H3K9me2 and H3K27me2 are important epigenetic marks associated with transcription repression, while H3K4me3 is associated with transcription activation. It has been shown that active and repressive ...histone methylations distribute in a mutually exclusive manner, but the underlying mechanism was poorly understood. Here we identified ceKDM7A, a PHD （plant homeodomain）- and JmjC domain-containing protein, as a histone demethylase specific for H3K9me2 and H3K27me2. We further demonstrated that the PHD domain of ceKDM7A bound H3K4me3 and H3K4me3 co-localized with ceKDM7A at the genome-wide level. Disruption of the PHD domain binding to H3K4me3 reduced the demethylase activity in vivo, and loss of ceKDM7A reduced the expression of its associated target genes. These results indicate that ceKDM7A is recruited to the promoter to demethylate H3K9me2 and H3K27me2 and activate gene expression through the binding of the PHD domain to H3K4me3. Thus, our study identifies a dual-specificity histone demethylase and provides novel insights into the regulation of histone methylation.
Chiral compounds/materials have important effects on the growth of plants. Chiral carbon dots (CDs), as an emerging chiral carbon nanomaterial, have great potential in bio-application and ...bio-nanotechnology. Herein, we report a hydrothermal method to synthesize chiral CDs from cysteine (cys) and citric acid. These chiral CDs were further demonstrated to have systemic effects on the growth of mung bean plants, in which case both l- and d-CDs can promote the growth of the root in mung bean plants, stem length of mung bean sprouts and water absorption of bean seeds. The elongation of mung bean sprouts presented an increasing trend with the treatment of chiral CDs of increasing concentration (below 500 μg mL-1). Furthermore, in the optimal concentration (100 μg mL-1), the l-CDs can improve root vigor and the activity of the Rubisco enzyme of bean sprouts by 8.4% and 20.5%, while the d-CDs increased by 28.9% and 67.5%. Due to more superior properties in improving root vigor and the activity of the Rubisco enzyme of mung bean sprouts, d-CDs are able to enhance photosynthesis better and accumulate more carbohydrate in mung bean plants.
•Minimizing self-excited thermoacoustic oscillations in cryogenic system is studied.•The dynamics of cryogenic thermoacoustic system subjected to acoustic forcing are investigated.•The phase ...relationships between self-excited and coupled waves are analyzed.•For small driving phase, the oscillation-free operation is achieved finally.
Self-excited thermoacoustic oscillations usually occur in many practical systems such as rocket motors, gas turbines and cryogenic distribution systems. We study the dynamics of a self-excited cryogenic thermoacoustic system subjected to acoustic forcing. The effect of the driving phase on the amplitude of the coupled oscillation is analyzed and the results present two states. To provide a guide for the selection of driving signal, the dynamics of a self-excited cryogenic thermoacoustic system subjected to acoustic forcing are investigated. When ϕ=30°, the radius of the limit cycle gradually shrinks, and self-oscillation amplitude is suppressed by 99.5%. For small driving phase, the self-oscillation can be suppressed, while for large driving phase, the phase portraits depict period-1 limit cycle oscillations. The results show that excessive driving phase has unfavorable effect on self-excited oscillation, and small drive phase can achieve oscillation suppression better. To reveal the coupling mechanism of externally forced oscillation and system self-excited oscillation, the phase relationships between self-excited oscillations and coupling pressure fluctuation waves in different periods are analyzed. Hence, the work indicates that under low-frequency disturbances, the system oscillation will have a phase delay, which will cause the hysteresis dissipation and restrain the system oscillation.
Chirality has attracted extensive attention in many fields ranging from chemistry to life sciences. Carbon dots (CDs) with good biocompatibility and unique photochemical properties have become a new ...star in the nanocarbon family. Endowed with chirality, CDs will exhibit more marvellous properties and bridge the fields of material chemistry and life sciences tightly. Herein, we report a facile one-step alkali-assisted electrochemical method to fabricate chiral CDs from cysteine (cys). We showed the chiral evolution of CDs with highly symmetrical circular dichroism (CD) signals in the range from 205 to 350 nm. These chiral CDs have been further demonstrated to be capable of tuning the activity of laccase: the l-CDs can improve the activity of the enzyme up to 20.2%, whereas the d-CDs decrease the activity to 10.4%. A series of experiments confirm that it is the synergistic effect of nanosize and chirality of CDs that induces the change in the structure of laccase and thus leads to the tuning of the laccase activity.
