Real-time single-molecule visualization using DNA curtains reveals the molecular mechanisms underlying DNA repair pathways.

The demand for direct observation of biomolecular interactions provides new insights into the molecular mechanisms underlying many biological processes. Single-molecule imaging techniques enable real-time visualization of individual biomolecules, providing direct observations of protein machines. Various single-molecule imaging techniques have been developed and have contributed to breakthroughs in biological research. One such technique is the DNA curtain, a novel, high-throughput, single-molecule platform that integrates lipid fluidity, nano-fabrication, microfluidics, and fluorescence imaging. Many DNA metabolic reactions, such as replication, transcription, and chromatin dynamics, have been studied using DNA curtains. In particular, the DNA curtain platform has been intensively applied in investigating the molecular details of DNA repair processes. This article reviews DNA curtain techniques and their applications for imaging DNA repair proteins.

Perovskite Nanocrystals Protected by Hermetically Sealing for Highly Bright and Stable Deep-Blue Light-Emitting Diodes.

Metal-halide perovskite nanocrystals (NCs) have emerged as suitable light-emitting materials for light-emitting diodes (LEDs) and other practical applications. However, LEDs with perovskite NCs undergo environment-induced and ion-migration-induced structural degradation during operation; therefore, novel NC design concepts, such as hermetic sealing of the perovskite NCs, are required. Thus far, viable synthetic conditions to form a robust and hermetic semiconducting shell on perovskite NCs have been rarely reported for LED applications because of the difficulties in the delicate engineering of encapsulation techniques. Herein, a highly bright and durable deep-blue perovskite LED (PeLED) formed by hermetically sealing perovskite NCs with epitaxial ZnS shells is reported. This shell protects the perovskite NCs from the environment, facilitates charge injection/transport, and effectively suppresses interparticle ion migration during the LED operation, resulting in exceptional brightness (2916 cd m-2 ) at 451 nm and a high external quantum efficiency of 1.32%. Furthermore, even in the unencapsulated state, the LED shows a long operational lifetime (T50 ) of 1192 s (≈20 min) in the air. These results demonstrate that the epitaxial and hermetic encapsulation of perovskite NCs is a powerful strategy for fabricating high-performance deep-blue-emitting PeLEDs.

Wavelength engineerable porous organic polymer photosensitizers with protonation triggered ROS generation.

Engineering excitation wavelength of photosensitizers (PSs) for enhanced reactive oxygen species (ROS) generation has inspired new windows for opportunities, enabling investigation of previously impracticable biomedical and photocatalytic applications. However, controlling the wavelength corresponding to operating conditions remains challenging while maintaining high ROS generation. To address this challenge, we implement a wavelength-engineerable imidazolium-based porous organic photocatalytic ROS generation system (KUP system) via a cost-effective one-pot reaction. Remarkably, the optimal wavelength for maximum performance can be tuned by modifying the linker, generating ROS despite the absence of metal ions and covalently attached heavy atoms. We demonstrate that protonated polymerization exclusively enables photosensitization and closely interacts with oxygen related to the efficiency of photosensitizing. Furthermore, superior tumor eradication and biocompatibility of the KUP system were confirmed through bioassays. Overall, the results document an unprecedented polymerization method capable of engineering wavelength, providing a potential basis for designing nanoscale photosensitizers in various ROS-utilizing applications.

Fiber-Optic Temperature Sensor Using Cholesteric Liquid Crystals on the Optical Fiber Ferrules.

