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481.
Akira SugaharaKimio Moriya Masaya EnomotoAtsushi Okazawa Norimichi Kojima 《Polyhedron》2011,30(18):3127-3130
Toward the realization of a ligand-driven light-induced spin change (LD-LISC) around room temperature, we have investigated the spin-crossover phenomenon in [Fe(stpy)4(X)2] (stpy = styrylpyridine, X = NCS, NCBH3) under high pressure. The spin transition temperature increases from 110 to 220 K with increasing applied pressure up to 0.75 GPa for [Fe(trans-stpy)4(NCS)2], while [Fe(cis-stpy)4(NCS)2] shows the high-spin state in the temperature region between 2 and 300 K even at 0.75 GPa. In the case of X = NCBH3, due to the stronger ligand field of NCBH3, the spin transition temperature increases from 240 to 360 K with increasing applied pressure up to 0.50 GPa for [Fe(trans-stpy)4(NCBH3)2]. In the case of [Fe(cis-stpy)4(NCBH3)2], the spin state is the high-spin state in the temperature region between 2 and 300 K. However, the spin transition appears at 125 K under 0.5 GPa and the transition temperature increases with increasing applied pressure. In this way, we have decided the applied pressure region of 0.65-1.09 GPa where [Fe(stpy)4(NCBH3)2] undergoes LD-LISC at room temperature. 相似文献
482.
Toshiki Nishiura Takehiro Ohta Takashi Ogura Jun Nakazawa Masaya Okamura Shiro Hikichi 《Molecules (Basel, Switzerland)》2022,27(19)
Conversion from superoxide (O2−) to hydroperoxide (OOH−) on the metal center of oxygenases and oxidases is recognized to be a key step to generating an active species for substrate oxidation. In this study, reactivity of cobalt(III)-superoxido complexes supported by facially-capping tridentate tris(3,5-dimethyl-4-X-pyrazolyl)hydroborate ([HB(pzMe2,X)3]−; TpMe2,X) and bidentate bis(1-methyl-imidazolyl)methylborate ([B(ImN-Me)2Me(Y)]−; LY) ligands toward H-atom donating reagent (2-hydroxy-2-azaadamantane; AZADOL) has been explored. The oxygenation of the cobalt(II) precursors give the corresponding cobalt(III)-superoxido complexes, and the following reaction with AZADOL yield the hydroperoxido species as has been characterized by spectroscopy (UV-vis, resonance Raman, EPR). The reaction of the cobalt(III)-superoxido species and a reducing reagent ([CoII(C5H5)2]; cobaltocene) with proton (trifluoroacetic acid; TFA) also yields the corresponding cobalt(III)-hydroperoxido species. Kinetic analyses of the formation rates of the cobalt(III)-hydroperoxido complexes reveal that second-order rate constants depend on the structural and electronic properties of the cobalt-supporting chelating ligands. An electron-withdrawing ligand opposite to the superoxide accelerates the hydrogen atom transfer (HAT) reaction from AZADOL due to an increase in the electrophilicity of the superoxide ligand. Shielding the cobalt center by the alkyl group on the boron center of bis(imidazolyl)borate ligands hinders the approaching of AZADOL to the superoxide, although the steric effect is insignificant. 相似文献
483.
484.
Praphawi Nattasit Kunimichi Niibe Masahiro Yamada Yumi Ohori-Morita Phoonsuk Limraksasin Watcharaphol Tiskratok Masaya Yamamoto Hiroshi Egusa 《Macromolecular bioscience》2023,23(7):2300021
Microenvironmental factors, including substrate stiffness, regulate stem cell behavior and differentiation. However, the effects of substrate stiffness on the behavior of induced pluripotent stem cell (iPSC)- derived embryoid bodies (EB) remain unclear. To investigate the effects of mechanical cues on iPSC-EB differentiation, a 3D hydrogel-sandwich culture (HGSC) system is developed that controls the microenvironment surrounding iPSC-EBs using a stiffness-tunable polyacrylamide hydrogel assembly. Mouse iPSC-EBs are seeded between upper and lower polyacrylamide hydrogels of differing stiffness (Young's modulus [E’] = 54.3 ± 7.1 kPa [hard], 28.1 ± 2.3 kPa [moderate], and 5.1 ± 0.1 kPa [soft]) and cultured for 2 days. HGSC induces stiffness-dependent activation of the yes-associated protein (YAP) mechanotransducer and actin cytoskeleton rearrangement in the iPSC-EBs. Moreover, moderate-stiffness HGSC specifically upregulates the mRNA and protein expression of ectoderm and mesoderm lineage differentiation markers in iPSC-EBs via YAP-mediated mechanotransduction. Pretreatment of mouse iPSC-EBs with moderate-stiffness HGSC promotes cardiomyocyte (CM) differentiation and structural maturation of myofibrils. The proposed HGSC system provides a viable platform for investigating the role of mechanical cues on the pluripotency and differentiation of iPSCs that can be beneficial for research into tissue regeneration and engineering. 相似文献