MicroRNA-34a (miR-34a), a transcriptional target of p53, is a well-known tumor suppressor gene. Here, we identified Fra-1 as a new target of miR-34a and demonstrated that miR-34a inhibits Fra-1 ...expression at both protein and messenger RNA levels. In addition, we found that p53 indirectly regulates Fra-1 expression via a miR-34a-dependant manner in colon cancer cells. Overexpression of miR-34a strongly inhibited colon cancer cell migration and invasion, which can be partially rescued by forced expression of the Fra-1 transcript lacking the 3'-untranslated region. The expression of matrix metalloproteinase (MMP)-1 and MMP-9, two enzymes involved in cell migration and invasion, was decreased in miR-34a-transfected cells, and this can be rescued by Fra-1 overexpression. Moreover, we found that miR-34a was downregulated in 25 of 40 (62.5%) colon cancer tissues, as compared with the adjacent normal colon tissues and that the expression of miR-34a was correlated with the DNA-binding activity of p53. Unexpectedly, the DNA-binding activity of p53 was not inversely correlated with Fra-1 expression, and a significant statistical inverse correlation between miR-34a and Fra-1 expression was only observed in 14 of 40 (35%) colon cancer tissues. Taken together, our in vitro data suggest that p53 regulates Fra-1 expression, and eventually cell migration/invasion, via a miR-34a-dependent manner. However, in vivo data indicate that the p53-miR-34a pathway is not the major regulator of Fra-1 expression in human colon cancer tissues.
During femtosecond laser fabrication, photons are mainly absorbed by electrons, and the subsequent energy transfer from electrons to ions is of picosecond order. Hence, lattice motion is negligible ...within the femtosecond pulse duration, whereas femtosecond photon-electron interactions dominate the entire fabrication process. Therefore, femtosecond laser fabrication must be improved by controlling localized transient electron dynamics, which poses a challenge for measuring and controlling at the electron level during fabrication processes. Pump-probe spectroscopy presents a viable solution, which can be used to observe electron dynamics during a chemical reaction. In fact, femtosecond pulse durations are shorter than many physical/chemical characteristic times, which permits manipulating, adjusting, or interfering with electron dynamics. Hence, we proposed to control localized transient electron dynamics by temporally or spatially shaping femtosecond pulses, and further to modify localized transient materials properties, and then to adjust material phase change, and eventually to implement a novel fabrication method. This review covers our progresses over the past decade regarding electrons dynamics control (EDC) by shaping femtosecond laser pulses in micro/nanomanufacturing: (1) Theoretical models were developed to prove EDC feasibility and reveal its mechanisms; (2) on the basis of the theoretical predictions, many experiments are conducted to validate our EDC-based femtosecond laser fabrication method. Seven examples are reported, which proves that the proposed method can significantly improve fabrication precision, quality, throughput and repeatability and effectively control micro/nanoscale structures; (3) a multiscale measurement system was proposed and developed to study the fundamentals of EDC from the femtosecond scale to the nanosecond scale and to the millisecond scale; and (4) As an example of practical applications, our method was employed to fabricate some key structures in one of the 16 Chinese National S&T Major Projects, for which electron dynamics were measured using our multiscale measurement system.
Colour produced by wavelength-dependent light scattering is a key component of visual communication in nature and acts particularly strongly in visual signalling by structurally-coloured animals ...during courtship. Two miniature peacock spiders (Maratus robinsoni and M. chrysomelas) court females using tiny structured scales (~ 40 × 10 μm
) that reflect the full visual spectrum. Using TEM and optical modelling, we show that the spiders' scales have 2D nanogratings on microscale 3D convex surfaces with at least twice the resolving power of a conventional 2D diffraction grating of the same period. Whereas the long optical path lengths required for light-dispersive components to resolve individual wavelengths constrain current spectrometers to bulky sizes, our nano-3D printed prototypes demonstrate that the design principle of the peacock spiders' scales could inspire novel, miniature light-dispersive components.
With the development of electronic information technology, the use of microwaves in military and civilian fields is becoming more and more widespread. The corresponding electromagnetic radiation ...pollution has become a global concern. Numerous efforts have been made to synthesize thin electromagnetic wave absorbing materials with a low density, wide absorption bandwidth and high absorption. Carbon-based materials have great potential in electromagnetic wave absorption because of their lightweight, high attenuation ability, large specific surface area and excellent physicochemical stability. The attenuation theory of absorption materials and the factors that influence their absorption performance are provided first. Next, we summarize the research status of carbon materials with different morphologies (such as 0D carbon spheres, 1D carbon nanotubes, 2D carbon platelets, and 3D porous carbons) and their composites with various materials such as magnetic substances, ceramics, metal sulfides, MXene and conductive polymers. The synthesis methods, properties and attenuation mechanisms of these absorbers are highlighted, and prospects and challenges are considered.
