Assembly Disassembly Research Articles

Label-Free Tracking of Hepatitis B Virus Core Protein Capsid Assembly in Real-Time Using Protein Charge Transfer Spectra.

Hepatitis B virions are double-shelled particles, with a diameter of 40-42 nm, consisting of a nucleocapsid called the HBV core protein (HBV Cp). It is an ordered assembly of 90-120 homodimers arranged in an icosahedral symmetry. Both the full-length HBV Cp and the first-149 residue domain, HBV Cp149, can spontaneously assemble in vitro into capsids with 120 Cp dimers (T = 4) or 90 Cp dimers (T = 3), triggered by high ionic strength of 0.25-0.5 M NaCl. The assembly disassembly of HBV Cp149 capsids are generally studied by light scattering, size-exclusion chromatography, atomic force microscopy, transmission electron microscopy, and other high-end expensive techniques. Here, we report a simple, yet robust, label-free technique exploiting protein charge transfer spectra (ProCharTS) to monitor the capsid assembly in real-time. ProCharTS absorption in the near UV-visible region (250-800 nm) arises when photoinduced electron transfer occurs from HOMO of COO- in glutamate (donor) to LUMO of NH3+ in lysine or polypeptide backbone (acceptor) of the protein. Alternatively, it can also occur from polypeptide backbone (donor) to acceptor in arginine, histidine, or lysine cation. ProCharTS is observed profusely among proximal charge clusters in folded proteins. Here, we show that, ProCharTS absorption among growing HBV capsids is amplified when HBV Cp homodimers assemble, generating new contacts among charged residues in the dimer-dimer interface. We notice a time-dependent sigmoidal increase in ProCharTS absorbance and luminescence during capsid formation in comparison to pure dimers. Additionally, a combined approach of anisotropy-based fluorescence assay is reported, where an increased fluorescence anisotropy was observed in capsids as compared to native and unfolded dimers. We conclude that ProCharTS can serve as a sensitive label-free tool for rapid tracking of capsid assembly in real-time and characterize the assembled capsids from dimers.

Design and teaching application of a virtual simulation training system for bridge engineering drawing recognition based on Unity3D

In response to the common issues in practical training in vocational engineering construction courses, such as dangerous operation of training equipment, insufficient number of training equipment, and ineffective teaching, a vivid and interactive virtual simulation training system was developed using Unity3D software, taking the U-shaped bridge abutment in the course of Bridge Engineering as an example. Detailed introduction to the development and design process of 3D model establishment, ZSpace device adaptation, file format conversion, model rendering and disassembly, model zooming in and out, script writing and function implementation, UI interface design, etc., in order to achieve immersive interaction functions such as free observation, assembly disassembly, and ZSpace integrated VR virtual experience in the virtual simulation training system. The practical results show that the interactive effect simulated through the simulation training system is superior to that of the physical system, which can enhance the sense of experience, improve learning enthusiasm, and deepen the understanding of the knowledge points in Bridge Engineering Drawing Recognition. After the system is successfully established and applied in the training and teaching process, it will provide an important reference for the training and teaching of relevant courses for students majoring in road and bridge engineering, and also enhance the cultivation of high-quality skilled personnel in engineering majors in vocational colleges.

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.

Utilizing augmented reality for the assembly and disassembly of panelized construction

Prefabricated construction allows for efficient resource usage while creating higher-quality products that can be assembled on-site within a short time. While this translates to significant benefits for the overall construction, challenges arise from an increased demand for trained prefabrication assembly workers. As prefabrication calls for skills differing from traditional construction, the local labor force can be negatively affected to impede the successful uptake of prefabricated construction. Upskilling the local workforce to take on prefabrication assembly and potential disassembly can solve this problem. This is more relevant to remote construction projects as they stand to gain more from prefabricated construction. This study presents two workflows for creating Augmented Reality (AR) solutions. The AR solutions are aimed to help workers transition between traditional and prefabrication assembly in a panelized construction project. They are: (1) using QR codes to identify a panel’s intended location and construction sequence and (2) using predefined markers to show required equipment and on-site assembly procedures. The solutions are delivered through smartphones, which are readily available and provide a cost-effective medium. Furthermore, developed workflows present an opportunity to implement Design for Disassembly (DfD) concepts in a project. The proposed workflows show the potential to substantially help communicate to the workers the instructions on both the panel assembly and disassembly activities and upskill the local workforce to support the transition to prefabrication assembly in construction projects.

