Superior structure stability and selectivity of hairpin nucleic acid probes with an l-DNA stem

Hairpin nucleic acid probes have been highly useful in many areas, especially for intracellular and in vitro nucleic acid detection. The success of these probes can be attributed to the ease with which their conformational change upon target binding can be coupled to a variety of signal transduction mechanisms. However, false-positive signals arise from the opening of the hairpin due mainly to thermal fluctuations and stem invasions. Stem invasions occur when the stem interacts with its complementary sequence and are especially problematic in complex biological samples. To address the problem of stem invasions in hairpin probes, we have created a modified molecular beacon that incorporates unnatural enantiomeric l-DNA in the stem and natural d-DNA or 2′-O-Me-modified RNA in the loop. l-DNA has the same physical characteristics as d-DNA except that l-DNA cannot form stable duplexes with d-DNA. Here we show that incorporating l-DNA into the stem region of a molecular beacon reduces intra- and intermolecular stem invasions, increases the melting temperature, improves selectivity to its target, and leads to enhanced bio-stability. Our results suggest that l-DNA is useful for designing functional nucleic acid probes especially for biological applications

A 3-dimensional coordination polymer with a rare lonsdaleite topology constructed from a tetrahedral ligand

A new 3D coordination polymer was solvothermally synthesized. The coordination polymer possesses a lon network built from 4-connecting Co-2 clusters and tetracarboxylate ligands, and exhibits selective gas sorption behavior as well as antiferromagnetic interactions.close131

Recent Advances in the Molecular Design and Delivery Technology of mRNA for Vaccination Against Infectious Diseases

Vaccines can prevent many millions of illnesses against infectious diseases and save numerous lives every year. However, traditional vaccines such as inactivated viral and live attenuated vaccines cannot adapt to emerging pandemics due to their time-consuming development. With the global outbreak of the COVID-19 epidemic, the virus continues to evolve and mutate, producing mutants with enhanced transmissibility and virulence; the rapid development of vaccines against such emerging global pandemics becomes more and more critical. In recent years, mRNA vaccines have been of significant interest in combating emerging infectious diseases due to their rapid development and large-scale production advantages. However, their development still suffers from many hurdles such as their safety, cellular delivery, uptake, and response to their manufacturing, logistics, and storage. More efforts are still required to optimize the molecular designs of mRNA molecules with increased protein expression and enhanced structural stability. In addition, a variety of delivery systems are also needed to achieve effective delivery of vaccines. In this review, we highlight the advances in mRNA vaccines against various infectious diseases and discuss the molecular design principles and delivery systems of associated mRNA vaccines. The current state of the clinical application of mRNA vaccine pipelines against various infectious diseases and the challenge, safety, and protective effect of associated vaccines are also discussed

A supramoleculear self-assembled flexible open framework based on the coordination of honeycomb layers possessing octahedral and tetrahedral Co-II geometries

A flexible open framework, {[Co2(L)Cl(DMF)2(H 2O)]??Sx}n (H3L = 4,4???,4??????-[1,3,5-benzenetriyltris(carbonylimino)]-trisbenzoic acid, DMF = dimethylformamide), was constructed based on a honeycomb coordination subunit with both octahedral and tetrahedral CoII sites, showing moderate MeOH sorption and antiferromagnetic properties.close0

Development of an UAS for Earthquake Emergency Response and Its Application in Two Disastrous Earthquakes

To support humanitarian action after a disaster, we require reliable data like high-resolution satellite images for analyses aimed to define the damages of facilities and/or infrastructures. However, we cannot obtain satellite images in few days after an event. Thus, in situ surveys are preferred. Advances in unmanned aircraft system (UAS) have promoted them to become precious tools for capturing and assessing the extents and volume of damages. Safety, flexibility, low cost, and ease of operation make UAS suitable for disaster assessment. In this chapter, we developed an example of UAS for swiftly acquiring disaster information. With the selected fixed-wing UAS, we successfully performed data acquisition at specified scales. For the image analysis, we applied a photogrammetric workflow to deal with the very high resolution of the images obtained without ground control points. The results obtained from two destructive earthquakes demonstrated that the presented system plays a key role on the processes of investigating and gathering information about a disaster in the earthquake epicentral areas, like road detection, structural damage survey, secondary disaster investigation, and quick disaster assessment. It can effectively provide disaster information in hardly entered areas to salvation headquarters for rapidly developing the relief measures

The Early Stage Wheel Fatigue Crack Detection Using Eddy Current Pulsed Thermography

The in-service wheel-set quality is one of critical challenges for railway safety, especially for the high-speed train. The defect in wheel tread, initiated by rolling contact fatigue (RCF) damage, is one of the most significant phenomena and has serious influence on rail industry. Eddy current pulsed thermography (ECPT) is studied to compensate the Ultrasonic Testing (UT) method for detection these early stage of fatigue cracks in wheel tread. This paper proposes several induction coils, such as linear coil, Yoke coil and Helmholtz coils, based ECPT method to meet the imaging of multiple cracks and irregular surface in wheel tread through numerical simulation and experimental results. Some features are extracted and studied also to quantify the fatigue crack in term of UT and ECPT. The proposed method greatly enhances the capability for cracks detection and quantitative evaluation compared with previous Non-Destructive Testing (NDT) method in railway

