Comparing the Effects of Static Stretching Alone and in Combination with Post-Activation Performance Enhancement on Squat Jump Performance at Different Knee Starting Angles.

We aimed to investigate the impact of isolated static stretching (4 sets of 30 seconds) and its combined form with 10 repetitive drop jumps on lower limb performance during squat jumps at different knee joint starting angles (60°, 90°, and 120°). Thirteen participants completed three randomly ordered experimental visits, each including a standardized warm-up and squat jumps at three angles, apart from the intervention or control. Information was gathered through a three-dimensional movement tracking system, electromyography system, and force platform. The electromyography data underwent wavelet analysis to compute the energy values across the four wavelet frequency bands. The average power (Pavg), peak power (Ppeak), peak ground reaction force (GRFpeak), peak center of mass velocity (Vpeak), and force-velocity relationship at peak power (SFv) were extracted from the force and velocity-time data. The results revealed no significant influence of isolated static stretching, or its combined form with drop jumps, on the energy values across the frequency bands of the gastrocnemius, biceps femoris and rectus femoris, or the Pavg or Ppeak (P > 0.05). However, at 120°, static stretching reduced the GRFpeak (P = 0.001, d = 0.86) and SFv (P < 0.001, d = 1.12), and increased the Vpeak (P = 0.001, d = 0.5). The GRFpeak, Pavg, Ppeak, and SFv increased with an increase in the joint angle (P < 0.05), whereas the Vpeak decreased (P < 0.05). These findings suggest that static stretching does not diminish power output during squat jumps at the three angles; however, it alters GRFpeak, Vpeak, and the relative contributions of force and velocity to peak power at 120°, which can be eliminated by post-activation performance enhancement. Moreover, compared to 60° and 90°, 120° was more favorable for power and peak force output.

In Situ Observation of Glucose Metabolism Dynamics of Endothelial Cells in Hyperglycemia with a Stretchable Biosensor: Research Tool for Bridging Diabetes and Atherosclerosis.

Diabetes is a metabolic syndrome associated with hyperglycemia, hypertension, atherosclerosis, and endothelial dysfunction. Applying the mechanical stretch on cells to simulate blood circulation while monitoring the cell glucose metabolism in a high-glucose environment is important for better comprehension of the underlying mechanisms of atherosclerosis caused by diabetes. Herein, we developed a facile strategy integrating zeolitic imidazolate framework-8-encapsulated glucose oxidase (GOx@ZIF-8) and an gold (Au) stretchable electrode (Au SE) to construct a flexible and stretchable glucose sensor (GOx@ZIF-8/Au SE) for investigating the glucose metabolism mechanism of stretched endothelial cells in hyperglycemia. The encapsulation of GOx with ZIF-8 prevents the aggregation and detachment of GOx from the sensing interface and endows the biosensor with high stability. Additionally, the Au SE with inherent stretchability can act as an integrated platform for mechanical stimulation as well as for transient signal sensing during the mechanotransduction process. Moreover, this flexible and stretchable glucose sensor is successfully used for monitoring the glucose metabolism of mechanically stimulated cells in hyperglycemia, and it was found for the first time that the glucose utilization ability of cells under static conditions is higher than that in the stretched state. This facile and straightforward method paves a promising route for designing a stable enzyme-based stretchable biosensor for detecting the underlying mechanisms of atherosclerosis caused by diabetes.

Enhanced Visible Light Photocatalytic Decolorization of Methylene Blue by Hierarchical Ternary Nanocomposites Cu-TiO2-Mesoporous-Silica Microsphere.

In this study, hierarchical ternary nanocomposites, i.e., Cu-TiO2-mesoporous silica microspheres (Cu-TiO2-MSM), were synthesized as ternary photocatalyst system to improve the visible light photocatalytic degradation of the environmental pollutant model dye methylene blue (MB). The innovation of this method is in situ depositing TiO2 and Cu2O nanoparticles sequentially onto the surface of mesoporous silica microspheres to form highly active heterostructure. The improved activity for the degradation of MB is attributed to: (1) the high adsorption capacity of the porous and interconnected-channel-structure MSM to MB; (2) the valence band electrons of TiO2 released from the conduction band generating abundant highly active free radicals, which directly reacted with adsorbed MB. The photocatalytic degradation efficiency to MB was found to be 98% in 5 min, and almost 100% in 20 min. This study paves a way for the development of a ternary-doped catalyst for visible light photocatalytic degradation and may exhibit widely application in industry.

