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Ohyama Kaname Oyamada Kana Kishikawa Naoya Arakawa Miyuki Ohba Yoshihito Kamino Masahiro Wada Mitsuhiro Nakashima Kenichiro Kuroda Naotaka 《Chromatographia》2009,70(9-10):1501-1504
A new class of chiral stationary phases (CSP) with peptide chiral selectors was prepared by solid-phase synthesis with a tert-butoxycarbonyl-L-amino acid on silica. The type of amino acid that is favorable for this class of CSP is discussed. Using the CSP with the phenylalanine peptide selector, the effect of peptide length on the enantioselectivity was investigated in normal-phase mode. The applicability of the CSP with a phenylalanine peptide to chiral ligand-exchange chromatography was also examined.
相似文献54.
Lawrence Asamoah Adutwum Naoya Kishikawa Kaname Ohyama Shiro Harada Kenichiro Nakashima Naotaka Kuroda 《Analytical and bioanalytical chemistry》2010,398(2):823-829
A sensitive and selective high performance liquid chromatography-peroxyoxalate chemiluminescence (PO-CL) method has been developed
for the simultaneous determination of chlorpheniramine (CPA) and monodesmethyl chlorpheniramine (MDCPA) in human serum. The
method combines fluorescent labeling with 4-(4,5-diphenyl-1H-imidazole-2-yl)phenyl boronic acid using Suzuki coupling reaction with PO-CL detection. CPA and MDCPA were extracted from
human serum by liquid–liquid extraction with n-hexane. Excess labeling reagent, which interfered with trace level determination of analytes, was removed by solid-phase
extraction using a C18 cartridge. Separation of derivatives of both analytes was achieved isocratically on a silica column
with a mixture of acetonitrile and 60 mM imidazole-HNO3 buffer (pH 7.2; 85:15, v/v) containing 0.015% triethylamine. The proposed method exhibited a good linearity with a correlation coefficient of 0.999
for CPA and MDCPA within the concentration range of 0.5–100 ng/mL. The limits of detection (S/N = 3) were 0.14 and 0.16 ng/mL
for CPA and MDCPA, respectively. Using the proposed method, CPA could be selectively determined in human serum after oral
administration. 相似文献
55.
Mitsuhiro Wada Rie Ikeda Naotaka Kuroda Kenichiro Nakashima 《Analytical and bioanalytical chemistry》2010,397(3):1039-1067
Hair has been focused on for its usability as an alternative biological specimen to blood and urine for determining drugs
of abuse in fields such as forensic and toxicological sciences because hair can be used to elucidate the long intake history
of abused drugs compared with blood and urine. Hair analysis consists of several pretreatment steps, such as washing out contaminates
from hair, extraction of target compounds from hair, and cleanup for instrumental analysis. Each step includes characteristic
and independent features for the class of drugs, e.g., stimulants, narcotics, cannabis, and other medicaments. In this review,
recently developed methods to determine drugs of abuse are summarized, and the pretreatment steps as well as the sensitivity
and applicability are critically discussed. 相似文献
56.
The purpose of this study was to examine the potential of diffusion-weighted (DW) three-dimensional (3D) MP-RAGE MRI for diffusion-tensor mapping of the rat brain in vivo. A DW-3D-MP-RAGE (3D-DWI) sequence was implemented at 2.0 T using six gradient orientations and a b value of 1000 s/mm2. In this sequence, the preparation sequence with a "90 degrees RF-motion proving gradient (MPG): MPG-180 degrees RF-MPG-90 degrees RF" pulse train (DW driven equilibrium Fourier transform) was used to sensitize the magnetization to diffusion. A centric k-space acquisition order was necessary to minimize saturation effects (T1 contamination) from tissues with short relaxation time. The image matrix was 128x128x128 (interpolated from 64x64x64 acquisitions), which resulted in small isotropic DW image data (voxel size: 0.273x0.273x0.273 mm3). Moreover, 3D-DWI-derived maps of the fractional anisotropy (FA), relative anisotropy (RA) and main-diffusion direction were completely free of susceptibility-induced signal losses and geometric distortions. Two well-known commissural fibers, the corpus callosum and anterior commissure, were indicated and shown to be in agreement with the locations of these known stereotaxic atlases. The experiment took 45 min, and shorter times should be possible in clinical application. The 3D-DWI sequence allows for in vivo 3D diffusion-tensor mapping of the rat brain without motion artifacts and susceptibility to distortion. 相似文献
57.
A highly sensitive method for the phosphorimetric assay of prekallikrein in human blood plasma is described. Prekallikrein is converted to kallikrein (active form) by reaction at 0°C with actin. p-Nitroaniline, formed enzymatically from H-d-prolyl-l-phenylalanyl-l-arginyl-p-nitroanilide, is extracted with ether and determined phosphorimetrically in a mixture of ether and ethanol. The method is precise and highly sensitive, requiring as little as 0.25 μl of human blood plasma. The limit of detection for p-nitroaniline formed enzymatically is 5 pmol. 相似文献
58.
Masatoshi Imada Masanori Kohno Hirokazu Tsunetsugu 《Physica B: Condensed Matter》2000,280(1-4):303-307
Proposals to enhance the spin excitation gap and the pairing correlations in doped Mott insulators are reviewed. Design and tuning of flat dispersions near the Fermi level extend the critical region of the metal-to-Mott insulator transition thereby inducing stronger pairing instabilities. Several one- and two-dimensional decorated lattices are studied. We also discuss the tuning for stronger d-wave pairing instabilities in a microscopic model of high-Tc cuprates. 相似文献
59.
Masayuki Takeuchi Tomoyuki Imada Seiji Shinkai 《Angewandte Chemie (International ed. in English)》1998,37(15):2096-2099
With increasing number of bound dicarboxylic acid molecules , the binding of further molecules by the title compound becomes more favorable (a 1:4 complex is depicted schematically on the right). The association constant for binding of the first guest molecule is small, since the increase in Gibbs free energy due to binding is outweighed by the energy loss asssociated with the suppression of rotation of the porphyrin rings. Once rotation has been suppressed, further guest molecules can be more effectively bound (positive allosteric effect). 相似文献
60.