Engineering of a DNAzyme-Based dimeric G-quadruplex rolling circle amplification for robust analysis of lead ion.

Detecting heavy metal pollution, particularly lead ion (Pb2⁺) contamination, is imperative for safeguarding public health. In this study, we introduced an innovative approach by integrating DNAzyme with rolling circle amplification (RCA) to propose an amplification sensing method termed DNAzyme-based dimeric-G-quadruplex (dimer-G4) RCA. This sensing approach allows for precise and high-fidelity Pb2⁺ detection. Strategically, in the presence of Pb2⁺, the DNAzyme undergoes substrate strand (S-DNA) cleavage, liberating its enzyme strand (E-DNA) to prime isothermal amplification. This initiates the RCA process, producing numerous dimer-G-Quadruplexes (dimer-G4) as the signal reporting transducers. Compared to conventional strategies using monomeric G-quadruplex (mono-G4) as the reporting transducers, these dimer-G4 structures exhibit significantly enhanced fluorescence when bound with Thioflavin T (ThT), offering superior target signaling ability for even detection of Pb2⁺ at low concentration. Conversely, in the absence of Pb2⁺, the DNAzyme structure remains intact so that no primers can be produced to cause the RCA initiation. This nucleic acid amplification-based Pb2⁺ detection method combing with the high specificity of DNAzymes for Pb2⁺ recognition ensures highly sensitive detection of Pb2+ with a detection limit of 0.058 nM, providing a robust tool for food safety analysis and environmental monitoring.

Advances, challenges, and opportunities for food safety analysis in the isothermal nucleic acid amplification/CRISPR-Cas12a era.

Global food safety stands out as a prominent public concern, affecting populations worldwide. The recurrent challenge of food safety incidents reveals the need for a robust inspection framework. In recent years, the integration of isothermal nucleic acid amplification with CRISPR-Cas12a techniques has emerged as a promising tool for molecular detection of food hazards, presenting next generation of biosensing for food safety detection. This paper provides a comprehensive review of the current state of research on the synergistic application of isothermal nucleic acid amplification and CRISPR-Cas12a technology in the field of food safety. This innovative combination not only enriches the analytical tools, but also improving assay performance such as sensitivity and specificity, addressing the limitations of traditional methods. The review summarized various detection methodologies by the integration of isothermal nucleic acid amplification and CRISPR-Cas12a technology for diverse food safety concerns, including pathogenic bacterium, viruses, mycotoxins, food adulteration, and genetically modified foods. Each section elucidates the specific strategies employed and highlights the advantages conferred. Furthermore, the paper discussed the challenges faced by this technology in the context of food safety, offering insightful discussions on potential solutions and future prospects.

Study on the Particle Deposition Characteristics of Transpiration Cooling Structures with Sintered Wire Mesh.

Transpiration cooling based on a porous structure has an ultra-high cooling efficiency, which is expected to be one solution to improve the cooling technology of aero-engine turbine blades. However, particulate impurities in the gas flow channel continue to deposit on the surface of turbine components, blocking cooling holes, which causes great harm to the cooling of turbine blades. In this study, a sintered metal mesh plate was selected as the transpiration cooling structure, and the evolution of particle deposition quality and deposition thickness on the transpiration cooling surface with time, as well as spatial distributions of particle deposition thickness at different times, were explored through experimental and simulation methods. The results showed that, with the increase in spray time, deposition quality and maximum deposition thickness of the transpiration cooling surface gradually increased. Along the main-stream direction, when spray time was short, deposition thickness was higher in a narrow range upstream of the experimental specimen. With the increase in spray time, deposition thickness gradually decreased along the direction of the transpiration cooling mainstream. In the spanwise direction, when spray time was very short, deposition thickness in the spanwise direction was more consistent and, after spray time increased further, the deposition thickness distribution began to tend to a "∩"-type distribution. It can be seen from the simulation results of the metal wire mesh particle deposition that particles were easily deposited on the windward side of the metal wire in the main-stream direction, which agreed with the experimental distribution characteristics of the metal wire mesh deposition. Moreover, the increase in blowing ratio reduced the deposition of particles on the wall of the metal wire mesh.

