Mitochondria–lysosome interactions are essential for maintaining intracellular homeostasis. Although various fluorescent probes have been developed to visualize such interactions, they remain unable to label mitochondria and lysosomes simultaneously and dynamically track their interaction. Here, we introduce a cell-permeable, biocompatible, viscosity-responsive, small organic molecular probe, Coupa, to monitor the interaction of mitochondria and lysosomes in living cells. Through a functional fluorescence conversion, Coupa can simultaneously label mitochondria with blue fluorescence and lysosomes with red fluorescence, and the correlation between the red–blue fluorescence intensity indicates the progress of mitochondria–lysosome interplay during mitophagy. Moreover, because its fluorescence is sensitive to viscosity, Coupa allowed us to precisely localize sites of mitochondria–lysosome contact and reveal increases in local viscosity on mitochondria associated with mitochondria–lysosome contact. Thus, our probe represents an attractive tool for the localization and dynamic tracking of functional mitochondria–lysosome interactions in living cells.

Abstract-The K ϩ channel mKv1.5 is thought to encode a 4-aminopyridine (4-AP)-sensitive component of the current I K,slow in the mouse heart. We used gene targeting to replace mKv1.5 with the 4-AP-insensitive channel rKv1.1 (SWAP mice) and directly test the role of Kv1.5 in the mouse ventricle. Kv1.5 RNA and protein were undetectable, rKv1.1 was expressed, and Kv2.1 protein was upregulated in homozygous SWAP hearts. The density of the K ϩ current I K,slow (depolarizations to ϩ40 mV, pA/pF) was similar in left ventricular myocytes isolated from SWAP homozygotes (17Ϯ1, nϭ27) and littermate controls (16Ϯ2, nϭ19). The densities and properties of I peak , I to,f , I to,s , and I ss were also unchanged. In homozygous SWAP myocytes, the 50-mol/L 4-AP-sensitive component of I K,slow was absent (nϭ6), the density of the 20-mmol/L tetraethylammonium-sensitive component of I K,slow was increased (9Ϯ1 versus 5Ϯ1, PϽ0.05), and no 100-to 200-nmol/L ␣-dendrotoxin-sensitive current was found (nϭ8). APD 90 in SWAP myocytes was similar to controls at baseline but did not prolong in response to 30 mol/L 4-AP. Similarly, QTc (ms) was not prolonged in anesthetized SWAP mice (64Ϯ2, homozygotes, nϭ9; 62Ϯ2, controls, nϭ9), and injection with 4-AP prolonged QTc only in controls (63Ϯ1, homozygotes; 72Ϯ2, controls; PϽ0.05). SWAP mice had no increase in arrhythmias during ambulatory telemetry monitoring. Thus, Kv1.5 encodes the 4-AP-sensitive component of I K,slow in the mouse ventricle and confers sensitivity to 4-AP-induced prolongation of APD and QTc. Compensatory upregulation of Kv2.1 may explain the phenotypic differences between SWAP mice and the previously described transgenic mice expressing a truncated dominant-negative Kv1.

The blood-brain barrier is made of polarized brain endothelial cells (BECs) phenotypically conditioned by the central nervous system (CNS). Although transport across BECs is of paramount importance for nutrient uptake as well as ridding the brain of waste products, the intracellular sorting mechanisms that regulate successful receptor-mediated transcytosis in BECs remain to be elucidated. Here, we used a synthetic multivalent system with tunable avidity to the low-density lipoprotein receptor–related protein 1 (LRP1) to investigate the mechanisms of transport across BECs. We used a combination of conventional and super-resolution microscopy, both in vivo and in vitro, accompanied with biophysical modeling of transport kinetics and membrane-bound interactions to elucidate the role of membrane-sculpting protein syndapin-2 on fast transport via tubule formation. We show that high-avidity cargo biases the LRP1 toward internalization associated with fast degradation, while mid-avidity augments the formation of syndapin-2 tubular carriers promoting a fast shuttling across.

