Assembly-disassembly Process Research Articles

Engineered self-assembled protein nanosheets for in situ biosynthesis of peptide anchored protein-semiconductor hybrids for efficient hydrogen production

Catalytic hydrogen production using solar energy is of great significance in addressing the global energy crisis. Herein, an efficient artificial photocatalytic hydrogen production system based on hierarchical protein self-assembly is designed and developed by in situ biosynthesis of peptide-anchored protein-semiconductor hybrids. The self-grown protein-CdS quantum dot hybrids stabilize and array orderly by the predesigned bioengineered proteins assembled into monolayer nanosheets, perfectly mimicking both the structure and function of the natural photosynthetic system. By mild deposition of Pt nanoparticles, the photocatalytic hydrogen production performance of the system is further enhanced to 69100 μmolh−1 (Cd2+) g −1, 80 times the catalytic activity of free CdS. Remarkably, the protein 2D network effectively enhances the water solubility, dispersibility, and solution stability of the inorganic catalytic centers, affording efficient photocatalytic hydrogen evolution. The system maintains 91.2 % catalytic efficiency after 30 days. Furthermore, its hydrogen production rate can be artificially regulated between 69100 and 52100 μmolh−1 (per g Cd2+) by the assembly-disassembly process of the protein templates. Thus, our work showcases the importance of the protein template and its assembly in maintaining the structural stability and high catalytic performance of the photocatalytic system and provides promising ideas for the simulation of natural photosynthetic systems.

Self-Regulated Assembly and Disassembly of Gold Nanoparticles for Low-Temperature Time Indication.

The color-changing self-assembly and autonomous disassembly of colloidal gold nanoparticles (AuNPs) is reported by simply mixing negatively charged phosphine ligand-capped AuNPs with partially oxidized polyethylene glycol (PEG). The assembly of AuNPs is initiated by PEG adsorption, which disrupts the hydration layer of AuNPs, leading to depletion attraction and reduction of hydration repulsion among the AuNPs. The oxidative species in PEG subsequently oxidize and remove the charged ligands from the AuNP surface, resulting in a decrease and reversal of the negative surface charge. This causes the PEG to adsorb on AuNPs in a tighter and more direct manner, providing strong steric shielding to the AuNPs, thereby triggering the disassembly of the AuNP assemblies. The self-regulated assembly-disassembly process can be tuned widely by controlling chemical conditions of PEG, nanoparticle concentration, and the environmental conditions, suggesting potential applications as colorimetric time-temperature indicators for food and medicine storage conditions. As a proof of concept, it is demonstrated that the lifetime of the color-changing assembly-disassembly process can be extended from tens of minutes to weeks when subjected to a refrigerated environment, with tunability achievable through varying polymer conditions and storage atmospheres.

Self-assembly technology engineering multi-functional slow-release packaging system with self-starting program for prolonged preservation of perishable products

The inadequacies in the release kinetics of extant active packaging films and coatings present formidable challenges in addressing issues pertaining to food waste and food safety, particularly in the context of microbial infections that occur during the storage and transportation of food. In response to this pressing challenge, this work pioneered an innovative multifunctional packaging system, distinguished by its autonomous and sustained release properties, denoted as TA/CA-CS films. This innovative system is constructed through the self-assembly of acid-sensitive tannin-cinnamaldehyde multifunctional fillers (TA/CA) in conjunction with a judicious selection of a weakly acidic chitosan (CS) film substrate, endowed with an intrinsic “built-in initiator”. Given that the weak acidity of the CS film can trigger the reverse disassembly of TA/CA by destroying the dynamic C–O bonds that serve as bridges inside TA/CA, the TA/CA-CS film achieved the controlled and slow release of active substances. The TA/CA-CS films preserved the intended functionalities of both TA and CA components throughout the assembly-disassembly process, thereby manifesting enhanced antibacterial, antifungal, and antioxidant properties. Notably, the DPPH· and ABTS·+ scavenging rate of the TA/CA0.3-CS film surpassed 89.7%, and its efficacy in eliminating bacteria and fungi exceeded 99.9%. Consequently, the TA/CA0.3-CS film exhibited exemplary preservation capabilities, significantly prolonging the shelf life of citrus by approximately 1.9 times. Furthermore, the augmented mechanical strength, heightened barrier properties, and demonstrated safety profile laid a robust foundation for its practical deployment. The gratifying attributes of the TA/CA0.3-CS film underscore its suitability for the efficient preservation of perishable products.

