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791.
By using a highly sensitive 27-MHz glucan-immobilized quartz-crystal microbalance, we could follow kinetically all processes (enzyme binding and release, kon and koff, and intramolecular hydrolysis rates, kcat) of glucan hydrolysis by glucoamylase by detecting directly the formation and decay of the enzyme-substrate complex as mass changes. 相似文献
792.
Murakami T Takahashi Y Fukushi E Kawabata J Hashimoto M Okuno T Harada Y 《Journal of the American Chemical Society》2004,126(30):9214-9220
Biosyntheses of lambertellols A (1) and B (2) as well as lambertellin (3) were investigated by isotope labeling experiments. Nearly 40% of specific incorporation of [1,2-(13)C(2)]acetate was achieved, and all the carbons in 1 and 2 were labeled. This high incorporation of the labeled acetate was realized by providing INADEQUATE spectra by employing only 0.4 and 0.7 mg of 1 and 2, respectively. Our studies revealed that 1-3 are biogenetically synthesized via loss of two carbons from octameric acetate. A biological assay against Monilinia fructicola revealed those remarkably inhibited hyphal germinations. However, neither of them killed the spores immediately, even in high concentration. These conditions induced the formation of microconidia. 相似文献
793.
Kawai H Katoono R Nishimura K Matsuda S Fujiwara K Tsuji T Suzuki T 《Journal of the American Chemical Society》2004,126(16):5034-5035
The preparation and complexation properties of a hydrindacene-based exoditopic receptor, that exhibits a positive homotropic allosteric binding process toward benzenediols, are described. The exoditopic receptors form 1:2 complexes with resorcinols, catechol, and 3-hydroxybenzyl alcohol with K2/K1 = 3-33. Both the entropy and the enthalpy terms are important in this allosteric system; the crystallographic studies provide the first clear evidence that the cooperativity in amide hydrogen bonding by polarization contributes to the positive homotropic allosteric binding property. 相似文献
794.
795.
796.
The piston-driven ultra rapid pressure swing adsorption (URPSA) equipment was developed and oxygen enrichment from air was examined as an example. The adsorbent bed is directly connected to the cylinder where a piston moves at high frequency. Thus pressurization and depressurization in the bed are driven by mechanical piston motion, which can achieve far more rapid cycles compared with the conventional pressure swing operation using valves. The cycle time is usually on the order of seconds or sub seconds. Oxygen enrichment from air up to about 60% or higher of oxygen concentration was achieved by small-scale equipment using zeolite 5A with a oxygen production capacity of 100 Nm3-product gas/m3-zeolite/hr, which is about ten times larger than those of commercialized PSAs for this purpose.A simplified numerical model describing the mass transfer taking place in URPSA was developed. The model could simulate fairly well the air separation characteristics in terms of oxygen concentration, oxygen production capacity and oxygen yield. The proposed model helps in the understanding of the basic nature of URPSA and possible applications. This novel PSA is promising as a compact yet high-capacity PSA to be utilized in a wide variety of applications. 相似文献
797.
Sound localization can be controlled by using head related transfer functions (HRTFs), which are related to the size of the head, the ears and so on. Since HRTFs are characterized by source directions and subjects, it is necessary to conduct measurements in all directions for all subjects. However, such measurement is expensive and time-consuming. In this paper, we propose a simpler and more useful method that investigates the relationship between HRTFs and physical size by multiple regression analysis. The estimated HRTFs are evaluated by objective and subjective measures. For objective results, the average spectral distortion score is 4.0 dB in a bandwidth ranging from 0 to 8 kHz. Subjective results indicate no significant difference between the measured and the estimated HRTFs in that frequency range. These results support the hypothesis that the proposed method is effective for estimating HRTFs. 相似文献
798.
Takafumi Saito Kenshu Fujiwara Yusuke Sano Takuto Sato Yoshihiko Kondo Uichi Akiba Yusuke Ishigaki Ryo Katoono Takanori Suzuki 《Tetrahedron letters》2018,59(14):1372-1376
In our previously reported method for the construction of the IJKLM-ring of ciguatoxin 3C (CTX3C), the lengthy synthetic process for the intermediate C42–C52 (L-ring) segment was problematic. Therefore, a new and improved procedure for the C42–C52 segment, having modified protecting groups, was developed. The new route includes a chirality transferring Ireland-Claisen rearrangement for the construction of the vicinal dimethyl branching at C47–48, a one-pot cyclization process for the establishment of the stereocenters at C45 and C46 as well as the γ-hydroxy δ-lactone framework corresponding to the L-ring, and Brown’s asymmetric crotylboration for the installation of the stereocenters at C43 and C44. The new C42–C52 segment was successfully coupled with the previously reported C32–C41 (I-ring) segment to produce the IJKLM-ring. 相似文献
799.
800.
Jinseok Kim Juwon Oh Takanori Soya Tomoki Yoneda Seongchul Park Manho Lim Atsuhiro Osuka Dongho Kim 《Angewandte Chemie (International ed. in English)》2020,59(13):5129-5134
Expanded porphyrins with appropriate metalation provide an excellent opportunity to study excited‐state aromaticity. The coordinated metal allows the excited‐state aromaticity in the triplet state to be detected through the heavy‐atom effect, but other metalation effects on the excited‐state aromaticity were ambiguous. Herein, the excited‐state aromaticity of gold(III) hexaphyrins through the relaxation dynamics was revealed via electronic and vibrational spectroscopy. The SQ states of gold [26]‐ and [28]‐hexaphyrins showed interconvertible absorption and IR spectra with those of counterparts in the ground‐state, indicating aromaticity reversal. Furthermore, while the T1 states of gold [28]‐hexaphyrins also exhibited reversed aromaticity according to Baird's rule, the ligand‐to‐metal charge‐transfer state of gold [26]‐hexaphyrins contributed by the gold metal showed non‐aromatic features arising from the odd‐number of π‐electrons. 相似文献