Cholesteric liquid crystals (CLCs) can be applied to various physical and chemical sensors because their alignment structures are changed by external stimuli. Here, we propose a CLC device fabricated by vertically forming the helical axis of the CLC between the cross-sections of two optical fiber ferrules. An optical fiber temperature sensor was successfully implemented using the proposed optical fiber ferrule-based CLC device. A wideband wavelength-swept laser with a center wavelength of 1073 nm and scanning range of 220 nm was used as a light source to measure the variations in the reflection spectrum band according to the temperature change in the CLC cell. The wavelength variation of the reflection spectrum band according to the temperature applied to the CLC cell was reversible and changed linearly with a change in the temperature, and the long-wavelength edge variation rate according to the temperature change was -5.0 nm/°C. Additionally, as the temperature applied to the CLC cell increased, the reflection spectrum bandwidth gradually decreased; the reflection spectrum bandwidth varied at a rate of -1.89 nm/°C. The variations in the refractive indices with temperature were calculated from the band wavelengths of the reflection spectrum. The pitch at each temperature was calculated based on the refractive indices and it gradually decreased as the temperature increased.

Development of a fluorescent nanoprobe based on an amphiphilic single-benzene-based fluorophore for lipid droplet detection and its practical applications.

Lipid droplets (LDs) are crucial biological organelles connected with metabolic pathways in biological systems and diseases. To monitor the locations and accumulation of LDs in lipid-related diseases, the development of a visualization tool for LDs has gained importance. In particular, LD visualization using fluorescent probes has gained attention. Herein, a new fluorescent nanoprobe, BMeS-Ali, is developed that can sense LDs based on an amphiphilic single benzene-based fluorophore (SBBF). BMeS-Ali consists of hydrophilic (-NH2) and hydrophobic (-C12H25) moieties and exists as a micelle nanostructure in aqueous media. BMeS-Ali has a weak fluorescence, but its emission was dramatically enhanced upon exposure to the LD components such as oleic acids (OA) by reassembling its nano-formulation. BMeS-Ali showed a selective LD staining ability and great biocompatibility in cells (cancer cells and stem cells). It also showed a practical sensing ability towards biologically derived lipids and can be applied to the visualization of human fingerprints. We found that the nanoprobe BMeS-Ali has significant potential to serve as a practical dye and sensor for lipids, especially for LD imaging in the biomedical research area and broader industrial applications.

Singlet Fission Dynamics of Colloidal Nanoparticles of a Perylenediimide Derivative in Solutions.

Singlet fission (SF) is an intriguing process in which a singlet exciton produces two triplet excitons in molecular aggregates. Perylenediimide (PDI) derivatives are promising materials for SF-based photovoltaics, and the SF process in PDI aggregates is important to investigate for their applications. In this work, we studied the entire SF process occurring in the colloidal nanoparticles of a PDI derivative in solutions by using time-resolved fluorescence and transient absorption (TA) experiments. PE-PDI was found to form the colloidal nanoparticles of H- and J-aggregates in polar solvents. The TA signals of PE-PDI aggregates in solutions were selectively measured by wavelength-dependent excitation. The TA signals were analyzed by using a global fitting analysis, and all kinetic parameters involved in the entire SF process were determined. Our current investigation has confirmed that fast SF occurs on the surface of the colloidal nanoparticles of PDI aggregates via the charge transfer mediated mechanism, giving a high quantum yield of triplet excitons.

Profiles of Working Moms' Daily Time Use: Exploring Their Impact on Leisure.

This paper identified latent profiles depending on the patterns of daily time usage amongst working moms in Korea and tested their relations to family- and work-related characteristics. The consequent differences in the levels of leisure attributes were further investigated. Taking a holistic approach, latent profile analysis, one of the person-centered methods, was conducted using data drawn from the seventh year of the Korean Longitudinal Survey of Women and Families (KLoWF), with a sample of 1074 women. The results of this study indicate that three different subtypes of individuals emerged: a low-level care group (82.1%), a medium-level care group (13.8%), and a high-level care group (4.1%). The factors determining the classification for the profiles were the existence of preschool children, household income, gender role attitudes, and domestic help. Work-related factors proved to have no significant effect on time-use patterns. Profile membership was related to leisure attributes as perceived by working moms: the low-level care group reported the highest level of leisure time adequacy and leisure satisfaction, while the high-level care group presented the lowest level of sufficiency and satisfaction in their leisure time. Based on these findings, the article discusses the practical implications for enhancing the quality of life of working mothers.