Dynamic carriers for therapeutic RNA delivery

Carriers for RNA delivery must be dynamic, first stabilizing and protecting therapeutic RNA during delivery to the target tissue and across cellular membrane barriers and then releasing the cargo in bioactive form. The chemical space of carriers ranges from small cationic lipids applied in lipoplexes and lipid nanoparticles, over medium-sized sequence-defined xenopeptides, to macromolecular polycations applied in polyplexes and polymer micelles. This perspective highlights the discovery of distinct virus-inspired dynamic processes that capitalize on mutual nanoparticle–host interactions to achieve potent RNA delivery. From the host side, subtle alterations of pH, ion concentration, redox potential, presence of specific proteins, receptors, or enzymes are cues, which must be recognized by the RNA nanocarrier via dynamic chemical designs including cleavable bonds, alterable physicochemical properties, and supramolecular assembly–disassembly processes to respond to changing biological microenvironment during delivery.

Translation initiation site of mRNA is selected through dynamic interaction with the ribosome

Initiation of protein synthesis from the correct start codon of messenger RNA (mRNA) is crucial to translation fidelity. In bacteria, the start codon is usually preceded by a 4- to 6-mer adenosine/guanosine-rich Shine–Dalgarno (SD) sequence. Both the SD sequence and the start codon comprise the core ribosome-binding site (RBS), to which the 30S ribosomal subunit binds to initiate translation. How the rather short and degenerate information inside the RBS can be correctly accommodated by the ribosome is not well understood. Here, we used single-molecule techniques to tackle this long-standing issue. We found that the 30S subunit initially binds to mRNA through the SD sequence, whereas the downstream RBS undergoes dynamic motions, especially when it forms structures. The mRNA is either dissociated or stabilized by initiation factors, such as initiation factor 3 (IF3). The initiator transfer RNA (tRNA) further helps the 30S subunit accommodate mRNA and unwind up to 3 base pairs of the RBS structure. Meanwhile, the formed complex of the 30S subunit with structured mRNA is not stable and tends to disassociate. IF3 promotes dissociation by dismissing the bound initiator tRNA. Thus, initiation factors may accelerate the dynamic assembly–disassembly process of 30S–mRNA complexes such that the correct RBS can be preferentially selected. Our study provides insights into how the bacterial ribosome identifies a typical translation initiation site from mRNA.

Disassembly and reassembly of diphenylalanine crystals through evaporation of solvent

HypothesisCrystalline self-assemblies of diphenylalanine (FF) are since long back considered to be related to Alzheimer's disease. An improved understanding of the mechanism behind the formation of such structures can lead to strategies for investigating the dynamic processes of assembly and disassembly of FF. ExperimentThe assembly, disassembly and reassembly of FF crystals are influenced by the solvent composition and can be triggered by evaporation of solvent. In this work these processes are directly monitored, and the structures obtained are analyzed. FindingsThe role of the solvent for assembly, disassembly and reassembly of diphenylalanine crystals has been demonstrated. The initial crystal structure formed via self-assembly of FF monomers can be transformed into needle-like crystals and further to hollow hexagonal microtubes through evaporation of the solvent. It is shown that all the assembly-disassembly processes are spontaneous and driven by thermodynamics. It is also found that some of the crystalline structures exhibit optical waveguiding properties.

Modularity in Design for Disassembly (DfD): Exploring the Strategy for a Better Sustainable Architecture

This paper explores the idea of modularity as one of the important design strategies that potentially creates a circular and more sustainable architecture. Modularity is a common design strategy used to generate form, create spatial efficiency, support mass production and prefabricated design, particularly in modern architecture. However, its contribution to sustainability is rarely discussed. This paper utilises Design for Disassembly (DfD) as a framework to investigate the potential of modularity in design, speculating that such design aspects can potentially minimize waste and improve efficiency in the systematic assembly and disassembly of building components. This paper employs two architectural projects designed with DfD approach as study cases, the Loblolly House and Cellophane House in the USA. The data are taken from works of literature and online secondary sources. The particular building components are mapped based on categories, such as building layers or joints and analysed based on its modular characteristics. The study reveals that the application of modules in particular building layers and separable joints with further use of the division-subdivision operation are significant design strategies found in each case. Such strategies provide better flexibility and interchangeability of building components during the assembly-disassembly process, proven by the calculation of construction waste. These findings arguably expand the discussion of modularity and encourage further study of modular design for a better sustainable architecture.