Overcoming the Stromal Barrier of the Cornea with a Peptide Conjugate Nano‐Assembly to Combat Fungal Keratitis (Adv. Healthcare Mater. 10/2023)

Fungal Keratitis In article 2202409, Shaozhen Zhao, Zhongwei Niu, Ruibo Yang, and co-workers report a peptide conjugate nano-assembly (PCNA) that permeates corneal stroma and kills the hyphae without irritating the ocular cornea. PCNA with a nano-assembled structure and assembly–disassembly behavior could serve as the foundation of a new therapy for fungal keratitis.

The patterned assembly and stepwise Vps4-mediated disassembly of composite ESCRT-III polymers drives archaeal cell division.

ESCRT-III family proteins form composite polymers that deform and cut membrane tubes in the context of a wide range of cell biological processes across the tree of life. In reconstituted systems, sequential changes in the composition of ESCRT-III polymers induced by the AAA-adenosine triphosphatase Vps4 have been shown to remodel membranes. However, it is not known how composite ESCRT-III polymers are organized and remodeled in space and time in a cellular context. Taking advantage of the relative simplicity of the ESCRT-III-dependent division system in Sulfolobus acidocaldarius, one of the closest experimentally tractable prokaryotic relatives of eukaryotes, we use super-resolution microscopy, electron microscopy, and computational modeling to show how CdvB/CdvB1/CdvB2 proteins form a precisely patterned composite ESCRT-III division ring, which undergoes stepwise Vps4-dependent disassembly and contracts to cut cells into two. These observations lead us to suggest sequential changes in a patterned composite polymer as a general mechanism of ESCRT-III-dependent membrane remodeling.

Controllable surfactant-directed zeolitic-imidazolate-8 growth on swollen 2D zeolites

To meet society’s need for more and more specialized materials, this work focuses on the preparation of porous metal–organic framework (MOF)–zeolite hybrid materials based on two 2D zeolites, namely, IPC-1P (Institute of Physical Chemistry - 1 Precursor) and the metal–organic framework ZIF-8 (Zeolitic Imidazolate Framework-8). Using the previously well-established assembly–disassembly–organization–reassembly method, the zeolite was (i) synthesized, (ii) hydrolyzed to a layered zeolite, (iii) the interlayer distance was increased using the swelling agent cetyltrimethylammonium chloride, and (iv) nanocrystals of ZIF-8 were grown stepwise on the zeolite surface but predominantly at the edges of the crystallites where the openings to the interlayer region are located. This selective MOF growth and attachment was facilitated by a combination of intercalation of the metal ions and the swelling agent between the zeolite layers. The influence of the solvent and the number of additional steps on the ZIF-8 growth on the zeolite was systematically investigated, and the synthesis protocol was successfully adapted to a further two-dimensional silicate RUB-18 (Ruhr-Universität Bochum - 18). This paves the way toward the controlled preparation of more MOF–zeolite hybrid materials, which might provide interesting properties for future applications.

Assembly and Production Line Designing, Balancing and Scheduling with Inaccurate Data: A Survey and Perspectives

Assembly lines (conveyors) are traditional means of large-scale and mass-scale productions. An assembly line balancing problem is needed for optimizing the assembly process by configuring and designing an assembly line for the same or similar types of final products. This problem consists of designing the assembly line and distributing the total workload for manufacturing each unit of the fixed product to be assembled among the ordered workstations along the constructed assembly line. The assembly line balancing research is focused mainly on simple assembly line balancing problems, which are restricted by a set of conditions making a considered assembly line ideal for research. A lot of published research has been carried out in order to describe and solve (usually heuristically) more realistic generalized assembly line balancing problems. Assembly line designing, balancing and scheduling problems with not deterministic (stochastic, fuzzy or uncertain) parameters have been investigated in many published research works. This paper is about the design and optimization methods for assembly and disassembly lines. We survey the recent developments for designing, balancing and scheduling assembly (disassembly) lines. New formulations of simple assembly line balancing problems are presented in order to take into account modifications and uncertainties characterized by real assembly productions.

Assembly and disassembly dynamics of nonmuscle myosin II control endosomal fission.