Deep Progressive Reinforcement Learning-Based Flexible Resource Scheduling Framework for IRS and UAV-Assisted MEC System.

The intelligent reflecting surface (IRS) and unmanned aerial vehicle (UAV)-assisted mobile edge computing (MEC) system is widely used in temporary and emergency scenarios. Our goal is to minimize the energy consumption of the MEC system by jointly optimizing UAV locations, IRS phase shift, task offloading, and resource allocation with a variable number of UAVs. To this end, we propose a flexible resource scheduling (FRES) framework by employing a novel deep progressive reinforcement learning that includes the following innovations. First, a novel multitask agent is presented to deal with the mixed integer nonlinear programming (MINLP) problem. The multitask agent has two output heads designed for different tasks, in which a classified head is employed to make offloading decisions with integer variables while a fitting head is applied to solve resource allocation with continuous variables. Second, a progressive scheduler is introduced to adapt the agent to the varying number of UAVs by progressively adjusting a part of neurons in the agent. This structure can naturally accumulate experiences and be immune to catastrophic forgetting. Finally, a light taboo search (LTS) is introduced to enhance the global search of the FRES. The numerical results demonstrate the superiority of the FRES framework, which can make real-time and optimal resource scheduling even in dynamic MEC systems.

In vivo recording of suprachiasmatic nucleus dynamics reveals a dominant role of arginine vasopressin neurons in circadian pacesetting.

The central circadian clock of the suprachiasmatic nucleus (SCN) is a network consisting of various types of neurons and glial cells. Individual cells have the autonomous molecular machinery of a cellular clock, but their intrinsic periods vary considerably. Here, we show that arginine vasopressin (AVP) neurons set the ensemble period of the SCN network in vivo to control the circadian behavior rhythm. Artificial lengthening of cellular periods by deleting casein kinase 1 delta (CK1δ) in the whole SCN lengthened the free-running period of behavior rhythm to an extent similar to CK1δ deletion specific to AVP neurons. However, in SCN slices, PER2::LUC reporter rhythms of these mice only partially and transiently recapitulated the period lengthening, showing a dissociation between the SCN shell and core with a period instability in the shell. In contrast, in vivo calcium rhythms of both AVP and vasoactive intestinal peptide (VIP) neurons in the SCN of freely moving mice demonstrated stably lengthened periods similar to the behavioral rhythm upon AVP neuron-specific CK1δ deletion, without changing the phase relationships between each other. Furthermore, optogenetic activation of AVP neurons acutely induced calcium increase in VIP neurons in vivo. These results indicate that AVP neurons regulate other SCN neurons, such as VIP neurons, in vivo and thus act as a primary determinant of the SCN ensemble period.

[Bionic optic nerve based on perovskite (CsPbBr 3) quantum-dots].

The bionic optic nerve can mimic human visual physiology and is a future treatment for visual disorders. Photosynaptic devices could respond to light stimuli and mimic normal optic nerve function. By modifying (Poly(3,4-ethylenedioxythio-phene):poly (styrenesulfonate)) active layers with all-inorganic perovskite quantum dots, with an aqueous solution as the dielectric layer in this paper, we developed a photosynaptic device based on an organic electrochemical transistor (OECT). The optical switching response time of OECT was 3.7 s. To improve the optical response of the device, a 365 nm, 300 mW·cm -2 UV light source was used. Basic synaptic behaviors such as postsynaptic currents (0.225 mA) at a light pulse duration of 4 s and double pulse facilitation at a light pulse duration of 1 s and pulse interval of 1 s were simulated. By changing the way light stimulates, for example, by adjusting the intensity of the light pulses from 180 to 540 mW·cm -2, the duration from 1 to 20 s, and the number of light pulses from 1 to 20, the postsynaptic currents were increased by 0.350 mA, 0.420 mA, and 0.466 mA, respectively. As such, we realized the effective shift from short-term synaptic plasticity (100 s recovery of initial value) to long-term synaptic plasticity (84.3% of 250 s decay maximum). This optical synapse has a high potential for simulating the human optic nerve.