Gold Nanocluster-Mediated Efficient Delivery of Cas9 Protein through pH-Induced Assembly-Disassembly for Inactivation of Virus Oncogenes

The CRISPR/Cas gene editing system has been successfully applied to combating bacteria, cancer, virus, and genetic disorders. While viral vectors have been used for the delivery of the CRISPR/Cas9 system, the time required for insert cloning, and virus packaging and standardization, hinders its efficient use. Additionally, the high molecular weight of the Cas9 endonuclease makes it not easy for packing into the vehicles. Herein we report the self-assembly of gold nanoclusters (AuNCs) with SpCas9 protein (SpCas9-AuNCs) under physiological conditions and the efficient delivery of SpCas9 into the cell nucleus. This assembly process is highly dependent on pH. SpCas9-AuNCs are stable at a higher pH but are disassembled at a lower pH. Significantly, this assembly-disassembly process facilitates the delivery of SpCas9 into cells and the cell nucleus, where the SpCas9 exerts its cleavage function. As a proof-of-concept, the assembled SpCas9-AuNCs nanoparticles are successfully used for efficient knockout of the E6 oncogene, restoring the function of tumor-suppressive protein p53 and inducing apoptosis in cervical cancer cells with little effect on normal human cells. The SpCas9-AuNCs are useful for sgRNA functional validation, sgRNA library screening, and genomic manipulation.

Reversible Self-Assembly of Nanoprobes in Live Cells for Dynamic Intracellular pH Imaging.

Self-assembly is a powerful tool to organize the elementary molecular units into functional nanostructures, which provide reversible stimulus-responsive systems for a variety of purposes. However, the ability to modulate the reversible self-assembly in live systems remains a great challenge owing to the chemical complexity of intracellular environments, which often damage synthetic assembled superstructures. Herein, we describe a robust reversible self-assembly system that is composed of a hydrophobic gold nanoparticle (AuNP) core and a shell of pH-responsive dye-incorporated block copolymers. The reversible assembly-disassembly processes were precisely controlled through mediating the molecular interactions between the copolymers and AuNPs. More importantly, the major endogenous biospecies such as proteins will not impair the reversible self-assembly, which was supported by free-energy calculations. The reversible pH-responsive nanostructures were employed as "smart" probes for visualizing the subtle dynamic pH changes among different intracellular compartments, facilitating the study of pH influence on biological processes.

White‐Light‐Emitting Materials Constructed from Supramolecular Approaches

AbstractWhite‐light emissive materials are gaining increasing attentions, ascribed to the potential applications in display and lighting devices as well as sensors. The realization of white‐light emission demands either the simultaneous emission of red, green, and blue colors or at least two complementary colors with similar distribution of emission intensities covering the entire visible spectrum. The introduction of supramolecular approaches not only relieves the negative effects of intermolecular interactions and energy transfer processes, but also endows the white‐light emissive materials with the capacity of color tunability and stimuli‐responsiveness, due to the dynamic and reversible nature of noncovalent interactions. Supramolecular materials with well‐ordered structures can regulate the energy transfer by the assembly–disassembly process, and meanwhile bring in extra fascinating attributes. This review mainly describes the recent reports on fabricating white‐light‐emitting materials from supramolecular approaches such as hydrogen bonding, host–guest interaction, π–π stacking, and metal coordination, which enriches the conceptions and pathways to afford such materials. Moreover, some perspectives together with pressing challenges are presented in the end, synchronously forecasting the potential trends of white‐light emissive materials.

Hierarchical Self-Assembly and Chiroptical Studies of Luminescent 4d-4f Cages.

