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991.
Fukuzumi S Kotani H Prokop KA Goldberg DP 《Journal of the American Chemical Society》2011,133(6):1859-1869
The electron-transfer and hydride-transfer properties of an isolated manganese(V)?oxo complex, (TBP8Cz)Mn(V)(O) (1) (TBP8Cz = octa-tert-butylphenylcorrolazinato) were determined by spectroscopic and kinetic methods. The manganese(V)?oxo complex 1 reacts rapidly with a series of ferrocene derivatives ([Fe(C5H4Me)2], [Fe(C5HMe4)2], and ([Fe(C5Me5)2] = Fc*) to give the direct formation of [(TBP8Cz)Mn(III)(OH)]? ([2-OH]?), a two-electron-reduced product. The stoichiometry of these electron-transfer reactions was found to be (Fc derivative)/1 = 2:1 by spectral titration. The rate constants of electron transfer from ferrocene derivatives to 1 at room temperature in benzonitrile were obtained, and the successful application of Marcus theory allowed for the determination of the reorganization energies (λ) of electron transfer. The λ values of electron transfer from the ferrocene derivatives to 1 are lower than those reported for a manganese(IV)?oxo porphyrin. The presumed one-electron-reduced intermediate, a Mn(IV) complex, was not observed during the reduction of 1. However, a Mn(IV) complex was successfully generated via one-electron oxidation of the Mn(III) precursor complex 2 to give [(TBP8Cz)Mn(IV)]+ (3). Complex 3 exhibits a characteristic absorption band at λ(max) = 722 nm and an EPR spectrum at 15 K with g(max)′ = 4.68, g(mid)′ = 3.28, and g(min)′ = 1.94, with well-resolved 55Mn hyperfine coupling, indicative of a d3 Mn(IV)S = 3/2 ground state. Although electron transfer from [Fe(C5H4Me)2] to 1 is endergonic (uphill), two-electron reduction of 1 is made possible in the presence of proton donors (e.g., CH3CO2H, CF3CH2OH, and CH3OH). In the case of CH3CO2H, saturation behavior for the rate constants of electron transfer (k(et)) versus acid concentration was observed, providing insight into the critical involvement of H+ in the mechanism of electron transfer. Complex 1 was also shown to be competent to oxidize a series of dihydronicotinamide adenine dinucleotide (NADH) analogues via formal hydride transfer to produce the corresponding NAD+ analogues and [2-OH]?. The logarithms of the observed second-order rate constants of hydride transfer (k(H)) from NADH analogues to 1 are linearly correlated with those of hydride transfer from the same series of NADH analogues to p-chloranil. 相似文献
992.
Morimoto Y Kotani H Park J Lee YM Nam W Fukuzumi S 《Journal of the American Chemical Society》2011,133(3):403-405
Rates of electron transfer from a series of one-electron reductants to a nonheme oxoiron(IV) complex, [(N4Py)Fe(IV)(O)](2+), are enhanced as much as 10(8)-fold by addition of metal ions such as Sc(3+), Zn(2+), Mg(2+), and Ca(2+); the metal ion effect follows the Lewis acidity of metal ions. The one-electron reduction potential of [(N4Py)Fe(IV)(O)](2+) is shifted to a positive direction by 0.84 V in the presence of Sc(3+) ion (0.20 M). 相似文献
993.
Abe R Ohashi H Iijima I Ihara M Takagi H Hohsaka T Ueda H 《Journal of the American Chemical Society》2011,133(43):17386-17394
Here, we describe a novel reagentless fluorescent biosensor strategy based on the antigen-dependent removal of a quenching effect on a fluorophore attached to antibody domains. Using a cell-free translation-mediated position-specific protein labeling system, we found that an antibody single chain variable region (scFv) that had been fluorolabeled at the N-terminal region showed a significant antigen-dependent fluorescence enhancement. Investigation of the enhancement mechanism by mutagenesis of the carboxytetramethylrhodamine (TAMRA)-labeled anti-osteocalcin scFv showed that antigen-dependency was dependent on semiconserved tryptophan residues near the V(H)/V(L) interface. This suggested that the binding of the antigen led to the interruption of a quenching effect caused by the proximity of tryptophan residues to the linker-tagged fluorophore. Using TAMRA-scFv, many targets including peptides, proteins, and haptens including morphine-related drugs could be quantified. Similar or higher sensitivities to those observed in competitive ELISA were obtained, even in human plasma. Because of its versatility, this "quenchbody" is expected to have a range of applications, from in vitro diagnostics, to imaging of various targets in situ. 相似文献
994.