Self-Assembly of Multivalent Aptamer-Tethered DNA Monolayers Dedicated to a Fluorescence Polarization-Responsive Circular Isothermal Strand Displacement Amplification for Salmonella Assay.

Pathogenic bacteria are pathogens widely spread that are capable of causing mild to life-threatening diseases in human beings or other organisms. Rationally organizing the simple helical motif of double-stranded DNA (dsDNA) tiles into designed ensemble structures with architecturally defined collective properties could lead to promising biosensing applications for pathogen detection. In this work, we facilely engineered multivalent hairpin aptamer probe-tethered DNA monolayers (MHAP-DNA monolayers) and applied them to build a fluorescence polarization-responsive circular isothermal strand displacement amplification (FP-CSDA) for Salmonella assay. In this system, the MHAP-DNA monolayers were constructed based on a dsDNA tile-directed self-assembly. A FAM-labeled reporting probe (RPFAM) with an inherent low FP signal serves as the signaling unit. The presence of target Salmonella leads to the trapping of F RPFAM into the super DNA monolayers via a target-triggered CSDA to peel off the tethered hairpin-structured aptamer probes (HAPs) responsible for the binding of RPFAM. As a result, the FP signal of the FAM fluorophore can be remarkably amplified due to the recycling of target Salmonella and the capacity of structural DNA materials to strongly restrict the free rotation of the FAM fluorophore but without a fluorescence quenching effect. Experimental results demonstrate that the FP assay is able to detect Salmonella with a low limit of detection (LOD) of 7.2 × 100 CFU/mL and high specificity. As a proof-of-concept study, we envision our study using DNA nanoarchitecture as the foundation to modulate CSDA-based FP assays, promising to open up a new avenue for disease diagnosis, food safety detection, and biochemical studies.

Self-Customized Multichannel Exponential Amplifications Regulate Powered Monitoring of Terminal Deoxynucleotidyl Transferase Activity.

The discovery and function analysis of terminal deoxynucleotidyl transferase (TdT) add a new dimension to the understanding of leukemia mechanisms and stimulate the development of new analytical tools for leukemia diagnosis. Herein, taking advantage of the inherent property of TdT for performing DNA synthesis using only single-stranded DNA as the nucleic acid substrate, we developed a self-customized multichannel exponential amplification (SMEA) system for the fluorescent sensing of TdT activity. The SMEA design employs an intermolecular DNA interaction made of a nicking site-incorporated elongation primer (EP) and a nicking site-incorporated poly-thymine tailed molecular beacon (Poly-T-MB). The absence of TdT is unable to bridge the relationship between EP and Poly-T-MB, ensuring the SMEA has an ultralow background. The presence of TdT, however, leads to the elongation of EP to poly-adenine tailed EP (Poly-A-EP) under a dATP pool responsible for further hybridization with numerous Poly-T-MB. With the aid of polymerase and nickase to react with the hybridization product of Poly-A-EP/(Poly-T-MB)n, it can cause bidirectional strand nicking, polymerization, and displacement in many cycles and channels. In this case, the SMEA is found to be associated with the configuration transformation and splitting of all Poly-T-MBs for a significant fluorescence enhancement. Depending on this high target signal amplification and strong background inhibition abilities, the SMEA sensing system is powerful for the qualitative and quantitative determination of TdT activity, showing that it has great promise for biomedical study and disease diagnosis.

Cell Type-Specific Genetic Manipulation and Impaired Circadian Rhythms in Vip tTA Knock-In Mice.

