/n, a = 8.465(5) ?, b = 13.649(5) ?, c = 13.304(5) ?, α = 90.000(5)°, β = 90.740(5)°, γ = 90.000(5)°, Z = 4. Both the compounds are planar with variation in their intermolecular hydrogen bonds between C–H···O and C–H···π. 相似文献
(5R,6S,7S,8S,9S,10R,13S,14S,17S,20R,22R)-6α,7α-epoxy-5α,17α,27-trihydroxy-1-oxo-22R-witha-2,24-dienolide has been isolated
from Withania somnifera leaves. Three-dimensional X-ray intensity data were collected at 293 K on Bruker CCD area-detector diffractometer equipped
with graphite-monochromated MoKα radiation (λ = 0.71073 ?). The compound crystallizes in monoclinic space group P21 with unit
cell parameters: a = 6.4540(2), b = 11.3656(4), c = 17.4982(5) ?, β = 90.730 o(2), Z = 2. The crystal structure was refined to a final R-value of 0.0419 for 6122 observed reflections. One water solvent molecule was observed. All the rings of the steroid skeleton
are trans connected. Rings A and B exists in a half-chair conformation, ring C a chair, and five membered ring D is intermediate between
half-chair and envelope. The δ-lactone ring E adopts a distorted sofa conformation. The characteristic pattern observed in
the packing diagram is the appearance of twisted chains of molecules. The packing of the molecules in the crystal is stabilized
by intra- and intermolecular O–H···O and C–H···O interactions. 相似文献