Charged Molecules Research Articles

Morphology-controlled metal–organic frameworks as molecular traps for enhanced ion dynamics in practical semi-solid lithium metal batteries

Controlling electrostatic interactions between charged molecules is crucial to enabling advanced batteries with reliable lithium (Li)-ion conductors. To address this issue, herein, we present a class of morphology-controlled metal–organic frameworks (MOFs) that serve as Li+ boosting molecular traps for fast Li+ conduction. A rod-like MOF is incorporated into semi-interpenetrating polymer networks to construct Li+ boosting fluidic nanochannels, which enable fast Li+ transport (σ = 1.5 mS cm−1, tLi+ = 0.76) through the ionic pathway. Molecular dynamics simulations further elucidate the Li+ transport mechanism in these MOF-based molecular traps. This unusual Li+ conduction behavior of MOF-based semi-solid electrolytes suppresses the anion-triggered ion concentration gradient and facilitates the electrochemical reaction kinetics at the electrodes, ultimately improving the rate performance and cycling retention of Li-metal cells (consisting of LiNi0.7Co0.2Mn0.1O2 cathodes and Li-metal anodes). Notably, a scalable pouch-type semi-solid Li-metal cell provides stable cycling performance for realistic batteries, exceeding those of previously reported Li batteries including porous crystalline frameworks.

Regulating the Distribution and Accumulation of Charged Molecules by Progressive Electroporation for Improved Intracellular Delivery.

The cell membrane separates the intracellular compartment from the extracellular environment, constraining exogenous molecules to enter the cell. Conventional electroporation typically employs high-voltage and short-duration pulses to facilitate the transmembrane transport of molecules impermeable to the membrane under natural conditions by creating temporary hydrophilic pores on the membrane. Electroporation not only enables the entry of exogenous molecules but also directs the intracellular distribution of the electric field. Recent advancements have markedly enhanced the efficiency of intracellular molecule delivery, achieved through the utilization of microstructures, microelectrodes, and surface modifications. However, little attention is paid to regulating the motion of molecules during and after passing through the membrane to improve delivery efficiency, resulting in an unsatisfactory delivery efficiency and high dose demand. Here, we proposed the strategy of regulating the motion of charged molecules during the delivery process by progressive electroporation (PEP), utilizing modulated electric fields. Efficient delivery of charged molecules with an expanded distribution and increased accumulation by PEP was demonstrated through numerical simulations and experimental results. The dose demand can be reduced by 10-40% depending on the size and charge of the molecules. We confirmed the safety of PEP for intracellular delivery in both short and long terms through cytotoxicity assays and transcriptome analysis. Overall, this work not only reveals the mechanism and effectiveness of PEP-enhanced intracellular delivery of charged molecules but also suggests the potential integration of field manipulation of molecular motion with surface modification techniques for biomedical applications such as cell engineering and sensitive cellular monitoring.

The membrane transporter SLC25A48 enables transport of choline into human mitochondria

Choline has important physiological functions as a precursor for essential cell components, signaling molecules, phospholipids, and the neurotransmitter acetylcholine. Choline is a water-soluble charged molecule requiring transport proteins to cross biological membranes. Although transporters continue to be identified, membrane transport of choline is incompletely understood and knowledge about choline transport into intracellular organelles such as mitochondria remains limited. Here we show that SLC25A48 imports choline into human mitochondria. Human loss-of-function mutations in SLC25A48 show impaired choline transport into mitochondria and are associated with elevated urine and plasma choline levels. Thus, our studies may have implications for understanding and treating conditions related to choline metabolism.

Charge induced frustration in C60 monolayers on h-BN/Ni(111)

Frustration in a system occurs when all interacting components cannot reach their minimum energy simultaneously. We report on the development of a frustrated adsorption configuration of a C60 monolayer on epitaxial hexagonal boron nitride (h-BN) grown on Ni(111). In the low-temperature adsorption configuration, we discover non-periodic patterns with striped and zigzag elements, which are characteristic of frustrated systems, formed by molceules with different orientational alignement. Using scanning probe techniques, we investigate these complex patterns' structural and electronic properties. We find two distinct C60 species, one of which is neutral, and the other is charged due to a locally preferred energy level alignment that favors an electron transfer from the Ni(111). Discharging single or multiple intrinsically charged C60 molecules creates local changes in the electrostatic potential, shifting the energy of surrounding molecular orbitals. This allows us to measure the inter-fullerene Coulomb interactions, which plays a crucial role in the formation of the frustrated structure. Monte Carlo simulations derived from the antiferromagnetic Ising model replicate the experimentally observed frustration pattern by considering competing attractive and repulsive intermolecular interactions. As such, the C60 h-BN/Ni(111) system opens a window for essential insights into charge-induced frustration and intermolecular interactions.

