Optically manipulating the local pH of a target solution in a microchannel, or reservoir, provides a mechanism for activating and controlling a variety of biological and chemical processes on Lab-on-a-Chip (LOC) devices and micro-total analysis systems (μ-TAS). A microscale pH gradient generator that exploits the light-activated molecular proton pumps found in the purple membranes (PM) of bacteriorhodopsin is described in this paper. The photo-electro-chemical transducer is an ultrathin layer (~13?nm) of oriented PM patches self-assembled on an Au-coated porous substrate. A biotin labeling and streptavidin molecular recognition technique is used to ensure that the extracellular side of all PM patches is attached to the porous substrate enabling unidirectional and efficient transport of ions across the transducer surface. The photo-induced proton pumps generate a flow of ions that produce a measurable change in pH between the separated solutions. The self-assembly procedure is experimentally quantified based on the capacitance characteristics of the bR membranes. The investigation confirms that the transducer is covered with the bR proton pumps at a mass density of 2.33?ng/cm2. Experimental tests also show that the proposed transducer can repeatedly generate pH gradients as high as 0.42 and absolute voltage differences as high as 25?mV when illuminated by an 18?mW, 568?nm light source. Furthermore, the ΔpH is observed to be nonlinear with respect to light intensity and exposure time. The ΔpH of the target solution is sufficient to cause a phenolphthalein indicator dye to change color or an ionic hydrogel micro-valve to expand. 相似文献
A kinetic analysis of the isothermal nitridation of high-purity oxide-free silicon powder is described. The kinetic analysis suggests that the and polymorphs of Si3N4 are formed by separate and parallel reaction paths. This analysis provides for the decoupling and quantitative kinetic interpretation of- and-Si3N4 formation reactions. Consistent with existing microstructural and thermodynamic evidence, the-forming reaction is shown to obey a first-order rate law, whereas a phase-boundary controlled rate law describes the-forming reaction. A kinetic model employing these rate laws is developed and is used to predict the/ phase ratio as a function of isothermal reaction temperature and extent of reaction. The/ phase ratios so obtained are shown to be in good agreement with experimental observations made under a variety of reaction conditions. 相似文献
Electrocaloric (EC) refrigeration, is accepted as an auspicious method to develop eco-friendly cooling devices. Here, the investigations on the EC response and energy storage performance of heterovalent-doped Ba(Sn, Ti)O3 relaxor ferroelectrics are carried out. Doping of aliovalent Mn or Nb elements into Ti site would regulate both the EC and energy storage behaviors. An enhanced EC temperature change up to 1.31 K, and a maximal recoverable energy storage density of 0.24 J cm??3 with the efficiency as high as 87.11?%, can be observed under 70 kV cm??1 in 0.5?% acceptor-doped Ba(Sn, Ti)O3 ceramics. It is found that the local internal stress, the local charge fluctuation, and the oxygen deficiencies would benefit the electrical behaviors of this system. These results would shed light on the effect of the heterovalent substitution on the electrical properties of lead-free BaTiO3 system and provide a novel and simple route to further improve the EC response and energy storage performance.
