Mechanics of water pore formation in lipid membrane under electric field

Transmembrane water pores are crucial for substance transport through cell membranes via membrane fusion, such as in neural communication. However, the molecular mechanism of water pore formation is not clear. In this study, we apply all-atom molecular dynamics and bias-exchange metadynamics simulations to study the process of water pore formation under an electric field. We show that water molecules can enter a membrane under an electric field and form a water pore of a few nanometers in diameter. These water molecules disturb the interactions between lipid head groups and the ordered arrangement of lipids. Following the movement of water molecules, the lipid head groups are rotated and driven into the hydrophobic region of the membrane. The reorientated lipid head groups inside the membrane form a hydrophilic surface of the water pore. This study reveals the atomic details of how an electric field influences the movement of water molecules and lipid head groups, resulting in water pore formation.

Nanoscale monitoring of mitochondria and lysosome interactions for drug screening and discover

Technology advances in genomics,proteomics,and metabolomics largely expanded the pool of potential therapeutic targets.Compared with the in vitro setting,cell-based screening assays have been playing a key role in the processes of drug discovery and development.Besides the commonly used strategies based on colorimetric and cell viability,we reason that methods that capture the dynamic cellular events will facilitate optimal hit identification with high sensitivity and specificity.Herein,we propose a live-cell screening strategy using structured illumination microscopy (SIM) combined with an automated cell colocalization analysis software,CellprofilerTM,to screen and discover drugs for mitochondria and lysosomes interaction at a nanoscale resolution in living cells.This strategy quantitatively benchmarks the mitochondria-lysosome interactions such as mitochondria and lysosomes contact (MLC) and mitophagy.The automatic quantitative analysis also resolves fine changes of the mitochondria-lysosome interaction in response to genetic and pharmacological interventions.Super-resolution live-cell imaging on the basis of quantitative analysis opens up new avenues for drug screening and development by targeting dynamic organelle interactions at the nanoscale resolution,which could facilitate optimal hit identification and potentially shorten the cycle of drug discovery.

Super-resolution quantification of nanoscale damage to mitochondria in live cells

Mitochondrial damage,characterized by altered morphological distribution and the damage of cristae,is closely associated with mitochondrial disease.However,imaging methods for capturing mitochondrial morphology at the nanoscale level in live samples remain unavailable,which seriously hinders the accurate evaluation and diagnosis of mitochondrial-related diseases.In response,we propose a super-resolution quantification strategy based on structured illumination microscopy(SIM)for the rapid,accurate evaluation of mitochondrial morphology.Using the strategy,we accurately captured the morphological distribution of mitochondria at the nanoscale level in a way generally applicable to checking various cell processes and identifying patients with mitochondrial disease who exhibit the SLC25A46 mutation.We also used algorithm-assisted super-resolution imaging to quantitatively analyze damage to mitochondrial cristae,which supports a novel drug screening strategy—high-resolution drug screening—for investigating drugs’pharmacodynamics on organelles in living cells.In short,our strategy improves the accurate examination of changes in mitochondrial morphology in living cells and indicates new ways in which SIM-imaging can assist in diagnosing mitochondrial disease at the single-cell level.

Heterogeneous oxidization of graphene nanosheets damages membrane

Graphene-based materials exhibit unique properties that have been sought to utilize for various potential applications. Many studies suggest that graphene-based materials can be cytotoxic, which may be attributed to destructive effects on cell membranes.However, there still are conflicting results regarding interactions between graphene-based materials and lipid membranes. Here,through cryo-electron microscopy(Cryo-EM) and dye-leakage experiments along with in silico methods, we found that graphene oxide nanosheets induce significant membrane damage, while the effect of pristine graphene is negligible. We revealed the importance of heterogeneous oxidization of graphene-based nanosheets in damaging vesicle membranes. Moreover, that not only the oxidization degree but also the oxidization loci and membrane tension play important roles in the cytotoxicity of the graphene-based nanosheets.

Single-vesicle imaging quantifies calcium’s regulation of nanoscale vesicle clustering mediated by α-synuclein

Although numerous studies have shown that the proteinα-synuclein(α-Syn)plays a central role in Parkinson’s disease,dementia with Lewy bodies,and other neurodegenerative diseases,the protein’s physiological function remains poorly understood.Furthermore,despite recent reports suggesting that,under the influence of Ca^(2+),α-Syn can interact with synaptic vesicles,the mechanisms underlying that interaction are far from clear.Thus,we used single-vesicle imaging to quantify the extent to which Ca^(2+)regulates nanoscale vesicle clustering mediated by α-Syn.Our results revealed not only that vesicle clustering requiredα-Syn to bind to anionic lipid vesicles,but also that different concentrations of Ca^(2+)exerted different effects on howα-Syn induced vesicle clustering.In particular,low concentrations of Ca^(2+)inhibited vesicle clustering by blocking the electrostatic interaction between the lipid membrane and the N terminus of α-Syn,whereas high concentrations promoted vesicle clustering,possibly due to the electrostatic interaction between Ca^(2+)and the negatively charged lipids that is independent of α-Syn.Taken together,our results provide critical insights intoα-Syn’s physiological function,and how Ca^(2+) regulates vesicle clustering mediated by α-Syn.