The suprachiasmatic nucleus (SCN), the central circadian clock in mammals, is a neural network consisting of various types of GABAergic neurons, which can be differentiated by the co-expression of specific peptides such as vasoactive intestinal peptide (VIP) and arginine vasopressin (AVP). VIP has been considered as a critical factor for the circadian rhythmicity and synchronization of individual SCN neurons. However, the precise mechanisms of how VIP neurons regulate SCN circuits remain incompletely understood. Here, we generated Vip tTA knock-in mice that express tetracycline transactivator (tTA) specifically in VIP neurons by inserting tTA sequence at the start codon of Vip gene. The specific and efficient expression of tTA in VIP neurons was verified using EGFP reporter mice. In addition, combined with Avp-Cre mice, Vip tTA mice enabled us to simultaneously apply different genetic manipulations to VIP and AVP neurons in the SCN. Immunostaining showed that VIP is expressed at a slightly reduced level in heterozygous Vip tTA mice but is completely absent in homozygous mice. Consistently, homozygous Vip tTA mice showed impaired circadian behavioral rhythms similar to those of Vip knockout mice, such as attenuated rhythmicity and shortened circadian period. In contrast, heterozygous mice demonstrated normal circadian behavioral rhythms comparable to wild-type mice. These data suggest that Vip tTA mice are a valuable genetic tool to express exogenous genes specifically in VIP neurons in both normal and VIP-deficient mice, facilitating the study of VIP neuronal roles in the SCN neural network.

Particle Deposition in the Vicinity of Multiple Film Cooling Holes.

Particle deposition on film cooling surface is an engineering issue that degrades the thermal protection of turbine blade. Here, we present a combined experimental and numerical investigation on the particle deposition in the vicinity of multiple film cooling holes to reveal the effect of interactions between cooling outflows on particle deposition. The numerical simulation of film cooling with a group of three rows of straight film cooling holes is conducted and validated by experimental data with blowing ratios ranging from 0 to 0.08. Wax particles with size range from 5 to 40 µm are added in the heated mainstream to simulate the particle deposition in the experiment. The simulation results show the decrease of particle deposition with blowing ratio and various deposition characteristics in different regions of the surface. The flow fields from numerical results are analyzed in detail to illustrate deposition mechanism of the particles in different regions under the interactions of cooling outflows. The cooling air from the holes in the first row reduces the particle concentration near the wall but causes particle deposition in or between the tail regions by the generated flow disturbance. The cooling air from the latter hole separates the diluted flow in the upstream from the wall, and creates a tail region without particle deposition. This revealed particle deposition characteristics under the effect of outflows interaction can benefit the understanding of particle deposition in engineering applications, where multi-row of cooling holes are utilized.

Experimental Investigation on the Transpiration Cooling Characteristics of Sintered Wire Mesh in Plain Weave.

We experimentally investigate the transpiration cooling characteristics of a porous material, sintered wire mesh. Three samples with different porosities in a plain weave structure are tested with various blowing ratios in an open-loop wind tunnel with a heated mainstream flow. The temperature on the surface of the porous material is measured by an infrared camera to obtain the cooling efficiency. The measurements reveal nonuniform distributions of the surface temperature and the cooling efficiency in both the flow direction and the transverse direction. The averaged cooling efficiency on the surface first decreases and then increases with the blowing ratio, but increases and then decreases with the porosity of the material. The internal cooling by forced convection and its combination with the external film cooling from the transpiration cooling are considered to be attributed to those two cooling characteristics, respectively. Finally, we propose a modified blowing ratio to collapse the minima of the blowing ratio for all tested samples, providing an universal transition for the decreasing and increasing branches for all tested samples in the relation between averaged cooling efficiency and blowing ratio.

A loop-mediated isothermal amplification-enabled analytical assay for the detection of SARS-CoV-2: A review.

