We found that a variety of compounds containing partial structures of tamoxifen showed activity as chemical modulators of large-conductance calcium-activated K+ channels (BK channels). 相似文献
A hierarchical hybrid of gold nanoparticles and titania nanotubes with high metal loading was prepared by a one-pot approach using a natural cellulosic substance as template. Gold nanoparticles were uniformly anchored onto titania nanotubes, and particle fusion at high temperature was suppressed by surface coating with an ultrathin titania layer. 相似文献
The intermolecular potential energy surface of O(2)-H(2)O was investigated at ab initio MP2 and MRSDCI levels using the aug-cc-pVTZ basis set. The vibrational levels were evaluated by numerically solving the Schr?dinger equations for the nuclear motions with the ab initio potential functions using one- to three-dimensional finite-element methods. On the basis of the calculated partition functions, the equilibrium constant of the complex, K(p), was studied. The K(p) values at atmospheric temperatures of 200-300 K were found to be 1-2 orders of magnitude less than previous estimates from the harmonic oscillator approximation. 相似文献
Oxidation of phenol, anisole and toluene with permonophosphoric acid in acetonitrile or water gives the corresponding ortho and para hydroxylated aromatics (HO-C6H4-X, X = OH, OMe, Me). The observed ortho :para ratio in a solvent acetonitrile are as follows: 5·0 with phenol, 3·5 with anisole and 2·0 with toluene. The oxidation rates for phenol and anisole in acetonitrile are expressed as: v = k″[ArH][H3PO5]2ho, where ho is the Hammett's acidity function and ArH is phenol or anisole. A mechanism involving a rate-determining attack of protonated dimeric perphosphoric acid 4 on aromatic carbon is presented and discussed. 相似文献
An electrospray dual sprayer, which generates separate sample and reference sprays by alternately switching the high voltage between the two sprayers, is described. The technique permits accurate mass measurements in nano-electrospray ionization mass spectrometry (ESI-MS) to be obtained using a quadrupole/orthogonal acceleration time-of-flight mass spectrometer (Q-TOF). Similar to the method employed with a dual ESI source (Wolff JC et al., Anal. Chem. 2001; 73: 2605), the two sprays are orthogonal with respect to each other, but can be independently sampled without any baffle between these sprays. The reference sprayer is used in the original configuration of the ESI source and was optimized for a 1-2 muL/min flow, whereas the sample sprayer can be either a conventional glass capillary or a borosilicate tip of the type used for nano-ESI. Both sprayers can be positioned close to the cone so as to give maximum ion currents. The sample and reference sprays are independently generated by raising the potentials on the sample and reference sprayers to 1.4 and 3.0 kV, respectively; the high voltages can be rapidly turned on and off in ca. 1 ms. A nano-ESI-MS or nano-flow LC/ESI-MS experiment using a Q-TOF coupled with the above system gave mass accuracies within 3 ppm for measurements of ions up to m/z 1000 using subpicomole samples. 相似文献
Two new ursane-type triterpenoids (1, 2) attached to isopropylidenedioxy group were isolated from the seeds of blackberry (Rubus fructicosus L., Rosaceae) along with two known ursane-type triterpenoids, 2,3-O-isopropylidenyl-2α,3α,19α-trihydroxyurs-12-en-28-oic acid (3) and 1β-hydroxyeuscaphic acid (4). The chemical structures of 1 and 2 were determined to be 2,3-O-isopropylidene-1β,2β,3β,19α-tetrahydroxyurs-12-en-28-oic acid and 1,2-O-isopropylidene-1β,2α,3α,19α-tetrahydroxyurs-12-en-28-oic acid, respectively, based on spectroscopic data. Additionally, their cytotoxic activity towards HL-60 human leukaemia cells was evaluated. Among them, 3 demonstrated a clear cytotoxic activity with 72.8 μM of IC50 value. 相似文献
Spin valves having thin oxide layers in the pinned and/or free layers were prepared by sputtering. MR ratios of the spin valves were increased from 8.1 to 11.9% by inserting the oxide layer into the pinned layer in Ta/PtMn/CoFe/Cu/CoFe/Ta spin valves. MR ratio of 13.9% and considerably large sheet ΔR of 2.55 Ω were obtained in the PtMn-based spin valves having the oxide layer in the pinned and free layer. Larger MR ratio of 17.3% and the sheet ΔR of 1.3 Ω were obtained in the PtMn-based dual-type spin valves having the oxide layer in both pinned layers. α-Fe2O3 based spin valves having thin oxide layers were also prepared. MR ratios of the spin valves were increased from 11.9 to 14.3% by inserting the oxide layer into the free layer in α-Fe2O3/CoFe/Cu/CoFe/Ta spin valves. The enhancement of the MR ratios may be attributed to the specular scattering effect of the conduction electrons by the thin oxide layers. 相似文献
The surface molecular motion of monodisperse polystyrene (PS) with various chain end groups was investigated on the basis of temperature‐dependent scanning viscoelasticity microscope (TDSVM). The surface glass transition temperatures, Tgss for the proton‐terminated PS (PS‐H) films with number‐average molecular weight, Mn of 4.9k–1,450k measured by TDSVM measurement were smaller than those for the bulk one, with corresponding Mns, and the Tgss for Mn smaller than ca. 50k were lower than room temperature (293 K). In the case of Mn = ca. 50k, the Tgss for the α,ω‐diamino‐terminated PS (α,ω‐PS(NH2)2) and α,ω‐dicarboxy‐terminated PS (α,ω‐PS(COOH)2) films were higher than that of the PS‐H film. On the other hand, the Tgs for the α,ω‐perfluoroalkylsilyl‐terminated PS (α,ω‐PS(SiC2CF6)2) film with the same Mn was much lower than those for the PS films with all other chain ends. The change of Tgs for the PS film with various chain end groups can be explained in terms of the depth distribution of chain end groups at the surface region. 相似文献
The enzyme, cutinase from Saccharomonospora viridis AHK190 (Cut190), can hydrolyze the inner block of polyethylene terephthalate (PET). Cut190 has a unique feature that both its activity and thermal stability are increased upon Ca2+ binding. In consideration of the glass transition temperature of PET, which is between 60 and 65 °C, the increased activity and thermal stability are of great interest to apply for PET bio-recycling. Our previous mutational analysis showed that the S226P/R228S mutant (Cut190*) has a higher activity and thermal stability than those of the wild type. In this study, we analyzed the folding thermodynamics of the inactive mutant of Cut190*, Cut190*S176A, using circular dichroism and differential scanning calorimetry. The results show that the denaturation temperature increases from 54 to 71 °C due to the addition of 250 mM Ca2+, in a Ca2+ concentration-dependent manner. The increased thermal stability is mainly due to the increased enthalpy change, partially compensated by the increased entropy change. Based on the crystal structure of Cut190*S176A bound to Ca2+, molecular dynamics simulations were carried out to analyze the effects of Ca2+ on the structural dynamics, showing that the Ca2+-bound structure fluctuated less than the Ca2+-free structure. Structural analysis indicates that Ca2+ binding increases the intramolecular interactions of the enzyme, while decreasing its fluctuation, which are in good correlation with the experimental results of the folding thermodynamics.