Search

DNA methyltransferase (MTase) is an important regulatory enzyme in various biological processes. However, current methods for investigating MTase activity are still limited in terms of sensitivity and/or generality. Herein, we proposed a dual amplification fluorescence strategy for the ultrasensitive detection of DNA adenine methylation methyltransferase (Dam MTase) activity based on strand displacement amplification (SDA) coupled with rolling circle amplification (RCA). In this study, the hairpin probe could not be cleaved by Nt.AlwI nicking endonuclease (Nt.AlwI) in the presence of Dam MTase, and the subsequent SDA-RCA reaction was blocked, resulting in a weak fluorescence signal. Moreover, the blocking effect was more pronounced at a higher concentration of Dam MTase. This assay provides a very low detection limit (down to 0.0067 U ml

Objectives Benzo[a]pyrene (B[a]P) is a member of the polycyclic aromatic hydrocarbon (PAH) family. Although the potent carcinogenicity of high-dose B[a]P has been extensively reported, the effects of long-term exposure to B[a]P on the progression of tongue squamous cell carcinoma (TSCC) are poorly understood. Methods In the present study, TSCC cells were treated with 5 or 50 nM of B[a]P for three months. The proliferation and chemoresistance of B[a]P-treated cells to 5-fluorouracil or cisplatin were detected by CCK8. The motility of the B[a]P-treated cells was evaluated with wound healing analysis, invasion assay, and three-dimensional culture in decellularized mouse tongue matrix. Xenograft assay was used to investigate the aggressiveness of B[a]P-treated cells. Immunofluorescence staining, terminal restriction fragment assay, and whole-genome sequence were used to determine the mutation spectrums. Results Long-term 50 nM B[a]P-treated cells exhibited increased aggressiveness and chemoresistance to 5-fluorouracil or cisplatin. In addition, data from whole-genome sequencing demonstrated that C:T to A:T transitions were the predominant nucleotide substitutions occurred in 50 nM B[a]P-treated CAL27 cells. Furthermore, 102 non-synonymous or stop-gain mutations were enriched in the extracellular-matrix-receptor interactive pathway. Conclusions B[a]P exposure may contribute to genomic instability, and therefore, B[a]P may promote the progression of TSCC.

The progression of early childhood caries (ECC) is caused by microbial colonized in dental plaque. However, the association framework both from 16s genus down to high resolution metagenomic strain level and from composition to genome function analysis on caries lacks. 16S rRNA sequence revealed the composition of 3–6 years dental caries (ECC, n = 29), and severe dental caries (SECC, n = 36) children are significantly different from caries-free controls (CF, n = 31). Especially, genus Neisseria is enriched in caries (P < 0.05). Metagenomics sequence of 3 ECCs, 3 SECCs, and 3 CFs reveals Neisseria bacilliformis ATCC BAA-1200 in genus Neisseria is also significantly enriched in caries (P < 0.05). Then, we recovered high-quality metagenomic assembly genomes (MAG), named bin 86, which have 99% identity with Neisseria bacilliformis ATCC BAA-1200 genome. Function analysis of Neisseria bacilliformis ATCC BAA-1200 genome shows its metabolism power of sugar and adhesion, colonization, acid production, and acid tolerance ability, which suggested Neisseria bacilliformis ATCC BAA-1200 may serve as a biomarker for childhood caries.

A simple electrochemical strategy is reported for continuous monitoring of dynamic DNA methylation process over time. An electrochemical sensor was prepared by co-assembling of DNA probe and 6-mercapto-1-hexanol onto a gold electrode. The top of the DNA probe was labeled with 6-ferrocenylhexanethiol modified gold nanoparticle. The charge density between the C•G base pair was verified to be slightly reduced by DNA methylation, and could be further decelerated by ~ 25% upon co-locating a Br group onto methylated cytosine (mC). Therefore, in the presence of NaIO4/LiBr, the progressively methylated DNA on the sensor showed a clearly decreasing current over methylation time. The dynamic DNA methylation process was indicated continuously from the current decrease ratio, with a limit of detection of 0.0372µM. The strategy is convenient, cost-effective, and enable continuous profiling methylation process without distortion. Besides, the strategy was successfully applied for the studies on inhibitor screening and flanking sequence preference of DNA methyltransferase 3a. The results show that the activity of DNA methyltransferase 3a can be mildly inhibited by epigallocatechin gallate, and varies towards different flanking sequence with an order of 5'-CCGG-3' < 5'-CGCG-3' < 5'-CGCA-3'.