Particle-in-cell simulations of EUV-induced hydrogen plasma in the vicinity of a reflective mirror

Particle-In-Cell (PIC) simulations were performed in this work to study the dynamics of the EUV-induced hydrogen plasma. The Monte-Carlo Collision (MCC) model was employed to deal with the collisions between charged particles and background gas molecules. The dynamic evolution of the plasma sheath, as well as the flux and energy distribution of ions impacting on the mirror surface, was discussed. It was found that the emission of secondary electrons under the EUV irradiation on the ruthenium mirror coating creates a positively charged wall and then prevents the ions from impacting on the mirror and therefore changes the flux and energy distribution of ions reaching the mirror. Furthermore, gas pressure has a notable effect on the plasma sheath and the characteristics of the ions impinging on the mirrors. With greater gas pressure, the sheath potential decreases more rapidly. The flux of ions received by the mirror grows approximately linearly and at the same time the energy corresponding to the peak flux decreases slightly. However, the EUV source intensity barely changes the sheath potential, and its influence on the ion impact is mainly limited to the approximate linear increase in ion flux.

Dynamics of reduced perylene bisimide cyclophane redox species by ultrafast spectroelectrochemistry.

Charged molecules play essential roles in many natural and artificial functional processes, ranging from photosynthesis to photovoltaics to chemical reactions and more. It is often difficult to identify the optical dynamic properties of relevant redox species because they cannot be easily prepared, their spectra overlap, or they evolve on a femtosecond timescale. Here, we address these challenges by combining spectroelectrochemistry, ultrafast transient absorption spectroscopy, and suitable data analysis. We illustrate the method with the various redox species of a cyclophane composed of two perylene bisimide subunits. While singular-value decomposition is a well-established tool in the analysis of time-dependent spectra of a single molecular species, we here use it additionally to separate transient maps of individual redox species. This is relevant because at any specific applied electrochemical potential, several redox species coexist in the ensemble, and our procedure allows disentangling their spectroscopic response. In the second step, global analysis is then employed to retrieve the excited-state lifetimes and decay-associated difference spectra. Our approach is generally suitable for unraveling ultrafast dynamics in materials featuring charge-transfer processes.

DIPG-40. LONG TERM SURVIVAL OF A 14 YEAR OLD GIRL WITH H3K27M MUTATED DIFFUSE MIDLINE GLIOMA FOLLOWING RADIOTHERAPY AND PROLONGED TUMOR TREATING FIELDS (TTFIELDS) -CASE REPORT

Abstract INTRODUCTION Pediatric diffuse midline H3K27M mutated glioma has a dismal prognosis. Most cases are treated by radiotherapy and oral chemotherapy, with surgical resection having a debatable role in some. Tumor-treating fields (TTFields) is a noninvasive modality in which alternating electrical fields exert biophysical force on charged and polarizable molecules known as dipoles. TTFields has been shown to extend survival for adult patients with newly diagnosed and recurrent GBM, and is FDA approved for these indications. There is sparse data about pediatric patients. CASE REPORT A 14-year-old girl presented with headache and vomiting. A large left thalamic tumor was diagnosed and underwent subtotal resection. Diagnosis was diffuse midline glioma, H3K27M positive, IDH negative. Molecular Panel: Tumor mutation burden low, microsatellite stable. Genomic findings: FGFR1, NF1, H3F3A -K28M, ATRX R666, MAP3K1 She was re-operated due to a fast tumor relapse within a few weeks, prior to radiotherapy, followed with radiotherapy with local field 59Gy. She then received temozolamide (12 months) concomitant with TTfields (Optune, Novocure). TTfields therapy was administered for 5 years without adverse effects and excellent compliance (above 85%). After 5 years, therapy was withheld, and she is now off therapy NED for another 15 months. DISCUSSION Diffuse midline H3K27M glioma harbors a poor prognosis in children. Children refrain from this treatment both for lack of evidence and because of the difficulty in adhering to a regimen that demands carrying a battery of 1.5-2kg all day and shaving all hair every 3 days. Our patient had a high compliance and as she wore a head scarf for religious customs, the device was not visible. To our knowledge this is the first pediatric reported case of long-term survival of H3K27mutatted midline glioma using TTFields. Further pediatric studies are warranted.

