The fluorescence of metal nanoclusters provides an amusing optic feature to be applied in various fields. However, rational design of dual functional fluorescent metal nanoclusters directed by active ...enzyme with targeted application remains little explored. In this work, we report a new strategy to construct enzyme functionalized fluorescent gold nanoclusters via a biomineralization process for the detection of hydrogen peroxide. Horseradish peroxidase (HRP) was used as a model functional template to direct the synthesis of fluorescent gold nanoclusters (Au NCs) at physiological conditions to form HRP−Au NCs bioconjugates. We found that the fluorescence of HRP−Au NCs can be quenched quantitatively by adding H2O2, indicating that HRP enzyme remains active and enables catalytic reaction of HRP−Au NCs and H2O2. Upon the addition of H2O2 under optimal conditions, the fluorescence intensity quenched linearly over the range of 100 nM to 100 μM with high sensitivity (LOD = 30 nM, S/N = 3). This study would be potentially extended to other functional proteins to generate dual functional nanoclusters and applied to real time monitoring of biologically important targets in living cells.
Sensitive and rapid identification of pathogenic microorganisms is of great importance for clinical diagnosis and treatment. In this study, we developed an ultrasensitive colorimetric sensor array ...(CSA) based on the interactions between aminoglycoside antibiotics (AMGs) and Ag nanoparticles decorated with β-cyclodextrin (AgNPs@β-CD) to discriminate microorganisms quickly and accurately. Microorganisms can absorb different amounts of AMGs after incubation. Upon the addition of AgNPs@β-CD, the corresponding extracellular AMG residues will bind to AgNPs@β-CD, leading to color changes due to the modifications in localized surface plasmon resonance. The array was developed using 4 AMGs as sensing elements and AgNPs@β-CD as the colorimetric probe to generate a unique colorimetric response pattern for each microorganism. Standard chemometric methods indicated excellent discrimination among 20 microorganisms at low concentrations of 2 × 10
6
CFU/mL. Therefore, this ultrasensitive CSA can be used for microbial discrimination portably and efficiently. Importantly, the concentration of microbial discrimination by our array is much lower than that of prior CSAs. This method of extracellular residue sensing also provided a new strategy to improve the sensitivity of conventional CSA in the discrimination of microorganisms, to measure the amount of intercellular uptake of AMGs by microorganisms, and to screen drugs that can easily be accumulated by the pathogenic microorganisms.
Graphical abstract
Herein, using DNA adenine methylation (Dam) methyltransferase (MTase) as a model analyte, a simple, rapid, and highly sensitive fluorescence sensing platform for monitoring the activity and ...inhibition of DNA MTase was developed on the basis of methylation-sensitive cleavage and nicking enzyme-assisted signal amplification. In the presence of Dam MTase, an elaborately designed hairpin probe was methylated. With the help of methylation-sensitive restriction endonuclease DpnI, the methylated hairpin probe could be cleaved to release a single-stranded DNA (ssDNA). Subsequently, this released ssDNA would hybridize with the molecular beacon (MB) to open its hairpin structure, resulting in the restoration of fluorescence signal as well as formation of the double-stranded recognition site for nicking enzyme Nt.BbvCI. Eventually, an amplified fluorescence signal was observed through the enzymatic recycling cleavage of MBs. Based on this unique strategy, a very low detection limit down to 0.06 U/mL was achieved within a short assay time (60 min) in one step, which is superior to those of most existing approaches. Owing to the specific site recognition of MTase toward its substrate, the proposed sensing system was able to readily discriminate Dam MTase from other MTase such as M.SssI and even detect the target in complex biological matrix. Furthermore, the application of the proposed sensing strategy for screening Dam MTase inhibitors was also demonstrated with satisfactory results. This novel method not only provides a promising platform for monitoring activity and inhibition of DNA MTases, but also shows great potentials in biological process researches, drugs discovery and clinical diagnostics.
Protein identification is very important in the field of clinical medicine and diagnosis. Here, we report a novel and simple sensor array for the detection and identification of proteins using pH ...buffer solutions as sensing elements. Different proteins in various pH solutions have different net surface charges including positive, negative or no charge. Such differences may allow a pattern recognition-based sensor array for protein identification. When using negatively charged CdSe/ZnS quantum dots as an indicator, the interactions between a charged protein and quantum dots result in fluorescence changes, generating a differential response pattern for the protein. The result shows that proteins with pI > 7, pI = 7 or pI < 7 can be differentiated successfully. Moreover, complex protein mixtures are also able to be identified and the results demonstrate that surface charge may play an important role in protein sensing. The HSA of different concentrations in water and human urine can also be detected by using the sensor array. It is demonstrated that the proposed sensor array has potential applications in clinical diagnosis and proteomics.