One-Step Pyrolysis Transformation of Mulberry Leaves Followed by Electrochemical Treatment: Preparing of M (M = Pt, Au) Nanoparticles Incorporated Nitrogen-Doped Carbon Nanoporous Structures as Efficient Electrocatalyst for Hydrogen Evolution Reaction.

To facilely develop low-cost and efficient hydrogen evolution electrocatalysts, catalyst with low content of platinum on nitrogen-doped carbon nanoporous structures were prepared for hydrogen evolution reaction (HER). This study firstly demonstrated the one-step pyrolysis transformation of conveniently accessible mulberry leaves to obtain nitrogen-doped nanoporous carbons (N-NPCs) for hydrogen evolution reaction. After electrochemical treatment, the obtained N-NPCs-ET with Pt as counter electrode exhibited an unexpected high hydrogen evolution activity, which had low onset overpotential of 100 mV and a Tafel slope of 60 mV dec-1. N-NPCs-ET maintained catalytic activity for at least 10 h in 0.5 M H2SO4 solution. The enhanced HER performance was relevant to the incorporation of Pt nanoparticles, which were dissolved from anodic Pt counter electrode in acid media and precipitated into cathodic N-NPCs surface again. Moreover, for the first time, we found that with a gold electrode as the counter electrode, Au nanoparticles could be incorporated into N-NPCs by electrochemical treatments and the formed Au nanoparticles decorated N-NPCs possessed efficient catalytic activity toward HER.

Bioinspired Cu-based metal-organic framework mimicking SOD for superoxide anion sensing and scavenging.

Superoxide anion (O2•-) is typically produced in living cells and organisms, while excess O2•- may cause unexpected damage, so monitoring and scavenging the O2•- is of considerable significance to exploring physiological and pathological process. In this study, a Cu-based metal-organic framework (Cu-MOF) which comprise sequential Cu metal ion and conductive organic 2,5-dicarboxylic acid-3,4-ethylene dioxythiophene is synthesized to mimic superoxide dismutase (SOD), in which Cu is the essence of active site. On one hand, the Cu-MOF possesses excellent electrocatalytic activity to detect O2•- at -0.05 V, biased at which potential the electrode showed good linearity toward O2•- with detection limit of 0.283 µM and interference immunity for AA, DA, UA, 5-HT and H2O2. The Cu-MOF modified microelectrode was applied for measuring the O2•- released from living cells real time and monitoring O2•- generation in rat brain. On the other hand, this Cu-MOF has the catalytic activity to mimic the superoxide dismutase for scavenging O2•- in HeLa cells effectively. This work provides a methodology to design metal ion based enzyme mimetic for analyzing and scavenging O2•- in cells and in vivo.

[2+2] Cyclo-Addition Reactions for Efficient Polymerization on a HOPG Surface at Ambient Conditions.

Polymers obtained by on-surface chemistry have emerged as a class of promising materials. Here, we propose a new strategy to obtain self-assembled 1D polymers by using photochemical [2+2] cyclo-addition or by using a mild thermal annealing. All nanostructures are fully characterized by using scanning tunneling microscopy at ambient conditions on a graphite surface. We demonstrated that nature of the stimulus strongly alters the overall quality of the resulting polymers in terms of length and number of defects. This new way is an efficient method to elaborate on-surface self-assembled 1D polymers.

Visualization and Comprehension of Electronic and Topographic Contrasts on Cooperatively Switched Diarylethene-Bridged Ditopic Ligand.

Diarylethene is a prototypical molecular switch that can be reversibly photoisomerized between its open and closed forms. Ligands bpy-DAE-bpy, consisting of a phenyl-diarylethene-phenyl (DAE) central core and bipyridine (bpy) terminal substituents, are able to self-organize. They are investigated by scanning tunneling microscopy at the solid-liquid interface. Upon light irradiation, cooperative photochromic switching of the ligands is recognized down to the submolecular level. The closed isomers show different electron density of states (DOS) contrasts, attributed to the HOMO or LUMO molecular orbitals observed. More importantly, the LUMO images show remarkable differences between the open and closed isomers, attributed to combined topographic and electronic contrasts mainly on the DAE moieties. The electronic contrasts from multiple HOMO or LUMO distributions, combined with topographic distortion of the open or closed DAE, are interpreted by density functional theory (DFT) calculations.

Role of rare-earth elements in enhancing bioelectrocatalysis for biosensing with NAD+-dependent glutamate dehydrogenase.