Multinuclear lanthanide-containing supramolecular cages have received increasing attention recently because of their unique electroptical and magnetic properties. Here we report the hierarchical self-assembly and chiroptical studies of a group of 4d-4f heterometallic cages synthesized from a preformed dimetalloligand [(bpy)2Pd212]2+ (2) (bpy = 2,2-bipyridine) and a variety of trivalent lanthanide ions (Ln = NdIII, EuIII, YbIII). The programmable self-assembly process leading to the trigonal bipyramidal cages formulated as {Ln2[(bpy)2Pd212]3}12+ (3) has been confirmed by one- and two-dimensional NMR, electro-spray-ionization time-of-flight mass-spectroscopy, and in one typical case by single-crystal X-ray diffraction studies. Circular dichroism and circular polarized luminescence spectra confirmed the strict control of stereoselectivity on the heterometallic cages, dictated by the chiral amide groups on the ligands. Excitation (up to 420 nm) on the dipalladium chromophores on these cages leads to the characteristic lanthanide luminescence at both the visible and the near-infrared regions, depending on the lanthanide ions used. Through the assembly-disassembly process, luminescent turn-off sensing toward penicillin among several widely used antibiotics has also been demonstrated with the Europium cage, featuring a limit of detection as low as 0.88 ppb (S/N = 3). Our results pave the way for the construction of chiral 4d-4f supramolecular cages which may find potential applications in luminescent sensing and/or labeling reagents.

Copper redox chemistry of plant frataxins

The presence of a conserved cysteine residue in the C-terminal amino acid sequences of plant frataxins differentiates these frataxins from those of other kingdoms and may be key in frataxin assembly and function. We report a full study on the ability of Arabidopsis (AtFH) and Zea mays (ZmFH-1 and ZmFH-2) frataxins to assemble into disulfide-bridged dimers by copper-driven oxidation and to revert to monomers by chemical reduction. We monitored the redox assembly-disassembly process by electrospray ionization mass spectrometry, electrophoresis, UV–Vis spectroscopy, and fluorescence measurements. We conclude that plant frataxins AtFH, ZmFH-1 and ZmFH-2 are oxidized by Cu2+ and exhibit redox cysteine monomer – cystine dimer interexchange. Interestingly, the tendency to interconvert is not the same for each protein. Through yeast phenotypic rescue experiments, we show that plant frataxins are important for plant survival under conditions of excess copper, indicating that these proteins might be involved in copper metabolism.

On-Demand Disassembly of Paramagnetic Nanoparticle Chains for Microrobotic Cargo Delivery

Paramagnetic nanoparticles are considered as attractive building blocks, particularly for robotic delivery of drugs. Although paramagnetic nanoparticles can be effectively gathered and transported using external magnetic fields, the disassembly process is yet to be fully investigated to avoid the formation of aggregations. In this paper, we report a novel method of controllable disassembly of paramagnetic nanoparticle chains using a predefined dynamic magnetic field. The dynamic field is capable of performing spreading and fragmentation of the particle chains simultaneously. Using the magnetic dipole–dipole repulsive forces, the final area covered by the particle chains swells up to 545% of the initial area. The final length distribution presents a strong relationship with the frequency of the dynamic field in deionized (DI) water and two kinds of biofluids. An analytical model of phase lag is proposed, which shows good agreement with the experimental results. Furthermore, we also present an assembly process using a rotating magnetic field, indicating that the assembly disassembly process is reversible. In addition, batch-cargo delivery of polystyrene microbeads using the nanoparticle chains as swarm-like nanorobots is demonstrated.

Nucleotide Dependence of Subunit Rearrangements in Short-Form Rubisco Activase from Spinach