An Allosteric-Probe for Detection of Alkaline Phosphatase Activity and Its Application in Immunoassay

A fluorescence strategy for alkaline phosphatase (ALP) assay in complicated samples with high sensitivity and strong stability is developed based on an allosteric probe (AP). This probe consists of two DNA strands, a streptavidin (SA) aptamer labeled by fluorophore and its totally complementary DNA (cDNA) with a phosphate group on the 5′ end. Upon ALP introduction, the phosphate group on the cDNA is hydrolyzed, leaving the unhydrolyzed cDNA sequence for lambda exonuclease (λ exo) digestion and releasing SA aptamer for binding to SA beads, which results in fluorescence enhancement of SA beads that can be detected by flow cytometry or microscopy. We have achieved a detection limit of 0.012 U/mL with a detection range of 0.02~0.15 U/mL in buffer and human serum. These figures of merit are better than or comparable to those of other methods. Because the fluorescence signal is localized on the beads, they can be separated to remove fluorescence background from complicated biological systems. Notably, the new strategy not only applies to ALP detection with simple design, easy operation, high sensitivity, and good compatibility in complex solution, but also can be utilized in ALP-linked immunosorbent assays for the detection of a wide range of targets

Synthesis and investigation of deoxyribonucleic acid/locked nucleic acid chimeric molecular beacons

To take full advantage of locked nucleic acid (LNA) based molecular beacons (LNA-MBs) for a variety of applications including analysis of complex samples and intracellular monitoring, we have systematically synthesized a series of DNA/LNA chimeric MBs and studied the effect of DNA/LNA ratio in MBs on their thermodynamics, hybridization kinetics, protein binding affinity and enzymatic resistance. It was found that the LNA bases in a MB stem sequence had a significant effect on the stability of the hair-pin structure. The hybridization rates of LNA-MBs were significantly improved by lowering the DNA/LNA ratio in the probe, and most significantly, by having a shared-stem design for the LNA-MB to prevent sticky-end pairing. It was found that only MB sequences with DNA/LNA alternating bases or all LNA bases were able to resist nonspecific protein binding and DNase I digestion. Additional results showed that a sequence consisting of a DNA stretch less than three bases between LNA bases was able to block RNase H function. This study suggested that a shared-stem MB with a 4 base-pair stem and alternating DNA/LNA bases is desirable for intracellular applications as it ensures reasonable hybridization rates, reduces protein binding and resists nuclease degradation for both target and probes. These findings have implications on the design of LNA molecular probes for intracellular monitoring application, disease diagnosis and basic biological studies

TaqMan probe array for quantitative detection of DNA targets

To date real-time quantitative PCR and gene expression microarrays are the methods of choice for quantification of nucleic acids. Herein, we described a unique fluorescence resonance energy transfer-based microarray platform for real-time quantification of nucleic acid targets that combines advantages of both and reduces their limitations. A set of 3′ amino-modified TaqMan probes were designed and immobilized on a glass slide composing a regular microarray pattern, and used as probes in the consecutive PCR carried out on the surface. During the extension step of the PCR, 5′ nuclease activity of DNA polymerase will cleave quencher dyes of the immobilized probe in the presence of nucleic acids targets. The increase of fluorescence intensities generated by the change in physical distance between reporter fluorophore and quencher moiety of the probes were collected by a confocal scanner. Using this new approach we successfully monitored five different pathogenic genomic DNAs and analyzed the dynamic characteristics of fluorescence intensity changes on the TaqMan probe array. The results indicate that the TaqMan probe array on a planar glass slide monitors DNA targets with excellent specificity as well as high sensitivity. This set-up offers the great advantage of real-time quantitative detection of DNA targets in a parallel array format

Interictal magnetoencephalographic findings related with surgical outcomes in lesional and nonlesional neocortical epilepsy

Purpose: To investigate whether interictal magnetoencephalography (MEG) concordant with other techniques can predict surgical outcome in patients with lesional and nonlesional refractory neocortical epilepsy (NE). Methods: 23 Patients with lesional NE and 20 patients with nonlesional NE were studied. MEG was recorded for all patients with a 275 channel whole-head system. Synthetic aperture magnetometry (SAM) with excess kurtosis (g2) and conventional Equivalent Current Dipole (ECD) were used for MEG data analysis. 27 Patients underwent long-term extraoperative intracranial video electroencephalography (iVEEG) monitoring. Surgical outcomes were assessed based on more than 1-year of post-surgical follow-up using Engel classification system. Results: As we expected, both favorable outcomes (Engel class I or II) and seizure freedom outcomes (Engel class IA) were higher for the concordance condition (MEG findings are concordant with MRI or iVEEG findings) versus the discordance condition. Also the seizure free rate was significantly higher (x2 = 5.24, P \u3c 0.05) for the patients with lesional NE than for the patients with nonlesional NE. In 30% of the patients with nonlesional NE, the MEG findings proved to be valuable for intracranial electrode implantation. Conclusions: This study demonstrates that a favorable post-surgical outcome can be obtained in most patients with concordant MEG and MRI results even without extraoperative iVEEG monitoring, which indicates that the concordance among different modalities could indicate a likelihood of better postsurgical outcomes. However, extraoperative iVEEG monitoring remains prerequisite to the patients with discordant MEG and MRI findings. For nonlesional cases, our results showed that MEG could provide critical information in the placement of intracranial electrodes