Dynamics of Photoinduced Energy Transfer in Fully and Partially Conjugated Polymers Bearing π-Extended Donor and Acceptor Monomers.

The photophysical properties of donor (D)-acceptor (A) polymers were studied by designing two types of polymers, (D-σ-A) n and (D-π-A) n , with non-conjugated alkyl (sp 3) and π-conjugated (sp 2) linkers using π-extended donor and acceptor monomers that exhibit planar A-D-A structures. The non-conjugated alkyl linker provides structural flexibility to the (D-σ-A) n polymers, while the π-conjugated linker retains the rigid structure of the (D-π-A) n polymers. Photoinduced energy transfer occurs from the large donor to acceptor units in both polymers. However, the photoinduced energy transfer dynamics are found to be dependent on the conformation of the polymers, where the difference is dictated by the types of linkers between the donor and acceptor units. In solution, intramolecular energy transfer is relatively favorable for the (D-σ-A) n polymers with flexible linkers that allow the donor and acceptor units to be proximally located in the polymers. On the other hand, intermolecular (or interchain) energy transfer is dominant in the two polymer films because the π-extended donor and acceptor units in polymers are closely packed. The structural flexibility of the linkers between the donor and acceptor repeating units in the polymers affects the efficiency of energy transfer between the donor and acceptor units and the overall photophysical properties of the polymers.

Visualizing mitochondria and mouse intestine with a fluorescent complex of a naphthalene-based dipolar dye and serum albumin.

We have explored a new research field of fluorophores through the manipulation of fluorophore-binding proteins. The development of a new imaging agent for tracing a specific organelle or a particular site within a living organism has been of great interest in the field of basic science as well as translational medicine. In this work and for the first time, we will disclose a new naphthalene-based dipolar dye and its complex, with serum albumin (SA), and show their applicability for the selective imaging of mitochondria in cells and the intestine in a mouse. The SA-binding dipolar dye, IPNHC, was synthesized straightforwardly, and we identified its photophysical properties and binding mode with SA. IPNHC-SA complex showed a bright emission in the blue wavelength range with a high quantum yield and stability. In the fluorescence imaging study, bright fluorescence images of mouse intestines were observed under a UV light, as well as two-photon (TP) deep tissue imaging after intravenous injection of IPNHC and IPNHC-SA complex. The present findings hold great promise for the application of the fluorescent complex for use in the tracing and tracking of intestine-related diseases at clinical sites.

Articulated Structures of D-A Type Dipolar Dye with AIEgen: Synthesis, Photophysical Properties, and Applications.

Articulated structures of naphthalene-based donor (D)-acceptor (A) type dipolar dye and aggregation-induced emission luminogen (AIEgen) based on tetraphenylethylene (TPE) were synthesized, and their photophysical properties were analyzed for the first time. There are many fluorophore backbones, which have dipolar structure and AIEgen. However, there has been neither property analysis nor research that closely articulates DA and AIE through non-conjugation linker. We have therefore prepared two representative fluorophores; DA-AIE series (DA-AIE-M and DA-AIE-D), and characterized their UV/vis absorption and emission properties with quantum chemical calculations. In addition, we utilized the unique photophysical properties of DA-AIE-D for monitoring a trace of dimethyl sulfoxide (DMSO) in aqueous media, including real water samples.

5H-Benzo[d]Benzo[4,5]Imidazo[2,1-b][1,3]Thiazine as a Novel Electron-Acceptor Cored High Triplet Energy Bipolar Host Material for Efficient Solution-Processable Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes.