A novel and simple fluorescence sensor array was developed for the detection and identification of proteins using pH buffer solutions as sensing elements.
Integrated atomistic and molecular dynamic simulations are used to characterize the role hydrogen bonding and interchain interactions on structures and phase transitions of novel bent-core-like ...mesogenic materials that exhibit new self-assembly features, attractive to the development of functional materials. Multi-step simulations were carried out to model phase transitions and various spectra of two complex mesogenic materials formed from acid functionalized azo compounds, 4-2,3,4-tri(octyloxy)phenylazo benzoic acid and 4-2,3,4- tri(heptyloxy)phenylazo benzoic acid. The simulations contain three consecutive steps, involving molecular quantum chemistry, molecular crystal packing, and super cell molecular dynamics calculations. These two mesogens are supposed to form phasmidic molecular conformers. However, simulations point to the formation of complex discotic bent-core-like liquid crystals with tetramer mesogenic assemblies, in very good agreement with experimental observations. The wide range agreements between simulations and experimental results include transitions of crystal structures to columnar and uniaxial nematic phases, x-ray diffraction patterns of columnar phases, the structure of the two-dimensional complex bent-core-like tetramers, molecular Raman spectra, Raman depolarization spectra, and order parameters of nematic phases. The multi-step simulation methodology and its results shed light on this unique behaviour of plasmids with flexible side chains for simulation design of novel bent-core-like mesogenic materials.
We report a novel PbS/Er co-doped silica fiber (PEDF) with improved spectral properties in O-band (1260-1360 nm). The results show that the gain of the PEDF exceeds 15 dB in the range of 1150-1360 ...nm. Compared to PbS-doped silica fiber, the PEDF has a gain improvement of 6.4-10.9 dB in O-band. In addition, the concentration of Pb and S in the PEDF core is significantly higher, and the size distribution of PbS nanoparticles is more concentrated in a narrow range. These factors may account for the enhanced gain characteristics of the PEDF. This work reveals the positive effect of co-doping Er 3+ ions on the gain characteristics of the PEDF in O-band, and suggests an important research direction for the design of broadband amplifiers and light sources for optical communication with zero dispersion.
The genome editors CRISPR/Cas9 (clustered regularly interspaced short palindromicrepeats/Cas9 nuclease-null) and TALENs (transcription activator-like effector nuclease) are popularly used for ...targeted modification of the mammalian genome. To date, few comparative studies have been carried out to investigate the differences between the use of CRISPR/Cas9 and TALENs in genome editing for goat breeding. Here, we compared CRISPR/Cas9 and TALEN technologies at multiple levels for generating a knock out (KO) of the Alpas cashmere goat myostatin (MSTN) gene, which negatively regulates the proliferation and differentiation of skeletal muscle cells. The electrotransfection efficiency observed using CRISPR/Cas9 was 8.1% more than that observed using TALEN for generating MSTN KO cells. In addition, the cutting efficiency of CRISPR/Cas9 for editing exon 1 of the MSTN gene was higher than that of TALENs. However, the off-target effects of the CRISPR/Cas9 system were also higher than those of TALENs. Further, we found that the frequency of obtaining MSTN−/- mutations by CRISPR/Cas9 was 8.5 times higher than that by TALEN. The CRISPR/Cas9-edited colonies involved longer deletions (up to 117 bp) than the TALEN-edited colonies (up to 13 bp). Remarkably, when embryos used to generate cloned goat via somatic cell nuclear transfer were compared, we found that the TALEN MSTN KO embryos easily developed to 8 cells and their cleavage rate was significantly higher than that of CRISPR/Cas9-edited embryos. Finally, we produced a MSTN KO lamb using CRISPR/Cas9, which suggested that a high level of targeted gene modification could be achieved in goat using CRISPR/Cas9. Taken together, our study indicates that although TALEN enables a variety of genome modifications and may have some advantages over CRISPR/Cas9, the latter provides a significant advantage by permitting precise and efficient gene editing. Thus, CRISPR/Cas9 has more potential to become a robust gene-engineering tool for application in the breeding of farm animals.
