Enzyme immobilization has been demonstrated to be a favorable protocol to promote industrialization of biomacromolecules. Despite tremendous efforts to develop new strategies and materials to reali...

Fabricating covalent organic framework capsules with commodious microenvironment for enzymes

Magnetic nanomaterials show promising applications in heterogeneous catalysis because of their ease of separation and good reusability. The magnetization saturation values of magnetic nanoparticles...

Applications of Magnetic Nanomaterials in Heterogeneous Catalysis

The Mechanism and Consequences of SARS-CoV-2 Spike-Mediated Fusion and Syncytia Formation.

The rapid development of advanced nanotechnology has continuously changed many aspects of society. One important nanostructured material, magnetic nanoparticles (NPs), has applications in many areas including clean energy, biology and engineering because of their special magnetic properties. The synthesis of magnetic nanomaterials with desired sizes and morphology has attracted great attention. Nanomaterials with different properties can be combined to construct multifunctional nanoplatforms through systematic surface engineering. The surface modification of magnetic NPs presents the opportunity for them to be used in many practical applications. Functionalized magnetic NPs have been successfully applied in catalysis, as thermoelectric materials, for drug delivery, as imaging agents in nuclear magnetic resonance and in biosensors. In this review, synthetic methods for magnetic NPs and some of their important properties are described. Then the latest progress of the application of magnetic NPs in energy and biology has been summarized and discussed. Finally, we discuss some issues that still need to be solved and the prospects for magnetic NPs.

https://iopscience.iop.org/article/10.1088/1361-6528/aadcec/pdf

Recent progress in magnetic nanoparticles: synthesis, properties, and applications.

Bone defects and diseases are devastating, and can lead to severe functional deficits or even permanent disability. Nevertheless, orthopedic implants and scaffolds can facilitate the growth of incipient bone and help us to treat bone defects and diseases. Currently, a wide range of biomaterials with distinct biocompatibility, biodegradability, porosity, and mechanical strength is used in bone-related research. However, most orthopedic implants and scaffolds have certain limitations and diverse complications, such as limited corrosion resistance, low cell proliferation, and bacterial adhesion. With recent advancements in materials science and nanotechnology, metallic and metallic oxide nanoparticles have become the subject of significant interest as they offer an ample variety of options to resolve the existing problems in the orthopedic industry. More importantly, these nanoparticles possess unique physicochemical and mechanical properties not found in conventional materials, and can be incorporated into orthopedic implants and scaffolds to enhance their antimicrobial ability, bioactive molecular delivery, mechanical strength, osteointegration, and cell labeling and imaging. However, many metallic and metallic oxide nanoparticles can also be toxic to nearby cells and tissues. This review article will discuss the applications and functions of metallic and metallic oxide nanoparticles in orthopedic implants and bone tissue engineering.

Functions and applications of metallic and metallic oxide nanoparticles in orthopedic implants and scaffolds.

Vesicle Shrinking and Enlargement Play Opposing Roles in the Release of Exocytotic Contents.

Lectin corona enhances enzymatic catalysis on the surface of magnetic nanoparticles

Cell entry by SARS-CoV-2 is accomplished by the S2 subunit of the spike S protein on the virion surface by capture of the host cell membrane and fusion with the viral envelope. Capture and fusion require the prefusion S2 to transit to its potent, fusogenic form, the fusion intermediate (FI). However, the FI structure is unknown, detailed computational models of the FI are unavailable, and the mechanisms and timing of membrane capture and fusion are not established. Here, we constructed a full-length model of the CoV-2 FI by extrapolating from known CoV-2 pre- and postfusion structures. In atomistic and coarse-grained molecular dynamics simulations the FI was remarkably flexible and executed large bending and extensional fluctuations due to three hinges in the C-terminal base. Simulations suggested a host cell membrane capture time of ∼ 2 ms. Isolated fusion peptide simulations identified an N-terminal helix that directed and maintained binding to the membrane but grossly underestimated the binding time, showing that the fusion peptide environment is radically altered when attached to its host fusion protein. The large configurational fluctuations of the FI generated a substantial exploration volume that aided capture of the target membrane, and may set the waiting time for fluctuation-triggered refolding of the FI that draws the viral envelope and host cell membrane together for fusion. These results describe the FI as a machinery designed for efficient membrane capture and suggest novel potential drug targets.