An efficient Bi2MoO6 adsorbent with a positive surface and abundant oxygen vacancies for the removal of humic acid contaminants

Humic acids (HAs) in water react with chlorine disinfectants and form carcinogenic chemicals. These molecules also inhibit environmental engineering processes aiming at the removal of toxic metals and organic contaminants from wastewater. For these reasons, low-cost adsorption strategies are being developed to take out HAs from water. Here, the metal oxide Bi2MoO6 with either exposed [001] (BMO-001-Br) or [010] (BMO-010-Br) facets prepared with the cetyltrimethylammonium bromide (CTAB) surfactant was evaluated for the adsorption of HAs. With a maximal adsorption capacity for HAs of 63.1 mg/g, BMO-001-Br nanosheets constituted a superior adsorbent capable of removing contaminants over a large pH range. BMO-001-Br was reusable and could separate HAs from multiple solutions including tap water, synthetic wastewater, and real pharmaceutical wastewater. The adsorption capacity of BMO-001-Br can be explained by its suitable specific surface area and its positive surface charge related to the presence of CTAB molecules attracting negatively charged HA molecules. A third feature of BMO-001-Br involved in HAs removal is a high abundance of oxygen vacancies, which are easier to form on a BMO surface with exposed crystal [001] facets. The notable performance of BMO-001-Br indicates that it can serve efficiently for the extraction of HAs from different aqueous solutions.

Enhanced Molecular Interaction of 3D Plasmonic Nanoporous Gold Alloys by Electronic Modulation for Sensitive Molecular Detection.

Three-dimensional gold and its alloyed nanoporous structures possess high surface areas and strong local electric fields, rendering them ideal substrates for plasmonic molecular detection. Despite enhancing plasmonic properties and altering molecular interactions, the effect of alloy composition on molecular detection capability has not yet been explored. Here, we report molecular interactions between nanoporous gold alloys and charged molecules by controlling the alloy composition. We demonstrate enhanced adsorption of negatively charged molecules onto the alloy surface due to positively charged gold atoms and a shifted d-band center through charge transfer between gold and other metals. Despite similar EM field intensities, nanoporous gold with silver (Au/Ag) achieves SERS enhancement factors (EF) up to 6 orders of magnitude higher than those of other alloys for negatively charged molecules. Finally, nanoporous Au/Ag detects amyloid-beta at concentrations as low as approximately 1 fM, with SERS EF up to 10 orders of magnitude higher than that of a monolayer of Au nanoparticles.

Regulation of renal organic cation transporters.

Transporters for organic cations (OCs) facilitate exchange of positively charged molecules through the plasma membrane. Substrates for these transporters encompass neurotransmitters, metabolic byproducts, drugs, and xenobiotics. Consequently, these transporters actively contribute to the regulation of neurotransmission, cellular penetration and elimination process for metabolic products, drugs, and xenobiotics. Therefore, these transporters have significant physiological, pharmacological, and toxicological implications. In cells of renal proximal tubules, the vectorial secretion pathways for OCs involve expression of organic cation transporters (OCTs) and multidrug and toxin extrusion proteins (MATEs) on basolateral and apical membrane domains, respectively. This review provides an overview of documented regulatory mechanisms governing OCTs and MATEs. Additionally, regulation of these transporters under various pathological conditions is summarized. The expression and functionality of OCTs and MATEs are subject to diverse pre- and post-translational modifications, providing insights into their regulation in various pathological conditions. Typically, in diseases, downregulation of transporter expression is observed, probably as a protective mechanism to prevent additional damage to kidney tissue. This regulation may be attributed to the intricate network of modifications these transporters undergo, shedding light on their dynamic responses in pathological contexts.

Pleiotropic Effects of Heparin and its Monitoring in the Clinical Practice.

