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951.
Dr. Kazuya Matsuo Yuki Nishikawa Marie Masuda Prof. Itaru Hamachi 《Angewandte Chemie (International ed. in English)》2018,57(3):659-662
The development of bioorthogonal approaches for labeling of endogenous proteins under the multimolecular crowding conditions of live cells is highly desirable for the analysis and engineering of proteins without using genetic manipulation. N‐Sulfonyl pyridone (SP) is reported as a new reactive group for protein sulfonylation. The ligand‐directed SP chemistry was able to modify not only purified proteins in vitro, but also endogenous ones on the surface of and inside live cells selectively and rapidly, which allowed to convert endogenous proteins to FRET‐based biosensors in situ. 相似文献
952.
Dr. Lauren Ray Dr. Kazuya Yamanaka Prof. Dr. Bradley S. Moore 《Angewandte Chemie (International ed. in English)》2016,55(1):364-367
Salinamide A belongs to a rare class of bicyclic depsipeptide antibiotics in which the installation of a (4‐methylhexa‐2,4‐dienoyl)glycine handle across a hexadepsipeptide core contributes to its chemical complexity and biological properties. Herein, we report the genetic and biochemical basis for salinamide construction in the marine bacterium Streptomyces sp. CNB‐091, which involves a novel intermolecular transesterification reaction catalyzed by a type I thioesterase. Heterologous expression studies revealed the central role of the nonribosomal peptide synthetase Sln9 in constructing and installing the distinctive acylglycine “basket handle” of salinamide. Biochemical characterization of the Sln9 thioesterase domain established that transesterification of the serine residue of desmethylsalinamide E with acylated glycyl thioesters yields desmethylsalinamide C. 相似文献
953.
Eiichiro Uemura Yasuo Yoshioka Toshiro Hirai Takayuki Handa Kazuya Nagano Kazuma Higashisaka Yasuo Tsutsumi 《Journal of nanoparticle research》2016,18(6):165
Although nanomaterials are used in an increasing number of commodities, the relationships between their immunotoxicity and physicochemical properties such as size or surface characteristics are not fully understood. Here we demonstrated that pretreatment with amorphous silica particles (SPs) of various sizes (diameters of 10–1000 nm), with or without amine surface modification, significantly decreased interleukin 6 production by RAW264.7 macrophages following lipopolysaccharide or peptidoglycan stimulation. Furthermore, nanosized, but not microsized, SPs significantly enhanced tumor necrosis factor-α production in macrophages stimulated with lipopolysaccharide. This altered cytokine response was distinct from the inflammatory responses induced by treatment with the SPs alone. Additionally, the uptake of SPs into macrophages by phagocytosis was found to be crucial for the suppression of macrophage immune response to occur, irrespective of particle size or surface modification. Together, these results suggest that SPs may not only increase susceptibility to microbial infection, but that they may also be potentially effective immunosuppressants. 相似文献
954.
Takuo Minato Dr. Kosuke Suzuki Dr. Kazuya Yamaguchi Prof. Dr. Noritaka Mizuno 《Angewandte Chemie (International ed. in English)》2016,55(33):9630-9633
The disassembly and reassembly of giant molecules are essential processes in controlling the structure and function of biological and artificial systems. In this work, the disassembly and reassembly of a giant ring‐shaped polyoxometalate (POM) without isomerization of the monomeric units is reported. The reaction of a hexavacant lacunary POM that is soluble in organic solvents, [P2W12O48]14?, with manganese cations gave the giant ring‐shaped POM [{γ‐P2W12O48Mn4(C5H7O2)2(CH3CO2)}6]42?. This POM is a hexamer of manganese‐substituted {P2W12O48Mn4} units, and its inner cavity was larger than any of those previously reported for ring‐shaped polyoxotungstates. It was disassembled into monomeric units in acetonitrile, and the removal of the capping organic ligands on the manganese cations led to reassembly into a tetrameric ring‐shaped POM, [{γ‐P2W12O48Mn4(H2O)6}4(H2O)4]24?. 相似文献
955.
We define a new concept of local states in the framework of algebraic quantum field theory (AQFT). Local states are a natural generalization of states and give a clear vision of localization in the context of QFT. In terms of them, we can find a condition from which follows automatically the famous DHR selection criterion in DHR-DR theory. As a result, we can understand the condition as consequences of physically natural state preparations in vacuum backgrounds. Furthermore, a theory of orthogonal decomposition of completely positive (CP) maps is developed. It unifies a theory of orthogonal decomposition of states and order structure theory of CP maps. Using it, localized version of sectors is formulated, which gives sector theory for local states with respect to general reference representations. 相似文献
956.
Dr. Qingde Zhuo Dr. Xiaoxi Zhou Dr. Takanori Shima Prof. Dr. Zhaomin Hou 《Angewandte Chemie (International ed. in English)》2023,62(19):e202218606
Dinitrogen (N2) activation and functionalization is of fundamental interest and practical importance. This review focuses on N2 activation and addition to unsaturated substrates, including carbon monoxide, carbon dioxide, heteroallenes, aldehydes, ketones, acid halides, nitriles, alkynes, and allenes, mediated by transition metal complexes, which afforded a variety of N−C bond formation products. Emphases are placed on the reaction modes and mechanisms. We hope that this work would stimulate further explorations in this challenging field. 相似文献
957.
