Decoding Biomechanical Cues Based on DNA Sensors.

Biological systems perceive and respond to mechanical forces, generating mechanical cues to regulate life processes. Analyzing biomechanical forces has profound significance for understanding biological functions. Therefore, a series of molecular mechanical techniques have been developed, mainly including single-molecule force spectroscopy, traction force microscopy, and molecular tension sensor systems, which provide indispensable tools for advancing the field of mechanobiology. DNA molecules with a programmable structure and well-defined mechanical characteristics have attached much attention to molecular tension sensors as sensing elements, and are designed for the study of biomechanical forces to present biomechanical information with high sensitivity and resolution. In this work, a comprehensive overview of molecular mechanical technology is presented, with a particular focus on molecular tension sensor systems, specifically those based on DNA. Finally, the future development and challenges of DNA-based molecular tension sensor systems are looked upon.

Highly Reversible Molecular Photoswitches with Transition Metal Dichalcogenides Electrodes.

The molecule-electrode coupling plays an essential role in photoresponsive devices with photochromic molecules, and the strong coupling between the molecule and the conventional electrodes leads to/ the quenching effect and limits the reversibility of molecular photoswitches. In this work, we developed a strategy of using transition metal dichalcogenides (TMDCs) electrodes to fabricate the thiol azobenzene (TAB) self-assembled monolayers (SAMs) junctions with the eutectic gallium-indium (EGaIn) technique. The current-voltage characteristics of the EGaIn/GaOx //TAB/TMDCs photoswitches showed an almost 100% reversible photoswitching behavior, which increased by ∼28% compared to EGaIn/GaOx //TAB/AuTS photoswitches. Density functional theory (DFT) calculations showed the coupling strength of the TAB-TMDCs electrode decreased by 42% compared to that of the TAB-AuTS electrode, giving rise to improved reversibility. our work demonstrated the feasibility of 2D TMDCs for fabricating SAMs-based photoswitches with unprecedentedly high reversibility.

Supramolecular Radical Electronics.

Supramolecular radical chemistry is an emerging area bridging supramolecular chemistry and radical chemistry, and the integration of radicals into the supramolecular architecture offers a new dimension for tuning their structures and functions. Although various efforts have been devoted to the fabrication of supramolecular junctions, the charge transport characterization through the supramolecular radicals remained unexplored due to the challenges in creating supramolecular radicals at the single-molecule level. Here, we demonstrate the fabrication and charge transport investigation of a supramolecular radical junction using the electrochemical scanning tunneling microscope-based break junction (EC-STM-BJ) technique. We found that the conductance of a supramolecular radical junction was more than 1 order of magnitude higher than that of a supramolecular junction without a radical and even higher than that of a fully conjugated oligophenylenediamine molecule with a similar length. The combined experimental and theoretical investigations revealed that the radical increased the binding energy and decreased the energy gap in the supramolecular radical junction, which leads to the near-resonant transport through the supramolecular radical. Our work demonstrated that the supramolecular radical can provide not only strong binding but also efficient electrical coupling between building blocks, which provides new insights into supramolecular radical chemistry and new materials with supramolecular radicals.

Ultrasensitive Detection of Organophosphorus Pesticides Using Single-Molecule Conductance Measurement.

Detection of organophosphorus pesticides (OPs) with high sensitivity in environmental samples is of vital importance for environmental safety and human health. However, it remains a challenge to achieve fM (10-15 mol/L) sensitivity for detecting OPs. Herein, we developed an acetylcholinesterase sensor based on 3,3',5,5'-tetramethylbenzidine (TMB) combining an enzyme-mediated strategy and scanning tunneling microscopy break junction (STM-BJ). Benefiting from the enzyme inhibition kinetics of OPs and the customized spectral clustering analysis method, our new strategy achieved the detection of methamidophos (MTMP) with a limit of 10 aM (10-17 mol/L) and 3 times higher selectivity in mixed OPs. As applied to natural lake waters, it also exhibited high reproducibility, high stability, and good recovery. This work paves a new avenue toward the application of single-molecule conductance characterizations for biochemical analysis and environmental monitoring.

Switching Quantum Interference in Single-Molecule Junctions by Mechanical Tuning.

