Microalgae have been an emerging biofuel resource; however, the germplasm improvement has been slow due to the lack of molecular tools. Pyruvate dehydrogenase kinase (PDK) deactivates the pyruvate ...dehydrogenase complex (PDC) which catalyzes the oxidative decarboxylation of pyruvate. Acetyl-CoA production via PDC is important in plant tissues that are active in fatty acid synthesis.
A 1261-bp cDNA of a putative PDK gene (PtPDK) was cloned from a diatom Phaeodactylum tricornutum, and PtPDK antisense knockdown transgenic diatoms were generated. Both PtPDK transcript abundance and enzyme activity were reduced significantly due to antisense knockdown of PtPDK. Neutral lipid content of transgenic diatom cells increased up to 82% as determined by Nile red staining, and fatty acid composition was not altered. Transgenic cells showed slightly lower growth rate but similar cell size with the wild type, hence retaining similar biomass productivity.
This work first obtained a successful engineered diatom regulating a key gene involved in lipid metabolism. Our findings also provide powerful indications in enhancing microalgal lipid production by metabolic engineering for biofuel industry.
The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields ...of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.
TiO2 has been widely used as a key catalyst in photocatalytic reactions; it also shows good catalytic activity for esterification reactions. Different sulfated M-TiO2 nanoparticles (M = Ag, Au, Rh, ...and Pt) were prepared by photodeposition and ultrasonic methods. The results show that the noble metal nanoparticles, which were loaded onto a TiO2 surface, slightly affected the crystal phase and particle size of TiO2. Among all the catalysts, S O 4 2 - /Au-TiO2 exhibited the best catalytic activity in the esterification reaction for the synthesis of citric acid n-butyl acetate and in the decomposition of methyl orange, as confirmed by a high conversion rate of up to 98.2% and 100% degradation rate, respectively. This can be attributed to an increase in the Lewis acidity of the catalyst and increased separation efficiency of electron-hole pairs. This superior catalyst has great potential applications in esterification reactions and wastewater treatments.
Although microfluidic devices have made remarkable strides in blood cell separation, there is still a need for further development and improvement in this area. Herein, we present a novel ultralow ...aspect ratio (
/
= 1:36) spiral channel microfluidic device with ordered micro-obstacles for sheathless and flow-rate-insensitive blood cell separation. By introducing ordered micro-obstacles into the spiral microchannels, reduced magnitude fluctuations in secondary flow across different loops can be obtained through geometric confinement. As a result, the unique Dean-like secondary flow can effectively enhance the separation efficiency of particles in different sizes ranging from 3 to 15 μm. Compared to most existing microfluidic devices, our system offers several advantages of easy manufacturing, convenient operation, long-term stability, highly efficient performance (up to 99.70% rejection efficiency, including platelets), and most importantly, insensitivity to cell sizes as well as flow rates (allowing for efficient separation of different-sized blood cells in a wide flow rate from 1.00 to 2.50 mL/min). The unique characteristics, such as ultralow aspect ratio, sequential micro-obstacles, and controlled secondary flow, make our device a promising solution for practical plasma extraction in biomedical research and clinical applications.
ZnO nanostructures with controllable morphology were obtained by hot mixing reverse micelles containing Zn(NO(3))(2) or monoethanol amine aqueous solution. The ratio of water to surfactant ...concentration (omega(0)) was found to play a decisive role in determining the final morphology, namely, nanotetrahedrons formed at a lower omega(0) value and nanorods formed at a higher value. However, the hot mixing technique is propitious for obtaining nanostructures with uniform size. The ZnO nanotetrahedrons obtained gave a strong blue emission arising from interface state, and the ZnO nanorods emitted green light related to donor defects. Our results indicate that the hot mixing of reverse micelles is a unique way to tune the morphology and properties of nanostructures.
TiO
2
has been widely used as a key catalyst in photocatalytic reactions; it also shows good catalytic activity for esterification reactions. Different sulfated M-TiO
2
nanoparticles (M = Ag, Au, Rh, ...and Pt) were prepared by photodeposition and ultrasonic methods. The results show that the noble metal nanoparticles, which were loaded onto a TiO
2
surface, slightly affected the crystal phase and particle size of TiO
2
. Among all the catalysts,
S
O
4
2
-
/Au-TiO
2
exhibited the best catalytic activity in the esterification reaction for the synthesis of citric acid
n
-butyl acetate and in the decomposition of methyl orange, as confirmed by a high conversion rate of up to 98.2% and 100% degradation rate, respectively. This can be attributed to an increase in the Lewis acidity of the catalyst and increased separation efficiency of electron-hole pairs. This superior catalyst has great potential applications in esterification reactions and wastewater treatments.