It has been reported that decreased Dicer expression leads to Alu RNAs accumulation in human retinal pigmented epithelium cells, and Dicer may process the endogenous SINE/B1 RNAs (the rodent ...equivalent of the primate Alu RNAs) into small interfering RNAs (siRNAs). In this study, we aimed to address whether Dicer can process Alu RNAs and their common ancestor, 7SL RNA. Using Solexa sequencing technology, we showed that Alu-derived small RNAs accounted for 0.6% of the total cellular small RNAs in HepG2.2.15 cells, and the abundance decreased when Dicer was knocked down. However, Alu-derived small RNAs showed different characteristics from miRNAs and siRNAs, the classic Dicer-processed products. Interestingly, we found that small RNAs derived from 7SL RNA accounted for 3.1% of the total cellular small RNAs in the control cells, and the abundance dropped about 3.4 folds in Dicer knockdown cells. Dicer-dependent biogenesis of 7SL RNA-derived small RNAs was validated by northern blotting. In vitro cleavage assay using the recombinant human Dicer protein also showed that synthetic 7SL RNA was processed by Dicer into fragments of different lengths. Further functional analysis suggested that 7SL RNA-derived small RNAs do not function like miRNAs, neither do they regulate the expression of 7SL RNA. In conclusion, the current study demonstrated that Dicer can process 7SL RNA, however, the biological significance remains to be elucidated.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To control the behavior of underwater bubbles, stainless steel meshes are treated through femtosecond laser processing, and the bubble absorption, bubble interception, and unidirectional bubble ...passage are realized by using structured meshes. The surface of the mesh presents a micro–sub‐micro–nano trinary‐scale structure (microscale mesh wires, sub‐microripples, and nanoparticles) after one‐step laser ablation on both sides. The surface shows superhydrophilic in air and superaerophobic once immersed in water. After further modified with fluoroalkylsilane, the wettability of the sample surface is switched to be superaerophilic in water with bubble being absorbed by the sample. When a plenty of underwater bubbles arrive at the structured stainless steel mesh surface, they can be blocked by the underwater superaerophobic mesh but pass through the underwater superaerophilic mesh. In addition, after the mesh being treated only one side and further modified, it is to be Janus mesh and presents asymmetrical wettability of aerophilicity/superaerophilicity. The Janus mesh shows the unidirectional passage of underwater bubbles. Bubbles can only penetrate from aerophilic side to superaerophilic side, but be blocked from the other direction. The mesh is verified to be used to eliminate the stuck bubbles in the container.
The underwater bubble bidirectional passage, bubble bidirectional interception, and bubble unidirectional passage are realized on a stainless steel mesh by combination of selective femtosecond laser scanning and modification of fluoroalkyl silane.
By using polybutene-1 as a typical example, we illustrate the initiation, development and stabilization of cavities in the sample during tensile deformation. Samples with the same crystallinity, long ...spacing and crystalline lamellar thickness but very different sizes of spherulites were prepared
via
changing the melt history. Dimension of cavities during stretching the samples was determined by
in situ
ultra small angle X-ray scattering techniques. It turned out that the size of the cavities was bigger in the sample with larger spherulites than the one with smaller spherulites. The results show clear evidence of initiating cavities within crystalline phase at the grain-boundary of crystalline blocks, growing of cavities passing through parallel stacked lamellar crystals and amorphous layers and finally stablized by tilted lamellae at both ends of the plate-like cavities within the spherulites.
We have investigated the microwave-absorbing properties for different shapes and aggregated states of carbonyl-iron particles dispersed in epoxy resin matrix at various volume concentrations. Here, ...we discuss the requirements of lower reflection coefficient for the microwave permittivity /spl epsiv//sub r/=/spl epsiv/'-j/spl epsiv/'' and permeability /spl mu//sub r/=/spl mu/'-j/spl mu/''. Compared to the aggregated sphere-shaped particles (SS), the de-aggregated flake-shaped carbonyl iron particles (FS) have higher permeability, lower permittivity, better filling characteristics in epoxy resin, and better absorbing properties in the frequency range of 2-18 GHz. For the FS composite with volume fraction of 0.60 at single-layer thickness of 1 mm, the calculated reflection loss at 2 GHz reaches -4.04 dB and the minimum reflection loss is -12.2 dB at 4.4 GHz, which indicates that the FS composite can be applied as a thinner microwave absorber in the S-band than if SS particles are used. The results also show that different volume concentrations can have high absorption at different wave bands, a fact on which the design of absorbing material can be based.
We have shown that Dicer processes 7SL RNA into different fragments ranging from ∼20 to more than 200 nucleotides. Here we addressed the molecular functions of these 7SL RNA fragments and found that ...some of them functioned as dominant-negative regulators of the full-length 7SL RNA, interfering with signal recognition particle (SRP) complex formation. Transfection of these 7SL RNA fragments inhibited the expression of cell surface glycoproteins, the targeting of a reporter protein to the endoplasmic reticulum, and the secretion of secreted alkaline phosphatase. These results suggest that some Dicer-processed 7SL RNA fragments interfered with SRP-mediated protein targeting. Moreover, we showed that Dicer knockdown enhanced SRP-mediated protein targeting and that transfection of a mixture of the 7SL RNA fragments partially restored this effect. Our data indicate that Dicer can fine-tune the efficiency of SRP-mediated protein targeting via processing a proportion of 7SL RNA into fragments of different lengths.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Recent studies have demonstrated that carbon nano-onion (CNO) is a promising candidate for high-power supercapacitors due to the nonporous outer shell, which is easily accessible to electrolyte ions. ...However, the nonporous ion-accessible outer shells also limit the energy density of the CNOs, which requires large specific surface area. Introducing porosity to the outer shells of CNOs can effectively improve the specific surface area by exposing the inner shells to electrolytes. In this study, the electrochemical performance of supercapacitor electrodes based on CNOs is improved through the controlled introduction of porosity on the outer shells of CNOs by chemical activation. The capacitance of the activated CNOs is five times larger than the pristine ones with a measured power density of 153kW/kg and an energy density of 8.5Wh/kg in a 2mol/l potassium nitrate electrolyte. The capacitance retention ratio of activated CNOs decreases slightly as the current density increases from 0.75 to 25A/g. About 71% of initial capacitance (at 0.75A/g) is preserved for activated CNOs at current densities up to 25A/g.
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