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981.
Yusuke Nakashima Kazunori Hirabayashi Masanori Yasui Fujiko Iwasaki 《Tetrahedron letters》2004,45(11):2301-2303
An optically pure seleninic acid was isolated as stable crystals for the first time by chiral crystallization. The relationship between the absolute configurations and the circular dichroism spectra of the enantiomers could be determined by X-ray crystallographic analysis. 相似文献
982.
Hideyuki Itabashi Yusuke Kamata Daisuke Kawaguchi Hiroshi Kawamoto 《Analytical sciences》2003,19(9):1277-1280
A commercial humic acid dissolved in water was fractionated to nine samples by means of ultrafiltration (UF); the nominal molecular weight used for UF membranes was 1 k-200 kDa. Concerning the nine samples, copper(II) complexing capacities (CuCC) and conditional stability constants (beta) of the formed copper(II) complexes were measured by a solvent extraction method. A total organic carbon (TOC) and the UV-VIS absorption ratio (E350 nm/E450 nm) were also measured. From a comparison of these data, it was found that a) humic acids in each fraction formed two kinds of copper(II) complexes with different stability; b) the beta values obtained from each fraction were almost the same; c) large CuCC values were observed in the molecular weight range from 10 kDa to 20 kDa and below 1 kDa; d) molecules with molecular weight higher than 50 kDa scarcely had any copper(II) complexing ability; e) the values of CuCC/TOC of each fraction were in the range from 1.7 to 3.4 x 10(-7) mol mg(-1). 相似文献
983.
Takafumi Hamaoka Takuya Osada Norio Murase Takayuki Sako Hiroyuki Higuchi Yuko Kurosawa Mitsuharu Miwa Toshihito Katsumura Britton Chance 《Optical Review》2003,10(5):493-497
The forearm muscles of five healthy males were monitored for changes in microvessel hemoglobin saturation (SO2-TRS) by near infrared time-resolved spectroscopy (NIRTRS) and changes in phosphorus metabolites by magnetic resonance spectroscopy (31P-MRS) during 12 min of resting arterial occlusion. Muscle oxygenation and phosphorus metabolites were also measured during grip exercises at varying intensities. Upon the initiation of occlusion, SO2-TRS fell progressively until it reached a plateau in the latter half of the occlusion. Phosphocreatine (PCr) began to decrease around 6 min after the initiation of arterial occlusion. The resting O2 store and O2 consumption were 295 μM and 0.95 μM/sec, respectively-values which reasonably agree with the reported results. A significant correlation was observed between the changes in SO2-TRS and PCr during exercise (r2 = 0.80, p < 0.001). These results indicate that NIRTRS is able to provide reliable information about resting metabolism and oxidative rate during exercise. NIRTRS and MRS are useful to monitor oxygenation and energetics noninvasively in the human muscle. 相似文献
984.
Shigemitsu Murase Atsushi Inoue Yoshiharu Miyashita Noritaka Kimura Yoshiyuki Nishio 《Journal of Polymer Science.Polymer Physics》2002,40(6):479-487
The structure of nylon‐6 hybrids with synthetic or natural clays was investigated for melt‐pressed films with Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, and differential scanning calorimetry in comparison with the nylon‐6 homopolymer. In contrast to the development of familiar α‐form crystals in plain nylon‐6 film, the hybrid films produced γ‐form crystals when nylon‐6 was conjugated with synthetic mica, whereas the hybridization with natural montmorillonite gave rise to both α‐ and γ‐crystalline modifications. The degree of crystallinity of the nylon‐6 hybrid with synthetic mica was the highest of the three series. Moisture sorption isotherms obtained for these nylon‐6‐based films were all typically sigmoid‐shaped, although the prevalence of a higher crystallinity in the hybrid samples lowered the degree of moisture regain. The sorption behavior was analyzed well in terms of the parameters of a Brunauer–Emmett–Teller multiplayer adsorption model and a Flory–Huggins treatment. It was also observed that the cluster formation of the water adsorbed into the nylon‐6 matrix tended to be restricted by the hybridization with clay. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 479–487, 2002; DOI 10.1002/polb.10106 相似文献
985.