Unfractionated heparin (UFH) was uncovered in 1916, has been used as an anticoagulant since 1935, and has been listed in the World Health Organization's Model List of Essential Medicines. Despite the availability of many other anticoagulants, the use of heparin (either low molecular weight heparin [LMWH] or UFH) is still substantial. Heparin has pleotropic effects including anticoagulant and several nonanticoagulant properties such as antiproliferative, anti-inflammatory activity, and anticomplement effects. Although UFH has been widely replaced by LMWH, UFH is still the preferred anticoagulant of choice for patients undergoing cardiopulmonary bypass surgery, extracorporeal membrane oxygenation, and patients with high-risk mechanical cardiac valves requiring temporary bridging with a parenteral anticoagulant. UFH is a highly negatively charged molecule and binds many positively charged molecules, hence has unpredictable pharmacokinetics, and variable anticoagulant effect on an individual patient basis. Therefore, anticoagulant effects of UFH may not be proportional to the dose of UFH given to any individual patient. In this review, we discuss the anticoagulant and nonanticoagulant activities of UFH, differences between UFH and LMWH, when to use UFH, different methods of monitoring the anticoagulant effects of UFH (including activated partial thromboplastin time, heparin anti-Xa activity level, and activated clotting time), while discussing pros and cons related to each method and comparison of clinical outcomes in patients treated with UFH monitored with different methods based on available evidence.

Tuning the interlayer spacing of graphene oxide membrane via surfactant intercalation for ultrafast nanofiltration

A facile method has been developed to fabricate lamellar composite graphene oxide (CGO) membranes by incorporating positively charged surfactants – cetyltrimethylammonium bromide (CTAB). The interlayer spacing of GO nanosheets was regulated by the sum of both vertical and horizontal alignment of CTAB on the GO surface via electrostatic interaction. The CTAB intercalated GO membrane exhibited an internal layer spacing of 16.97 Å compared to 8.26 Å for the GO membrane. The obtained CGO lamellar membrane with well-defined nanochannels showed ultrafast pure water flux of ∼1112 L h−1 m−2 bar−1 and an excellent separation efficiency of >99 % towards negatively charged organic dye molecules at a high permeation flux of ∼932 L h−1 m−2 bar−1, which was nearly 2.5-fold enhancement compared with that of the pristine GO membrane (∼400 L h−1 m−2 bar−1). The electrostatic and π–π interaction forces between the CGO membrane and organic dye molecules played a major role in the overall dye separation mechanism. Furthermore, the CGO membrane demonstrated excellent stability with no loss in separation performance (>96 % organic molecules rejection) after exposure to various pH solutions and deionized water (DI) water. The current work provides a straightforward approach for the formation of highly tunable and stable CTAB-intercalated GO membranes for ultrafast molecular separation.

Prospects and Challenges in Developing mRNA Vaccines for Infectious Diseases and Oncogenic Viruses.

mRNA vaccines have emerged as an optimistic technological platform for vaccine innovation in this new scientific era. mRNA vaccines have dramatically altered the domain of vaccinology by offering a versatile and rapid approach to combating infectious diseases and virus-induced cancers. Clinical trials have demonstrated efficacy rates of 94-95% in preventing COVID-19, and mRNA vaccines have been increasingly recognized as a powerful vaccine platform. Although mRNA vaccines have played an essential role in the COVID-19 pandemic, they still have several limitations; their instability and degradation affect their storage, delivery, and over-all efficiency. mRNA is typically enclosed in a transport mechanism to facilitate its entry into the target cell because it is an unstable and negatively charged molecule. For instance, mRNA that is given using lipid-nanoparticle-based vaccine delivery systems (LNPs) solely enters cells through endocytosis, establishing an endosome without damaging the cell membrane. The COVID-19 pandemic has accelerated the development of mRNA vaccine platforms used to treat and prevent several infectious diseases. This technology has the potential to change the future course of the disease by providing a safe and effective way to combat infectious diseases and cancer. A single-stranded genetic sequence found in mRNA vaccines instructs host cells to produce proteins inside ribosomes to elicit immunological responses and prepare the immune system to fight infections or cancer cells. The potential applications of mRNA vaccine technology are vast and can lead to the development of a preferred vaccine pattern. As a result, a new generation of vaccinations has gradually gained popularity and access to the general population. To adapt the design of an antigen, and even combine sequences from different variations in response to new changes in the viral genome, mRNA vaccines may be used. Current mRNA vaccines provide adequate safety and protection, but the duration of that protection can only be determined if further clinical research is conducted.

