DNA methyltransferases catalyze the transfer of a methyl group from S-adenosylmethionine to the target adenine or cytosine, eventually inducing the DNA methylation in both prokaryotes and eukaryotes. ...Herein, we developed a novel electrochemiluminescence biosensor to quantify DNA adenine methylation (Dam) methyltransferase (MTase) employing signal amplification of GO/AgNPs/luminol composites to enhance the assay sensitivity. The method was developed by designing a capture probe DNA, which was immobilized on gold electrode surface, to hybridize with azide complementary DNA to form the azide-terminated dsDNA. Then, alkynyl functionalized GO/AgNPs/luminol composites as the signal probe were immobilized to azide-terminated dsDNA modified electrode via click chemistry, resulting in a high electrochemiluminescence (ECL) signal. Once the DNA hybrid was methylated (under catalysis of Dam MTase) and further cleaved by Dpn I endonuclease (a site-specific endonuclease recognizing the duplex symmetrical sequence of 5′-G-Am-T-C-3′), GO/AgNPs/luminol composites release from the electrode surface to the solution, leading to significant reduction of the ECL signal. The change of the ECL intensity is related to the methylation status and MTase activity, which forms the basis of MTase activity assay and site-specific methylation determination. This novel strategy can be further used as a universal method for other transferase determination by designing various transferase-specific DNA sequences. In addition, this method can be used for the screening of antimicrobial drugs and has a great potential to be further applied in early clinical diagnosis.
•We reported a novel ECL biosensor for sensitive analysis of DNA methyltransferase activity.•Click chemistry was used to assemble the ECL reagent.•GO/AgNPs/luminol composites were firstly used as the ECL signal amplification nanoprobe.•Highly sensitive detection of Dam MTase activity and inhibition was achieved.
Herein, a sensitive and selective sensor for biothiols based on colorimetric assay is reported. S-adenosyl-L-methionine (SAM) could induce the selective aggregation of unmodified gold nanoparticles ...(AuNPs) by electrostatic interaction. In the presence of biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), AuNPs prefer to react with thiols of biothiols rather than SAM due to the formation of Au-S bond. Thus, the AuNPs turn from the aggregation to the dispersion state, and the corresponding color variation in the process of anti-aggregation of AuNPs can be used for the quantitative screening of biothiols through UV-vis spectroscopy or by the naked eye. Under optimized conditions, a good linear relationship in the range of 0.4-1.2 µM is obtained for Cys, 0.2-0.9 µM for GSH, and 0.6-3.0 µM for Hcys. The detection limits of this assay for GSH, Cys and Hcys are 35.8 nM, 21.7 nM, and 62.4 nM, respectively. This colorimetric assay exhibits rapid operation (within 5 min), high selectivity and sensitivity towards biothiols with tunable dynamic ranges.
Golden gates: Conformational change of single‐strand, duplex, and triplex structures triggered by Ag+ and Hg2+ has been used to construct electronic logic gates (AND, NAND, and NOR) by ...metal‐ion‐mediated base pairs (C‐Ag+‐C and T‐Hg2+‐T; see scheme).
Protein lysine acetylation is a type of reversible post-translational modification that plays a vital role in many cellular processes, such as transcriptional regulation, apoptosis and cytokine ...signaling. To fully decipher the molecular mechanisms of acetylation-related biological processes, an initial but crucial step is the recognition of acetylated substrates and the corresponding acetylation sites. In this study, we developed a position-specific method named PSKAcePred for lysine acetylation prediction based on support vector machines. The residues around the acetylation sites were selected or excluded based on their entropy values. We incorporated features of amino acid composition information, evolutionary similarity and physicochemical properties to predict lysine acetylation sites. The prediction model achieved an accuracy of 79.84% and a Matthews correlation coefficient of 59.72% using the 10-fold cross-validation on balanced positive and negative samples. A feature analysis showed that all features applied in this method contributed to the acetylation process. A position-specific analysis showed that the features derived from the critical neighboring residues contributed profoundly to the acetylation site determination. The detailed analysis in this paper can help us to understand more of the acetylation mechanism and can provide guidance for the related experimental validation.
•This is the first report on the peroxidase-like activity of CoOOH nanoflakes for the detection of MTase activity.•The peroxidase-like activity of CoOOH nanoflakes can be improved by adsorbing ...ssDNA.•The colorimetric sensor with a low detection limit of 0.069 U/mL for M.SssI MTase activity detection.•The colorimetric sensor allows detection of M.SssI MTase in cell lysates of lung cancer cells (A549).