Topical use of small interfering RNA (siRNA) as a therapeutic nucleic acid is increasingly studied for the treatment of skin diseases and for the improvement of skin properties. However, naked siRNA transdermal delivery is limited by its low stability in the body and low permeability into target cells. This is due to various skin barriers such as the stratum corneum that has multiple lipid bilayers and epidermal layers that have tight junctions. In this study, we investigate non-invasive transdermal siRNA delivery using two functional peptides: AT1002, which is a tight junction modulator and 6-mer synthetic peptide belonging to a novel class of compounds that reversibly increases paracellular transport of molecules across the epithelial barrier; and Tat, which is a cell-penetrating peptide applicable as a transdermal siRNA delivery enhancer. We examined whether expression of the tight junction protein zonula occludens protein 1 (ZO-1) was detected in mouse skin applied with AT1002. Additionally, siRNA stabilities for RNaseA using Tat and AT1002 were assessed. We also determined the intradermal delivery efficiency of siRNA using functional peptides by confocal laser microscopy of fluorescently labeled siRNA in mouse skin. We found that the Tat analog and AT1002 strongly increased siRNA stability against RNaseA. In addition, ZO-1 disappeared from the skin after treatment with AT1002, yet recovered with time after washing. Finally, we also found that Tat and AT1002 peptides accelerate transdermal siRNA delivery both widely and effectively. Thus, combination of Tat and AT1002 is expected to be a transdermal delivery enhancer of siRNA. 相似文献
995.
Novel potent cytotoxic peptides bisebromoamide (1) and norbisebromoamide (2) have been isolated from the marine cyanobacterium Lyngbya sp. The planar structure of these peptides was elucidated through the extensive application of 1D and 2D NMR techniques. The absolute stereostructure of 1 was determined by chemical degradation followed by chiral HPLC analysis. Recently, Tao and co-workers achieved synthesis of bisebromoamide, and the configuration of thiazoline moiety was revised. We re-investigated the stereochemistry of thiazoline moiety of 1. The structure-activity relationships of bisebromoamide (1) were investigated with the use of natural and synthetic analogs. Furthermore, bisebromoamide (1) potently inhibited protein kinase: the phosphorylation of ERK in NRK cells by PDGF-stimulation was selectively inhibited by treatment with 10-0.1 μM of 1. 相似文献
996.
A chiral acid-base organocatalyst was found to promote an aza-MBH domino process between α,β-unsaturated carbonyl compounds and N-tosylimines to afford tetrahydropyridine derivatives with high enantioselectivity. 相似文献
997.
Prof. Dr. Masahiro Sadakane Niklas Rinn Sachie Moroi Hiroaki Kitatomi Tomoji Ozeki Mariko Kurasawa Masaya Itakura Shinjiro Hayakawa Kazuo Kato Mayumi Miyamoto Shuhei Ogo Yusuke Ide Tsuneji Sano 《无机化学与普通化学杂志》2011,637(11):1467-1474
RuII‐ and RuIII‐substituted α‐Keggin‐type phosphotungstates with a dimethyl sulfoxide (DMSO) ligand, [PW11O39RuIIDMSO]5– ( 1 ) and [PW11O39RuIIIDMSO]4– ( 2 ), were synthesized. Compound 1 was prepared by reaction of [PW11O39]7– with [RuII(DMSO)4]Cl2 in water at 125 °C under hydrothermal conditions and was isolated as a cesium salt. Compound 2 was prepared by reaction of 1 with bromine in water at 60 °C and was isolated as a cesium salt. The compounds were characterized by cyclic voltammetry, elemental analysis, UV/Vis, IR,31P NMR, 183W NMR, 1H NMR, and XANES (Ru K‐edge and L3‐edge)spectroscopic methods. Single crystal structural analysis of 1 revealed that RuII is incorporated in the α‐Keggin framework and coordinated by DMSO through a Ru–S bond. Cyclic voltammetry of 1 indicated that the incorporated RuII‐DMSO is reversibly oxidizable to the RuIII‐DMSO derivative 2 . Compound 1 showed catalytic activity for water oxidation in the presence of cerium ammonium nitrate as an oxidant. 相似文献
998.