Applications of rechargeable non-lithium-ion batteries (Na, K, Ca, Mg, and Al NLIBs) are significantly hampered by the deficiency of suitable electrode materials. Searching for anode materials with desirable electrochemical performance is urgent for the large-scale energy storage demands of next generation renewable energy technologies. In this study, three types of recently synthesized borophenes are predicted to serve as high-performing anodes for NLIBs based on density functional theory. All the borophenes considered here are metallic with favorable in-plane stiffness. Dirac fermions were identified in two types of borophenes, guaranteeing their high electron mobility. Moreover, borophene configuration-dependent metal-ion migration, theoretical capacities, and open-circuit voltages were demonstrated with respect to the different adsorption behaviors and atom mass densities of anode materials. Our results provide insights into the configuration-dependent electrode performance of borophene and the corresponding metal-ion storage mechanism.

Interface engineering is imperative to boost the extraction capability in perovskite solar cells (PSCs). We propose a promising approach to enhance the electron mobility and charge transfer ability of tin oxide (SnO2) electron transport layer (ETL) by introducing a two-dimensional carbide (MXene) with strong interface interaction. The MXene-modified SnO2 ETL also offers a preferable growth platform for perovskite films with reduced trap density. Through a spatially resolved imaging technique, profoundly reduced non-radiative recombination and charge transport losses in PSCs based on MXene-modified SnO2 are also observed. As a result, the PSC achieves an enhanced efficiency of 20.65% with ultralow saturated current density and negligible hysteresis. We provide an in-depth mechanistic understanding of MXene interface engineering, offering an alternative approach to obtain efficient PSCs.

K-ion batteries attract extensive attention and research efforts because of the high energy density, low cost, and high abundance of K. Although they are considered suitable alternatives to Li-ion batteries, the absence of high-performance electrode materials is a major obstacle to implementation. On the basis of density functional theory, we systematically study the feasibility of a recently synthesized C 6 BN monolayer as anode material for K-ion batteries. The specific capacity is calculated to be 553 mAh/g (K 2 C 6 BN), i.e., about twice that of graphite. The C 6 BN monolayer is characterized by high strength (in-plane stiffness of 309 N/m), excellent flexibility (bending strength of 1.30 eV), low output voltage (average open circuit voltage of 0.16 V), and excellent rate performance (diffusion barrier of 0.09 eV). We also propose two new C 6 BN monolayers. One has a slightly higher total energy (0.10 eV) than the synthesized C 6 BN monolayer, exhibiting enhanced electronic properties and affinity to K. The other is even energetically favorable due to B–N bonding. All three C 6 BN monolayers show good dynamical, thermal, and mechanical stabilities. We demonstrate excellent cyclability and improved conductivity by K adsorption, suggesting great potential in flexible energy-storage devices.

The rapid development of wearable electronics has revealed an urgent need for low-cost, highly flexible, and high-capacity power sources. In this sense, emerging rechargeable potassium-ion batteries (KIBs) are promising candidates owing to their abundant resources, low cost, and lower redox potential in nonaqueous electrolytes compared to lithium-ion batteries. However, the fabrication of flexible KIBs remains highly challenging because of the lack of high-performance flexible electrode materials. In this work, we investigated the mechanical properties and electrochemical performance of a recently developed hydrogen boride (BH) monolayer as a high-performance anode material on the basis of density functional theory formalism. We demonstrated that (i) BH presents ultralow out-of-plane bending stiffness, rivaling that of graphene, which endows it with better flexibility to accommodate the repeated bending, rolling, and folding on wearable device operation; (ii) high in-plane stiffness (157 N/m along armchair and 109 N/m along zigzag) of BH makes the electrode stable against pulverization upon external and internal strains. More importantly, a BH electrode delivers a low voltage of ∼0.24 V in addition to desired K-ion affinity and hopping resistance, which remains very stable with the bending curvature. Emerged H vacancies in electrodes were found to improve both the K-ion intercalation and K-ion hopping, yielding a high theoretical capacity (1138 mAh/g), which was among the highest reported values in the literature for K-ion anode materials. All of the presented results suggested that a BH electrode could be used as a brand-new flexible and lightweight KIB anode with high capacity, low voltage, and desired rate performance.

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