The number of words: 4645, the number of figures: 4, the number of tables: 1The outbreak of COVID-19 in December 2019 caused a global pandemic of acute respiratory disease, and with the increasing virulence of mutant strains and the number of confirmed cases, this has resulted in a tremendous threat to global public health. Therefore, an accurate diagnosis of COVID-19 is urgently needed for rapid control of SARS-CoV-2 transmission. As a new molecular biology technology, loop-mediated isothermal amplification (LAMP) has the advantages of convenient operation, speed, low cost and high sensitivity and specificity. In the past two years, rampant COVID-19 and the continuous variation in the virus strains have demanded higher requirements for the rapid detection of pathogens. Compared with conventional RT-PCR and real-time RT-PCR methods, genotyping RT-LAMP method and LAMP plus peptide nucleic acid (PNA) probe detection methods have been developed to correctly identified SARS-CoV-2 variants, which is also why LAMP technology has attracted much attention. LAMP detection technology combined with lateral flow assay, microfluidic technology and other sensing technologies can effectively enhance signals by nucleic acid amplification and help to give the resulting output in a faster, more convenient and user-friendly way. At present, LAMP plays an important role in the detection of SARS-CoV-2.

Explaining mobile government social media continuance from the valence perspective: A SEM-NN approach.

Different from many previous studies explain mobile social media usage from a technical-center perspective, the present study investigates the factors that influence citizens' mobile government social media (GSM) continuance based on the valence framework. The research model was calculated by using data collected from 509 citizens who are the mobile GSM users in China. A structural equation modeling (SEM)-neural network (NN) method was employed to test the research model. The results of SEM indicated that the positive utilities included social value and hedonic value positively affect mobile GSM continuance, while the negative utility reflected by self-censorship negative affect mobile GSM continuance. This is further supported by the results of the neural network model analysis which indicated that hedonic value is more influencing predictor of continuous usage of mobile GSM, following by social value and self-censorship.

High-dose nitrate therapy recovers the expression of subtypes α1 and ß-adrenoceptors and Ang II receptors of the renal cortex in rats with myocardial infarction-induced heart failures.

BACKGROUND: Few studies examined the effect of long-acting nitrates on renal function in chronic heart failure (CHF). Thus, we aimed to investigate the effect of long-acting nitrate on the expression of adrenoceptors (AR) and angiotensin II receptor (ATR) subtypes of the renal cortex, in rats with myocardial infarction-induced CHF. METHODS: Rats were randomly divided into the following groups: control, sham-operated, CHF, low- and high-dose nitrate, positive drug control (olmesartan), and high-dose of long-acting nitrate + olmesartan. Ultrasound echocardiography markers were compared, and the levels of AR subtypes, AT1R, and AT2R were measured using reverse transcription-polymerase chain reaction and western blot analysis. Histopathology of the kidney was determined on hematoxylin and eosin-stained sections. RESULTS: CHF significantly increased plasma renin activity (PRA) and angiotensin II levels, upregulated AT1R expression and downregulated α1A-, ß1-, ß2-AR, and AT2R expression compared to the sham control. High-dose nitrate or olmesartan alone, and especially in combination, decreased the levels of PRA and angiotensin II and downregulated the CHF-induced expression of AT1R, α1A-, ß1-, and ß2-AR, and AT2R. CHF resulted in significant impairment of the renal tissue, including inflammatory cells infiltration to the tubular interstitium and surrounding the renal glomerulus, and tubular necrosis, which was alleviated in all treatment groups to different degrees. CONCLUSIONS: Long-acting nitrates could reverse CHF-induced changes in AR and ATR subtypes in the kidney, and improve cardiac function to protect renal function. Compared with monotherapy, the combination of nitrates and olmesartan shows more significant benefits in regulating AR and ATR subtypes.

Novel Consensus Docking Strategy to Improve Ligand Pose Prediction.

Molecular docking, which mainly includes pose prediction and binding affinity calculation, has become an important tool for assisting structure-based drug design. Correctly predicting the ligand binding pose to a protein target enables the estimation of binding free energy using various tools. Previous studies have shown that the consensus method can be used to improve the docking performance with respect to compound scoring and pose prediction. In this report, a novel consensus docking strategy was proposed, which uses a dynamic benchmark data set selection to determine the best program combinations to improve the docking success rate. Using the complexes from PDBbind as a benchmark data set, a 4.9% enhancement in success rate was achieved compared with the best program.

[Chemical constituents from Pteris dispar and their anti-tumor activity in vitro].