Jacobsen Ø Maekawa H Ge NH Görbitz CH Rongved P Ottersen OP Amiry-Moghaddam M Klaveness J 《The Journal of organic chemistry》2011,76(5):1228-1238
Short peptides are important as lead compounds and molecular probes in drug discovery and chemical biology, but their well-known drawbacks, such as high conformational flexibility, protease lability, poor bioavailability and short half-lives in vivo, have prevented their potential from being fully realized. Side chain-to-side chain cyclization, e.g., by ring-closing olefin metathesis, known as stapling, is one approach to increase the biological activity of short peptides that has shown promise when applied to 3(10)- and α-helical peptides. However, atomic resolution structural information on the effect of side chain-to-side chain cyclization in 3(10)-helical peptides is scarce, and reported data suggest that there is significant potential for improvement of existing methodologies. Here, we report a novel stapling methodology for 3(10)-helical peptides using the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction in a model aminoisobutyric acid (Aib) rich peptide and examine the structural effect of side chain-to-side chain cyclization by NMR, X-ray diffraction, linear IR and femtosecond 2D IR spectroscopy. Our data show that the resulting cyclic peptide represents a more ideal 3(10)-helix than its acyclic precursor and other stapled 3(10)-helical peptides reported to date. Side chain-to-side chain stapling by CuAAC should prove useful when applied to 3(10)-helical peptides and protein segments of interest in biomedicine. 相似文献
999.
Tamura M Inada M Nakazato T Yamamoto K Endo S Uchida K Horie M Fukui H Iwahashi H Kobayashi N Morimoto Y Tao H 《Talanta》2011,84(3):802-808
This paper describes a method for determination of multiwall carbon nanotubes (MWCNTs) in rat lungs after intratracheal instillation exposure. The MWCNTs were quantitatively decomposed to CO2 by combustive oxidation and were then determined by non-dispersive infrared analysis. Samples were pretreated by acid digestion, muffle ashing and in situ preheating to remove interferences due to coexisting biological carbon from the lung tissue sample, while preserving the MWCNTs as in its their original form. The preservation was confirmed by transmission electron microscopic observation of the pretreated samples of exposed lung tissues and by the fact that the recoveries of MWCNTs spiked to the lung tissues were close to 100%. The detection limit for MWCNTs obtained by the proposed method was 0.30 μg and the repeatability as expressed by the relative standard deviation was 5.6% (n = 4). The method was sufficiently sensitive and precise to apply to real samples of rat lung to investigate the in vivo persistence of intratracheally instilled MWCNTs. To our knowledge, this is the first report of this type of sample pretreatment and direct determination of pristine MWCNTs without modification or tagging. Conventional indirect methods use tagging with other compounds or metal impurities in the CNTs for detection, and the detachment of these tags can increase uncertainties in the determination of the CNTs. The tags can also change how the CNTs persist in vivo, which can lead to an incorrect understanding of the persistence of pristine CNTs in vivo. 相似文献
1000.
Thu Lan Nguyen Takashi Yano Huy Quang Nguyen Tsuyoshi Nishimura Hiroaki Fukushima Tetsumi Sato Takashi Morihara Yoritaka Hashimoto 《Applied Acoustics》2011,(11):814-822
To formulate Vietnamese and global noise policies, social surveys on community response to aircraft noise and combined noise from aircraft and road traffic were carried out in Ho Chi Minh City from August to September 2008 and in Hanoi from August to September 2009. In total, 1562 and 1397 responses were obtained in Ho Chi Minh City and Hanoi, respectively. The aircraft noise was measured for seven successive days, and the combined noise was measured for 24 h. Aircraft and combined noise exposures ranged from 53 to 71 dB and 73 to 83 dB Lden in Ho Chi Minh City and from 48 to 61 dB and 70 to 82 dB Lden in Hanoi, respectively. The dose–response curve for aircraft noise for Vietnam was established and fitted onto the curve for the European Union. For the same noise exposure, the aircraft noise annoyance in Hanoi was higher than that in Ho Chi Minh City because of the lower background noise level in Hanoi. 相似文献