The charge transport through single-molecule electronic devices can be controlled mechanically by changing the molecular geometrical configuration in situ, but the tunable conductance range is typically less than two orders of magnitude. Herein, we proposed a new mechanical tuning strategy to control the charge transport through the single-molecule junctions via switching quantum interference patterns. By designing molecules with multiple anchoring groups, we switched the electron transport between the constructive quantum interference (CQI) pathway and the destructive quantum interference (DQI) pathway, and more than four orders of magnitude conductance variation can be achieved by shifting the electrodes in a range of about 0.6 nm, which is the highest conductance range ever achieved using mechanical tuning.

High-risk features of basilar artery atherosclerotic plaque.

Introduction: High-resolution magnetic resonance imaging (HR-MRI) is used to characterize atherosclerotic plaque. The present study aimed to determine the high-risk features of the basilar artery (BA) atherosclerotic plaque. Methods: Patients with advanced BA stenosis were screened. The features including the ruptured fibrous cap (RFC), lipid core, intraplaque hemorrhage (IPH), plaque enhancement, and calcification were assessed by using high-resolution MRI. The relationship between the features and acute infarction was analyzed. Results: From 1 June 2014 to 31 December 2018, a total of 143 patients with 76 new strokes were included. RFC was identified in 25% of symptomatic and 10.4% of asymptomatic patients. IPH was identified in 48.7% of symptomatic and 25.4% of asymptomatic patients. RFC (3.157, 95% CI 1.062 to 9.382, p = 0.039) and IPH (2.78, 95% CI 1.127 to 6.505, p = 0.026) were independent risk factors for acute infarction. Conclusion: Our study showed that RFC and IPH of BA plaque were independent risk factors for acute infarction.

The prevalence and clinical significance of intracranial vertebral artery terminated in posterior inferior cerebellar artery: A multicenter hospital-based study in China.

Objective: Intracranial vertebral artery terminated in the posterior inferior cerebellar artery (PICA-VA) is the most popular variant of the posterior inferior cerebellar artery, while its prevalence and clinical significance remained unclear. In the present study, we aimed to investigate the prevalence and clinical significance of PICA-VA. Methods: This was a multicenter hospital-based cross-sectional study. Patients were enrolled for cerebral MRI and MRA within 1 week of stroke onset. Clinical characteristics were recorded. PICA-VA is termed as a vertebral artery that does not communicate with the basilar artery but terminates in an ipsilateral PICA. We observed the prevalence of PICA-VA and identified a relationship between PICA-VA and vertebrobasilar stroke. Results: From 1 August 2015 to 31 May 2017, a total of 2,528 patients were enrolled in the present study. Among them, 95 patients (3.76%, 95/2,528) had the variation of PICA-VA, 51 of which (53.7%) were located on the right side. The prevalence of vertebrobasilar stroke was considerably higher in patients with PICA-VA than those without (40.2%, 37/92 vs. 17.1%, 417/2,436, p < 0.01). PICA-VA was an independent risk for vertebrobasilar stroke after being adjusted for a history of intracranial hemorrhage, diabetes, body mass index, and triglyceride. Conclusion: The present study showed that 3.76% of patients with acute stroke had PICA-VA, which independently increased the risk of acute vertebrobasilar stroke.

Increased Proximal Wall Shear Stress of Basilar Artery Plaques Associated with Ruptured Fibrous Cap.

Plaque rupture of the basilar artery is one of the leading causes of posterior circulation stroke. The present study aimed to investigate the role of fluid dynamics in the ruptured fibrous cap of basilar artery plaques. Patients with basilar artery plaques (50−99% stenosis) were screened. Integrity of the fibrous cap was assessed by high-resolution MRI. Computational fluid dynamics models were built based on MR angiography to obtain the wall shear stress and velocity. A total of 176 patients were included. High-resolution MRI identified 35 ruptured fibrous caps of basilar artery plaques. Ruptured fibrous cap was significantly associated with acute infarction (27/35 vs. 96/141, p < 0.05) in the territory of the basilar artery. Proximal wall shear stress of stenosis was positively related with the ruptured fibrous cap (OR 1.564; 95% CI, 1.101−2.222; p = 0.013). The threshold of wall shear stress for the ruptured fibrous cap of basilar artery plaques was 4.84 Pa (Area under ROC 0.732, p = 0.008, 95%CI 0.565−0.899). The present study demonstrated that increased proximal wall shear stress of stenosis was associated with ruptured fibrous caps of basilar artery plaques.

