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Many viruses undergo transient conformational change to surveil their environments for receptors and host factors. In Hepatitis B virus (HBV) infection, after the virus enters the cell, it is transported to the nucleus by interaction of the HBV capsid with an importin α/β complex. The interaction between virus and importins is mediated by nuclear localization signals on the capsid protein’s C-terminal domain (CTD). However, CTDs are located inside the capsid. In this study, we asked where does a CTD exit the capsid, are all quasi-equivalent CTDs created equal, and does the capsid structure deform to facilitate CTD egress from the capsid? Here, we used Impβ as a tool to trap transiently exposed CTDs and examined this complex by cryo-electron microscopy. We examined an asymmetric reconstruction of a T = 4 icosahedral capsid and a focused reconstruction of a quasi-6-fold vertex (3.8 and 4.0 Å resolution, respectively). Both approaches showed that a subset of CTDs extended through a pore in the center of the quasi-6-fold complex. CTD egress was accompanied by enlargement of the pore and subtle changes in quaternary and tertiary structure of the quasi-6-fold. When compared to molecular dynamics simulations, structural changes were within the normal range of capsid flexibility. Although pore diameter was enlarged in the Impβ-bound reconstruction, simulations indicate that CTD egress does not exclusively depend on enlarged pores. In summary, we find that HBV surveillance of its environment by transient exposure of its CTD requires only modest conformational change of the capsid. 

Acidophilic algae-based microrobots swim in extreme acid and operate in harsh GI environment. 

There has been considerable interest in developing synthetic micromotors with biofunctional, versatile, and adaptive capabilities for biomedical applications. In this perspective, cell membrane‐functionalized micromotors emerge as an attractive platform. This new class of micromotors demonstrates enhanced propulsion and compelling performance in complex biological environments, making them suitable for various in vivo applications, including drug delivery, detoxification, immune modulation, and phototherapy. This article reviews various proof‐of‐concept studies based on different micromotor designs and cell membrane coatings in these areas. The review focuses on the motor structure and performance relationship and highlights how cell membrane functionalization overcomes the obstacles faced by traditional synthetic micromotors while imparting them with unique capabilities. Overall, the cell membrane‐functionalized micromotors are expected to advance micromotor research and facilitate its translation towards practical uses.

 

Non‐enveloped RNA viruses pervade all domains of life. In a cell, they co‐assemble from viral RNA and capsid proteins. Virus‐like particles can form in vitro where virtually any non‐cognate polyanionic cargo can be packaged. How only viral RNA gets selected for packaging in vivo, in presence of myriad other polyanionic species, has been a puzzle. Through a combination of charge detection mass spectrometry and cryo‐electron microscopy, it is determined that co‐assembling brome mosaic virus (BMV) coat proteins and nucleic acid oligomers results in capsid structures and stoichiometries that differ from the icosahedral virion. These previously unknown shell structures are strained and less stable than the native one. However, they contain large native structure fragments that can be recycled to form BMV virions, should a viral genome become available. The existence of such structures suggest the possibility of a previously unknown regulatory pathway for the packaging process inside cells.

 

To meet growing energy demands, degradation mechanisms of energy storage devices must be better understood. As a non‐destructive tool, X‐ray Computed Tomography (CT) has been increasingly used by the battery community to perform in situ experiments that can investigate dynamic phenomena. However, few have used X‐ray CT to study representative battery systems over long cycle lifetimes (>100 cycles). Here, the in situ CT study of Zn–Ag batteries is reported and the effects of current collector parasitic gassing over long‐term storage and cycling are demonstrated. Performance representative in situ CT cells are designed that can achieve >250 cycles at a high areal capacity of 12.5 mAh cm⁻². Combined with electrochemical experiments, the effects of current collector parasitic gassing are revealed with micro‐scale CT. The volume expansion and evolution of ZnO and Zn depletion are quantified with cycling and elevated temperature testing. The experimental insights are utilized to develop larger form‐factor (4 cm²) cells with electrochemically compatible current collectors. With this, over 500 cycles at a high capacity of 12.5 mAh cm⁻²for a 4 cm²form‐factor are demonstrated. This work demonstrates that in situ X‐ray CT used in long cycle‐lifetime studies can be applied to examine a multitude of battery chemistries to improve performances.