Endocytic vesicular trafficking requires merging of two lipid bilayers, but how the two lipid bilayers can come close together during fusion and fission in endocytic trafficking is not well explored. Here, we establish that knocking down nonmuscle myosin IIs (NM IIs) by small interfering RNA (siRNA) or inhibition of their activities by (-) blebbistatin causes the formation of a ring-like assembly of early endosomes (raEE). Inhibition of NM II assembly by an inhibitor of regulatory light-chain (RLC) kinase results in the formation of raEE, whereas inhibition of NM II disassembly by inhibitors of heavy chain kinases, protein kinase C (PKC) and casein kinase 2 (CK2), causes the dispersion of early endosomes. The raEEs retain EEA1, Rab7, and LAMP2 markers. Overexpression of an assembly incompetent form, RLC-AA, and disassembly incompetent form, NMHCIIB-S6A or NMHCIIA-1916A, induces such defects, respectively. Altogether, these data support that NM II assembly and disassembly dynamics participate in endocytic trafficking by regulating fission to maintain the size of early endosomes.

Assembly–disassembly switching of chiral sheet assembly for controlled circularly polarized luminescence

AbstractAlthough substantial advances have been made regarding synthetic chiral assemblies, obtaining the two‐dimensional (2D) system with a sophisticated supramolecular chirality remains challenging. Herein, we report the switchable supramolecular chiral 2D materials via donor‐acceptor interaction between a pyrene amphiphile and 7,7,8,8‐tetracyanoquinodimethane (TCNQ). The resulting supramolecular chiral sheets spontaneously disassemble when TCNQ is irreversibly photo‐reduced to its anion. Subsequent additions of TCNQ drive the disassembled molecules to repeatedly form optically active sheet structures, demonstrating that the assembled materials exist transiently only while TCNQ is supplied. The chiral sheets emit intense circularly polarized light with a large luminescence dissymmetric factor (glum).

Dishevelled phase separation promotes Wnt signalosome assembly and destruction complex disassembly.

The amplitude of Wnt/β-catenin signaling is precisely controlled by the assembly of the cell surface-localized Wnt receptor signalosome and the cytosolic β-catenin destruction complex. How these two distinct complexes are coordinately controlled remains largely unknown. Here, we demonstrated that the signalosome scaffold protein Dishevelled 2 (Dvl2) undergoes liquid-liquid phase separation (LLPS). Dvl2 LLPS is mediated by an intrinsically disordered region and facilitated by components of the signalosome, such as the receptor Fzd5. Assembly of the signalosome is initiated by rapid recruitment of Dvl2 to the membrane, followed by slow and dynamic recruitment of Axin1. Axin LLPS mediates assembly of the β-catenin destruction complex, and Dvl2 attenuates LLPS of Axin. Compared with the destruction complex, Axin partitions into the signalosome at a lower concentration and exhibits a higher mobility. Together, our results revealed that Dvl2 LLPS is crucial for controlling the assembly of the Wnt receptor signalosome and disruption of the phase-separated β-catenin destruction complex.

Plasma membrane flipping of Syntaxin-2 regulates its inhibitory action on insulin granule exocytosis

Enhancing pancreatic β-cell secretion is a primary therapeutic target for type-2 diabetes (T2D). Syntaxin-2 (Stx2) has just been identified to be an inhibitory SNARE for insulin granule exocytosis, holding potential as a treatment for T2D, yet its molecular underpinnings remain unclear. We show that excessive Stx2 recruitment to raft-like granule docking sites at higher binding affinity than pro-fusion syntaxin-1A effectively competes for and inhibits fusogenic SNARE machineries. Depletion of Stx2 in human β-cells improves insulin secretion by enhancing trans-SNARE complex assembly and cis-SNARE disassembly. Using a genetically-encoded reporter, glucose stimulation is shown to induce Stx2 flipping across the plasma membrane, which relieves its suppression of cytoplasmic fusogenic SNARE complexes to promote insulin secretion. Targeting the flipping efficiency of Stx2 profoundly modulates secretion, which could restore the impaired insulin secretion in diabetes. Here, we show that Stx2 acts to assist this precise tuning of insulin secretion in β-cells, including in diabetes.

