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41.
Yu Suzuki Takanori Higashi Takahiro Yamamoto Hideyasu Okamura Takehiro K. Sato Tetsuo Asakura 《Molecules (Basel, Switzerland)》2022,27(2)
Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned 1H, 13C, and 15N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the 15N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed. 相似文献
42.
This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility. 相似文献
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Controllable Electronic Structures and Photoinduced Processes of Bay‐Linked Perylenediimide Dimers and a Ferrocene‐Linked Triad 下载免费PDF全文
Haruki Horinouchi Dr. Hayato Sakai Prof. Yasuyuki Araki Prof. Tomo Sakanoue Prof. Taishi Takenobu Prof. Takehiko Wada Prof. Nikolai V. Tkachenko Prof. Taku Hasobe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9631-9641
A series of perylene‐3,4,9,10‐bis(dicarboximide) (PDI) dimers linked through the bay regions was systematically synthesized to examine the electronic structures and photophysical properties in dependence on the distance and orientation between the two PDI units. The spectroscopic and electrochemical measurements suggested that the coupling value of a directly linked PDI dimer (PDI)2 is much larger than those of para‐ and meta‐phenylene‐bridged PDI dimers p‐(PDI)2 and m‐(PDI)2. The width of Davydov splitting was quantitatively evaluated to compare the coupling values between the two PDI units in these dimers by absorption spectroscopy in frozen 2‐methyl‐THF. Excimer formation of PDI dimers induced the strong fluorescence quenching and large red‐shifts. Femtosecond transient absorption revealed a broad absorption derived from an excimer in the range from about 600 nm to the near‐IR region. The rate constants of formation and decay of the excimer are strongly dependent on the coupling values. Time‐resolved measurements on ferrocene‐linked p‐(PDI)2 revealed a competition between the photoinduced processes of electron transfer and excimer formation in PhCN, which is in sharp contrast with the sole electron‐transfer process in toluene. 相似文献
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Abstract We have compared the effect of hydrostatic pressure on the threshold current, Ith, and lasing energy, Elase, of 1.3 pm quantum-well devices based upon AlGaInAs and InGaAsP. Whilst we observe a very similar dependence of Elase on pressure for the two materials, we measure strikingly different variations of Ith. By applying pressure to 1.3 μm InGaAsP lasers, Ith typically decreases by ~ 10% over 1 GPa consistent with the reduction of Auger recombination, which forms ~ 50% of Ith at room temperature. However, for the 1.3 μm AlGaInAs-based lasers, we observe an increase in Ith by ~ 8% over the same pressure range. From these results we conclude that non-radiative recombination accounts for only ~ 20% of Ith in AlGaInAs-based devices. This is in good agreement with previous temperature dependence measurements and shows why AlGaInAs-based devices exhibit a reduced temperature sensitivity of Ith which is very important for telecommunications applications. 相似文献
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A new route for (2S,3S,4S)-form, the physiologically active stereoisomer of dehydroxymethylepoxyquinomicin (DHMEQ), a potent NF-κB inhibitor, was established by chemoenzymatic approach. Elaboration on the asymmetric epoxidation of a p-benzoquinone monoketal with benzylcinchonidinium tert-butylhydroperoxide yielded an epoxyenone, in 79.8% ee and 57% yield in reproducible manner. By way of the transformation of this key intermediate to enantiomerically pure (2S,3S,4S)-DHMEQ, the contaminating undesired enantiomer could be effectively removed by applying Burkholderia cepacia lipase-catalyzed hydrolysis of diacylated precursor. The above integrated combination of chemical asymmetric synthesis and enzyme-catalyzed kinetic resolution enabled us to prepare active DHMEQ in a large-scale. 相似文献
49.
Toshinori Taishi Hideaki Ise Yu Murao Takayuki Osawa Masashi Suezawa Yuki Tokumoto Yutaka Ohno Keigo Hoshikawa Ichiro Yonenaga 《Journal of Crystal Growth》2010,312(19):2783-2787
Oxygen-containing germanium (Ge) single crystals with low density of grown-in dislocations were grown by the Czochralski (CZ) technique from a Ge melt, both with and without a covering by boron oxide (B2O3) liquid. Interstitially dissolved oxygen concentrations in the crystals were determined by the absorption peak at 855 cm−1 in the infrared absorption spectra at room temperature. It was found that oxygen concentration in a Ge crystal grown from melt partially or fully covered with B2O3 liquid was about 1016 cm−3 and was almost the same as that in a Ge crystal grown without B2O3. Oxygen concentration in a Ge crystal was enhanced to be greater than 1017 cm−3 by growing a crystal from a melt fully covered with B2O3; with the addition of germanium oxide powder, the maximum oxygen concentration achieved was 5.5×1017 cm−3. The effective segregation coefficients of oxygen in the present Ge crystal growth were roughly estimated to be between 1.0 and 1.4. 相似文献
50.
Tomohiro Hirano Kousuke Higashi Makiko Seno Tsuneyuki Sato 《Journal of polymer science. Part A, Polymer chemistry》2004,42(19):4895-4905
We have reported that intramolecular chain‐transfer reaction takes place in radical polymerization of itaconates at high temperatures and/or at low monomer concentrations. In this article, radical polymerizations of di‐n‐butyl itaconate (DBI) were carried out in toluene at 60 °C in the presence of amide compounds. The 13C‐NMR spectra of the obtained poly(DBI)s indicated that the intramolecular chain‐transfer reaction was suppressed as compared with in the absence of amide compounds. The NMR analysis of DBI and N‐ethylacetamide demonstrated both 1:1 complex and 1:2 complex were formed at 60 °C through a hydrogen‐bonding interaction. The ESR analysis of radical polymerization of diisopropyl itaconate (DiPI) was conducted in addition to the NMR analysis of the obtained poly(DiPI). It was suggested that the suppression of the intramolecular chain‐transfer reaction with the hydrogen‐bonding interaction was achieved by controlling the conformation of the side chain at the penultimate monomeric unit of the propagating radical with an isotactic stereosequence. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4895–4905, 2004 相似文献