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991.
Excessive amounts of reactive oxygen species (ROS) induced by ultraviolet (UV) radiation cause skin aging via basement membrane/extracellular matrix degradation resulting from the action of matrix metalloproteinases (MMPs). Recently, phloroglucinol (1,3,5-trihydroxybenzene) was demonstrated to attenuate the cell damage induced by oxidative stress by quenching ROS and stimulating antioxidant systems. In the current study, the effect of phloroglucinol on UVB-induced photoaging was investigated in human HaCaT keratinocytes. Phloroglucinol significantly inhibited the UVB-induced (1) upregulation of MMP-1 mRNA, protein and activity; (2) augmentation of intracellular Ca(2+) levels; (3) phosphorylation of mitogen-activated protein kinases (MAPKs); (4) expression of c-Fos and phospho c-Jun; and (5) enhancement of activator protein-1 (AP-1) binding to the MMP-1 promoter. In addition, the knockdown of MAPKs significantly inhibited UVB-induced MMP-1 expression. The results of this study suggest that phloroglucinol may be useful as a photoprotective compound for the skin. 相似文献
992.
A novel electrochemical detection methodology is described for the femtomolar detection of proteins which utilizes both DNA aptamer-functionalized nanoparticles and a surface enzymatic reaction. Immunoglobulin E (IgE) was used as a model protein biomarker, which possesses two distinct epitopes for antibody (anti-IgE) and DNA aptamer binding. A surface sandwich assay format was utilized involving the specific adsorption of IgE onto a gold electrode surface that was pre-modified with a monolayer of aptamer-nanoparticle conjugates followed by the specific interaction of alkaline phosphatase (ALP) conjugated anti-IgE. To clearly demonstrate the signal enhancement associated with nanoparticle use, anodic current measurements of the ALP catalyzed oxidation of the enzyme substrate 4-aminophenylphosphate (APP) were also compared with electrode surfaces upon which the aptamer was directly attached. The detection of an unlabelled protein at concentrations as low as 5 fM is a significant improvement compared to conventional electrochemical-based immunoassay approaches and provides a foundation for the practical use and incorporation of nanoparticle-enhanced detection into electrochemical biosensing technologies. 相似文献
993.
An artificial nose was developed to mimic aspects of sensory transduction of the peripheral mammalian olfactory system. We directly cultured and differentiated rat olfactory sensory neurons (OSNs) on indium-tin oxide electrodes of planar triode substrates without a coupling agent. Direct voltage (~50 μV) and current (~250 nA) signals were measured simultaneously when OSNs on the planar triode substrates were exposed to odorant mixtures. The response signals were sensitive to the concentration of the odorant mixture, with a typical lifetime, shape, and adaptation profile as seen in responses upon repeated stimulation in vivo. We found that the rising time to the peak current was ~161 ms, while the signal back to baseline was in 1.8 s, which are in agreement with the natural intracellular electrophysiological responses. These results provide the first evidence that mature OSNs grown in a planar triode device are able to detect direct electrophysiological responses to odorants. 相似文献
994.
W Wang Y Lee TG Lee B Mun AG Giri J Lee H Kim D Hahn I Yang J Chin H Choi SJ Nam H Kang 《Organic letters》2012,14(17):4486-4489
A chemical investigation of a Korean marine sponge, Phorbas sp., yielded unprecedented sesterterpenoids phorone A (1) and isophorbasone A (2) along with ansellone B (3) and phorbasone A acetate (4). Their complete structures were elucidated by the combination of spectroscopic data and chemical manipulation. Phorone A (1) and isophorbasone A (2) have the new "phorane"(5) and "isophorbasane"(6) sesterterpenoid carbon skeletons, respectively. Ansellone B (3) and phorbasone A acetate (4) exhibited potent inhibitory activity on nitric oxide production in RAW 264.7 LPS-activated mouse macrophage cells with IC(50) values of 4.5 and 2.8 μM, respectively. 相似文献
995.
Rao AS Kim D Nam H Jo H Kim KH Ban C Ahn KH 《Chemical communications (Cambridge, England)》2012,48(26):3206-3208
An acedan derivative containing Zn(II)-DPA has been developed as a two-photon probe for nucleoside phosphates, which shows enhanced fluorescence toward ATP and ADP at physiological pH 7.4 among other competing anions including AMP; the probe is permeable to cell membranes and thus can be directly used for two-photon imaging of ATP and ADP in live cells. 相似文献
996.
