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81.
Tryptophan (Trp), an aromatic amino acid, is a constituent of peptides/proteins and is also a precursor of serotonin, kynurenine derivatives, and nicotinamide adenine dinucleotides. There have been a number of reports on photochemical reactions involving peptides/proteins which contain Trp that showed significant photodegradation, dimerization, and photoionization. The photochemical properties of Trp have not been fully elucidated, and this would provide novel insight into the handling of Trp-containing peptides/proteins. Consequently, we have been trying to evaluate the photochemical properties of Trp, as well as other essential amino acids, focusing on their photosensitivity, photodegradation, and their ability to induce lipid peroxidation. Among all the essential amino acids tested, Trp exhibited the maximal level of superoxide anion generation under 18 h of light exposure (30000 lux). UV spectral analysis of Trp suggested the absorbability of UVA/B light, and exposure of Trp, in both solid and solution states, to UVA/B light resulted in significant photodegradation (t(0.5): 18 h) and gradual color changes. In addition, photoirradiated Trp generated lipoperoxidant, a causative agent of photoirritation, and this might be associated with ROS generation. 相似文献
82.
83.
Revisiting the Bromination of CH Bonds with Molecular Bromine by Using a Photo‐Microflow System
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Dr. Yoshiyuki Manabe Yuriko Kitawaki Masahiro Nagasaki Prof. Koichi Fukase Prof. Hiroshi Matsubara Yoshiko Hino Prof. Takahide Fukuyama Prof. Ilhyong Ryu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12750-12753
The photobromination of C?H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous‐flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition. 相似文献
84.
Percec V Glodde M Peterca M Rapp A Schnell I Spiess HW Bera TK Miura Y Balagurusamy VS Aqad E Heiney PA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(24):6298-6314
Semifluorinated first-generation self-assembling dendrons attached via a flexible spacer to electron-donor molecules induce pi-stacking of the donors in the center of a supramolecular helical pyramidal column. These helical pyramidal columns self-organize in various columnar liquid crystal phases that mediate self-processing of large single crystal liquid crystal domains of columns and self-repair their intracolumnar structural defects. In addition, all supramolecular columns exhibit a columnar phase at lower temperatures that maintains the helical pyramidal columnar supramolecular structure and displays higher intracolumnar order than that in the liquid crystals phases. The results described here demonstrate the universality of this concept, the power of the fluorous phase or the fluorophobic effect in self-assembly and the unexpected generality of pyramidal liquid crystals. 相似文献
85.
Nishiguchi GA Graham J Bouraoui A Jacobs RS Little RD 《The Journal of organic chemistry》2006,71(16):5936-5941
We (a) describe the completion of a total synthesis of 7,11-epi-thyrsiferol (4), (b) compare the antimitotic activities of thyrsiferol (2), Delta15,28-dehydrothyrsiferol (3), and 7,11-epi-thyrsiferol (4), (c) evaluate the synergistic behavior of the title compound and colchicine to inhibit cell proliferation, and (d) describe the results of conformational searches that provide additional insight concerning the SAR profile of the thyrsiferol family of natural products. 相似文献
86.
Yamauchi A Sakashita Y Hirose K Hayashita T Suzuki I 《Chemical communications (Cambridge, England)》2006,(41):4312-4314
Pseudorotaxane formed by reacting beta-cyclodextrin bearing a phenylboronic acid residue with 1-heptyl-4-(4'-dimethylaminostyryl)pyridinium functioned as a novel fluorescent saccharide receptor having unique responses. 相似文献
87.
A method of separating a Slater determinant wave function with a two-center neck structure into spatially localized subsystems is proposed, and it is applied to α + α Margenau–Brink cluster wave functions and antisymmetrized molecular dynamics wave functions of the ground state in 10Be and a negative-parity largely deformed state in 35S. 相似文献
88.