Controllable synthesis of Si–C nanostructures was realized in a laser ablation system by adopting solid silicon target and n-heptane vapor as starting materials. Ultrafine SiC nanocrystals and ...graphite-coated SiC nanocrystals were synthesized with the laser frequency of 1
Hz and 20
Hz, respectively. According to the real-time observation on the plasma evolvement, we proposed a formation mechanism of Si–C nanostructure related to vapor-phase reaction. Our method can be extended to other material systems for diverse novel nanostructures.
Bacteroides fragilis,
one of the potential next-generation probiotics, but its protective mechanism is not yet known. We aimed to characterize the anti-inflammatory effect of
B. fragilis
ATCC25285 ...and to elucidate its mechanism through in vivo and in vitro experiments. An in vitro model of inflammation by induction of colonic cells with TNF-a, and co-cultured with
B. fragilis
to detect cell viability, apoptosis and invasive capacity. Furthermore, critical proteins of the TLR/NF-κB pathway and the inflammatory cytokines were measured. For animal trials, C57BL/6 J male mice were orally administered
B. fragilis
or PBS once daily for 21 days. Colitis was induced by drinking 2.5% DSS from days 0 to 7. The mice were weighed daily and rectal bleeding, stool condition and blood in the stool were recorded. We found that
B. fragilis
treatment alone was harmless and had no effect on cell viability or apoptosis. While predictably TNF-α decreased cell viability and increased apoptosis,
B. fragilis
attenuated this deterioration. The NF-κB pathway and inflammatory cytokines IL-6 and IL-1β activated by TNF-α were also blocked by
B. fragilis
. Notably, the metabolic supernatant of
B. fragilis
also has an anti-inflammatory effect. Animal studies showed that live
B. fragilis
rather than dead strain ameliorated DSS-induced colitis, as evidenced by weight loss, shortened colon length and enhanced barrier function. The colonic tissue levels of inflammatory cytokines (TNF-α, IL-1β, IL-6) were decreased and IL-10 was increased as a result of
B. fragilis
administration. In conclusion,
B. fragilis
ATCC25285 exhibited anti-inflammatory effects whether in vivo or in vitro, and it may be a potential probiotic agent for improving colitis.
Herein, we for the first time report a novel activatable photoacoustic (PA) imaging nano-probe for in vivo detection of cancer-related matrix metalloproteinases (MMPs). A black hole quencher 3 (BHQ3) ...which absorbs red light is conjugated to near-infrared (NIR)-absorbing copper sulfide (CuS) nanoparticles via a MMP-cleavable peptide linker. The obtained CuS-peptide-BHQ3 (CPQ) nano-probe exhibits two distinctive absorption peaks at 630 nm and 930 nm. Inside the tumor microenvironment where MMPs present, the MMP-sensitive peptide would be cleaved, releasing BHQ3 from the CuS nanoparticles, the former of which as a small molecule is then rapidly cleared out from the tumor, whereas the latter of which as large nanoparticles would retain inside the tumor for a much longer period of time. As the result, the PA signal at 680 nm which is contributed by BHQ3 would be quickly diminished while that at 930 nm would be largely retained. The PA signal ratio of 680 nm / 930 nm could thus serve as an in vivo indicator of MMPs activity inside the tumor. Our work presents a novel strategy of in vivo sensing of MMPs based on PA imaging, which should offer remarkably improved detection depth compared with traditional optical imaging techniques.
Controlled synthesis of transition‐metal hydroxides and oxides with earth‐abundant elements have attracted significant interest because of their wide applications, for example as battery electrode ...materials or electrocatalysts for fuel generation. Here, we report the tuning of the structure of transition‐metal hydroxides and oxides by controlling chemical reactions using an unfocused laser to irradiate the precursor solution. A Nd:YAG laser with wavelengths of 532 nm or 1064 nm was used. The Ni2+, Mn2+, and Co2+ ion‐containing aqueous solution undergoes photo‐induced reactions and produces hollow metal‐oxide nanospheres (Ni0.18Mn0.45Co0.37Ox) or core–shell metal hydroxide nanoflowers (Ni0.15Mn0.15Co0.7(OH)2(NO3)0.2⋅H2O), depending on the laser wavelengths. We propose two reaction pathways, either by photo‐induced redox reaction or hydrolysis reaction, which are responsible for the formation of distinct nanostructures. The study of photon‐induced materials growth shines light on the rational design of complex nanostructures with advanced functionalities.
Photoneninduzierte Reaktionen: Zwei verschiedene Reaktionswege, nämlich die photoneninduzierte Redoxreaktion durch Einstrahlung von 532‐nm‐Laserlicht und die Hydrolyse durch Einstrahlung von 1064‐nm‐Laserlicht, wurden vergleichend untersucht. Abhängig von der Wellenlänge können somit spezifische hydroxidische oder oxidische Übergangsmetallnanostrukturen durch Laserbestrahlung der wässrigen Vorstufenlösungen hergestellt werden.
PDF
