Simulation, Design, and Test of a Dual-Differential D-Dot Overvoltage Sensor Based on the Field-Circuit Coupling Method.

Accurate measurement of overvoltage in power grids is of great significance to study the characteristics of overvoltage and design of insulation coordination. Based on the research of D-dot voltage sensor, we designed a Dual-Differential D-dot overvoltage sensor. In order to quantify the structural parameters of the sensor, improve the performance and measurement accuracy of the sensor. The Field-Circuit Coupling method was proposed to be used in the parameter design of D-dot overvoltage sensor. The joint simulation of space electromagnetic field model and equivalent circuit model of the Dual-Differential D-dot overvoltage sensor was established with the finite element simulation software Ansoft Maxwell and circuit simulation software Simplorer. Finally, the actual sensor was manufactured. A test platform was built to verify the steady-state and transient performance of the sensor. The results show that the Dual-Differential D-dot sensor has excellent steady-state and transient performance, the error of phase and amplitude are small, and the sensor can achieve the non-contact measurement of power transmission line. Simultaneously, the rationality of the Field-Circuit Coupling method was further verified.

Inhibition of HMGB1 improves necrotizing enterocolitis by inhibiting NLRP3 via TLR4 and NF-κB signaling pathways.

OBJECTIVE: To explore the relationship between high-mobility group box 1 (HMGB1) and NLR pyrin domain containing 3 (NLRP3) in the development of necrotizing enterocolitis (NEC). METHODS: NEC rat models were constructed and treated with HMGB1 inhibitor glycyrrhizin (GL) with different concentration. An inflammatory condition of intestinal tissue in newborn NEC rats was observed by hematoxylin and eosin staining. The messenger RNA (mRNA) and protein expression of HMGB1, NLRP3, toll-like receptor 4 (TLR4), nuclear factor-κB (NF-κB), and caspase 1 were determined by real-time polymerase chain reaction and western blot analysis, respectively. The content of interleukin (IL)-1ß and tumor necrosis factor-α (TNF-α) was determined by enzyme-linked immunosorbent assay. Human intestinal epithelial cell lines were induced to NEC by lipopolysaccharides (LPSs). LPS-induced cells were transfected with small interfering RNA-HMGB1 and NLRP3 plasmid vector. The mRNA and protein expression of HMGB1, NLRP3, TLR4, NF-κB, caspase 1, IL-1ß, and TNF-α were determined by real-time PCR and western blot analysis, respectively. RESULTS: The mRNA and protein expression of HMGB1 and NLRP3 in the NEC group was significantly higher than the control group. Inhibition of HMGB1 expression improved intestinal inflammation in newborn NEC rats. The expression of HMGB1, NLRP3, TLR4, NF-κB, and caspase 1 was upregulated in NEC and was weakened after treating with GL. LPS induction to intestinal epithelial cells markedly increased the expression of HMGB1, NLRP3, TLR4, NF-κB, caspase 1, IL-1ß, and TNF-α. The knockdown of HMGB1 abolished the increase of expression, whereas further transfection with NLRP3 plasmid vector recovered the increase. CONCLUSION: HMGB1 and NLRP3 were all upregulated in the development of NEC. Inhibition on HMGB1 could improve the intestinal inflammation in NEC by inhibiting NLRP3 via TLR4 and NF-κB signaling pathways.

Dynamic sandwich-type electrochemical assay for protein quantification and protein-protein interaction.

The study of protein-protein interactions (PPIs) plays an important role in the understanding of biological systems; however, the established methods for PPI analysis often involve cumbersome sample preparation, multiple detecting steps, and costly instruments. Here we report a versatile and sensitive electrochemical method based on PPI-induced distinctive migration behavior of DNA deoxyribozyme (DNAzyme) on an electrode surface. In this method, the cleavage activity of DNAzyme toward the substrate DNA modified on the electrode surface is inversely correlated with the hydrodynamic diameter of the macromolecule attached to it. By making full use of this principle in an inexpensive electrochemical format that is named the dynamic sandwich-type electrochemical assay (dSTEA), we can probe into the presence of large macromolecules in a single-step procedure. Moreover, we can not only detect sub-picomolar protein interaction events but also analyze the assembly of kinase in the whole cell extract. This novel signaling mechanism proposed in this work may broaden the applicability of DNAzyme-based electrochemical assays and it may also have great potential for applications in other interfacial sensor developments.

Flexible regulation of DNA displacement reaction through nucleic acid-recognition enzyme and its application in keypad lock system and biosensing.

