Cryo‐electron microscopy (cryo‐EM) can now be used to determine high‐resolution structural information on a diverse range of biological specimens. Recent advances have been driven primarily by ...developments in microscopes and detectors, and through advances in image‐processing software. However, for many single‐particle cryo‐EM projects, major bottlenecks currently remain at the sample‐preparation stage; obtaining cryo‐EM grids of sufficient quality for high‐resolution single‐particle analysis can require the careful optimization of many variables. Common hurdles to overcome include problems associated with the sample itself (buffer components, labile complexes), sample distribution (obtaining the correct concentration, affinity for the support film), preferred orientation, and poor reproducibility of the grid‐making process within and between batches. This review outlines a number of methodologies used within the electron‐microscopy community to address these challenges, providing a range of approaches which may aid in obtaining optimal grids for high‐resolution data collection.
This paper describes different approaches that cryo‐EM users can take to improve the quality of their sample distribution and ice for high‐resolution single‐particle cryo‐EM.
Accurate quantitative elemental and isotope analysis of nanoparticles at the single-particle level is crucial for better understanding their origin, properties and behaviors. Single particle ...inductively coupled plasma-mass spectrometry (spICP-MS) has emerged as a promising technique for nanoparticle analysis. However, challenges persist in obtaining accurate and consistent element profiles and ratios for small-sized nanoparticles by conventional quadrupole (QMS) or time-of-flight mass analyzers (TOF-MS) due to their low level and transient nature. In this paper, we present a novel analytical method for single nanoparticle analysis using multiple collector ICP-MS (MC-ICP-MS) combined with a modern high-speed digital oscilloscope. The single particle events are acquired using an “event-triggered signal capture” (ETSC) technique, which enables the simultaneously capture and visualization of multiple isotopes of transient individual particle profiles with nanosecond time resolution. This greatly facilitates precise and efficient analysis of nanoparticles. The minimum detectable particle size is calculated to be as small as 8 nm (∼1 ag 109Ag) for AgNPs. Based on the 109/107Ag ratios obtained from 2000 particles, the precisions of 109/107Ag ratio measurements on 20 nm, 40 nm, 60 nm, 80 nm and 100 nm were approximately 0.086 (SD), 0.063 (SD), 0.051 (SD), 0.040 (SD), and 0.029 (SD), which is limited by counting statistics of the isotopic signals. Furthermore, the achieved standard error of 109/107Ag can be reduced to sub-permil level (0.7 ‰) even for the measurement of 20 nm AgNPs (N = 17,000). These results demonstrate that the ETSC provides a unique method for isotope analysis of single particles, holding great potential for enhancing our understanding of nanoparticles.
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•Sensitive, precise isotope analysis of single nanoparticles is achieved by MC-ICP-MS.•ETSC system enables recording of single particle profile with ns time resolution.•The ETSC system allows for efficient elimination of erroneous particle events.•The achieved standard error of 109/107Ag can be reduced to sub-permil level.
A Cu2O superstructure is constructed through a recrystallization‐induced self‐assembly strategy. Single Cu2O superstructure particle exhibits an outstanding surface‐enhanced Raman spectroscopy ...performance with the limit of detection as low as 10−9 mol L−1 and metal comparable enhancement factor (8 × 105) due to the synergetic effect of vacancies defect‐facilitated charge‐transfer process and copper vacancies defect‐induced electrostatic adsorption.
As electric vehicles, portable electronic devices, and tools have increasingly high requirements for battery energy density and power density, constantly improving battery performance is a research ...focus. Accurate measurement of the structure–activity relationship of active materials is key to advancing the research of high‐performance batteries. However, conventional performance tests of active materials are based on the electrochemical measurement of porous composite electrodes containing active materials, polymer binders, and conductive carbon additives, which cannot establish an accurate structure–activity relationship with the physical characterization of microregions. In this review, in order to promote the accurate measurement and understanding of the structure–activity relationship of materials, the electrochemical measurement and physical characterization of energy storage materials at single‐particle scale are reviewed. The potential problems and possible improvement schemes of the single particle electrochemical measurement and physical characterization are proposed. Their potential applications in single particle electrochemical simulation and machine learning are prospected. This review aims to promote the further application of single particle electrochemical measurement and physical characterization in energy storage materials, hoping to achieve 3D unified evaluation of physical characterization, electrochemical measurement, and theoretical simulation at the single particle scale to provide new inspiration for the development of high‐performance batteries.
Highly unified 3D evaluation of the physical characterization, electrochemical measurement, and theoretical simulation of active material single particle is a powerful means to deeply understand the structure–activity relationship of active materials and promote the rational design of the high‐performance battery material and structure.
DNA is typically impermeable to the plasma membrane due to its polyanionic nature. Interestingly, several different DNA nanostructures can be readily taken up by cells in the absence of transfection ...agents, which suggests new opportunities for constructing intelligent cargo delivery systems from these biocompatible, nonviral DNA nanocarriers. However, the underlying mechanism of entry of the DNA nanostructures into the cells remains unknown. Herein, we investigated the endocytotic internalization and subsequent transport of tetrahedral DNA nanostructures (TDNs) by mammalian cells through single‐particle tracking. We found that the TDNs were rapidly internalized by a caveolin‐dependent pathway. After endocytosis, the TDNs were transported to the lysosomes in a highly ordered, microtubule‐dependent manner. Although the TDNs retained their structural integrity within cells over long time periods, their localization in the lysosomes precludes their use as effective delivery agents. To modulate the cellular fate of the TDNs, we functionalized them with nuclear localization signals that directed their escape from the lysosomes and entry into the cellular nuclei. This study improves our understanding of the entry into cells and transport pathways of DNA nanostructures, and the results can be used as a basis for designing DNA‐nanostructure‐based drug delivery nanocarriers for targeted therapy.