Anh T. H. Le Nam H. Vu Thach S. Dinh Thi M. Cao Hung M. Le 《Theoretical chemistry accounts》2012,131(3):1158-13
Molecular dissociation of chlorine peroxide (ClOOCl), which consists of two elementary dissociation channels (of Cl–O and
O–O), is investigated using molecular dynamics simulations on a neural network-fitted potential energy surface constructed
by MP2 calculations with the 6-311G(d,p) basis set. When relaxed scans of the surface are executed, we observe that Cl–O dissociation
is extremely reactive with a low barrier height of 0.1928 eV (18.602 kJ/mol), while O–O bond scission is less reactive (0.7164 eV
or 69.122 kJ/mol). By utilizing the “novelty sampling” method, 35,006 data points in the ClOOCl configuration hyperspace are
collected, and a 40-neuron feed-forward neural network is employed to fit approximately 90% of the data to produce an analytic
potential energy function. The mean absolute error and root mean squared error of this fit are reported as 0.0078 eV (0.753 kJ/mol)
and 0.0137 eV (1.322 kJ/mol), respectively. Finally, quasi-classical molecular dynamics is executed at various levels of internal
energy (from 0.8 to 1.3 eV) to examine the bond ruptures. The two first-order rate coefficients are computed statistically,
and the results range from 5.20 to 22.67 ps−1 for Cl–O dissociation and 3.72–8.35 ps−1 for O–O dissociation. Rice-Ramsperger-Kassel theory is utilized to classically correlate internal energies to rate coefficients
in both cases, and the plots exhibit very good linearity, thus can be employed to predict rate coefficients at other internal
energy levels with good reliability. 相似文献
997.
Ki-Woong Chae Ta-Ryeong Park Chae Il Cheon Nam In Cho Jeong Seog Kim 《Journal of luminescence》2012,132(9):2293-2301
A novel synthesis was developed for enhanced luminescence in sesquioxide phosphors containing Eu3+ activator. It consisted of two annealing steps: reduction under vacuum with gaseous H2 at 10 Torr and 1300 °C and re-oxidation at 300–1500 °C in air. The integrated luminescence intensity of the monoclinic Eu2O3 phosphor was enhanced ca. 21 times by this method compared with conventional processing. The photoluminescence (PL) intensity was maximized at re-oxidation temperatures of 500–1100 °C. The PL characteristics of monoclinic Eu2O3 and Gd2O3:0.06Eu samples were compared with a commercial cubic Y2O3:Eu phosphor. The evolution of physical characteristics during the two-step annealing was studied by Raman spectroscopy, XPS, XRD, PL decay analysis, and SEM. PL decay lifetime increased proportionally to the PL intensity over the range 0.5–100 μs. Additional vibrational modes appeared at 490, 497, and 512 cm?1 after the two-step annealing. The increase in PL intensity was ascribed to the formation of excess oxygen vacancies and their redistribution during annealing. Resonance crossovers between the charge transfer state and the emitting 5DJ states are discussed in relation to reported luminescence saturation mechanisms for oxysulfides Ln2O2S:Eu3+ (Ln=Y, La). 相似文献
998.
Park SR Han J Kim C Koh YY Kim C Lee H Choi HJ Han JH Lee KD Hur NJ Arita M Shimada K Namatame H Taniguchi M 《Physical review letters》2012,108(4):046805
We performed angle-resolved photoemission (ARPES) experiments with circularly polarized light and first-principles density functional calculation with spin-orbit coupling to study surface states of a topological insulator Bi2Se3. We observed circular dichroism (CD) as large as 30% in the ARPES data with upper and lower Dirac cones showing opposite signs in CD. The observed CD is attributed to the existence of local orbital-angular momentum (OAM). First-principles calculation shows that OAM in the surface states is significant and is locked to the electron momentum in the opposite direction to the spin, forming chiral OAM states. Our finding opens a new possibility for strong light-induced spin-polarized current in surface states. We also provide a proof for local OAM origin of the CD in ARPES. 相似文献
999.
Quoc Thanh Phung Van Khai Vu An Bang Ngac Huy Sinh Nguyen Nam Nhat Hoang 《Journal of magnetism and magnetic materials》2012
The magnetic and transport properties of the perovskites La0.67Ca0.33Mn1-xTMxO3 were found to be sufficiently changed with the substitution of Mn-sites by other 3d transition-metal cations (TM=Cu,Zn; x=0.15). The values of TC, TM−I, and TCMR were surveyed when Mn was replaced by Cu and Zn. The magnetic field induced resistivity and magnetic entropy change of these samples showed abrupt changes near TC (194.2 and 201.5 K for Cu and Zn-doped case respectively) and attained the highest values among the doped cases (up to 20% Cu). The maximum values (obtained at H=4 kOe) of magnetoresistance ratio (CMR) were 27.8%, and 24.5% and of magnetic entropy change (−ΔSM) were 3.9 and 3.2 J/kg K for Cu and Zn-doped, respectively. 相似文献
1000.
Multiple color states have been realized in single unit cell using double electrochromic (EC) reaction. The precise control of bistability in EC compounds which can maintain several colors on the two separated electrodes allows this new type of pixel to be realized. The specific electrical driving gives a way to maintain both sides in the reduced EC states and this colors overlapping in the vertical view direction can achieve the black state. The four color states (G, B, W, BK) in one cell/pixel can make a valuable progress to achieve a high quality color devices such like electronic paper, outdoor billboard, smart window and flexible display using external light source. 相似文献