Molecular Model of Norfloxacin Translocation Through the <i>Yersinia pseudotuberculosis</i> OmpF Porin Channel

The interaction of Yersinia pseudotuberculosis OmpF (YpOmpF) porin with the fluoroquinolone antibiotic norfloxacin (Nf) and its derivatives (mono- and dihydrochloride) was studied using methods based on the use of bilayer lipid membranes (BLM), molecular modeling, and antibacterial activity testing. Asymmetric behavior of charged Nf (NfH+1) and (Nf2H+2) molecules was found to move through the YpOmpF channel depending on the membrane voltage and the side of antibiotic addition. Electrophysiological data were confirmed by computer modeling. For charged forms of the antibiotic, the presence of two peripheral high-affinity binding sites (NBS1 and NBS2), as well as an asymmetric current blocking site near the channel constriction zone (NBS3), was detected. The NBS1 site located near the channel mouth has almost the same affinity for both charged forms of Nf, while the localization of the more energetically favorable NBS2 site for the two salt forms of the antibiotic differs significantly. Nf has only one binding site near the channel constriction zone, which is a cluster of sites with lower overall affinity compared to the peripheral binding sites mentioned above. Slight differences were found in the antibacterial activity of the three forms of Nf, which is likely due to their different charge states and, accordingly, different permeability and/or ability to bind within the YpOmpF channel.

Paper Spray Mass Spectrometry with On‐Paper Electrokinetic Manipulations: Part‐Per‐Trillion Detection of Per/Polyfluoroalkyl Substances in Water and Opioids in Urine

AbstractWe developed a simple, paper‐based device that enables sensitive detection by mass spectrometry (MS) without solid phase extraction or other sample preparation. Using glass fiber filter papers within a 3D printed holder, the device employs electrokinetic manipulations to stack, separate, and desalt charged molecules on paper prior to spray into the MS. Due to counter‐balanced electroosmotic flow and electrophoresis, charged analytes stack on the paper and desalting occurs in minutes. One end of the paper strip was cut into a sharp point and positioned near the inlet of a MS. The stacked analyte bands move toward the paper tip with the EOF where they are ionized by paper spray. The device was applied to analysis of PFAS in tap water with sub part‐per‐trillion detection limits in less than ten minutes with no sample pretreatment. Analysis of opioids in urine also occurs in minutes. The crucial parameters to enable stacking, separation, and MS ionization of both positively and negatively charged analytes were determined and optimized. Experimental and computational modeling studies confirm the electrokinetic stacking and analyte transport mechanisms. On‐paper separations were carried out by stacking analyte bands at different locations depending on their electrophoretic mobility, achieving baseline separation in some cases.

Paper Spray Mass Spectrometry with On-Paper Electrokinetic Manipulations: Part-Per-Trillion Detection of Per/Polyfluoroalkyl Substances in Water and Opioids in Urine.

We developed a simple, paper-based device that enables sensitive detection by mass spectrometry (MS) without solid phase extraction or other sample preparation. Using glass fiber filter papers within a 3D printed holder, the device employs electrokinetic manipulations to stack, separate, and desalt charged molecules on paper prior to spray into the MS. Due to counter-balanced electroosmotic flow and electrophoresis, charged analytes stack on the paper and desalting occurs in minutes. One end of the paper strip was cut into a sharp point and positioned near the inlet of a MS. The stacked analyte bands move toward the paper tip with the EOF where they are ionized by paper spray. The device was applied to analysis of PFAS in tap water with sub part-per-trillion detection limits in less than ten minutes with no sample pretreatment. Analysis of opioids in urine also occurs in minutes. The crucial parameters to enable stacking, separation, and MS ionization of both positively and negatively charged analytes were determined and optimized. Experimental and computational modeling studies confirm the electrokinetic stacking and analyte transport mechanisms. On-paper separations were carried out by stacking analyte bands at different locations depending on their electrophoretic mobility, achieving baseline separation in some cases.

Streaming Potential and Associated Electrokinetic Effects through a Channel Filled with Electrolyte Solution Surrounded by a Layer of Immiscible and Dielectric Liquid.

The present article deals with the streaming potential-mediated pressure-driven flow across a channel in which the electrolyte solution is surrounded by a layer of cell membrane. Such a membrane of a biological cell may be modeled as an immiscible and dielectric liquid, which may bear free lipid molecules or charged surfactants. The presence of such additional charged molecules may lead to formation of liquid-liquid interfacial charge. In addition, the dielectric gradient-mediated ion partitioning effect further plays an important role in two-phase electrokinetic motion. We aim to study the generation of streaming potential and electrokinetic conversion efficiency as well as associated electroviscous effect for the undertaken problem. The mathematical model is based on the Poisson-Boltzmann equation for electrostatic potential and the Stokes equation for fluid flow, and the problem is studied considering suitable interfacial conditions for the flow variables along the liquid-liquid interface. The explicit analytical results for velocity and streaming field, electrokinetic energy conversion efficiency, and the parameter indicating the electroviscous effect are derived under the Donnan limit and within the Debye-Hückel electrostatic framework. We further numerically calculated the aforementioned intrinsic electrokinetic parameter associated with the problem undertaken for a wide range of pertinent parameters. The results are illustrated to indicate the impact of pertinent parameters on the generation of the streaming potential and associated electrokinetic effects.