Toehold-mediated DNA strand displacement reaction (SDR) plays pivotal roles for the construction of diverse dynamic DNA nanodevices. To date, many elements have been introduced into SDR system to achieve controllable activation and fine regulation. However, as the most relevant stimuli for nucleic acid involved reaction, nucleic acid-recognizing enzymes (NAEs) have received nearly no attention so far despite SDR often takes place in NAEs-enriched environment (i.e., biological fluids). Herein, we report a set of NAEs-controlled SDR strategies, which take full advantage of NAEs' properties. In this study, three different kinds of enzymes belonging to several classes (i.e., exonuclease, endonuclease and polymerase) have been used to activate or inhibit SDR, and more importantly, some mechanisms behind these strategies on how NAEs affect SDR have also been revealed. The exploration to use NAEs as possible cues to operate SDR will expand the available toolbox to build novel stimuli-fueled DNA nanodevices and could open the door to many applications including enzyme-triggered biocomputing and biosensing.

In Vitro Analysis of DNA-Protein Interactions in Gene Transcription Using DNAzyme-Based Electrochemical Assay.

The interaction between protein and DNA elements controls a variety of functions of genomes. The development of a convenient and cost-effective method for investigating the sequence specificity of DNA-binding proteins represents an important challenge. In response, we have introduced an electrochemical assay in this work for specific and sensitive analysis of interaction between protein and nucleic acid in nucleic extracts, based on the protein-induced distinctive motion behavior of DNA deoxyribozyme (DNAzyme) on an electrode surface. As a proof of principle, we have also presented assays for the rapid, sensitive, and selective detection of three transcription factors (NF-κB, SP6 RNA polymerase, and HNF-4α), as well as the analysis of binding affinity of the mutated protein-binding sequence, and even screening of the binding sequence of HNF-4α protein in vitro. This work may open new opportunity for in-depth profiling of the sequence specificity of DNA-binding proteins and study of nucleotide polymorphisms in known protein-binding sites.

Simple and fast screening of G-quadruplex ligands with electrochemical detection system.

Small molecules that may facilitate and stabilize the formation of G-quadruplexes can be used for cancer treatments, because the G-quadruplex structure can inhibit the activity of telomerase, an enzyme over-expressed in many cancer cells. Therefore, there is considerable interest in developing a simple and high-performance method for screening small molecules binding to G-quadruplex. Here, we have designed a simple electrochemical approach to screen such ligands based on the fact that the formation and stabilization of G-quadruplex by ligand may inhibit electron transfer of redox species to electrode surface. As a proof-of-concept study, two types of classical G-quadruplex ligands, TMPyP4 and BRACO-19, are studied in this work, which demonstrates that this method is fast and robust and it may be applied to screen G-quadruplex ligands for anticancer drugs testing and design in the future.

Electrochemical detection of Nanog in cell extracts via target-induced resolution of an electrode-bound DNA pseudoknot.

Nanog is among the most important indicators of cell pluripotency and self-renew, so detection of Nanog is critical for tumor assessment and monitoring of clinical prognosis. In this work, a novel method for Nanog detection is proposed by using electrochemical technique based on target-induced conformational change of an electrode-bound DNA pseudoknot. In the absence of Nanog, the rigid structure of the pseudoknot will minimize the connection between the redox tag and the electrode, thus reducing the obtained faradaic current. Nevertheless, the Nanog binding may liberate the flexible single-stranded element that transforms the DNA pesudokont into DNA hairpin structure due to steric hindrance effect, thus making the electrochemical tag close to the electrode surface. Consequently, electron transfer can be enhanced and very well electrochemical response can be observed. By using the proposed method, Nanog can be determined in a linear range from 2nM to 25nM with a detection limit of 163 pM. Furthermore, the proposed method can be directly used to assay Nanog not only in purified samples but also in complex media (cell extracts), which shows potential applications in Nanog functional studies as well as clinical diagnosis in the future.

Dynamic light scattering (DLS)-based immunoassay for ultra-sensitive detection of tumor marker protein.

A novel dynamic light scattering (DLS)-based immunoassay that utilizes manganese dioxide nanosheet-modified gold nanoparticles (MnO2-GNPs) as an activatable nanoprobe has been developed to detect tumor markers down to femtomolar levels.

Inertial measurements of upper limb motion.

We present an inertial sensor based monitoring system for measuring upper limb movements in real time. The purpose of this study is to develop a motion tracking device that can be integrated within a home-based rehabilitation system for stroke patients. Human upper limbs are represented by a kinematic chain in which there are four joint variables to be considered: three for the shoulder joint and one for the elbow joint. Kinematic models are built to estimate upper limb motion in 3-D, based on the inertial measurements of the wrist motion. An efficient simulated annealing optimisation method is proposed to reduce errors in estimates. Experimental results demonstrate the proposed system has less than 5% errors in most motion manners, compared to a standard motion tracker.