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91.
Tachibana Y Otsuka K Terabe S Arai A Suzuki K Nakamura S 《Journal of chromatography. A》2003,1011(1-2):181-192
A robust and simple interface for microchip electrophoresis-mass spectrometry (MCE-MS) was developed using a spray nozzle connected to the exit of the separation channel of the microchip. The spray nozzle was attached to the microchip using a polyether ether ketone screw without adhesive, thus allowing easy replaced. Sample injection and electrophoretic separation was performed by control of the voltage only. The analysis of a few basic drugs was performed using the optimized MCE-MS system. The separation was improved by using a high-viscosity separation buffer and a spray nozzle with a small bore size. This system was also applied to the separation of peptides and protein-trypsin digests. Sample adsorption was minimized by adding acetonitrile to the separation buffer when using a quartz microchip. 相似文献
92.
A mononuclear five-coordinate molybdenum(IV) monosulfide complex, (Et4N)2[MoS(L)2] (L = cyclohexene-1,2-dithiolate) (1), was obtained and characterized by IR, UV-vis spectroscopic methods, and X-ray crystallography. 1 was oxidized by an equivalent ferrocenium cation to give the corresponding mononuclear molybdenum(V) complex, (Et4N)[MoS(L)2] (2), which was stable for a few minutes under a lower concentration than 0.3 mM and then further dimerized to (Et4N)2[Mo(L)2]2(mu-S)2 (3). 相似文献
93.
Nakamura K Suzuki T Hasegawa M Kato Y Sasaki H Inouye K 《Journal of chromatography. A》2003,1009(1-2):133-139
An affinity sorbent, hydrophilic polymer-based carrier of different pore size (Toyopearl) with immobilized p-aminobenzamidine (ABA), has been prepared. Its basic properties and some applications for protein purification were studied. ABA, which is a synthetic inhibitor for trypsin-like proteases, was covalently immobilized to Toyopearl by reductive amination. The ligand density and binding capacity for porcine trypsin varied depending on the pore size of Toyopearl. The maximum binding capacity of the immobilized p-aminobenzamidine Toyopearl (ABA-Toyopearl) for trypsin was more than 40 mg/ml gel. ABA-Toyopearl thus obtained was very stable below pH 8 and was successfully used for high-performance affinity chromatography of trypsin-like proteases such as trypsin, thrombin, tissue-type plasminogen activator or urokinase in a single step at 25 degrees C. 相似文献
94.
By using an oligopeptide chain as a functional linker and introducing coumarin 2 and coumarin 343 at the chain ends, an effective photo-induced energy transfer system was constructed and energy transfer from coumarin 2 to coumarin 343 was switched on and off by a solvent-induced helix-coil secondary transition of the oligopeptide chain. 相似文献
95.
Kodera M Shimakoshi H Nishimura M Okawa H Iijima S Kano K 《Inorganic chemistry》1996,35(17):4967-4973
A mononucleating tripyridine ligand, 2-(bis(2-pyridyl)methyl)-6-methylpyridine (L(1)), and a dinucleating hexapyridine ligand, 1,2-bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane (L(2)), have been prepared. The reaction of a carbanion of 2,6-lutidine with 2-bromopyridine affords L(1) which is converted to L(2) quantitatively by treating with tert-butyllithium and 1,2-dibromoethane. (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) complexes [Fe(2)(O)(OAc)(2)(L(1))(2)](ClO(4))(2) (1) and [Fe(2)(O)(OAc)(2)L(2)](ClO(4))(2) (2) have been synthesized and characterized by means of infrared, UV/vis, mass, and M?ssbauer spectroscopies and by measuring magnetic susceptibility and cyclic voltammograms. All the spectral data are consistent with the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure in both 1 and 2. A relatively strong molecular ion peak at m/z 865 corresponding to [{Fe(2)O(OAc)(2)L(2)}(ClO(4))](+) in a FAB mass spectrum of 2 suggests the stabilization of the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure by L(2) in a solution state. The compound 2.DMF.2-PrOH.H(2)O, chemical formula C(44)Cl(2)Fe(2)H(51)N(7)O(16), crystallizes in the monoclinic space group C2/c with a = 22.034(6) ?, b = 12.595(5) ?, c = 20.651(7) ?, beta = 121.49(2) degrees, and Z = 4. The cation has 2-fold symmetry with the bridging oxygen atom on the 2-fold axis: Fe-(&mgr;-O) = 1.782(5) ?, Fe-O-Fe = 123.6(6) degrees, and Fe.Fe = 3.142(3) ?. The diiron(III) core structure of 2 seems to be stabilized by encapsulation of the ligand. Compound 2 is the first example of a discrete (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) complex with a dinucleating ligand. 相似文献
96.
[reaction: see text] Allylzirconium reagents are effective for radical allylation of alpha-halo carbonyl compounds. The key steps would be homolytic cleavage of the zirconium-carbon bond and halogen abstraction by the resulting Cp(2)ZrCl(III). Zirconocene-olefin complex can be also utilized for the allylation of alpha-halo compounds. 相似文献
97.
