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101.
Kazuharu Sugawara Naoto Kamiya George Hirabayashi Hideki Kuramitz 《Analytical sciences》2005,21(8):897-900
Avidin, which is one type of glycoprotein, has a strong affinity with biotin (Ka = 10(15) M(-1)). Iminobiotin also forms a complex with avidin (Ka = 10(8) M(-1) at pH 9.5). The avidin-iminobiotin complex changes to the avidin-biotin complex in the presence of biotin because of the difference of the binding constant to avidin. In this study, the interaction between avidin and iminobiotin labeled with an electroactive compound was investigated by voltammetry. After avidin and the labeled iminobiotin (LI) were incubated in 0.1 M phosphate buffer (pH 7.0), the peak currents of LI were measured in various concentrations of biotin. The peak currents increased with increasing the concentration of biotin. Thus, this observation indicates the formation of avidin-biotin complex. On the other hand, the formation of avidin-iminobiotin complex depended on the pH of the solution. LI combines with the avidin at pH 5.6-8.9 and dissociates at pH 4.6. 相似文献
102.
Xiao Tong Satoru Ohuchi Takehiro Tanikawa Ayumi Harasawa Taichi Okuda Yoshinobu Aoyagi Toyohiko Kinoshita Shuji Hasegawa 《Applied Surface Science》2002,190(1-4)
The evolution of Si 2p core-level photoemission during a structural conversion from the Si (1 1 1)–
-Ag to the Si(1 1 1)–
-Ag superstructures induced by Ag adatoms adsorption at 140 K was studied using synchrotron radiation. The component from the top-layer Si-trimer atoms on the former surface was found to split into two components in the latter surface. The result is discussed in terms of a relaxation in some of the Si trimers induced by Ag adatoms sitting on the nearby Ag triangles of the
-Ag substrate. The intensity ratio between the split components is a key to exclude some structure models proposed so far for the
phases. 相似文献
103.
Nobuyasu Itoh Takamitsu Otake Masahiko Numata Yoshie Aoyagi Mayumi Matsuo Takashi Yarita 《Analytical sciences》2008,24(9):1129-1133
To improve the extraction of polycyclic aromatic hydrocarbons (PAHs) from sediment samples, we optimized the conditions of pressurized liquid extraction (PLE). The yields increased as the extraction temperature increased from 100 to 190 degrees C, but the effect of increasing pressure (from 15 to 20 MPa) was small. Parameters of 190 degrees C and 20 MPa, near the maximum of the equipment, gave the highest yield. Under these conditions, the yields of 17 PAHs were 1.5 - 34 times those obtained by the Japanese official method (shaking and ultrasonic extraction with acetone at room temperature). 相似文献
104.
Nobuyasu Itoh Masahiko Numata Yoshie Aoyagi Takashi Yarita 《Analytical sciences》2008,24(9):1193-1197
For the accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in environmental samples by isotope-dilution mass spectrometry (IDMS) and gas chromatography-mass spectrometry (GC-MS), we used deuterium-labeled PAHs (D-PAHs) as internal standards for microg g(-1)-level certified reference materials and corresponding calibration solutions. Although pressurized liquid extraction (PLE) causes significant biases in the analytical results for ng g(-1)-level samples (2.4 - 15%), biases in the analytical results by PLE (190 degrees C, 20 MPa, 2 cycles) were small (<2.3%) and negligible for microg g(-1)-level samples when expanded uncertainty (coverage factor k = 2) was considered. 相似文献
105.
A manifold is described which permits the analysis of less than 1 ml of sample solution. Water- and air-compensation methods for the introduction of the carrier stream into the nebulizer are effective in obtaining sensitive and reproducible measurements of magnesium, but air-compensation gives higher peak responses. 相似文献
106.
K. Ishibashi Y. Aoyagi S. Namba Y. Ochiai M. Kawabe K. Gamo 《Superlattices and Microstructures》1991,9(4)
Magnetoresistance measurements have been performed in narrow GaAs/AlGaAs wires in order to study the scattering process in mesoscopic wires. Amplitude analysis of the Shubnikov -de Haas oscillations shows that electrons have two scattering times, depending upon the magnetic field range. The critical field which separates these scattering times seems to be determined by the relation between the wire width and the electron cyclotron radius. This effect is discussed in terms of the electron trajectories in a wire under the magnetic field. 相似文献
107.
Masayasu Tasaka Satoshi Tamura Naoto Takemura Keisuke Morimoto 《Journal of membrane science》1982,12(2):169-182
Electroosmosis and streaming potential measurements were carried out across charged membranes made of collodion and sulfonated polystyrene. Experiments were confined to the range where linear flux/force relationships hold. Saxén's relationship holds between electroosmosis and streaming potential; for porous charged membranes these exhibit an approximate inverse proportionality to ionic mobility at the limit of low electrolyte concentration. Both tend towards zero at the limit of high electrolyte concentration. 相似文献
108.
The addition of arylboronic acids 1 to azodicarboxylates 2 in the presence of a catalytic amount of a copper salt under mild reaction conditions gives aryl-substituted hydrazines 3 in high yields. The reaction is tolerant of a wide variety of functional groups. 相似文献
109.
Dutta S Abe H Aoyagi S Kibayashi C Gates KS 《Journal of the American Chemical Society》2005,127(43):15004-15005
Fasicularin is a structurally novel thiocyanate-containing alkaloid isolated from the ascidian Nephteis fasicularis. Early biological experiments suggested that this compound's cytotoxic properties may stem from its ability to damage cellular DNA. Sequence gel analysis reveals that treatment of a 5'-32P-labeled DNA duplex with fasicularin in pH 7.0 buffer causes strand cleavage selectively at guanine residues. Further experiments indicate that production of these base-labile lesions in DNA involves alkylation of guanine residues by a fasicularin-derived aziridinium ion. This work reveals fasicularin as the first natural product found to generate a DNA-alkylating aziridinium ion via a mechanism analogous to the clinically used anticancer drugs mechlorethamine, melphalan, and chlorambucil. 相似文献
110.
The first measurements of magnetization hysteresis loops on a diluted single crystal of [(Pc)2Ho]-.TBA+ (Pc = phthalocyaninato, TBA = tetrabutylammonium) in the subkelvin temperature range are reported. Characteristic staircase-like structure was observed, indicating the occurrence of the quantum tunneling of magnetization (QTM), which is a characteristic feature of SMMs. The quantum process in the new lanthanide SMMs is due to resonant quantum tunneling between entangled states of the electronic and nuclear spin systems, which is an essentially different mechanism from those of the known transition-metal-cluster SMMs. Evidence of the two-body quantum process was also observed for the first time in lanthanide complex systems. 相似文献