Assembly and disassembly mechanics of a spherical snap fit

The snap fit is a common mechanical mechanism. We have studied the spherical snap fit carefully for its physical asymmetry, which is easy to assemble but difficult to disassemble. Because of the complexity of spherical snap fit, it is difficult to get a theoretical formula to describe its physical asymmetry. In this paper, the pushing assembly and pulling disassembly of spherical snap fit are studied by both finite element analysis and experiments. The theoretical formulaes of spherical snap fit have been obtained based on numerical simulations and theoretical results of cylindrical snap fit.

Magnetically Controlled Modular Cubes With Reconfigurable Self-Assembly and Disassembly

Reconfigurable modular robots, which can actively assemble and disassemble on command, offer the possibility of mesoscale (milliscale and microscale) manufacturing with robustness and controllability. In this study, we present a design of a scalable modular subunit with embedded permanent magnets in a 3-D printed cubic body. The subunit can be wirelessly controlled by an external uniform magnetic field. We also present controlled assembly–disassembly techniques for these subunits. Our modular robotic platform is highly reconfigurable and can create programmable, predetermined patterns based on open-loop control. The 2-D motion planner computes all reachable polyomino shapes from an arbitrary initial configuration and provides the shortest movement sequences to form each shape. Experimental results match computational modeling, demonstrating robust and reproducible behavior of the modular robotic platform that is promising for mesoscale manufacturing applications. Two cube sizes were tested: 10-mm edge lengths and 2.8-mm edge lengths.

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.

Motor Cooperation During Mitosis and Ciliogenesis.

Cilia and mitotic spindles are microtubule (MT)-based, macromolecular machines that consecutively assemble and disassemble during interphase and M phase of the cell cycle, respectively, and play fundamental roles in how eukaryotic cells swim through a fluid, sense their environment, and divide to reproduce themselves. The formation and function of these structures depend on several types of cytoskeletal motors, notably MT-based kinesins and dyneins, supplemented by actin-based myosins, which may function independently or collaboratively during specific steps in the pathway of mitosis or ciliogenesis. System-specific differences in these pathways occur because, instead of conforming to a simple one motor-one function rule, ciliary and mitotic motors can be deployed differently by different cell types. This reflects the well-known influence of natural selection on basic molecular processes, creating diversity at subcellular scales. Here we review our current understanding of motor function and cooperation during the assembly-disassembly, maintenance, and functions of cilia and mitotic spindles.

SCM-25: A Zeolite with Ordered Meso-cavities Interconnected by 12×12×10-Ring Channels Determined by 3D Electron Diffraction.

Zeolites with large cavities that are accessible via wide pore windows are desirable but very rare. They have been dominantly used as catalysts in industry. Here we report a novel porous germanosilicate SCM-25, the zeolite structure containing ordered meso-cavities (29.9 × 7.6 × 6.0 Å3) interconnected by 10- and 12-ring channels. SCM-25 was synthesized as nanosized crystals by using a simple organic structure-directing agent (OSDA). Three-dimensional (3D) electron diffraction shows that SCM-25 crystallizes in the orthorhombic space group Cmmm with a = 14.62 Å, b = 51.82 Å, c = 13.11 Å, which is one of the zeolites with the largest unit cell dimensions. We demonstrate that 3D electron diffraction is a powerful technique for determining the complex structure of SCM-25, including the disorders and distributions of framework atoms silicon and germanium. SCM-25 has a high surface area (510 m2/g) and high thermal stability (700 °C). Furthermore, we propose a potential postsynthetic strategy for the preparation of zeolites with ordered meso-cavities by applying the ADOR (assembly–disassembly–organization–reassembly) approach.

Harnessing solution and solid-state emissive materials from aliphatic biogenic amine-induced transient assembly and spontaneous disassembly

This work represents the harnessing of water-soluble emissive materials for bioimaging applicationviabiogenic amine-induced transient assembly and disassembly.

Correction: In situ flow pair distribution function analysis to probe the assembly–disassembly–organisation–reassembly (ADOR) mechanism of zeolite IPC-2 synthesis

Correction for ‘In situ flow pair distribution function analysis to probe the assembly–disassembly–organisation–reassembly (ADOR) mechanism of zeolite IPC-2 synthesis’ by Samantha E. Russell et al., Mater. Adv., 2021, DOI: 10.1039/d1ma00335f.

The Role of Water Loading and Germanium Content in Germanosilicate Hydrolysis

The Assembly–Disassembly–Organization–Reassembly (ADOR) process has been used extensively to prepare new zeolite frameworks based on germanosilicate precursors. The disassembly step exploits the la...