Hanaoka K Kikuchi K Terai T Komatsu T Nagano T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(3):987-995
Magnetic resonance imaging (MRI) permits noninvasive three-dimensional imaging of opaque organisms. Gadolinium (Gd(3+)) complexes have become important imaging tools as MRI contrast agents for MRI studies, though most of them are nonspecific and report solely on anatomy. Recently, MRI contrast agents have been reported whose ability to relax water protons is triggered or greatly enhanced by recognition of a particular biomolecule. This new class of MRI contrast agents could open up the possibility of reporting on the physiological state or metabolic activity deep within living specimens. One possible strategy for this purpose is to utilize the increase in the longitudinal water proton r(1) relaxivity that occurs upon slowing the molecular rotation of a small paramagnetic complex, a phenomenon which is known as receptor-induced magnetization enhancement (RIME), by either binding to a macromolecule or polymerization of the agent itself. Here we describe the design and synthesis of a novel beta-galactosidase-activated MRI contrast agent, the Gd(3+) complex [Gd-5], by using the RIME approach. beta-Galactosidase is commonly used as a marker gene to monitor gene expression. This newly synthesized compound exhibited a 57% increase in the r(1) relaxivity in phosphate-buffered saline (PBS) with 4.5% w/v human serum albumin (HSA) in the presence of beta-galactosidase. Detailed investigations revealed that RIME is the dominant factor in this increase of the observed r(1) relaxivity, based on analysis of Gd(3+) complexes [Gd-5] and [Gd-8], which is generated from [Gd-5] by the activity of beta-galactosidase, and spectroscopic analysis of their corresponding Tb(3+) complexes, [Tb-5] and [Tb-8]. 相似文献
958.
Yamaguchi M Nakayama D Shima K Kuyama H Ando E Okamura TA Ueyama N Nakazawa T Norioka S Nishimura O Tsunasawa S 《Rapid communications in mass spectrometry : RCM》2008,22(20):3313-3319
We have developed a new method to determine the N-terminal amino acid sequences of proteins, regardless of whether their N-termini are modified. This method consists of the following five steps: (1) reduction, S-alkylation and guanidination for targeted proteins; (2) coupling of sulfo-NHS-SS-biotin to N(alpha)-amino groups of proteins; (3) digestion of the modified proteins by an appropriate protease followed by oxidation with performic acid; (4) specific isolation of N-terminal peptides from digests using DITC resins; (5) de novo sequence analysis of the N-terminal peptides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) using the CAF (chemically assisted fragmentation) method or tandem mass spectrometric (MS/MS) analysis according to unblocked or blocked peptides, respectively. By employing DITC resins instead of avidin resins used in our previous method (Yamaguchi et al., Rapid Commun. Mass Spectrom. 2007; 21: 3329), it has been possible to isolate selectively N-terminal peptides from proteins regardless of modification of N-terminal amino acids. Here we propose a universal method for N-terminal sequence analysis of proteins. 相似文献
959.
DNA liquid-crystalline gel as adsorbent of carcinogenic agent 总被引:1,自引:0,他引:1
Dobashi T Furusawa K Kita E Minamisawa Y Yamamoto T 《Langmuir : the ACS journal of surfaces and colloids》2007,23(3):1303-1306
DNA liquid crystalline gel (LCG) has been newly prepared by a dialysis of concentrated DNA solutions into concentrated metal cation solutions. The condition for forming DNA LCG is examined by means of the insolubilization reaction. The shrinking ratio and the ratio of the thickness of LCG layer, delta, and the diameter of the dialysis tube, d0, do not depend on d0. The adsorption of one of carcinogenic agents, acridine orange is demonstrated. From the experimental results, the mechanism for forming DNALCG is discussed. 相似文献
960.
The concentrations of dissolved silica species in electrolyte solutions were derived from the relative intensities of silica
species, obtained from FAB-MS measurements (fast atom bombardment mass spectrometry), and the total concentration of dissolved
silica. Generally, silica species in aqueous solutions form various complexes with cations such as sodium (Na+) or calcium (Ca2+), and it has been difficult to determine the concentration of each species. From the observed results from FAB-MS, the chemical
species of silica dissolved in lithium chloride (LiCl) and magnesium chloride (MgCl2) solutions do not include complexes with these cations, and thus Li+ and Mg2+ do not replace protons of the silanol groups in silica. Therefore, in LiCl and MgCl2 solutions, all of the simple structures of silicate species can be identified. The concentration of each silica species was
estimated on the basis of its mass spectra peak intensities and the total concentration of silica as determined by colorimetry.
This study yields the concentration of each silica species within small errors, whereas conventional methods (such as 29Si-NMR) have not yielded the concentrations of individual silica species. From these results, dimers and cyclic tetramers
are concluded to be the main species in silica solutions with concentrations of at most 0.1 to 0.2 μmol⋅dm−3. This tendency should also occur in NaCl and CaCl2 solutions, which are major electrolytes in natural waters. 相似文献