A label-free colorimetric assay for MTase activity based on the nanozyme activity of cobalt oxyhydroxide (CoOOH) nanoflakes and the difference in affinity of the nanoflakes with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) has been developed. In this strategy, ssDNA can enhance the nanozyme activity of CoOOH nanoflakes, which could be attributed to the electrostatic attraction and π-π stacking interaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and ssDNA. The proposed method presents a wide linear range from 0.08 to 50 U/mL and a low detection limit (LOD) of 0.069 U/mL. Additionally, this colorimetric sensor also has been proved to detect MTase in the cell lysates of lung cancer cells (A549) with good recovery and reproducibility. Furthermore, the novel strategy can be applied for high-throughput evaluation and screening the inhibitors for M.SssI MTase by using representative anticancer drugs as model inhibitors, therefore, the colorimetric sensor can not only achieve the purpose of sensitively detecting the activity of MTase, but also has the potential in clinical diagnostics and drug discovery.
A novel dopamine sensor was fabricated by forming the 6-ferrocenylhexanethiol (HS(CH2)6Fc) functionalized Fe3O4@Au nanoparticles (NPs) films on the surface of a carbon paste electrode with the aid of ...a permanent magnet. HS(CH2)6Fc, which acted as the redox mediator, was self-assembled to Fe3O4@Au NPs via Au–S bond. Transmission electron microscopy, UV–visible absorption spectroscopy, Fourier transform infrared spectra, and cyclic voltammetry were used to characterize the properties of the Fe3O4@Au NPs/HS(CH2)6Fc nanocomposite. It is shown that the prepared ferrocene-functionalized Fe3O4@Au NPs composite shuttled electrons between analyte and electrode, increased the mediator loading, and more importantly prevented the leakage of the mediator during measurements, which resulted in the substantially enhanced stability and reproducibility of the modified electrode. The electrooxidation of dopamine could be catalyzed by Fc/Fc+ couple as a mediator and had a higher electrochemical response due to the unique performance of Fe3O4@Au NPs. The nanocomposite modified electrode exhibited fast response (3s) and the linear range was from 2.0×10−6 to 9.2×10−4M with a detection limit of 0.64μM. This immobilization approach effectively improved the stability of the electron transfer mediator and is promising for construction of other sensors and bioelectronic devices.
Plasmonic photocatalysis is an effective strategy to solve radioactive uranium hazards in wastewater. A plasmonic photocatalyst Bi/Bi2O3−x@COFs was synthesized by in-situ growth of covalent organic ...frameworks (COFs) on Bi/Bi2O3−x surface for the U(VI) adsorption and plasmonic photoreduction in rare earth tailings wastewater. The presence of oxygen vacancy in Bi/Bi2O3−x and Schottky potential well formed by Bi and Bi2O3−x interface increased the number of free electrons, which induced localized surface plasmon resonance (LSPR) and enhanced the light absorption performance of composites. In addition, oxygen vacancy improved the Fermi level of Bi/Bi2O3−x, leading to another potential well between Bi2O3−x and COFs interface. The electron transport direction was reversed, thus increasing the electron density of COFs layer. COFs was an N-type semiconductor with specific binding U(VI) groups and suitable band structure, which could be used as an active reaction site. Bi/Bi2O3−x@COFs had 1411.5 mg g−1 removal capacity and high separation coefficient for U(VI) due to the synergistic action of photogenerated electrons and hot electrons. Moreover, the removal rate of uranium from rare earth tailings wastewater by regenerated Bi/Bi2O3−x@COFs was over 93.9%. The scheme of introducing LSPR and Schottky potential well provides another way to improve the photocatalytic effect.
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•Bi/Bi2O3−x@COFs with core-shell structure was synthesized in-situ.•Oxygen vacancies in Bi2O3−x induced LSPR and increased light absorption.•The double Schottky potential well increased the electron density of COFs.•U(VI) was reduced by the synergistic action of photogenerated and hot electrons.•Regenerated Bi/Bi2O3−x@COFs had high cyclic stability.
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•MI-TBPAFs acted as a palladium capture platform through three synergistic mechanisms.•The MI-TBPAFs with numerous tailored binding sites exhibited extraordinary selective affinity ...with palladium.•Pd2+ was reduced into Pd0 by MI-TBPAFs via photocatalytic and chemical reduction effects.•MI-TBPAF-3 showed ultra-high adsorption capacity for palladium (435.4 mg/g) under simulated sunlight radiation.