Hiroshi Tanaka Tsuyoshi Hasegawa Narumi Kita Hiroko Nakahara Takahiro Shibata Sho Oe Makoto Ojika Koji Uchida Takashi Takahashi 《化学:亚洲杂志》2006,1(5):669-677
An efficient solution‐phase synthesis of rac‐15‐deoxy‐Δ12,14‐PGJ2 (15dPGJ2) derivatives that contain variable α and ω chains based on a polymer‐assisted strategy and their neurite‐outgrowth‐promoting activity are described. The strategy for the synthesis of PGJ2 derivatives involves the use of a vinyl iodide bearing cyclopentenone as a key intermediate, which undergoes Suzuki–Miyaura coupling and subsequent Lewis acid catalyzed aldol condensation for incorporation of the ω and α chains, respectively. For easy access to the PGJ2 derivatives, a polymer‐supported catalyst and scavengers were adapted for use in these four diverse steps, in which workup and purification can be performed by simple filtration of the solid‐supported reagents. By using this methodology, we succeeded in the synthesis of 16 PGJ2 derivatives with four alkyl boranes and four aldehydes. The neurite‐outgrowth‐promoting activity of the 16 synthetic compounds in PC12 cells revealed that the side‐chains play a major role in modulating their biological activity. The carboxylic acid on the α chain improved the biological activity, although it was not absolutely required. Furthermore, a PGJ2 derivative with a phenyl moiety on the ω chain was found to exhibit an activity comparable to that of natural 15dPGJ2. 相似文献
98.
Iori Inoue Dr. Koji Yamamoto Prof. Dr. Shigeyoshi Sakaki Prof. Dr. Tetsuro Murahashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(41):10558-10562
A heterometallic M−M′ bond formation is a key to construct atomically precise bimetallic clusters and materials. However, it is sometimes not straightforward to construct a heterometallic M−M′ bond through conventional methods including redox condensation. Here, we found that a sandwich framework of π-conjugated unsaturated hydrocarbon ligands provides a unique coordination environment that facilitates unusual coupling of d8 RhI and d10 M0 (M=Pd, Pt). The molecular orbital analysis showed that the electron-accepting ability of the sandwich framework through back-donation allows the formation of a dσ-type Rh−Pd bond in a (d–d)18 electron system. 相似文献
99.
Shinji Suzuki Furitsu Suzuki Yasumasa Kanie Koji Tsujitani Asako Hirai Hironori Kaji Fumitaka Horii 《Cellulose (London, England)》2012,19(3):713-727
The structure and crystallization of carefully isolated sub-elementary fibrils (SEFs) of bacterial cellulose have been investigated
using TEM, WAXD, and high-resolution solid-state 13C NMR. The addition of a suitable amount of fluorescent brightener (FB) to the incubation medium of Acetobacter xylinum effectively suppressed the aggregation of the SEFs into the microfibrils, as previously reported. However, this study confirmed
for the first time that serious structural change in the SEFs occurs during the removal of excess FB by washing with buffer
solutions having pH values higher than 6 or with the alkaline aqueous solution that was frequently used in previous studies.
In contrast, the isolation of unmodified SEFs was successfully performed by utilizing a washing protocol employing pH 7 citrate–phosphate
buffer solution containing 1% sodium dodecyl sulfate. High-resolution solid-state 13C NMR and WAXD measurements revealed that the SEFs thus isolated are in the noncrystalline state in which the pyranose rings
of the almost parallel cellulose chains appear to be stacked on each other. The respective CH2OH groups of the SEFs adopt the gt conformation instead of the tg conformation found in cellulose I
α
and I
β
crystals, and undergo significantly enhanced molecular motion in the absence of intermolecular hydrogen bonding associated
with these groups. The main chains are also subject to rapid motional fluctuations while maintaining the parallel orientation
of the respective chains, indicating that the SEFs have a liquid crystal-like structure with high molecular mobility. Moreover,
the SEFs crystallize into cellulose I
β
when the FB molecules that may adhere to the surface of the SEFs are removed by extraction with boiling 70 v/v% ethanol and
0.1N NaOH aqueous solution. On the basis of these results, the crystallization of the SEFs into the I
α
and I
β
forms is discussed, including the possible formation of the crystalline-noncrystalline periodic structure in native cellulose. 相似文献
100.
Akane Sakaguchi-Mikami Miho Kameya Stefano Ferri Wakako Tsugawa Koji Sode 《Applied biochemistry and biotechnology》2013,170(3):710-717
Fructosamine-6-kinases (FN6Ks) that catalyze phosphorylation of glycated amino acids, i.e., fructosyl amino acids (FAs), have been shown as a potential recognition element for glycated protein detection. However, there are only two available FN6Ks: those from Escherichia coli which is specific for ε-fructosyl lysine (ε-FK) and Bacillus subtilis which recognizes both ε-FK and α-FA as substrates. In this study, we characterized an FN6K homologue isolated from Arthrobacter, some of whose species are reported to assimilate FA. The BLAST searches of Arthrobacter genomic database, using the bacterial FN6K primary structure information, revealed the presence of an FN6K homologue in Arthrobacter aurescens TC1 strain. Indeed, enzymatic assays confirmed that the putative FN6K from A. aurescens is an FN6K that is specific for ε-FK, although the primary sequence alignments showed similarity of A. aurescens FN6Ks with FN6Ks from B. subtilis and E. coli at the same level. In this study, we describe for the first time the presence of FN6K in Arthrobacter spp. and ε-FK-specific degradation pathway from Gram-positive bacteria, providing important information for the development of FA-recognizing molecules as well as for the FA assimilation system in bacteria. 相似文献