•We successfully generated an MSTN KO lamb using CRISPR/Cas9.•We compared utility of CRISPR/Cas9 and TALEN for generating Alpas cashmere goats with myostatin (MSTN) gene knockout (KO).•Compared with CRISPR/Cas9 embryos, TALEN MSTN KO embryos reached 8-cell stage at significantly higher cleavage rate.•Compared with TALEN, CRISPR/Cas9 showed greater gene editing efficiency, but with higher number of off-target effects.•CRISPR/Cas9 has high potential to become a robust gene-engineering tool for application farm animal breeding.
In this study, we screened novel two-dimensional metal–organic framework (MOF) materials, which can be used as efficient electrocatalysts in the N2 reduction reaction (NRR) and CO2 reduction reaction ...(CO2RR) through density functional theory (DFT) calculations. By systematically investigating the adsorption behaviors of N2 and CO2 in different MOF-TMs (TM = Fe, Co, Ni, Cu, Zn) and their electrocatalytic hydrogenation processes, we found that 2D MOF-Fe, MOF-Co, and MOF-Ni can be used as catalysts for electrocatalytic NRR. The free energy increase in the corresponding potential-limiting step is calculated to be 0.84 eV on MOF-Fe, 1.00 eV on MOF-Co, and 1.17 eV on MOF-Ni, all of which are less than or at least comparable to those reported values for the NRR. Moreover, only 2D MOF-Fe was identified as a suitable electrocatalyst for CO2RR. Instead of other hydrocarbons, the product CH3OH is selectively obtained in an electrocatalytic CO2 reduction reaction on a 2D MOF-Fe with a free energy increase of 0.84 eV in the potential-limiting step. Overall, the results of this study not only facilitate the potential application of 2D MOF-TMs as electrocatalysts but also provide new guidelines for rationally designing novel electrocatalysts for the NRR and CO2RR.
•PbS-doped silica optical fiber materials have been fabricated by ALD technique.•PbS-doped silica optical fiber materials are characterized through XPS, Raman and optical properties.•The local ...structure model of PbS-3MR for the PbS-doped optical fiber materials is built, and its optical properties are investigated using DFT.•The computed results of absorption and emission peaks are at 325.7 and 769.8nm, which are good agreement with our experiment results.
Optical properties of PbS-doped silica optical fiber materials and theoretical simulation are investigated. PbS is deposited on silica optical fiber materials by Atomic Layer Deposition (ALD) technique with Pb(tmhd)2 and H2S as Pb and S precursors, respectively. Its stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence states of S and Pb element are −2 and +2, respectively. The Raman spectra further reveal that PbS has been doped into optical fiber materials almost without destroying irregular rings structure in silica material network. And there are distinct absorption bands at 248 and 352nm. Fluorescence spectra are obtained with 330 and 350nm pumping, two fluorescence peaks at 768 and 808nm, respectively. In addition, the microstructure models for PbS-doped optical fiber materials are built on Gaussian09 platform, and its optical properties of the absorption and emission spectra are calculated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. There are obvious absorption and emission peaks at 325.7 and 769.8nm, respectively, which are in good agreement with experiments.
Er-doped optical fiber (EDF) with ultra-broad gain bandwidth is urgently needed given the rapid advancement of optical communication. However, the weak crystal field of the host silica glass severely ...restricts the bandwidth of traditional EDF at 1.5 μm. In this study, we theoretically explored the introduction of PbS nanomaterials in the silica network assisted with the non-bridging oxygen. This can significantly increase the crystal field strength of Er3+ ions in the local structure, leading to their energy level splitting and expanding the fluorescence bandwidth. Additionally, the PbS/Er co-doped optical fiber (PEDF) with improved fluorescence and gain characteristics was fabricated using modified chemical vapor deposition combined with the atomic layer deposition technique. The presence of PbS nanomaterials in the fiber core region, which had an average size of 4 nm, causes the 4I13/2 energy level of Er3+ ions to divide, increasing the fluorescence bandwidth from 32 to 39 nm. Notably, the gain bandwidth of PEDF greater than 20 dB increased by approximately 12 nm compared to that of EDF. The obtained PEDF would play an important role in the optical fiber amplifier and laser applications.