A general and effective approach was proposed to fabricate a new family of Co-based bimetallic phosphide ultrathin nanosheets (CoM-P-NS, M = Ni, Mn, Cu, Zn) with homogeneous composition and unique porous architecture using ultrathin metal–organic framework nanosheets (MOFNs) as precursors for the first time, which yielded synergistically active sites, mass transport and dynamic modulations for the oxygen evolution reaction (OER). The optimized samples showed remarkable oxygen evolution activity in alkaline electrolytes, outperforming both the commercial RuO2 and Ir/C benchmarks and ranking the best among all the metal-phosphide electrocatalysts reported to date.

Due to the remarkable electronic, optical, thermal, and mechanical properties, graphene-based materials have shown great potential in a wide range of technique applications. Particularly, the high transparency, conductivity, flexibility, and abundance make graphene materials highly attractive for polymer solar cells (PSCs). Graphene-based materials have been regarded as one promising candidate used in various parts in PSCs not only as electrodes, but also as interfacial layers and active layers with an aim to boost the power conversion efficiency of the devices. In this review, we summarize the recent progress about the design and synthesis of graphene-based materials for efficient PSCs along with the related challenges and future perspectives.

Due to the remarkable electronic, optical, thermal, and mechanical properties, graphene-based materials have shown great potential in a wide range of technique applications. Particularly, the high transparency, conductivity, flexibility, and abundance make graphene materials highly attractive for polymer solar cells (PSCs). Graphene-based materials have been regarded as one promising candidate used in various parts in PSCs not only as electrodes, but also as interfacial layers and active layers with an aim to boost the power conversion efficiency of the devices. In this review, we summarize the recent progress about the design and synthesis of graphene-based materials for efficient PSCs along with the related challenges and future perspectives.

Due to unique planar structures and remarkable thermal, electronic, and mechanical properties, chemically modified graphenes (CMGs) such as graphene oxides, reduced graphene oxides, and the related derivatives are recognized as the attractive building blocks for “bottom‐up” nanotechnology, while self‐assembly of CMGs has emerged as one of the most promising approaches to construct advanced functional materials/systems based on graphene. By virtue of a variety of noncovalent forces like hydrogen bonding, van der Waals interaction, metal‐to‐ligand bonds, electrostatic attraction, hydrophobic–hydrophilic interactions, and π–π interactions, the CMGs bearing various functional groups are highly desirable for the assemblies with themselves and a variety of organic and/or inorganic species which can yield various hierarchical nanostructures and macroscopic composites endowed with unique structures, properties, and functions for widespread technological applications such as electronics, optoelectronics, electrocatalysis/photocatalysis, environment, and energy storage and conversion. In this review, significant recent advances concerning the self‐assembly of CMGs are summarized, and the broad applications of self‐assembled graphene‐based materials as well as some future opportunities and challenges in this vibrant area are elucidated.

Genomic 5-methylcytosine (5-mC) modification is known to extensively regulate gene expression. The sensitive and convenient analysis of gene-specific methylation is wishful but challenging due to the lack of means that can sensitively and sequence-selectively discriminate 5-mC from cytosine without the need for polymerase chain reaction. Here we report a chemical-oxidation cleavage triggered exponential amplification reaction (EXPAR) method named COEXPAR for gene-specific methylation analysis. EXPAR was proved to not only have rapid amplification kinetics under isothermal condition but also show excellent sequence-selectivity and linear-dependence on EXPAR trigger. Further initiation of EXPAR by chemical-cleavage of DNA at 5-mC, the COEXPAR showed high specificity for methylated and nonmethylated DNA, and ∼10(7) copies of triggers were replicated in 20 min, which were used to quantify the methylation level at the methylation loci. As a result, the gene-specific methylation level of a p53 gene fragment, as a target model, was analyzed in two linear ranges of 10 fM-1 pM and 1 pM-10 nM, and limits of detection of 411 aM (S/N = 3) by fluorescence, and 576 aM (S/N = 3) by electrochemistry. The method fulfilled the assay in an isothermal way in ∼5 h without the need for tedious sample preparation and accurate thermocycling equipment, which is likely to be a facile and ultrasensitive way for gene-specific methylation analysis.