Herein, molecular imprinting technology (MIT) was introduced into construction of molecularly imprinted triazine-based porous aromatic frameworks (MI-TBPAFs) via Heck-coupling reaction for palladium extracting from wastewater. According to the decorating Pd-vinylpyridine complex (Pd@Vpy), MI-TBPAFs were given considerable tailor-made binding sites with strong affinities for palladium, which captured palladium from various metal ions precisely. The adsorption experiments showed that the extraction capacity of MI-TBPAF-3 was improved by 59.0% (435.4 mg/g) under simulated sunlight radiation. Mechanism analysis proved that Pd2+ was reduced into Pd0 by MI-TBPAF-3 via photocatalytic and chemical reduction effects originating from triazine base and pyridine nitrogen atoms in the extended π-conjugated framework respectively, thereby greatly increasing adsorption capacity by the sorption-reduction strategy. Organically combining the advantages of MIT, photocatalytic reduction and chemical reduction, three synergistic mechanisms, not only provides a new strategy for highly efficient palladium extraction, but also inspires new insights for precious metal recovery.
The traditional detection of telomerase activity is mainly based on the polymerase chain reaction (PCR), which has the disadvantages of being time-consuming and susceptible to interferences; thus, ...here, we propose a facile method for the fabrication of fluorescent tungsten oxide quantum dots (WO
QDs) and employ them for telomerase activity sensing. It is found that the fluorescence of WO
QDs can be significantly quenched by hemin based on the inner filter effect (IFE). However, in the presence of telomerase, the primer-DNA can be extended to generate repeating units of TTAGGG to form G-quadruplex and thus, hemin can be encapsulated to reduce its absorbance, resulting in decreased IFE and efficient fluorescence recovery of WO
QDs. Based on the fluorescence changes of IFE between hemin and WO
QDs, the telomerase activity within the range of 50-30 000 HeLa cells can be detected and the lowest detection amount can reach 17 cells. The method exhibits good versatility that can also be applied to telomerase detection in A549 and L929 cells. In addition, because of the good biocompatibility of the sensor, it can be used for the real-time monitoring of telomerase activity in living cells, thus showing great potential in tumor diagnosis and inhibitor drug screening.
Photocatalytic reduction of UVI to UIV can help remove U from the environment and thus reduce the harmful impacts of radiation emitted by uranium isotopes. Herein, we first synthesized Bi4Ti3O12 (B1) ...particles, then B1 was crosslinked with 6-chloro-1,3,5-triazine-diamine (DCT) to afford B2. Finally, B3 was formed using B2 and 4-formylbenzaldehyde (BA-CHO) to investigate the utility of the D-π-A array structure for photocatalytic UVI removal from rare earth tailings wastewater. B1 lacked adsorption sites and displayed a wide band gap. The grafted triazine moiety in B2 introduced active sites and narrowed the band gap. Notably, B3, a Bi4Ti3O12 (donor)-triazine unit (π-electron bridge)-aldehyde benzene (acceptor) molecule, effectively formed the D-π-A array structure, which formed multiple polarization fields and further narrowed the band gap. Therefore, UVI was more likely to capture electrons at the adsorption site of B3 and be reduced to UIV due to energy level matching effects. UVI removal capacity of B3 under simulated sunlight was 684.9 mg g−1, 2.5 times greater than B1 and 1.8 times greater than B2. B3 was still active after multiple reaction cycles, and UVI removal from tailings wastewater reached 90.8%. Overall, B3 provides an alternative design scheme for enhancing photocatalytic performance.
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Photocatalytic UVI reduction is one of the most promising methods to reduce radioactive uranium contamination in tailings wastewater. Herein, a Bi4Ti3O12 (donor)-triazine (π-electron bridge)-aldehyde benzene (acceptor) crosslinked molecule, named B3, was formed D-π-A array structure for significantly improving photocatalytic UVI removal performance from tailings wastewater. The improved performance of B3 is due to the increased adsorption sites on the triazine and the increased electron push-pull effect of aldehyde group benzene as a weak acceptor for extended electron delocalization, resulting in the formation of multiple polarization fields. The modulation of D-π-A array structure provides an alternative means to improve photocatalytic performance.
•Bi4Ti3O12-triazine unit-aldehyde benzene molecule formed D-π-A array structure.•The D-π-A array structure can form multiple polarization fields.•The D-π-A array structure can regulate band gap width and charge transfer.•The modulation of D-π-A structure can improve photocatalytic performance.
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