Episodic Occurrence of Field‐Aligned Energetic Ions on the Dayside

The tens of kiloelectron volt ions observed in the ring current region at L ~ 3–7 generally have pancake pitch angle distributions, that is, peaked at 90°. However, in this study, by using the Van Allen Probe observations on the dayside, unexpectedly, we have found that about 5% time, protons with energies of ~30 to 50 keV show two distinct populations, having an additional field‐aligned population overlapping with the original pancake population. The newly appearing field‐aligned populations have higher occurrence rates at ~12–16 magnetic local time during geomagnetically active times. In particular, we have studied eight such events in detail and found that the source regions are located around 12 to 18 magnetic local time which coincides with our statistical result. Based on the ionospheric and geosynchronous observations, it is suggested that these energetic ions with field‐aligned pitch angle distributions probably are accelerated near postnoon in association with ionospheric disturbances that are triggered by tail injections.Plain Language SummaryProtons of different sources have different pitch angle distributions (PADs). For example, warm plasma cloak protons, which come directly from the ionosphere, have field‐aligned PADs, while ring current protons that generally originate from tail plasma sheet have pancake‐shaped PADs. In this study, unexpectedly, we have found that about 5% of the time on the dayside, protons of ring current energies show two distinct populations according to their PADs: higher fluxes of field‐aligned populations overlapping with the original pancake populations. The newly appeared field‐aligned populations have higher occurrence rates at ~12–16 magnetic local time during geomagnetically active times. In order to find the mechanism that generates these field‐aligned energetic proton populations, we have studied eight such events in detail by using the low‐altitude DMSP, POES satellites, and the NOAA‐LANL satellite at the geosynchronous orbit. The results imply that these energetic ions with field‐aligned PADs probably are accelerated by ionospheric disturbances that are triggered by tail injections. These results provide evidence of another possibly important source of the ring current ions.Key PointsWe have found that about 5% of the time on the dayside, protons with energies of ~30 to 50 keV have strong field‐aligned PADsThe field‐aligned PADs have higher occurrence rates at ~12‐16 MLT during geomagnetically active timesThese energetic field‐aligned ions possibly are accelerated by ionospheric disturbances triggered by tail injectionsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153687/1/grl60102_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153687/2/grl60102.pd

Amino Acid Coordinated Self-Assembly

Self-assembly of highly important biomolecules, such as proteins and peptides, has attracted tremendous interest in supramolecular construction of functional materials. However, as proteins and peptides are often immunogenic and their structures are complex, there is a strong demand to use amino acids as simpler building blocks. Still, mimicking the sophisticated structures and functions of natural materials by self-assembly of simpler and more basic units of biomolecules, such as amino acids, remains a formidable challenge. Inspired by metalion-associated crystallization of L-cystine in the urinary system, amino acid coordinated self-assembly is discussed as an original strategy for supramolecular construction of biomimetic materials. The resulting materials possess the features of uniform size, hierarchical architecture, and structural resemblance to biological structures. In addition, the self-assembly process can readily be adapted to simultaneous integration of various functional modules, providing materials with promising properties for biomimetic and biomedical applications.</p

Self-Assembling Peptide-Based Nanoarchitectonics

Self-assembly is omnipresent in nature. While natural self-assembly systems are complicated in structure, the simplification of natural systems while maintaining their inherent functionalities has proven to be a highly promising route towards artificial nanoarchitectonics with great potential for application. In this review, we summarize our recent works on self-assembling peptide-based nanoarchitectonics, where peptides with a simple molecular structure can modulate the assembly of various species in a flexible and controllable way and efficiently construct nanoarchitectonics with desired functionalities. Our recent findings regarding the applications of self-assembling peptides in the fields of biomimetic photosystems, oriented microtubes for optical waveguiding, and phototherapy are discussed in detail. In addition, the self-assembly mechanism and the effects of peptides on self-assembly are reviewed. This review is expected to provide an understanding of the role of peptides in the assembly of nanoarchitectonics and guidance towards the future design and application of novel functional peptide-modulated self-assembling materials

Peptide Supramolecular Self-Assembly: Structural Precise Regulation and Functionalization

Biomolecular self-assembly plays a significant role for physiological function. Inspired by this, the construction of functional structures and architectures by biomolecular self-assembly has attracted tremendous attentions. Peptides can be assembled into diverse nanostructures, exhibiting important potential for biomedical and green-life technology applications. How to achieve the structural precise regulation of various nanostructures and functionalization by precise control of structures is the two key challenges in the field of peptide self-assembly. As the assembly process is a spontaneous thermodynamic and kinetic driven process, and is determined by the cooperation of various intermolecular non-covalent interactions, including hydrogen-bonding, electrostatic, p-p stacking, hydrophobic, and van der Waals interactions, the reasonable regulation of these non-covalent interactions is a critical pathway to achieve the two goals. To modulate these non-covalent interactions, one of the common used methods is to change the kinetic factors/external environment, including pH, ionic strength, and temperature, etc. These kinetic factors can effectively influence the interactions between peptides and solvents, resulting in dynamic and responsive variations in structures through multiple length scales and ultimate morphologies. However, the fatal disadvantage is the lacking of the precise regulation of assembled structures in the molecular level with consideration of both thermodynamics and kinetics. Compared with changing the external environment, the specific and precise molecular design is more favorable to achieve the structural precise regulation. The molecular structures and the component of building blocks can be rationally designed. For example, one can modulate the interactions between two or more than two building blocks by changing the physicochemical properties of each building block, enabling self-assembly and structural diversity of the final nanostructures. Furthermore, by combining peptides and other functional biomolecules (such as porphyrins), the functionalization of assembled nanostructures and architectures can be achieved more easily and flexibly. In this review, we will focus on the structural precise regulation and the functionalization of assembled peptide nanostructures. It is believed that the precise regulation of nanostructures is promising to promote the development of peptide-based materials towards green-life technology applications.</p