The dried whole plant of Pteris dispar were milled and extracted with 95% EtOH. The resulting dried extract was isolated by kinds of chromatographic column, including polyamide, Sephadex LH-20, preparative HPLC. As a result, ten diterpenes were isolated from the plant. By analyzing of ESI-MS and NMR spectroscopic data, the structures were established as geopyxin B(1), geopyxin E(2), ent-11α-hydroxy-18-acetoxykaur-16-ene(3), ent-14ß-hydroxy-18-acetoxykaur-16-ene(4), neolaxiflorin L(5), ent-3ß,19-dihydroxy-kaur-16-ene(6), ent-3ß-hydroxy-kaur-16-ene(7), 7ß,17-dihydroxy-16α-ent-kauran-19-oic acid 19-O-ß-D-glucopyranoside ester(8), crotonkinin C(9)and crotonkinin C(10). Compounds 1-10 were obtained from P. dispar for the first time. Compounds 1 and 2 showed moderate activities against Bel-7402 with IC50 values of 7.50 and 10.60 µmol•L⁻¹, and against HepG2 with IC50 values of 6.68,11.80 µmol•L⁻¹, respectively.

[Bioactive lignans from Silybum marianum].

The seeds of Silybum marianum were extracted by hot water, and the extract was isolated by D101 macroporous resin, MCI resin, MPLC, HPLC, et al. As a result, 7 compounds including tricin 4'-O-[threo-ß-guaiacyl-(7″-O-methyl)-glyceryl] ether(1), tricin 4'-O-[erythro-ß-guaiacyl-(7″-O-methyl)-glyceryl] ether(2), 5'-methoxyhydnocarpin-D(3),palstatin(4),(8R,7'S,8'R)-5,5'-dimethoxy-7-oxolariciresinol 9'-O-D-xylopyranoside(5), 9-O-D-glucopyranoside(6), and(-)-haplomyrtoside(7) were isolated and identified for the first time. Compounds 1, 3, 4, and 5 exhibited activity against influenza A(H5N1)with IC50 value of 0.65, 0.21, 0.32, and 0.56 µmol•L⁻¹, respectively. Compounds 1, 2, 6, and 7 exhibited cytotoxity against HepG-2 with IC50 value of 0.35, 0.25, 0.53, 0.66 µmol•L⁻¹, respectively.

[Bioactive quinolizidine alkaloids from Sophora tonkinensis].

Twelve quinolizidine alkaloids were isolated from Sophora tonkinensis by means of silica gel, preparative MPLC, and preparative HPLC. On analysis of NMR spectroscopic data, their structures were established as 3-(4-hydroxyphenyl)-4-(3-methoxy-4-hydroxyphenyl)-3,4-dehydroquinolizidine(1), lanatine A(2), cermizines C(3), senepodines G(4), senepodines H(5), jussiaeiines A(6), jussiaeiines B(7),(+)-5α-hydroxyoxysophocarpine(8),(-)-12ß-hydroxyoxysophocarpine(9),(-)-clathrotropine(10),(-)-cytisine(11), and (-)-N-methylcytisine(12), respectively. Compounds 1-7 were first isolated from Sophora L. plant. In the in vitro assays,the isolated compounds 1, 3, 6-10 exhibited potent activity against CVB3 with IC50 of 6.40, 3.25, 4.66, 3.21, 0.12, 0.23 and 1.60, and with selective index values(SI=TC50/IC50)of 12.0, 5.6, 13.0, 15.1, 50.1, 26.2, and 23.6, respectively. Compounds 1, 3, and 7 exhibited activity against staphylococcus aureus(ATCC 29213)with MICvalues of 8.0, 3.5, 6.0 g•L⁻¹, respectively. Compounds 1, 3, 7, and 12 exhibited activity against staphylococcus aureus(ATCC 33591)with MIC values of 18.0, 7.5, 8.0, 12.0 g•L⁻¹, respectively. Compounds 2, 6, 7 exhibited activity against Escherichia coli(ATCC 25922) with MIC values of 1.0, 3.2, 0.8 g•L⁻¹.