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-Methyldeoxyadenosine (6mA) has recently been shown to exist and play regulatory roles in eukaryotic genomic DNA (gDNA). However, the biological functions of 6mA in mammals have yet to be ...adequately explored, largely due to its low abundance in most mammalian genomes. Here, we report that mammalian mitochondrial DNA (mtDNA) is enriched for 6mA. The level of 6mA in HepG2 mtDNA is at least 1,300-fold higher than that in gDNA under normal growth conditions, corresponding to approximately four 6mA modifications on each mtDNA molecule. METTL4, a putative mammalian methyltransferase, can mediate mtDNA 6mA methylation, which contributes to attenuated mtDNA transcription and a reduced mtDNA copy number. Mechanistically, the presence of 6mA could repress DNA binding and bending by mitochondrial transcription factor (TFAM). Under hypoxia, the 6mA level in mtDNA could be further elevated, suggesting regulatory roles for 6mA in mitochondrial stress response. Our study reveals DNA 6mA as a regulatory mark in mammalian mtDNA.
TET proteins oxidize 5-methylcytosine (5mC) on DNA and play important roles in various biological processes. Mutations of TET2 are frequently observed in myeloid malignance. Here, we present the ...crystal structure of human TET2 bound to methylated DNA at 2.02 Å resolution. The structure shows that two zinc fingers bring the Cys-rich and DSBH domains together to form a compact catalytic domain. The Cys-rich domain stabilizes the DNA above the DSBH core. TET2 specifically recognizes CpG dinucleotide and shows substrate preference for 5mC in a CpG context. 5mC is inserted into the catalytic cavity with the methyl group orientated to catalytic Fe(II) for reaction. The methyl group is not involved in TET2-DNA contacts so that the catalytic cavity allows TET2 to accommodate 5mC derivatives for further oxidation. Mutations of Fe(II)/NOG-chelating, DNA-interacting, and zinc-chelating residues are frequently observed in human cancers. Our studies provide a structural basis for understanding the mechanisms of TET-mediated 5mC oxidation.
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•The Cys-rich and DSBH domains form a compact catalytic domain•TET2-dsDNA structure shows specific recognition of CpG dinucleotide by TET2•5mC is inserted into the catalytic cavity through a base-flipping mechanism•The catalytic cavity can accommodate 5mC and its derivatives for oxidation
The crystal structure of TET2 with dsDNA shows that TET2 specifically recognizes CpG dinucleotide through a base-flipping mechanism and that the catalytic cavity allows TET2 to accommodate 5mC and its derivatives for oxidation.
In this report, the relationship between microstructure and corrosion behavior of weathering steel (WS) was investigated. Meanwhile, a series of immersion tests in three solutions (S1: 3.5 wt.% NaCl, ...S2: 3.5 wt.% NaCl+0.052 wt.% NsHSO3, S3: 3.5 wt.% NaCl+0.907 wt.% NaHCO3) and the characterization of rust after immersion were carried out. The presence of a high proportion of the random grain boundaries in WS facilitates the formation of rust in corrosive environment. Moreover, a small amount of HSO3- accelerates corrosion, while the acceleration effect of HCO3- occurs only at the beginning of immersion. This work would be valuable to bring insight into the effect of typical ions on corrosion behavior of WS.
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•A high fraction of random grain boundaries increase the corrosion sensitivity.•It is difficult to form rust under the combined effect of HSO3-and Cl-.•HCO3- initially accelerates corrosion compared with the solution containing Cl-.•Morphology and components of rust notably affect the corrosion behavior of steel.
The microstructure and corrosion behavior of weathering steel in three solutions (S1: 3.5 wt.% NaCl, S2: 3.5 wt.% NaCl+0.052 wt.% NaHSO3, S3: 3.5 wt.% NaCl+0.907 wt.% NaHCO3) were investigated. A high proportion of random boundaries is responsible for strong corrosion sensitivity. The thickness of rust increases with immersion time and is in the order of S1＞S3＞S2. The rust formed in S1 and S2 solutions mainly consists of γ-FeOOH phase, but the latter is less protective. The rust formed in S1 solution is dense and thick resulting in its protection being similar to that in S3 solution.