Self-Assembling Proteins for Design of Anticancer Nanodrugs

Inspired by the diverse protein-based structures and materials in organisms, proteins have been expected as promising biological components for constructing nanomaterials toward various applications. In numerous studies protein-based nanomaterials have been constructed with the merits of abundant bioactivity and good biocompatibility. However, self-assembly of proteins as a dominant approach in constructing anticancer nanodrugs has not been reviewed. Here, we provide a comprehensive account of the role of protein self-assembly in fabrication, regulation, and application of anticancer nanodrugs. The supramolecular strategies, building blocks, and molecular interactions of protein self-assembly as well as the properties, functions, and applications of the resulting nanodrugs are discussed. The applications in chemotherapy, radiotherapy, photodynamic therapy, photothermal therapy, gene therapy, and combination therapy are included. Especially, manipulation of molecular interactions for realizing cancer-specific response and cancer theranostics are emphasized. By expounding the impact of molecular interactions on therapeutic activity, rational design of highly efficient protein-based nanodrugs for precision anticancer therapy can be envisioned. Also, the challenges and perspectives in constructing nanodrugs based on protein self-assembly are presented to advance clinical translation of protein-based nanodrugs and next-generation nanomedicine

Peptide-based Supramolecular Colloids

Peptide-based supramolecular colloids are assembled systems based on weak interactions between peptides (such as hydrogen bonding, electrostatic forces, hydrophobic effects, pi-pi interactions, and van der Waals forces), spontaneously formed in a bottom-up manner. Peptide-based supramolecular colloids have ordered molecular arrangements and regular structures, with characteristics of both traditional colloids and supramolecular systems. Constructing functional supramolecular colloids via weak intermolecular interactions assists in understanding the process of biomolecular self-assembly in vivo and provides an effective strategy for designing supramolecular materials with excellent performance. Peptides, consisting of several amino acids, are elegant building blocks in supramolecular chemistry as well as colloid and interface chemistry because of their biological origin, clear composition, low immunogenicity, structural programmability, excellent biosafety, and high biodegradability. Based on the approach of supramolecular self-assembly, peptides can be manipulated to form multiscale and multifunctional colloidal systems, which have widespread applications in medicine, catalysis, energy, nanotechnology, and other fields. However, the realization of precise control of the structures and functions of these supramolecular colloids through peptide design and intermolecular interactions regulation remains an important issue to be addressed. To study the assembly process and physicochemical mechanism of supramolecular colloids at the molecular scale, and to explore the relationship between colloidal structure and function, the construction and functionalization of supramolecular colloids must be achieved. This work is a systematic summary of the assembly mechanism, structures, and functions as well as the state of the art of peptide-based supramolecular colloids with emphasis on the regulation of intermolecular interactions and structure-function relationships. The research progress of peptide-based supramolecular colloids in the following fields is summarized herein: i) biomimetic photosynthesis, including light capture and charge separation; and ii) tumor phototherapies, including photothermal therapy (PTT) and photodynamic therapy (PDT). Currently, it is feasible to induce functional enhancement of peptide colloids via supramolecular assembly. The most important aspect is to design the primary structure of the peptide building block, to precisely control the weak interactions between peptide molecules and rationally optimize the self-assembly process, and control the size and structure of the assemblies. Followup studies should focus on the design of molecular precursors, the combination of basic research and practical application of peptide-based supramolecular colloids will be essential. The advantages of peptide-based supramolecular colloids, including their ordered organization, flexible structures, and versatile functions, will open up novel avenues for various applications of supramolecular colloids in fields such as green energy and medicine. It is hoped that this review will provide inspiration and broaden ideas to further drive the development and application of supramolecular colloids

Functional Nanomaterials Based on Self-Assembly of Endogenic NIR-Absorbing Pigments for Diagnostic and Therapeutic Applications

Endogenic pigments derived from hemoglobin have been successfully applied in the clinic for both imaging and therapy based on their inherent photophysical and photochemical properties, including light absorption, fluorescence emission, and producing reactive oxygen species. However, the clinically approved endogenic pigments can be excited only by UV/vis light, restricting the penetration depth of in vivo applications. Recently, endogenic pigments with NIR-absorbing properties have been explored for constructing functional nanomaterials. Here, the overview of NIR-absorbing endogenic pigments, mainly bile pigments, and melanins, as emerging building blocks for supramolecular construction of diagnostic and therapeutic nanomaterials is provided. The endogenic origins, synthetic pathways, and structural characteristics of the NIR-absorbing endogenic pigments are described. The self-assembling approaches and noncovalent interactions in fabricating the nanomaterials are emphasized. Since bile pigments and melanins are inherently photothermal agents, the resulting nanomaterials are demonstrated as promising candidates for photoacoustic imaging and photothermal therapy. Integration of additional diagnostic and therapeutic agents by the nanomaterials through chemical conjugation or physical encapsulation toward synergetic effects is also included. Especially, the degradation behaviors of the nanomaterials in biological environments are summarized. Along with the challenges, future perspectives are discussed for accelerating the ration design and clinical translation of NIR-absorbing nanomaterials