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361.
Shimono S Tamura R Ikuma N Takimoto T Kawame N Tamada O Sakai N Matsuura H Yamauchi J 《The Journal of organic chemistry》2004,69(2):475-481
A synthetic procedure for optically active and racemic alpha-nitronyl nitroxides (alpha-NNs) having a stereogenic center at the 4-position of the imidazolyl ring is described. This procedure consists of (1) the synthesis of a dissymmetric vic-dinitro compound by Kornblum reaction, (2) the enantiomeric resolution of the racemate by a diastereomer method for obtaining the optically active sample, (3) the quick reduction of the optically active or racemic vic-dinitro compound to the bis(hydroxyamino) derivative with Al/Hg, (4) the solvent-free condensation of the bis(hydroxyamino) compound with an aldehyde to give the 1,3-dihydroxyimidazolidine, and (5) the final oxidation of the alpha-NN precursor with aqueous NaIO(4). The absolute configuration of the optically active alpha-NNs was assigned by correlating with the X-ray crystal structure of the (-)-(1S,4R)-camphanic acid ester derivative of the optically active vic-dinitro compound. The molecular conformation of the optically active alpha-NNs was found to be folded both in solution and in the solid state by CD spectroscopy and energy minimization with the Monte Carlo method. The magnetic properties of both optically active and racemic alpha-NNs in solution and in the solid state were characterized by EPR spectroscopy and magnetic susceptibility measurement, respectively. 相似文献
362.
Capillary electrophoretic studies on the photogenotoxic potential of pharmaceutical substances 总被引:1,自引:0,他引:1
Drug-induced phototoxic skin responses, including photoirritation, photoallergy and photogenotoxicity, are identified as adverse reactions. In this study, we attempted to develop effective analytical tools to predict the photogenotoxic potential of pharmaceutical substances with the use of pBR322 DNA, a plasmid DNA. pBR322 DNA was irradiated with simulated solar light in the presence of photosensitizers, and its structural conversion was assessed by agarose gel electrophoresis (AGE), transmission electron microscopy (TEM) and capillary gel electrophoresis (CGE). The generation of reactive oxygen species (ROS) from photoirradiated photosensitizers was also assessed by spectrophotometrical determination. Concomitant ultraviolet (UV) exposure of pBR322 DNA and photosensitizers resulted in significant oxidative damage to the DNA, as evidenced by AGE, TEM and CGE data, indicating a structural transition from supercoiled form to open circular form. Photosensitizer-induced DNA damage was attenuated by the addition of radical scavengers, especially sodium azide, a typical scavenger of singlet oxygen (1 O2), and enhanced by the addition of deuterium water, an enhancer of the life time of 1 O2. These data, taken together with the results of the ROS assay, suggest that singlet oxygen might act as a major toxic species in quinine-induced photogenotoxicity. The structural analysis of plasmid DNA by CGE after exposure to UVA/B in the presence of photosensitizers could be automated, allowing easy, fast and highly reliable prediction for the photogenotoxic potential of a large number of drug candidates. 相似文献
363.
Okoshi K Sano N Okumura T Tagaya A Magoshi J Koike Y Fujiki M Watanabe J 《Journal of colloid and interface science》2003,263(2):473-477
A novel coloration phenomenon in a colloidal dispersion with an amphiphilic polymer was found. The dispersion consists of tetrahydrofuran (THF), an aqueous solution of sodium thiosulfate (Na(2)S(2)O(3).5H(2)O), and hydroxypropylcellulose (HPC). The dispersion was emulsified by HPC as an amphiphilic polymer, so that the aqueous phase was confined in droplets in the THF matrix. It typically appeared bluish violet at room temperature and turned into blue with increasing temperature. In this system, the refractive indices of the inside and outside of the droplet coincided at a certain wavelength at which the light passes through without scattering, which is called the Christiansen effect. The color observed was successfully simulated by Mie's scattering theory in combination with the Christiansen effect. 相似文献
364.
Dr. Ryuichi Sawa Dr. Yoshiaki Takahashi Dr. Hideki Hashizume Dr. Kazushige Sasaki Dr. Yoshimasa Ishizaki Maya Umekita Dr. Masaki Hatano Hikaru Abe Dr. Takumi Watanabe Naoko Kinoshita Yoshiko Homma Chigusa Hayashi Kunio Inoue Syunichi Ohba Toru Masuda Dr. Masayuki Arakawa Dr. Yoshihiko Kobayashi Dr. Masa Hamada Dr. Masayuki Igarashi Dr. Hayamitsu Adachi Dr. Yoshio Nishimura Dr. Yuzuru Akamatsu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15772-15781
The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X‐ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans‐decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad‐spectrum antibiotic against Gram‐positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors. 相似文献
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367.
Hiroyuki Tsurumi 《Mathematische Nachrichten》2023,296(4):1651-1668
We consider the stationary Navier–Stokes equations in the two-dimensional torus . For any , we show the existence, uniqueness, and continuous dependence of solutions in homogeneous toroidal Besov spaces for given small external forces in when . These spaces become closer to the scaling invariant ones if the difference ε becomes smaller. This well-posedness is proved by using the embedding property and the para-product estimate in homogeneous Besov spaces. In addition, for the case , we can show the ill-posedness, even in the scaling invariant spaces. Actually in such cases of p and q, we can prove that ill-posedness by showing the discontinuity of a certain solution map from to . 相似文献