Development and Characterization of Heparin-Containing Hydrogel/3D-Printed Scaffold Composites for Craniofacial Reconstruction.

Regeneration of cartilage and bone tissues remains challenging in tissue engineering due to their complex structures, and the need for both mechanical support and delivery of biological repair stimuli. Therefore, the goal of this study was to develop a composite scaffold platform for anatomic chondral and osteochondral repair using heparin-based hydrogels to deliver small molecules within 3D-printed porous scaffolds that provide structure, stiffness, and controlled biologic delivery. We designed a mold-injection system to combine hydrolytically degradable hydrogels and 3D-printed scaffolds that could be employed rapidly (<30min) in operating room settings (~23°C). Micro-CT analysis demonstrated the effectiveness of our injection system through homogeneously distributed hydrogel within the pores of the scaffolds. Hydrogels and composite scaffolds exhibited efficient loading (~94%) of a small positively charged heparin-binding molecule (crystal violet) with sustained release over 14days and showed high viability of encapsulated porcine chondrocytes over 7days. Compression testing demonstrated nonlinear viscoelastic behavior where tangent stiffness decreased with scaffold porosity (porous scaffold tangent stiffness: 70%: 4.9MPa, 80%: 1.5MPa, and 90%: 0.20MPa) but relaxation was not affected. Lower-porosity scaffolds (70%) showed stiffness similar to lower ranges of trabecular bone (4-8MPa) while higher-porosity scaffolds (80% and 90%) showed stiffness similar to auricular cartilage (0.16-2MPa). Ultimately, this rapid composite scaffold fabrication method may be employed in the operating room and utilized to control biologic delivery within load-bearing scaffolds.

Phytochemical Modulation of Ion Channels in Oncologic Symptomatology and Treatment.

Modern chemotherapies offer a broad approach to cancer treatment but eliminate both cancer and non-cancer cells indiscriminately and, thus, are associated with a host of side effects. Advances in precision oncology have brought about new targeted therapeutics, albeit mostly limited to a subset of patients with an actionable mutation. They too come with side effects and, ultimately, 'self-resistance' to the treatment. There is recent interest in the modulation of ion channels, transmembrane proteins that regulate the flow of electrically charged molecules in and out of cells, as an approach to aid treatment of cancer. Phytochemicals have been shown to act on ion channels with high specificity regardless of the tumor's genetic profile. This paper explores the use of phytochemicals in cancer symptom management and treatment.

The Enigma of Tau Protein Aggregation: Mechanistic Insights and Future Challenges.

Tau protein misfolding and aggregation are pathological hallmarks of Alzheimer's disease and over twenty neurodegenerative disorders. However, the molecular mechanisms of tau aggregation in vivo remain incompletely understood. There are two types of tau aggregates in the brain: soluble aggregates (oligomers and protofibrils) and insoluble filaments (fibrils). Compared to filamentous aggregates, soluble aggregates are more toxic and exhibit prion-like transmission, providing seeds for templated misfolding. Curiously, in its native state, tau is a highly soluble, heat-stable protein that does not form fibrils by itself, not even when hyperphosphorylated. In vitro studies have found that negatively charged molecules such as heparin, RNA, or arachidonic acid are generally required to induce tau aggregation. Two recent breakthroughs have provided new insights into tau aggregation mechanisms. First, as an intrinsically disordered protein, tau is found to undergo liquid-liquid phase separation (LLPS) both in vitro and inside cells. Second, cryo-electron microscopy has revealed diverse fibrillar tau conformations associated with different neurodegenerative disorders. Nonetheless, only the fibrillar core is structurally resolved, and the remainder of the protein appears as a "fuzzy coat". From this review, it appears that further studies are required (1) to clarify the role of LLPS in tau aggregation; (2) to unveil the structural features of soluble tau aggregates; (3) to understand the involvement of fuzzy coat regions in oligomer and fibril formation.