Broad Applicability of Electrochemical Impedance Spectroscopy to the Measurement of Oxygen Nonstoichiometry in Mixed Ion and Electron Conductors.

Oxygen nonstoichiometry is a fundamental feature of mixed ion and electron conductors (MIECs). In this work, a general electrochemical method for determining nonstoichiometry in thin film MIECs, via measurement of the chemical capacitance, is demonstrated using ceria and ceria-zirconia (Ce0.8Zr0.2O2-δ) as representative materials. A.C. impedance data are collected from both materials at high temperature (750-900 °C) under reducing conditions with oxygen partial pressure (pO2) in the range 10-13 to 10-20 atm. Additional measurements of ceria-zirconia films are made under relatively oxidizing conditions with pO2 in the range 0.2 to 10-4 atm and temperatures of 800-900 °C. Under reducing conditions, the impedance spectra are described by a simple circuit in which a resistor is in series with a resistor and capacitor in parallel, and thickness-dependent measurements are used to resolve the capacitance into interfacial and chemical terms. Under more oxidizing conditions, the impedance spectra (of Ce0.8Zr0.2O2-δ) reveal an additional diffusional feature, which enables determination of the ionic resistance of the film in addition to the capacitance, and hence the transport properties. A generalized mathematical formalism is presented for recovering the nonstoichiometry from the chemical capacitance, without recourse to defect chemical models. The ceria nonstoichiometry values are in good agreement with literature values determined by thermogravimetric measurements but display considerably less scatter and are collected on considerably shorter time scales. The thermodynamic analysis of Ce0.8Zr0.2O2-δ corroborates earlier findings that introduction of Zr into ceria enhances its reducibility.

Incidence, risk, and treatment of binary restenosis after vertebral artery stenting.

BACKGROUND: In-stent restenosis (ISR) is the major concern of vertebral artery stenting (VAS). We aimed to investigate the feasibility and outcome of redo angioplasty for ISR of vertebral artery. METHOD: The patients were retrospectively reviewed for the significant ISR (>50%). Redo angioplasty including balloon angioplasty and stenting was performed for symptomatic ISR (>50%) or asymptomatic ISR (≥70%). The clinical follow-up was performed on the 1, 3, 6, and 12 months and then yearly in the clinic or by telephone. The angiographic follow-up was performed at 6-12 months after redo angioplasty. RESULT: A total of 72 patients had significant ISR and 48 redo angioplasty (92.3%, 48/52) were successfully achieved with 13 located in the V4 and 35 in the ostium of vertebral artery. Twenty-six lesions were implanted by the second stent and the others received balloon angioplasty. No stroke or transient ischemic attack (TIA) occurred in the perioperative time. One patient died 2 months after redo angioplasty due to nonstroke cause. Redo angioplasty nonsignificantly decreased the stroke or TIA compared with medical treatment. Sixteen patients developed the binary restenosis, which was lower in the patients receiving stent implantation than balloon angioplasty. CONCLUSION: Redo angioplasty was a feasible method for the ISR of VAS and redo stenting might be the first choice.

Cooperative Stabilization of the [Pyridinium-CO2-Co] Adduct on a Metal-Organic Layer Enhances Electrocatalytic CO2 Reduction.

Pyridinium has been shown to be a cocatalyst for the electrochemical reduction of CO2 on metal and semiconductor electrodes, but its exact role has been difficult to elucidate. In this work, we create cooperative cobalt-protoporphyrin (CoPP) and pyridine/pyridinium (py/pyH+) catalytic sites on metal-organic layers (MOLs) for an electrocatalytic CO2 reduction reaction (CO2RR). Constructed from [Hf6(µ3-O)4(µ3-OH)4(HCO2)6] secondary building units (SBUs) and terpyridine-based tricarboxylate ligands, the MOL was postsynthetically functionalized with CoPP via carboxylate exchange with formate capping groups. The CoPP group and the pyridinium (pyH+) moiety on the MOL coactivate CO2 by forming the [pyH+--O2C-CoPP] adduct, which enhances the CO2RR and suppresses hydrogen evolution to afford a high CO/H2 selectivity of 11.8. Cooperative stabilization of the [pyH+--O2C-CoPP] intermediate led to a catalytic current density of 1314 mA/mgCo for CO production at -0.86 VRHE, which corresponds to a turnover frequency of 0.4 s-1.