Dehydrogenases (DHs) are widely explored bioelectrocatalysts in the development of enzymatic bioelectronics like biosensors and biofuel cells. However, the relatively low intrinsic reaction rates of DHs which mostly depend on diffusional coenzymes (e.g., NAD+) have limited their bioelectrocatalytic performance in applications such as biosensors with a high sensitivity. In this study, we find that rare-earth elements (REEs) can enhance the activity of NAD+-dependent glutamate dehydrogenase (GDH) toward highly sensitive electrochemical biosensing of glutamate in vivo. Electrochemical studies show that the sensitivity of the GDH-based glutamate biosensor is remarkably enhanced in the presence of REE cations (i.e., Yb3+, La3+ or Eu3+) in solution, of which Yb3+ yields the highest sensitivity increase (ca. 95%). With the potential effect of REE cations on NAD+ electrochemistry being ruled out, homogeneous kinetic assays by steady-state and stopped-flow spectroscopy reveal a two-fold enhancement in the intrinsic reaction rate of GDH by introducing Yb3+, mainly through accelerating the rate-determining NADH releasing step during the catalytic cycle. In-depth structural investigations using small angle X-ray scattering and infrared spectroscopy indicate that Yb3+ induces the backbone compaction of GDH and subtle ß-sheet transitions in the active site, which may reduce the energetic barrier to NADH dissociation from the binding pocket as further suggested by molecular dynamics simulation. This study not only unmasks the mechanism of REE-promoted GDH kinetics but also paves a new way to highly sensitive biosensing of glutamate in vivo.

ZIF-67 as a Template Generating and Tuning "Raisin Pudding"-Type Nanozymes with Multiple Enzyme-like Activities: Toward Online Electrochemical Detection of 3,4-Dihydroxyphenylacetic Acid in Living Brains.

Due to its unique structure and high porosity, metal-organic frameworks (MOFs) can act not only as nanozyme materials but also as carriers to encapsulate natural enzymes and thus have received extensive attention in recent years. However, a few research studies have been conducted to investigate MOF as a template to generate and tune nanozymes in the structure and performance. In this work, the "raisin pudding"-type ZIF-67/Cu0.76Co2.24O4 nanospheres (ZIF-67/Cu0.76Co2.24O4 NSs) were obtained by rationally regulating the weight ratio of ZIF-67 and Cu(NO3)2 in the synthesis process. Here, ZIF-67 not only acts as a template but also provides a cobalt source for the synthesis of cobalt copper oxide on the surface of ZIF-67/Cu0.76Co2.24O4 NSs with multiple enzyme-like activities. The ZIF-67/Cu0.76Co2.24O4 NSs can mimic four kinds of enzymes with peroxidase-like, glutathione peroxidase-like, superoxide dismutase-like, and laccase-like activities. Based on its laccase-like activity, an online electrochemical system for continuous monitoring of 3,4-dihydroxyphenylacetic acid with good linearity in the range of 0.5-20 µM and a detection limit of 0.15 µM was established. Furthermore, the alteration of DOPAC in the brain microdialysate before and after ischemia of the rats' brain was also successfully recorded. This work not only raises a new idea for the synthesis of nanozyme materials with multiple enzyme activities but also provides a new solution for the detection of neurotransmitters in living brains.

A non-enzymatic electrochemical biosensor based on Au@PBA(Ni-Fe):MoS2 nanocubes for stable and sensitive detection of hydrogen peroxide released from living cells.

Hydrogen peroxide (H2O2) is the main product of enzymatic reactions and plays an important role in biological processes. The detection of H2O2 inside organisms or cells is critical. Here, we report a nickel-iron Prussian blue analogue nanocube doped with molybdenum disulfide and Au nanoparticles (Au@PBA(Ni-Fe):MoS2) as an electrochemical sensing material for the stable detection of H2O2 in neutral solutions for a long time. First, the Prussian blue analogue (PBA(Ni-Fe)) is synthesized by a simple charge-assembly technology, and then etched into PBA(Ni-Fe):MoS2 hollow nanocubes by a high-temperature hydrothermal reaction. Finally, Au nanoparticles are reduced inside the PBA(Ni-Fe):MoS2in situ to generate Au@PBA(Ni-Fe):MoS2 nanocubes. Ni-doping enhances the nanocube's stability in neutral solutions; as a result, the sensor can maintain a stable current response towards H2O2 reduction for more than 1 h. The sensing material can meet the needs of a long-time test. The introduction of Au enhances the electron transfer efficiency, which endows the sensor with good reduction ability for H2O2 at 0 V over a wide linear range (0.5-200 µM and 210-3000 µM) and with a low detection limit (0.23 µM (S/N = 3)), which fulfills the requirements for the detection of H2O2 in a biological system. The sensor can sense H2O2 released from cells stimulated by ascorbic acid. Au@PBA(Ni-Fe):MoS2 provides good guidance for the future development of efficient biosensors to be applied in cell biology.