Higher-plant Rubisco activase (Rca) plays a critical role in regulating the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). In vitro, Rca is known to undergo dynamic assembly-disassembly processes, with several oligomer stoichiometries coexisting over a broad concentration range. Although the hexamer appears to be the active form, changes in quaternary structure could play a role in Rubisco regulation. Therefore, fluorescent labels were attached to the C-termini of spinach β-Rca, and the rate of subunit mixing was monitored by measuring energy transfer as a function of nucleotide and divalent cation. Only dimeric units appeared to exchange. Poorly hydrolyzable substrate analogues provided locked complexes with high thermal stabilities (apparent Tm = 60 °C) and an estimated t1/2 of at least 7 h, whereas ATP-Mg provided tight assemblies with t1/2 values of 30-40 min and ADP-Mg loose assemblies with t1/2 values of <15 min. Accumulation of ADP to 20% of the total level of adenine nucleotide substantially accelerated equilibration. An initial lag period was observed with ATP·Mg, indicating inhibition of subunit exchange at low ADP concentrations. The ADP Ki value was estimated to exceed the Km for ATP (0.772 ± 96 mM), suggesting that the equilibration rate is a function of the relative contributions of high- and low-affinity states. C-Terminal cross-linking generated covalent dimers, required the N-terminal extension to the AAA+ domain, and provided evidence of different classes of sites. We propose that oligomer reorganization may be stalled during periods of high Rubisco reactivation activity, whereas changes in quaternary structure are stimulated by the accumulation of ADP at low light levels.

Fluorescent Supramolecular Polymeric Materials.

Fluorescent supramolecular polymeric materials are rising stars in the field of fluorescent materials not only because of the inherent optoelectronic properties originating from their chromophores, but also due to the fascinating stimuli-responsiveness and reversibility coming from their noncovalent connections. Especially, these noncovalent connections influence the fluorescence properties of the chromophores because their state of aggregation and energy transfer can be regulated by the assembly-disassembly process. Considering these unique properties, fluorescent supramolecular polymeric materials have facilitated the evolution of new materials useful for applications in fluorescent sensors, probes, as imaging agents in biological systems, light-emitting diodes, and organic electronic devices. In this Review, fluorescent supramolecular polymeric materials are classified depending on the types of main driving forces for supramolecular polymerization, including multiple hydrogen bonding, electrostatic interactions, π-π stacking interactions, metal-coordination, van der Waals interactions and host-guest interactions. Through the summary of the studies about fluorescent supramolecular polymeric materials, the status quo of this research field is assessed. Based on existing challenges, directions for the future development of this field are furnished.

Kinetics Aspects of the Reversible Assembly of Copper in Heterometallic Mo3CuS4 Clusters with 4,4'-Di-tert-butyl-2,2'-bipyridine.

Treatment of the triangular [Mo3S4Cl3(dbbpy)3]Cl cluster ([1]Cl) with CuCl produces a novel tetrametallic cuboidal cluster [Mo3(CuCl)S4Cl3(dbbpy)3][CuCl2] ([2][CuCl2]), whose crystal structure was determined by X-ray diffraction (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine). This species, which contains two distinct types of Cu(I), is the first example of a diimine-functionalized heterometallic M3M'S4 cluster. Kinetics studies on both the formation of the cubane from the parent trinuclear cluster and its dissociation after treatment with halides, supported by NMR, electrospray ionization mass spectrometry, cyclic voltammetry, and density functional theory calculations, are provided. On the one hand, the results indicate that addition of Cu(I) to [1]+ is so fast that its kinetics can be monitored only by cryo-stopped flow at -85 °C. On the other hand, the release of the CuCl unit in [2]+ is also a fast process, which is unexpectedly assisted by the CuCl2- counteranion in a process triggered by halide (X-) anions. The whole set of results provide a detailed picture of the assembly-disassembly processes in this kind of cluster. Interconversion between trinuclear M3S4 clusters and their heterometallic M3M'S4 derivatives can be a fast process occurring readily under the conditions employed during reactivity and catalytic studies, so their occurrence is a possibility that must be taken into account in future studies.

Luminescence and magnetic properties of novel nanoparticle-sheathed 3D Micro-Architectures of Fe0.5R0.5(MoO4)1.5:Ln3+ (R = Gd3+, La3+), (Ln = Eu, Tb, Dy) for bifunctional application