/pdf/host-cell-membrane-capture-by-the-sars-cov-2-spike-protein-49j2iz3r0j.pdf

Host cell membrane capture by the SARS CoV-2 spike protein fusion intermediate

Cell entry of SARS-CoV-2 is accomplished by the S2 subunit of the spike S protein on the virion surface by fusion of the viral envelope and host cell membrane. Fusion requires the prefusion S2 to transit to its potent, fusogenic form, the fusion intermediate (FI). However, the FI structure is unknown, detailed computational models of the FI are unavailable, and the mechanisms of fusion and entry remain unclear. Here, we constructed a full-length model of the CoV-2 FI by extrapolating from known CoV-2 pre- and postfusion structures. Atomistic and coarse-grained simulations showed the FI is a remarkably flexible mechanical assembly executing large orientational and extensional fluctuations due to three hinges in the C-terminal base. Fluctuations generate a large fusion peptide exploration volume and may aid capture of the host cell target membrane and define the clock for fluctuation-triggered refolding and membrane fusion. This work suggests several novel potential drug targets.

https://www.biorxiv.org/content/biorxiv/early/2021/04/10/2021.04.09.439051.full.pdf

Large fluctuations of the fusion intermediate help SARS-CoV-2 capture host cell membranes

During exocytosis secretory vesicles fuse with a target membrane and release neurotransmitters, hormones or other bioactive molecules through a membrane fusion pore. The initially small pore may subsequently dilate for full contents release, as commonly observed in amperometric traces. The size, shape and evolution of the pore is critical to the course of contents release, but exact fusion pore solutions accounting for membrane tension and bending energy constraints have not been available. Here we obtained exact solutions for fusion pores between two membranes. We find three families: a narrow pore, a wide pore and an intermediate tether-like pore. For high tensions these are close to the catenoidal and tether solutions recently reported for freely hinged membrane boundaries. We suggest membrane fusion initially generates a stable narrow pore, and the dilation pathway is a transition to the stable wide pore family. The unstable intermediate pore is the transition state that sets the energy barrier for this dilation pathway. Pore dilation is mechanosensitive, as the energy barrier is lowered by increased membrane tension. Finally, we study fusion pores in nanodiscs, powerful systems for the study of individual pores. We show that nanodiscs stabilize fusion pores by locking them into the narrow pore family. Significance During neurotransmission, hormone release and other fundamental processes, secretory vesicles fuse their membranes with target membranes to release contents through an initially small membrane fusion pore that subsequently dilates. Dilation is assisted by proteins such as SNAREs and synaptotagmin. While macroscopic soap film shapes are well characterized, finding exact solutions for microscopic cellular membrane surfaces is made more complex by bending energy constraints. Here, computational analysis revealed three families of fusion pores between two membranes. Our work suggests membrane fusion generates a member of the narrow pore family, and pore dilation is a transition to the wide pore family. The energy barrier that SNAREs or synaptotagmin must surmount to achieve dilation is set by a third unstable intermediate pore family.

Rui Su

Papers

Vesicle Shrinking and Enlargement Play Opposing Roles in the Release of Exocytotic Contents.

Lectin corona enhances enzymatic catalysis on the surface of magnetic nanoparticles

Host cell membrane capture by the SARS CoV-2 spike protein fusion intermediate

Large fluctuations of the fusion intermediate help SARS-CoV-2 capture host cell membranes

Three membrane fusion pore families determine the pathway to pore dilation