Isokinetic muscle strength characteristics of lower limb joints in long jumpers / Características da força muscular isocinética das articulações dos membros inferiores dos saltadores de salto em distância / Características de la fuerza muscular isocinética de las articulaciones de los miembros inferiores en saltadores de longitud

ABSTRACT Introduction: Joint strength of the lower limbs plays a decisive role in the competitive ability of long jumpers. Special strength training based on science and targeted at the strength of the lower limb joints is an essential topic for long jumpers. Objective: To analyze isokinetic muscle strength characteristics of lower limb joints in long jumpers. Methods: Voluntary jumpers were submitted to isokinetic concentric contraction tests of the lower limbs and hip joints. We also analyzed the effect of strength training on lower limb joint injury. Results: The knee muscles of the athletes have reduced eccentric contractility. The ankle of the athlete has the most vulnerable joint to injuries in the sport. Conclusion: The explosive force and eccentric contractility of long jumpers' lower limb extensor muscles have the most significant impact on joint thrust and extension speed. Athletes need muscle strength training to develop isokinetic muscle strength. This can effectively prevent injury to lower extremity joint movements. The research findings of this paper can provide a specific theoretical basis for formulating scientific training for long jumpers. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

RESUMO Introdução: A força conjunta dos membros inferiores desempenha um papel decisivo na capacidade competitiva nos saltadores de salto em distância. O treinamento de força especial baseado na ciência e direcionado para a força das articulações dos membros inferiores é um tópico essencial para os saltadores. Objetivo: Analisar as características de força muscular isocinética das articulações dos membros inferiores em saltadores de salto em distância. Métodos: Saltadores voluntários foram submetidos à testes de contração concêntrica isocinética dos membros inferiores e articulação do quadril. Efetuou-se também a análise do efeito do treinamento de força na lesão das articulações dos membros inferiores. Resultados: Os músculos dos joelhos dos atletas têm uma contratilidade excêntrica reduzida. O tornozelo dos atletas possui a articulação mais vulnerável a lesões no esporte. Conclusão: A força de explosão e a capacidade de contração excêntrica dos músculos extensores dos membros inferiores dos saltadores de salto longo têm o impacto mais significativo no empuxo das articulações e na velocidade de extensão. Os atletas precisam de treinamento de força muscular para desenvolver a força muscular isocinética. Isto pode efetivamente evitar lesões nos movimentos das extremidades inferiores das articulações. Os resultados da pesquisa deste trabalho podem fornecer uma base teórica específica para a formulação do treinamento científico para os saltadores de salto longo. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento.

RESUMEN Introducción: La fuerza articular de los miembros inferiores desempeña un papel decisivo en la capacidad competitiva de los saltadores de longitud. El entrenamiento de fuerza especial basado en la ciencia y dirigido a la fuerza de las articulaciones de los miembros inferiores es un tema esencial para los saltadores. Objetivo: Analizar las características de la fuerza muscular isocinética de las articulaciones de los miembros inferiores en saltadores de longitud. Métodos: Los saltadores voluntarios fueron sometidos a pruebas de contracción concéntrica isocinética de los miembros inferiores y de las articulaciones de la cadera. También se realizó un análisis del efecto del entrenamiento de fuerza en las lesiones de las articulaciones de los miembros inferiores. Resultados: Los músculos de la rodilla de los atletas tienen una contractilidad excéntrica reducida. El tobillo de los atletas tiene la articulación más vulnerable a las lesiones en el deporte. Conclusión: La fuerza de explosión y la contractilidad excéntrica de los músculos extensores de las extremidades inferiores de los saltadores de longitud tienen el impacto más significativo en el empuje articular y la velocidad de extensión. Los atletas necesitan entrenar la fuerza muscular para desarrollar la fuerza muscular isocinética. Esto puede prevenir eficazmente las lesiones en los movimientos de las articulaciones de las extremidades inferiores. Los resultados de la investigación de este trabajo pueden proporcionar una base teórica específica para la formulación del entrenamiento científico de los saltadores de longitud. Nivel de evidencia II; Estudios terapéuticos - investigación de los resultados del tratamiento.