Yamagishi Y Shoji I Miyagawa S Kawakami T Katoh T Goto Y Suga H 《Chemistry & biology》2011,18(12):1562-1570
Naturally occurring peptides often possess macrocyclic and N-methylated backbone. These features grant them structural rigidity, high affinity to targets, proteolytic resistance, and occasionally membrane permeability. Because such peptides are produced by either nonribosomal peptide synthetases or enzymatic posttranslational modifications, it is yet a formidable challenge in degenerating sequence or length and preparing libraries for screening bioactive molecules. Here, we report a new means of synthesizing a de novo library of “natural product-like” macrocyclic N-methyl-peptides using translation machinery under the reprogrammed genetic code, which is coupled with an in vitro display technique, referred to as RaPID (random nonstandard peptides integrated discovery) system. This system allows for rapid selection of strong binders against an arbitrarily chosen therapeutic target. Here, we have demonstrated the selection of anti-E6AP macrocyclic N-methyl-peptides, one of which strongly inhibits polyubiqutination of proteins such as p53. 相似文献
986.
Nagaoka S Fukuzawa H Prümper G Takemoto M Takahashi O Yamaguchi K Kakiuchi T Tabayashi K Suzuki IH Harries JR Tamenori Y Ueda K 《The journal of physical chemistry. A》2011,115(32):8822-8831
In an aim to create a "sharp" molecular knife, we have studied site-specific fragmentation caused by Si:2p core photoionization of bridged trihalosilyltrimethylsilyl molecules in the vapor phase. Highly site-specific bond dissociation has been found to occur around the core-ionized Si site in some of the molecules studied. The site specificity in fragmentation and the 2p binding energy difference between the two Si sites depend in similar ways on the intersite bridge and the electronegativities of the included halogen atoms. The present experimental and computational results show that for efficient "cutting" the following conditions for the two atomic sites to be separated by the knife should be satisfied. First, the sites should be located far from each other and connected by a chain of saturated bonds so that intersite electron migration can be reduced. Second, the chemical environments of the atomic sites should be as different as possible. 相似文献
987.
Wu KC Yamauchi Y Hong CY Yang YH Liang YH Funatsu T Tsunoda M 《Chemical communications (Cambridge, England)》2011,47(18):5232-5234
Mesoporous titania nanoparticles (MTNs) with excellent biocompatibility (LC(50)≈ 400 μg mL(-1)) and a large surface area (ca. 237.3 m(2) g(-1)) were synthesized and further functionalized with a phosphate-containing fluorescent molecule (i.e. flavin mononucleotide; FMN) and loaded with an anticancer drug (i.e. Doxorubicin) for successful intracellular bioimaging and drug delivery, respectively, in human breast cancer cells BT-20. 相似文献
988.
Under UV-light irradiation, the anti-Markovnikov hydration of internal arylalkynes proceeds in the cavity of an electron-deficient coordination cage to give benzyl ketones; the reaction is triggered by cage-mediated, photo-induced electron transfer from the alkynes to the cage. 相似文献
989.
Wang X Ervithayasuporn V Zhang Y Kawakami Y 《Chemical communications (Cambridge, England)》2011,47(4):1282-1284
An acid-base switchable dendritic complex was constructed by self-assembly between dibenzo-24-crown-8 terminated T(10)-POSS dendrimer and dibenzylammonium hexafluorophosphate salt based on T(8)-POSS. The formation and its threading-dethreading property were characterized by (1)H NMR and UV-visible absorption spectroscopy. 相似文献
990.
Miyauchi Y Kourist R Uemura D Miyamoto K 《Chemical communications (Cambridge, England)》2011,47(26):7503-7505
Using three rounds of structure-guided directed evolution, the catalytic activity of the (S)-selective arylmalonate decarboxylase variant G74C/C188S could be increased up to 920-fold. The best variant had a 220-fold improved activity in the production of (S)-naproxen with excellent enantioselectivity (>99% ee). 相似文献