Organic entities that can transport electrons are seldom available to develop adequate bipolar host materials applicable for solution-processable thermally activated delayed fluorescence (TADF)-organic light-emitting diodes (OLEDs). Therefore, the introduction of new electron-affine entities that plausibly demonstrate high triplet energy (E T) is of urgent need. In this contribution, we introduced benzimidazo[1,2-a][3,1]benzothiazine (BBIT) as a novel electron-affine entity and developed two new bipolar host materials, CzBBIT and 2CzBBIT. Both host materials exhibit high E T of 3.0 eV, superior thermal robustness with the thermal decomposition temperature of up to 392°C, a glass transition temperature of up to 161°C, and high solubility in common organic solvents. Consequently, the solution-processable OLEDs fabricated using a recognized IAcTr-out as the green TADF emitter doped into CzBBIT as the host, realized a maximum external quantum efficiency (EQE) of 23.3%, while the 2CzBBIT:IAcTr-out blend film-based device displayed an EQE of 18.7%. These outcomes corroborated that this work could shed light on the scientific community on the design of new electron-affine entities to establish the effective use of bipolar host materials toward proficient solution-processable TADF-OLEDs.

Significantly Improved Morphology and Efficiency of Nonhalogenated Solvent-Processed Solar Cells Derived from a Conjugated Donor-Acceptor Block Copolymer.

A highly crystalline conjugated donor (D)-acceptor (A) block copolymer (PBDT2T-b-N2200) that has good solubility in nonhalogenated solvents is successfully synthesized. PBDT2T-b-N2200 shows a broad complementary absorption behavior owing to a wide-band gap donor (PBDT2T) present as a D-block and a narrow-band gap acceptor (N2200) present as an A-block. Polymer solar cells (PSCs) with conjugated block copolymer (CBCP) are fabricated using a toluene solution and PSC created with an annealed film showing the highest power conversion efficiency of 6.43%, which is 2.4 times higher than that made with an annealed blend film of PBDT2T and N2200. Compared to the blend film, the PBDT2T-b-N2200 film exhibits a highly improved surface and internal morphology, as well as a faster photoluminescence decay lifetime, indicating a more efficient photoinduced electron transfer. In addition, the PBDT2T-b-N2200 film shows high crystallinity through an effective self-assembly of each block during thermal annealing and a predominant face-on chain orientation favorable to a vertical-type PSC. Moreover, the CBCP-based PSCs exhibit an excellent shelf-life time of over 1020 h owing to their morphological stability. From these results, a D-A block copolymer system is one of the efficient strategies to improve miscibility and morphological stability in all polymer blend systems.

A bright blue fluorescent dextran for two-photon in vivo imaging of blood vessels.

Fluorescence-based in vivo imaging is one of the most important tools for monitoring of biological processes in cells and tissues of live animal models. Fluorescence imaging agents have also been used to monitor the microcirculation. Tracking microcirculation of the blood is vital to gain further insight into various vascular disease-related anomalies within the human body. As monitoring of vascular circulation is performed with visualization of both immune cells and pathogens, which are mainly labelled with red and green, the favorable color option for blood vessels could be blue. However, currently available blueish color-labeled agents for vascular monitoring is generally confronted with quick bleaching, because of its short excitation and emission wavelengths. Hereby, what we propose in this report is a newly generated bright blue fluorescent dextran, named HCD-70K that monitors the blood vessels using blue and inter-compatible typical fluorescent materials. DBCO-functionalized dextran-70K was fabricated with hydroxy-coumarin dye via metal-free bioorthogonal click chemistry, and generated HCD-70K, which can flow within the blood vessel and decipher the whole structure of the blood vessel successfully. The synthesis, spectroscopic analysis, and quantum chemical calculations were conducted. Using two-photon microscopy, efficient deep in vivo blood vessel imaging of a mouse model revealed exceptional bio-imaging capabilities of the HCD-70K and consequently it provided a promising opportunity for efficient vascular visualization in various research areas.

High Stability of a Donor-Acceptor Type Oxazepine-Containing Fluorophore and Its Applications in Cellular Imaging and Two-Photon Deep Tissue Imaging.

A new donor (D)-acceptor (A) type naphthalene-based oxazepine-containing fluorophore, OXN-1, is reported, which shows unusually high stability in various environments. Its photophysical properties and structural stabilities under harsh conditions are thoroughly examined. The high stability of OXN-1 is explained by quantum chemical calculations. Its exceptional bioimaging capabilities for cells with low cytotoxicity are verified. In addition, its deep tissue imaging ability with two-photon microscopy (TPM) is evaluated.

