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71.
The selectivity of substrate in substrate–enzyme complexation of heptaprenyl diphosphate synthase was directly investigated
using colloidal probe atomic force microscopy (AFM). This enzyme is composed of two dissociable subunits, which exhibits a
catalytic activity only when they are associated together in the presence of a cofactor, Mg2+, and a substrate, farnesyl diphosphate (FPP). We have recently succeeded to directly demonstrate a specific interaction involved
in this enzyme reaction and obtain new insights into the molecular mechanism of the reaction using the approach based on the
colloidal probe AFM. The AFM measurement showed the adhesive force between the subunits only in the presence of both Mg2+ and FPP. In this study, we studied the substrate selectivity in the complexation by monitoring the adhesive force. The substrates
studied are pyrophosphate (PPi), isopentenyl diphosphate (IPP), geranyl diphosphate (GPP), farnesyl monophosphate (FP), and
farnesyl geranyl diphosphate (FGPP). No adhesion was observed in the case of PPi, IPP, and GPP. On the other hand, the significant
adhesion was observed for phosphate derivatives, which bear prenyl units longer than three. This is in good agreement with
the selectivity of the substrates by this enzyme, which catalyzes the condensation reaction of four IPP molecules with FPP
to give heptaprenyl (C35) diphosphates. Our study showed a useful methodology for examining the elemental processes of biological reactions. 相似文献
72.
Population study of sizes and components of self-reproducing giant multilamellar vesicles 总被引:1,自引:0,他引:1
Toyota T Takakura K Kageyama Y Kurihara K Maru N Ohnuma K Kaneko K Sugawara T 《Langmuir : the ACS journal of surfaces and colloids》2008,24(7):3037-3044
Population analysis of a system of self-reproducing giant multilamellar vesicles (GMVs) was carried out by means of flow cytometry. The multidimensional distribution of forward light scattering (FS), side light scattering (SS), and fluorescence (FL) intensities originating from each GMV provided information about changes in a population composed of 104 vesicles. FS-FL dot plots indicated that, after the addition of the membrane precursor, the size distribution of the newly generated vesicles was nearly the same as that of the original, but the catalyst content was reduced. This result can be interpreted as evidence for the occurrence of the self-reproduction of GMVs. Moreover, the new GMVs recovered the amount of catalyst to the initial value, keeping their size distribution constant, when a solution of the catalyst was added to the new GMVs. These results are the first experimental evidence for a novel phenomenon on GMV size distribution during their self-reproducing cycle. 相似文献
73.
Hiraka K Kanehisa M Tamai M Asayama S Nagaoka S Oyaizu K Yuasa M Kawakami H 《Colloids and surfaces. B, Biointerfaces》2008,67(1):54-58
We prepared an anticancer drug based on a pH-sensitive liposome retaining Fe-porphyrin as an SOD mimic. The liposomes contained cationic/anionic lipid combinations and were composed of Fe-porphyrin, 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine, dimethylditetradecylammonium bromide, sodium oleate, and Tween-80. The Fe-porphyrin was released from the liposome at low pH, and the cytotoxicity for cancer cells by the liposome depended on the acidic environments of the endosomes in the cells. Furthermore, although the liposome exhibited an excellent anticancer effect on a gastric cancer cell line, the SOD activity of Fe-porphyrin was shown to have a significant influence on the cytotoxicity toward cancer cells. These findings suggest that the pH-sensitive liposome retaining the Fe-porphyrin as an SOD mimic promises to be a novel anticancer drug for endosomal escape. 相似文献
74.
Toyoda S. Kaneko A. Ooba N. Yamada H. Kurihara T. Okamoto K. Imamura S. 《Photonics Technology Letters, IEEE》1999,11(9):1141-1143
A wavelength tunable optical filter is a beneficial optical component for dense wavelength-division-multiplexed systems. We report a high-performance polymeric arrayed-waveguide grating (AWG)-based tunable filter made of cross-linked silicone and operating around 1.55 μm. This filter exhibited a TE-TM polarization shift of <0.03, a crosstalk of <-35 dB, an insertion loss of <3 dB, and an 8.8-nm tuning range in the 25°C-75°C temperature region 相似文献
75.
Youhei Fujimoto Suprakas Sinha Ray Masami Okamoto Akinobu Ogami Kazunobu Yamada Kazue Ueda 《Macromolecular rapid communications》2003,24(7):457-461
Via a batch process in an autoclave, the foam processing of neat polylactide (PLA) and two different types of PLA/layered silicate nanocomposites has been conducted using supercritical carbon dioxide as a foaming agent. The morphological correlation between the dispersed silicate particles with nanometer dimensions in the bulk and the obtained closed‐cell structure of the foam is discussed. This is the first report that deals with the possibility of preparing biodegradable nanocellular polymeric foams via nanocomposite technology.
76.
77.
78.
High performance of Me-BIPAM for enantioselective hydrogenation of α-dehydroamino esters, enamides, and dimethyl itaconate was demonstrated. [Rh(Me-BIPAM)(diene)]X (diene = cod, nbd; X = BF4, PF6, SbF6) gave optically active β-aryl α-amino esters up to 99% ee, 1-arylethylamines up to 97% ee, methyl 2-acetylaminobutanoate with 90% ee, and dimethyl 2-methylsuccinate with 97% ee under 0.3−0.8 MPa dihydrogen with 0.1−1 mol % catalyst loading. 相似文献
79.
Jacqueline De Souza Eunice Kazue Kano Eunice Emiko Mori Koono Simone Grigoleto Schramm Valentina Porta Sílvia Storpirtis 《Chromatographia》2009,69(2):231-235
This study describes an accurate, sensitive, and specific chromatographic method for the simultaneous quantitative determination of lamivudine and zidovudine in human blood plasma, using stavudine as an internal standard. The chromatographic separation was performed using a C8 column (150 × 4.6 mm, 5 μm), and ultraviolet absorbency detection at 270 nm with gradient elution. Two mobile phases were used. Phase A contained 10 mM potassium phosphate and 3% acetonitrile, whereas Phase B contained methanol. A linear gradient was used with a variability of A-B phase proportion from 98–2% to 72–28%, respectively. The drug extraction was performed with two 4 mL aliquots of ethyl acetate. 相似文献
80.
Yasunori Yamamoto Dr. Kazunori Kurihara Dr. Norio Miyaura Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(24):4414-4416
Ligand design by‐pam : A ruthenium‐catalyzed asymmetric arylation of aldehydes with arylboronic acids has been developed, giving chiral diarylmethanols in good yields. The use of a chiral bidentate phosphoramidite ligand ((R,R)‐Me‐bipam) led to excellent enantioselectivities.