Topographic location of unisolated pontine infarction.

BACKGROUND: The topographic location of acute pontine infarction is associated with clinical syndromes and prognosis. Previous studies focused on isolated pontine infarction, but the topographic location of unisolated pontine infarction has remained unclear. METHODS: This was a prospective, multicenter, longitudinal registry study. Patients with acute pontine infarction confirmed by magnetic resonance imaging (MRI) were enrolled. Based on the territory of the pontine artery, the topographic location was divided into anteromedial, anterolateral, tegmental, bilateral and unilateral multiple infarctions. RESULTS: From May 1, 2003, to Oct 31, 2017, 1003 patients were enrolled, and 330 had unisolated pontine infarction. For isolated pontine infarction, 44.9, 19.8, 16.0, 13.1 and 6.2% of patients had anteromedial, anterolateral, tegmental, bilateral and unilateral multiple pontine infarctions, respectively. For unisolated pontine infarction, 30.3, 19.7, 24.5, 15.2 and 10.3% of patients had anteromedial, anterolateral, tegmental, bilateral and unilateral multiple pontine infarctions, respectively. CONCLUSION: In this large series study, our data revealed fewer anteromedial infarctions and more tegmental and unilateral multiple infarctions in patients with unisolated pontine infarction than in patients with isolated pontine infarction.

Two-Dimensional Metal-Organic Layers on Carbon Nanotubes to Overcome Conductivity Constraint in Electrocatalysis.

Application of metal-organic frameworks (MOFs) in electrocatalysis is of great interest, but is limited by low electrical conductivities of most MOFs. To overcome this limitation, we constructed a two-dimensional version of MOF-metal-organic layer (MOL) on conductive multiwalled carbon nanotubes (CNTs) via facile solvothermal synthesis. The redox-active MOLs supported on the CNT efficiently catalyze the electrochemical oxidation of alcohols to aldehydes and ketones. Interestingly, this CNT/MOL assembly also endowed the selectivity for primary versus secondary alcohols via well-designed interfacial interactions. This work opens doors toward a variety of designer electrocatalysts built from functional MOFs.

Ag2Se to KAg3Se2: Suppressing Order-Disorder Transitions via Reduced Dimensionality.

We report an order-disorder phase transition in the 2D semiconductor KAg3Se2, which is a dimensionally reduced derivative of 3D Ag2Se. At ∼695 K, the room temperature ß-phase (CsAg3S2 structure type, monoclinic space group C2/ m) transforms to the high temperature α-phase (new structure type, hexagonal space group R3̅ m, a = 4.5638(5) Å, c = 25.4109(6) Å), as revealed by in situ temperature-dependent X-ray diffraction. Significant Ag+ ion disorder accompanies the phase transition, which resembles the low temperature (∼400 K) superionic transition in the 3D parent compound. Ultralow thermal conductivity of ∼0.4 W m-1 K-1 was measured in the "ordered" ß-phase, suggesting anharmonic Ag motion efficiently impedes phonon transport even without extensive disordering. The optical and electronic properties of ß-KAg3Se2 are modified as expected in the context of the dimensional reduction framework. UV-vis spectroscopy shows an optical band gap of ∼1 eV that is indirect in nature as confirmed by electronic structure calculations. Electronic transport measurements on ß-KAg3Se2 yielded n-type behavior with a high electron mobility of ∼400 cm2 V-1 s-1 at 300 K due to a highly disperse conduction band. Our results thus imply that dimensional reduction may be used as a design strategy to frustrate order-disorder phenomena while retaining desirable electronic and thermal properties.

Out-of-Plane Ionic Conductivity Measurement Configuration for High-Throughput Experiments.