Hydrazine Exposé: The Next-Generation Fluorescent Probe.

Hydrazine (N2H4) is one of the most important pnictogen hydride chemicals, and is utilized within a wide spectrum of industries. As a result of its extensive use, hydrazine's monitoring methods have constantly come under fire due to its potential health risk and the subsequent environmental pollution. Fluorometric molecular sensing systems generally report with a major emphasis on the merit of fluorescence analysis. What we are proposing within this report is a next-generation fluorescent probe that allows hydrazine to become fully traceable, within multifarious environments that show fast and intuitional fluorescence transformation. A new sensing moiety, ortho-methoxy-methyl-ether ( o-OMOM) incorporated electron donor (D)-acceptor (A) type naphthaldehyde provides high selectivity and sensitivity amidst its superiority within practical applications for sensing hydrazine. The new probe overcomes most of the drawbacks of currently used fluorescent probes, and due to its successful demonstrations, such as real-time spray-based sensing, soil analysis, and two-photon tissue imaging, its potential for practical application is beyond reproach.

Discriminative Molecular Detection Based on Competitive Absorption by a Luminescent Metal-Organic Framework.

Distinguishing specific molecules from similar chemical species with minor structural differences is challenging, and differentiation has typically been based on analyte-dependent host-guest interactions upon irradiation with a single wavelength. In this study, we prepared a Cd-based metal-organic framework exhibiting nearly constant emission intensity over a wide range of excitations. Because of its unique emission characteristics, this material facilitated the differentiation of specific molecules amidst structurally similar chemical species via competitive absorption. Such discriminative identification was uniquely achieved based on the use of different excitation wavelengths and is demonstrated to be applicable to the recognition of a target analyte in sensory applications.

High-Performance Polymer Solar Cell with Single Active Material of Fully Conjugated Block Copolymer Composed of Wide-Band gap Donor and Narrow-Band gap Acceptor Blocks.

We synthesized a novel fully conjugated block copolymer, P3, in which a wide-band gap donor block (P1) was connected to a narrow-band gap acceptor block (P2). As P3 contains P1 block with a wide bandgap and P2 block with a narrow bandgap, it exhibits a very wide complementary absorption. Transient photoluminescence measurement using P3 dilute solution demonstrated intramolecular charge transfer between the P1 block and the P2 block, which was not observed in a P1/P2 blend solution. A P3 thin film showed complete PL quenching because the photoinduced inter-/intramolecular charge transfer states were effectively formed. This phenomenon can play an important role in the photovoltaic properties of P3-based polymer solar cells. A single active material polymer solar cell (SAMPSC) fabricated from P3 alone exhibited a high power conversion efficiency (PCE) of 3.87% with a high open-circuit voltage of 0.93 V and a short-circuit current of 8.26 mA/cm2, demonstrating a much better performance than a binary P1-/P2-based polymer solar cell (PCE = 1.14%). This result facilitates the possible improvement of the photovoltaic performance of SAMPSCs by inducing favorable nanophase segregation between p- and n blocks. In addition, owing to the high morphological stability of the block copolymer, excellent shelf-life was observed in a P3-based SAMPSC compared with a P1/P2-based PSC.

Electronic relaxation dynamics of PCDA-PDA studied by transient absorption spectroscopy.