Satoshi Yamasaki Daisuke Nishiguchi Ken Kojio Mutsuhisa Furukawa 《Journal of Polymer Science.Polymer Physics》2007,45(7):800-814
The effects of the dynamic polymerization method and temperature on the molecular aggregation structure and the mechanical and melting properties of thermoplastic polyurethanes (TPUs) were successfully clarified. TPUs were prepared from poly (ethylene adipate) glycol (Mn = 2074), 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol by the one‐shot (OS) and the prepolymer (PP) methods in bulk at dynamic polymerization temperatures ranging from 140 to 230 °C. Glass‐transition temperatures (Tgs) of the soft segment and melting points (Tms) of the hard segment domains of OS‐TPUs increased and decreased, respectively, with increasing polymerization temperatures, but those of PP‐TPUs were almost independent of the polymerization temperature. Tgs of the soft segment and Tms of the hard segment domains of these TPUs polymerized above 190 °C were almost the same regardless of the polymerization method. Solid‐state nuclear magnetic resonance spectroscopy (NMR) analyses of OS‐ and PP‐TPUs showed that the relative proton content of fast decay components, which corresponds to the hard segment domains, in these TPUs decreased with increasing polymerization temperatures. These results clearly show that the degree of microphase separation becomes weaker with increasing polymerization temperatures. The temperature dependence of dynamic storage modulus and loss tangent of OS‐TPUs coincided with those of PP‐TPUs at polymerization temperature above 190 °C. The apparent shear viscosity for OS‐ and PP‐TPUs polymerized above 190 °C approached a Newtonian behavior at low shear rates regardless of the polymerization method. These results indicate that TPUs polymerized at higher temperatures form almost the same molecular aggregation structures irrespective of the dynamic polymerization method. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 800–814, 2007 相似文献
89.
Liquid ionization mass spectrometry is a soft ionization technique used with liquid samples under atmospheric pressure. It facilitates the handling of reagents and the observation of ion–molecule reactions in the ion source. The differentiation of isomers by characteristic fragment ions, for example those resulting from asymmetrical cleavage of a cyclobutane ring, and by molecular adduct ion formation was studied. The samples studied were cyclobutane derivatives, alkyl 4-(3-oxo-3-pIienyl-l-aIkenyl)benzoate dimers, and reagents having two functional groups were used to produce adduct ions to clarify the difference between isomers. The reagents act on a sample molecule at two functional groups to form hydrogen bonds. Some correlations were observed between the structure of the sample and the relative abundances of molecular adduct ions and also fragment ions produced by collisionally activated dissociation. 相似文献
90.
Identification of organic residues in tertiary effluents by GC/EI-MS,GC/CI-MS and GC/TSQ-MS 总被引:1,自引:0,他引:1
Wang-Hsien Ding Yoshiko Fujita Roland Aeschimann Martin Reinhard 《Analytical and bioanalytical chemistry》1996,354(1):48-55
A method was developed for the analysis of non-volatile dissolved organic residues in tertiary treated wastewater effluents.
This method involved concentration of samples by rotary evaporation, propylation using propanol/formic acid/acetyl chloride,
and separation, detection and quantitation by capillary GC/EI and CI-MS and GC/TSQ-MS analysis. Ethylenediamine tetraacetic
acid (EDTA) was the most prominent compound found in both granular activated carbon (GAC) and chlorinated GAC effluents (110
and 140 μg/L, respectively). Other compounds identified included nitrilotriacetic acid (NTA), carboxyalkylphenoxy ethoxy carboxylates,
poly(propoxy), poly(ethoxy) or poly(ethoxy)(propoxy) compounds, small aliphatic dicarboxylic acids and aldehydes, all at lg/L
levels. Approximately 80% of all chromatographically separated compounds were positively or tentatively identified. The identified
compounds are estimated to account for approximately 10% of the dissolved organic carbon.
Received: 8 August 1994/Revised: 14 February 1995/Accepted: 16 February 1995
Correspondence to: W.-H. Ding 相似文献