An approach for measuring conductivity of thin-film electrolytes in an out-of-plane configuration, amenable to high-throughput experimentation, is presented. A comprehensive analysis of the geometric requirements for success is performed. Using samaria-doped ceria (Ce0.8Sm0.2O1.9, SDC) excellent agreement between bulk samples and thin films with continuous and patterned electrodes, 100-500 µm in diameter, is demonstrated. Films were deposited on conductive Nb-doped SrTiO3, and conductivity was measured by AC impedance spectroscopy over the temperature range from ∼200 to ∼500 °C. The patterned electrode geometry, which encompassed an array of microdot metal electrodes for making top contact, enabled measurements at hundreds of positions on the film, implying the potential for measuring hundreds of composition in a single library.

Networking Pyrolyzed Zeolitic Imidazolate Frameworks by Carbon Nanotubes Improves Conductivity and Enhances Oxygen-Reduction Performance in Polymer-Electrolyte-Membrane Fuel Cells.

A high-performance nonprecious-metal oxygen-reduction electrocatalyst is prepared via in situ growth of bimetallic zeolitic imidazolate frameworks on multiwalled carbon nanotubes (CNTs) followed by adsorption of furfuryl alcohol and pyrolysis. The networking boosts the conductivity and performance in a polymer electrolyte membrane fuel cell, yielding a maximal power density of 820 mW cm-2 .

Self-Supporting Metal-Organic Layers as Single-Site Solid Catalysts.

Metal-organic layers (MOLs) represent an emerging class of tunable and functionalizable two-dimensional materials. In this work, the scalable solvothermal synthesis of self-supporting MOLs composed of [Hf6O4(OH)4(HCO2)6] secondary building units (SBUs) and benzene-1,3,5-tribenzoate (BTB) bridging ligands is reported. The MOL structures were directly imaged by TEM and AFM, and doped with 4'-(4-benzoate)-(2,2',2''-terpyridine)-5,5''-dicarboxylate (TPY) before being coordinated with iron centers to afford highly active and reusable single-site solid catalysts for the hydrosilylation of terminal olefins. MOL-based heterogeneous catalysts are free from the diffusional constraints placed on all known porous solid catalysts, including metal-organic frameworks. This work uncovers an entirely new strategy for designing single-site solid catalysts and opens the door to a new class of two-dimensional coordination materials with molecular functionalities.

Förster Energy Transport in Metal-Organic Frameworks Is Beyond Step-by-Step Hopping.

Metal-organic frameworks (MOFs) with light-harvesting building blocks designed to mimic photosynthetic chromophore arrays in green plants provide an excellent platform to study exciton transport in networks with well-defined structures. A step-by-step exciton random hopping model made of the elementary steps of energy transfer between only the nearest neighbors is usually used to describe the transport dynamics. Although such a nearest neighbor approximation is valid in describing the energy transfer of triplet states via the Dexter mechanism, we found it inadequate in evaluating singlet exciton migration that occurs through the Förster mechanism, which involves one-step jumping over longer distance. We measured migration rates of singlet excitons on two MOFs constructed from truxene-derived ligands and zinc nodes, by monitoring energy transfer from the MOF skeleton to a coumarin probe in the MOF cavity. The diffusivities of the excitons on the frameworks were determined to be 1.8 × 10(-2) cm(2)/s and 2.3 × 10(-2) cm(2)/s, corresponding to migration distances of 43 and 48 nm within their lifetimes, respectively. "Through space" energy-jumping beyond nearest neighbor accounts for up to 67% of the energy transfer rates. This finding presents a new perspective in the design and understanding of highly efficient energy transport networks for singlet excited states.

Pre-concentration and energy transfer enable the efficient luminescence sensing of transition metal ions by metal-organic frameworks.

The 2,2'-bipyridyl moieties lining the channels of two designer metal-organic frameworks (MOFs), UiO-bpydc and Eu-bpydc (bpydc is 2,2'-bipyridine 5,5'-dicarboxylic acid), recognize and pre-concentrate metal ion analytes and, in the case of Eu-bpydc, transfer energy to the Eu(3+) centers, to provide highly sensitive luminescence sensors for transition metal ions.

Erratum: 1-[4-(Di-methyl-amino)-benzyl-idene]-4-o-tolyl-thio-semicarbazide. Corrigendum.

The correspondence address in the paper by Huang et al. [Acta Cryst. (2013), E69, o906-o907] is corrected.[This corrects the article DOI: 10.1107/S1600536813012890.].