For the first time, we report the successful synthesis of novel nanoparticle-sheathed bipyramid-like and almond-like Fe0.5R0.5(MoO4)1.5:Ln3+ (R = Gd3+, La3+), (Ln = Eu, Tb, Dy) 3D hierarchical microstructures through a simple disodium ethylenediaminetetraacetic acid (Na2EDTA) facilitated hydrothermal method. Interestingly, time-dependent experiments confirm that the assembly-disassembly process is responsible for the formation of self-aggregated 3D architectures via Ostwald ripening phenomena. The resultant products are characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and magnetic measurements. The growth and formation mechanisms of the self-assembled 3D micro structures are discussed in detail. To confirm the presence of all the elements in the microstructure, the energy loss induced by the K, L shell electron ionization is observed in order to map the Fe, Gd, Mo, O, and Eu components. The photo luminescence properties of Fe0.5R0.5(MoO4)1.5 doped with Eu3+, Tb3+, Dy3+ are investigated. The room temperature and low temperature magnetic properties suggest that the interaction between the local-fields introduced by the magnetic Fe3+ ions and the R3+ (La, Gd) ions in the dodecahedral sites determine the magnetism in Fe0.5R0.5(MoO4)1.5:Eu3+. This work provides a new approach to synthesizing the novel Fe0.5R0.5(MoO4)1.5:Ln3+ for bi-functional magnetic and luminescence applications.

Amphiphiles Self-Assembly: Basic Concepts and Future Perspectives of Supramolecular Approaches

Amphiphiles are synthetic or natural molecules with the ability to self-assemble into a wide variety of structures including micelles, vesicles, nanotubes, nanofibers, and lamellae. Self-assembly processes of amphiphiles have been widely used to mimic biological systems, such as assembly of lipids and proteins, while their integrated actions allow the performance of highly specific cellular functions which has paved a way for bottom-up bionanotechnology. While amphiphiles self-assembly has attracted considerable attention for decades due to their extensive applications in material science, drug and gene delivery, recent developments in nanoscience stimulated the combination of the simple approaches of amphiphile assembly with the advanced concept of supramolecular self-assembly for the development of more complex, hierarchical nanostructures. Introduction of stimulus responsive supramolecular amphiphile assembly-disassembly processes provides particularly novel approaches for impacting bionanotechnology applications. Leading examples of these novel self-assembly processes can be found, in fact, in biosystems where assemblies of different amphiphilic macrocomponents and their integrated actions allow the performance of highly specific biological functions. In this perspective, we summarize in this tutorial review the basic concept and recent research on self-assembly of traditional amphiphilic molecules (such as surfactants, amphiphile-like polymers, or lipids) and more recent concepts of supramolecular amphiphiles assembly which have become increasingly important in emerging nanotechnology.

The Isolation of Single MMX Chains from Solution: Unravelling the Assembly–Disassembly Process

Herein, we provide a systematic theoretical and experimental study of the structural and optical properties of MMX (M=metal, X=halide) chains. The influence of solvent, temperature, and concentration has been analyzed to find suitable parameters for initial building-block associations in solution. By using density functional calculations, we have computed the dissociation energy of different MMX oligomers (up to the tetramer) in the gas phase. On the basis of these findings, we discuss the most likely disassembly scenario and propose a new interpretation of these compounds. We also calculated the charge redistribution that occurs upon MM+XMMX binding in vacuum. Time-dependent density functional theory (TDDFT) is used to calculate the UV/visible spectra of different MMX chains up to the tetramer in the gas phase. The implications of these theoretical findings in the analysis of our experiments are discussed in the text. The overall body of data presented suggests a new way of looking at such linear structures. By taking into account these new data, we have been able to isolate single/few MMX chains on mica.

Poly(d-glucose carbonate) Block Copolymers: A Platform for Natural Product-Based Nanomaterials with Solvothermatic Characteristics

A natural product-based polymer platform, having the characteristics of being derived from renewable materials and capable of breaking down, ultimately, into natural byproducts, has been prepared through the ring-opening polymerization (ROP) of a glucose-based bicyclic carbonate monomer. ROP was carried out via chain extension of a polyphosphoester (PPE) macroinitiator in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) organocatalyst to afford the PPE-b-poly(D-glucose carbonate) (PDGC) block copolymer. This new copolymer represents a functional architecture that can be rapidly transformed through thiol-yne reactions along the PPE segment into a diverse variety of amphiphilic polymers, which interestingly display stimuli-sensitive phase behavior in the form of a lower critical solution temperature (LCST). Below the LCST, they undergo self-assembly to form spherical core-shell nanostructures that display a poorly defined core-shell morphology. It is expected that hydrophobic patches are exposed within the micellar corona, reminiscent of the surface complexity of proteins, making these materials of interest for triggered and reversible assembly disassembly processes.