TP53 gene mutations occur in 70% of oesophageal adenocarcinomas (OACs). Given the central role of p53 in controlling cellular response to therapy we investigated the role of mutant (mut-) p53 and SLC7A11 in a CRISPR-mediated JH-EsoAd1 TP53 knockout model. Response to 2 Gy irradiation, cisplatin, 5-FU, 4-hydroxytamoxifen, and endoxifen was assessed, followed by a TaqMan OpenArray qPCR screening for differences in miRNA expression. Knockout of mut-p53 resulted in increased chemo- and radioresistance (2 Gy survival fraction: 38% vs. 56%, p < 0.0001) and in altered miRNA expression levels. Target mRNA pathways analyses indicated several potential mechanisms of treatment resistance. SLC7A11 knockdown restored radiosensitivity (2 Gy SF: 46% vs. 73%; p = 0.0239), possibly via enhanced sensitivity to oxidative stress. Pathway analysis of the mRNA targets of differentially expressed miRNAs indicated potential involvement in several pathways associated with apoptosis, ribosomes, and p53 signaling pathways. The data suggest that mut-p53 in JH-EsoAd1, despite being classified as non-functional, has some function related to radio- and chemoresistance. The results also highlight the important role of SLC7A11 in cancer metabolism and redox balance and the influence of p53 on these processes. Inhibition of the SLC7A11-glutathione axis may represent a promising approach to overcome resistance associated with mut-p53. 相似文献
Thiosulfate in the form of sodium thiosulfate (STS) is a major oxidation product of hydrogen sulfide (H2S), an endogenous signaling molecule and the third member of the gasotransmitter family. STS is currently used in the clinical treatment of acute cyanide poisoning, cisplatin toxicities in cancer therapy, and calciphylaxis in dialysis patients. Burgeoning evidence show that STS has antioxidant and anti-inflammatory properties, making it a potential therapeutic candidate molecule that can target multiple molecular pathways in various diseases and drug-induced toxicities. This review discusses the biochemical and molecular pathways in the generation of STS from H2S, its clinical usefulness, and potential clinical applications, as well as the molecular mechanisms underlying these clinical applications and a future perspective in kidney transplantation. 相似文献
Brillouin scattering (BS), photon correlation spectroscopy (PCS), and ultrasonic (US) measurements were conducted to study the curing process of diglycidyl ether of bisphenol A with butane-1,4-diol at a curing temperature of 100°C. The experimental techniques probe the primary glass-rubber transition during the curing reaction. The primary relaxation time τ obtained from the BS and US velocity and absorption increases with curing time and hence the BS experiment measures τ at earlier stages of cure than the US experiment. The relaxation times at a different extent of reaction and for different measuring temperatures are consistent with BS, US, PCS, and DSC measurements and conform to a single reduced Vogel–Fulcher–Hesse–Tamann equation. Furthermore, the US experiments show evidence of secondary relaxations in the epoxy system. 相似文献
A technique for the synthesis of monosubstituted fatty amides at low temperature and ambient pressure was developed. This
method involved the condensation of an amine with a triacylglycerol. The primary amine (ethyl,n-butyl,n-hexyl andn-octyl were tested) acted as reagent and solvent for the fatty substrates. No additional organic solvent or catalyst was added.
Tallow, vegetable oils and fish oil all served well as substrates, as did pure tripalmitin. The rate of amidation was dependent
upon temperature and the ratio of fat to amine. In a series of experiments conducted with tallow andn-butylamine at a fat:amine molar ratio of 1:16, amidation could be carried out at 20°C, producingn-butyltallowamide in 83% yield in 24 hr. When the fat:amine molar ratio was reduced to 1:8, and the temperature raised to
45°C, the amide yield was 87.6% in 24 hr. When the reaction was carried out at the boiling point ofn-butylamine (78°C) and at a fat:amine ratio of 1:8, the amide yield was 93.2% in 4 hr. The reaction progressed more rapidly
with higher molecular weight amines. The identity and purity of the amides was assessed by thin-layer chromatography and confirmed
by elemental analyses and infrared and C13 nuclear magnetic resonance spectroscopy. 相似文献
In the study of mass transfer between partially miscible liquids, temperature perturbations have been found to have an important effect in the generation of interfacial activity. Micro- and macro-generated interfacial convection usually occurs in combination with one another even in fairly simple heat or mass transfer events. These combinations are responsible for the enhancement of mass transfer rates. In an effort to acquire a better understanding of the heat transfer effects in ternary liquid-liquid systems, temperature difference profiles were measured when contacting two partially miscible phases. A vertical and a rotational transfer cell were designed to contact the partially miscible phases without inducing external disturbances. Five thermocouples were immersed in the bottom liquid phase at predetermined positions below the interface. In order to understand the influence of the convection generated, the vertical cell was designed to hinder convection in one phase, while the rotational cell permits convection in both phases. The experimental results showed larger temperature differences in the rotational cell after the contact of the phases. Also, systems which were initially unsaturated presented larger heat effects than those in which the partially miscible solvents were initially saturated. Several parameters indicating the importance of heat effects in the ternary systems studied are reported. 相似文献