Photo-curable polymers originating from 10,12-pentacosadiynoic acid (PCDA-PDA) are commonly used polydiacetylenes (PDAs). PCDA-PDA exhibits thermochromic properties undergoing a unique colorimetric transition from blue to red as the temperature is increased from low to high. In this work, we have carefully studied the temperature-dependent optical properties of PCDA-PDA by using UV-visible absorption, FTIR, Raman, and transient absorption (TA) spectroscopy in combination with quantum chemical calculations. Temperature-dependent UV-visible absorption spectra indicate that PCDA-PDA exhibits reversible thermochromic properties up to 60 °C and its thermochromic properties become irreversible above 60 °C. Such distinct thermochromic properties are also manifested in TA signals so that the electronically excited PCDA-PDA relaxes to the ground state via an intermediate state at 20 °C (blue form) but it relaxes directly back to the ground state at 80 °C (red form). The electronic relaxation dynamics of PCDA-PDA are comprehensively analyzed based on different kinetic models by using the global fitting analysis method. The intermediate state in the blue form of PCDA-PDA is clearly found to be responsible for fluorescence quenching. FTIR and Raman spectroscopy and quantum chemical calculations confirm that the H-bonds between the carboxylic acid groups in PCDA-PDA are broken at high temperatures leading to an irreversible structural change of PCDA-PDA.

Association between Diurnal Variation of Ozone Concentration and Stroke Occurrence: 24-Hour Time Series Study.

BACKGROUND AND PURPOSE: Increasing ozone concentrations have been known to damage human health and ecosystems. Although ozone tends to display diurnal variation, most studies have reported only on the association between daily ozone concentrations and ischemic stroke occurrence on the same day, or with a 1-day lag. We investigated the effect of the diurnal variation of ozone on ischemic stroke occurrence during the same day. METHODS: We included a consecutive series of 1,734 patients from January 1, 2008, to December 31, 2014, at a single tertiary hospital in Seoul, South Korea. We evaluated differences between temperature and pollutants at the time of stroke onset for each time interval and averaged those parameters across the 7-year study period. RESULTS: During the interval from 13:00 to 16:59, we found a positive association between ischemic stroke occurrence and ozone concentration relative to other time periods. Upper median ozone levels from 13:00 to 16:59 were positively correlated with ischemic stroke (odds ratio, 1.550; 95% confidence intervals, 1.220 to 1.970; P = <0.001) when compared with lower median levels. CONCLUSIONS: The results show diurnal patterns of ischemic stroke occurrence based on upper and lower median ozone levels for a 24-hour period, which extends understanding of the association between stroke occurrence and environmental influences.

Activation of the phosphatidylinositol 3-kinase pathway plays important roles in reduction of cerebral infarction by cilnidipine.

Cerebral infarction causes permanent neuronal loss inducing severe morbidity and mortality. Because hypertension is the main risk factor for cerebral infarction and most patients with hypertension take antihypertensive drugs daily, the neuroprotective effects and mechanisms of anti-hypertensive drugs need to be investigated. Cilnidipine, a long-acting, new generation 1,4-dihydropyridine inhibitor of both L- and N-type calcium channels, was reported to reduce oxidative stress. In this study, we investigated whether cilnidipine has therapeutic effects in an animal model of cerebral infarction. After determination of the most effective dose of cilnidipine, a total of 128 rats were subjected to middle cerebral artery occlusion. Neurobehavioral function test and brain MRI were performed, and rats with similar sized infarcts were randomized to either the cilnidipine group or the control group. Cilnidipine treatment was performed with reperfusion after 2-h occlusion. Western blots and immunohistochemistry were also performed after 24-h occlusion. Initial infarct volume on diffusion-weighted MRI was not different between the cilnidipine group and the control group; however, fluid-attenuated inversion recovery MRI at 24 h showed significantly reduced infarct volume in the cilnidipine group compared with the control group. Cilnidipine treatment significantly decreased the number of triphosphate nick end labeling-positive cells compared to the control group. Western blot and immunohistochemistry showed increased expression of phosphorylated Akt (Ser473), phosphorylated glycogen synthase kinase-3ß, and Bcl-2 and decreased expression of Bax and cleaved caspase-3. These results suggest that cilnidipine, which is used for the treatment of hypertension, has neuroprotective effects in the ischemic brain through activation of the PI3K pathway. We investigated whether cilnidipine has neuroprotective effects on ischemic stroke in an animal model. We have demonstrated that the neuroprotective effect of cilnidipine is associated with the activation of the PI3K pathway. Considering the daily use of antihypertensive drugs for patients with hypertension, cilnidipine could be beneficial for patients with ischemic stroke.