Thermoacoustic oscillations generally exist in combustion devices and cryogenic systems, causing system instability and other problems. The actual cryogenic system has complex pipe connections, ...however, there are few studies on the thermoacoustic oscillation of complex structures, which brings challenges to suppressing thermoacoustic instability. Therefore, this study focuses on the T-shaped helium tube existing in the actual cryogenic system and explores the oscillation characteristics of the complex cryogenic thermoacoustic system. With the change of branch position and length, mode transition phenomenon appears. We obtained the effects of the branch position and length on the amplitude and frequency of each mode and found that the self-excited oscillation in the T-shaped tube could be suppressed to some extent by choosing the proper length and position of the branch tube. Further research found that the first mode of the oscillating pressure in the main and branch tube was in-phase synchronized, and the second mode was antiphase synchronized. By linking the flow direction with the oscillation mode, it is found that the first mode corresponds to the first flow direction, and the second mode corresponds to the second or third flow direction. The finding is valuable for understanding thermoacoustic oscillations in T-tubes and provides a reference for controlling the self-excited oscillation of complex cryogenic systems.
•The effects of two critical parameters on thermoacoustic oscillations of T-shaped cryogenic helium tubes are studied.•The mode transition phenomenon is found, and the mode variation law is obtained.•Choosing the proper branch position and length can suppress self-excited oscillation.•The asynchrony of oscillation pressure in the main and branch tube is reflected in the second mode.•The corresponding relationship between the oscillation mode and the flow direction is revealed.
Strongly coupling CoPi-CDs composite exhibits effective and stable photocatalytic activity towards overall water splitting.
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Hydrogen and oxygen produced by water splitting under solar ...energy are ideal future energy sources. At present, obtaining the efficient, stable and inexpensive photocatalyst for photocatalytic overall water splitting is still a huge challenge. Cobalt phosphate (Co3PO4, CoPi) possesses proper band positions for water splitting. However, the fast recombination of photogenerated electron and hole pairs for CoPi restricts its application. Herein, strongly coupling Co3PO4-carbon dots (CoPi-CDs) composite was constructed as an effective strategy to depress the fast recombination behavior of photogenerated electron and hole pairs. CoPi-CDs show superior photocatalytic water splitting activity than that of single CoPi. When the concentration of CDs in the composite is 0.002 gCDs/gcatalyst, the hydrogen production rate was obtained for approximately 0.592 μmol h−1, as well as the oxygen evolution rate about 0.258 μmol h−1 (with 2:1 stoichiometry), which are both nearly 33 times than that of pristine CoPi. This enhanced photocatalytic activity of CoPi-CDs should ascribe to the efficient coupling effect between CoPi and CDs, which allows fast electron transfer at the interface of CoPi and CDs and thus effectively boosts the photocatalytic water splitting. The strongly coupling nanocomposites should be inspiring for further nanocomposite building for photocatalytic overall water splitting.
The microstructure and corrosion behavior of Al-Zn-Mg alloy (namely 7×××) after natural aging treatment (NAT) and artificial aging treatment (AAT) in aqueous NaCl solutions containing different ...aggressive ions have been investigated in current work. Results of microstructure characterization demonstrate that the aging treatment has a great influence on the grain size and precipitates. The grain size is relatively sizeable and no evident precipitates are observed in alloy after NAT comparable with that after AAT. The electrochemical corrosion behavior of alloy was studied by polarization curve and electrochemical impedance spectroscopy (EIS). The corrosion potential (Ecorr) of the aluminum alloy is more negative in 3.5 wt.% NaCl containing 0.052 wt.% NaHSO3 solution than that in 3.5 wt.% NaCl solutions with or without 0.907 wt.% NaHCO3. Charge transfer resistance (Rct) results reveal that alloy after AAT has an enhancement of corrosion resistance compare with that after NAT. With the immersion time increasing, mostly pitting spreads over the surface of the alloy only in NaCl solution, whereas exfoliation corrosion mainly occurs in NaCl solutions containing NaHSO3 or NaHCO3.
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