Transported to a better place: The endocytotic internalization of tetrahedral DNA nanostructures (TDNs) into cells by a caveolin‐dependent pathway was investigated through single‐particle tracking. The subsequent microtubule‐dependent transport of the TDNs to the lysosomes for digestion (see figure) could be redirected to the nucleus by functionalization of the TDNs.
Summary
Phagocytosis is a remarkably complex and versatile process: it contributes to innate immunity through the ingestion and elimination of pathogens, while also being central to tissue ...homeostasis and remodeling by clearing effete cells. The ability of phagocytes to perform such diverse functions rests, in large part, on their vast repertoire of receptors. In this review, we address the various receptor types, their mobility in the plane of the membrane, and two modes of receptor crosstalk: priming and synergy. A major section is devoted to the actin cytoskeleton, which not only governs receptor mobility and clustering but also is instrumental in particle engulfment. Four stages of the actin remodeling process are identified and discussed: (i) the ‘resting’ stage that precedes receptor engagement, (ii) the disruption of the cortical actin prior to formation of the phagocytic cup, (iii) the actin polymerization that propels pseudopod extension, and (iv) the termination of polymerization and removal of preassembled actin that are required for focal delivery of endomembranes and phagosomal sealing. These topics are viewed in the larger context of the differentiation and polarization of the phagocytic cells.
The formal concept of a workflow to single‐particle analysis of cryo‐electron microscopy (cryo‐EM) images in the RELION program is described. In this approach, the structure‐determination process is ...considered as a graph, where intermediate results in the form of images or metadata are the vertices, and different functionalities of the program are the edges. The new implementation automatically logs all user actions, facilitates file management and disk cleaning, and allows convenient browsing of the history of a project. Moreover, new functionality to iteratively execute consecutive jobs allows on‐the‐fly image processing, which will lead to more efficient data acquisition by providing faster feedback on data quality. The possibility of exchanging data‐processing procedures among users will contribute to the development of standardized image‐processing procedures, and hence increase accessibility for new users in this rapidly expanding field.
The formal description of a workflow to cryo‐EM structure determination in the RELION program allows standardization of procedures and on‐the‐fly image processing during data acquisition.
•Comparative analysis of reduced-order and approximation models with the DFN model.•Implementation of approximation methods for solving the solid phase diffusion.•Evaluation of simplifications for ...high-energy and high-power Li-ion batteries.•Sensitivity analysis for the DFN model and two reduced-order models.
Physics-based electrochemical battery models, such as the Doyle-Fuller-Newman (DFN) model, are valuable tools for simulating Li-ion battery behavior and understanding internal battery processes. However, the complexity and computational demands of such models limit their applicability for battery management systems and long-term aging simulations. Reduced-order models (ROMs), such as the Extended Single Particle Model (ESPM), Single Particle Model (SPM) and Polynomial and Padé approximations, here all referred to as simplifications, lead to faster computational speeds. Choosing the appropriate simplification method for a specific cell type and operating condition is a challenge. This study investigates the simulation accuracy and calculation speed of various simplifications for high-energy (HE) and high-power (HP) batteries at different current loading conditions and compares those to the full-order DFN model. The results indicate that among the ROMs, the ESPM consistently offers the best combination of high computational speed and relatively good accuracy in most conditions in comparison to the full-order DFN model. Among the approximations, higher-order polynomial approximation, third and fourth-order Padé approximation perform the best in terms of accuracy. The higher-order polynomial approximation shows an advantage in terms of computing speed, while the fourth-order Padé approximation achieves the highest overall accuracy among the different approximations.
Cerium dioxide nanoparticles (CeO
2
NPs) are among the most broadly used engineered nanoparticles that will be increasingly released into the environment. Thus, understanding their uptake, ...transportation, and transformation in plants, especially food crops, is critical because it represents a potential pathway for human consumption. One of the primary challenges for the endeavor is the inadequacy of current analytical methodologies to characterize and quantify the nanomaterial in complex biological samples at environmentally relevant concentrations. Herein, a method was developed using single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) technology to simultaneously detect the size and size distribution of particulate Ce, particle concentration, and dissolved cerium in the shoots of four plant species including cucumber, tomato, soybean, and pumpkin. An enzymatic digestion method with Macerozyme R-10 enzyme previously used for gold nanoparticle extraction from the tomato plant was adapted successfully for CeO
2
NP extraction from all four plant species. This study is the first to report and demonstrate the presence of dissolved cerium in plant seedling shoots exposed to CeO
2
NPs hydroponically. The extent of plant uptake and accumulation appears to be dependent on the plant species, requiring further systematic investigation of the mechanisms.
From its early beginnings in characterizing aerosol particles to its recent applications for investigating natural waters and waste streams, single particle inductively coupled plasma-mass ...spectrometry (spICP-MS) has proven to be a powerful technique for the detection and characterization of aqueous dispersions of metal-containing nanomaterials. Combining the high-throughput of an ensemble technique with the specificity of a single particle counting technique and the elemental specificity of ICP-MS, spICP-MS is capable of rapidly providing researchers with information pertaining to size, size distribution, particle number concentration, and major elemental composition with minimal sample perturbation. Recently, advances in data acquisition, signal processing, and the implementation of alternative mass analyzers (e.g., time-of-flight) has resulted in a wider breadth of particle analyses and made significant progress toward overcoming many of the challenges in the quantitative analysis of nanoparticles. This review provides an overview of spICP-MS development from a niche technique to application for routine analysis, a discussion of the key issues for quantitative analysis, and examples of its further advancement for analysis of increasingly complex environmental and biological samples.
Graphical Abstract
Single particle ICP-MS workflow for the analysis of suspended nanoparticles
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