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991.
992.
Cholesterol-based hydrogen-bonded liquid crystals 总被引:1,自引:0,他引:1
Hydrogen bonding is a powerful tool for assembling molecules and building new liquid crystalline structures. In this study, non-symmetric dimesogens were prepared by intermolecular hydrogen bonding between rationally designed H-bond donor (3-cholesteryloxycarbonylpentanoic acid) and acceptor (4-(pyridine-4-ylmethyleneimino)phenyl 4-alkoxybenzoate) moieties. Their liquid crystalline properties were investigated by differential scanning calorimetry, polarized optical microscopy and X-ray diffraction. Cholesteric and smectic phases were observed. As for the covalently linked dimesogens, several types of smectic periodicities occur for these H-bonded cholesteryl compounds depending on the molecular parameters. 相似文献
993.
X. H. Liu M. Sun J. J. Yue Y. X. Yin X. L. Liu F. M. Miao 《Journal of Molecular Structure》2003,620(2-3):227-230
In this paper, we carried out a theoretical study on the active site structures of the Mn-SOD with ab initio Hartree–Fock SCF method, and analyzed the molecular orbital energies, charges and atomic orbital contribution to the frontier molecular orbital. 相似文献
994.
Suńol J. J. Saurina J. Carrillo F. Colom X. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):753-758
Comparison of Lyocell, modal and viscose fibers was performed by means of differential scanning calorimetry, thermogravimetry
and scanning electron microscopy. Thermal analysis was performed in air atmosphere. Samples were mercerized (21.3 g 100 mL-1)
or submitted to solar radiation (seven months). Solar degraded samples presents a higher thermal stability and are initially
less degraded. Furthermore, Lyocell fiber is the most stable under thermal degradation conditions. Heating produces a reduction
of the fiber diameter (about 50%).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
995.
Gert E. V. Zubets O. V. Shishonok M. V. Torgashov V. I. Kaputskii F. N. 《Russian Journal of Applied Chemistry》2003,76(4):595-599
The capability of cotton and wood cellulose in the common and microcrystalline forms to transform into cellulose-II under the action of 68-69% HNO3 was studied. The influence of temperature on the course of the phase transition in cellulose samples differing in origin and morphological structure and the dynamics of concomitant hydrolytic degradation and esterification of these materials were studied. 相似文献
996.
Two fluorophore-nitrilotriacetic acid conjugates, Pro-Q Sapphire 365 and Pro-Q Sapphire 488 oligohistidine gel stains, have been developed for the fluorescence detection of fusion proteins containing oligohistidine tags directly in sodium dodecyl sulfate polyacrylamide gels, without the requirement for electroblotting, reporter enzymes or secondary detection reagents. Pro-Q Sapphire 365 oligohistidine gel stain exhibits bright-blue fluorescence (emission maximum = 450 nm) when illuminated with UV-A or UV-B light from a standard ultraviolet transilluminator. Pro-Q Sapphire 488 oligohistidine gel stain exhibits bright-green fluorescence (emission maximum = 515 nm) when illuminated with visible light from a laser-based gel scanner equipped with a 470 nm second-harmonic generation (SHG) or 488 nm argon-ion laser source. Typically, 25-65 ng of oligohistidine-tagged fusion protein in whole cell lysates is detectable using either stain. After documenting the fluorescence signal from the Pro-Q Sapphire dyes, gels may be post-stained with the red-fluorescent SYPRO Ruby protein gel stain in order to reveal the total protein pattern. 相似文献
997.
998.
PHOTOCYTOTOXICITY OF CURCUMIN 总被引:5,自引:0,他引:5
Thomas A. Dahll Piotr Bilski Krzysztof J. Reszka Colin F. Chignell 《Photochemistry and photobiology》1994,59(3):290-294
Curcumin, bis (4-hydroxy-3-methoxyphenyl)-l,6-diene-3,5-dione, is a yellow-orange dye derived from the rhizome of the plant Curcuma longa. Curcumin has demonstrated phototoxicity to several species of bacteria under aerobic conditions (Dahl, T. A., et al. , 1989, Arch. Microbiol. 151 183), denoting photodynamic inactivation. We have now found that curcumin is also phototoxic to mammalian cells, using a rat basophilic leukemia cell model, and that this phototoxicity again requires the presence of oxygen. The spectral and photochemical properties of curcumin vary with environment, resulting in the potential for multiple or alternate pathways for the exertion of photodynamic effects. For example, curcumin photogenerates singlet oxygen and reduced forms of molecular oxygen under several conditions relevant to cellular environments. In addition, we detected carbon-centered radicals, which may lead to oxidation products (see accompanying paper). Such products may be important reactants in curcumin's phototoxicity since singlet oxygen and reduced oxygen species alone could not explain the biological results, such as the relatively long lifetime (t12 = 27 s) of the toxicant responsible for decreased cell viability. 相似文献
999.
Shul'ga Yu. M. Chernushevich I. V. Dzhardimalieva G. I. Roshchupkina O. S. Dodonov A. F. Pomogailo A. D. 《Russian Chemical Bulletin》1994,43(6):983-987
Russian Chemical Bulletin - The monomer [Cr3O(OCOCH=CH2)6]OH was produced by reaction of acrylic acid with fresh chromium hydroxide. This monomer was investigated by a number of physicochemical... 相似文献
1000.
M. F. Budyka G. V. Zakharova O. D. Laukhina M. V. Alfimov 《Russian Chemical Bulletin》1992,41(9):1589-1596
The reaction of the photochemical synthesis of 2,7-dimethylacridine from di(para-tolyl)amine and bromoform was studied utilizing the method of microsecond impulse photolysis. The proposed new scheme for the formation of acridine assumes the recombination of the primary alkyl radicals at the nitrogen atom of the cation radical and/or the radical of the amine as the main route of the reaction. The data obtained indicate the common character of the nature of some intermediate stages and the structures of the intermediates in the photochemical formation of acridine compounds and triphenylmethane dyes from aromatic amines and halogenomethanes.Institute of Chemical Physics, Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2044–2052, September, 1992. 相似文献