Dipeptide Nanostructure Assembly and Dynamics via in Situ Liquid-Phase Electron Microscopy

Abstract

In this paper, we report the in situ growth of FF nanotubes examined via liquid-cell transmission electron microscopy (LCTEM). This direct, high spatial, and temporal resolution imaging approach allowed us to observe the growth of peptide-based nanofibrillar structures through directional elongation. Furthermore, the radial growth profile of FF nanotubes through the addition of monomers perpendicular to the tube axis has been observed in real-time with sufficient resolution to directly observe the increase in diameter. Our study demonstrates that the kinetics, dynamics, structure formation, and assembly mechanism of these supramolecular assemblies can be directly monitored using LCTEM. The performance of the peptides and the assemblies they form can be verified and evaluated using post-mortem techniques including time-of-flight secondary ion mass spectrometry (ToF-SIMS).

Direct Observation of Emulsion Morphology, Dynamics, and Demulsification

“…We verified the identity of the phases first on the basis of solvent density, which should be directly proportional to its contrast, indicating that the dark droplets observed were the aqueous phase (as described above) for the water-in-oil emulsion, as intended (Figure ). However, to further corroborate this conclusion, citrate-stabilized aqueous gold nanoparticles were included in the aqueous phase (Figure A). These nanoparticles do not disperse in the oil phase and are of sufficient contrast to be easily distinguishable against either solvent.…”

Visualizing Dynamic Environmental Processes in Liquid at Nanoscale via Liquid-Phase Electron Microscopy

“…Inaccurate understanding on the physical, geochemical, and biological factors that control contaminant transport, transformation, uptake, and fate seriously hinders predicting and controlling the impacts of contaminants on ecosystems. − LP-S/TEM helps to visualize the dynamic process of transformation in fluid with sufficient temporal and spatial resolution, especially in the actual state of reaction in liquid. According to recent research, Gianneschi et al captured the growth of electron-beam-sensitive peptide-based nanofibrillar structures (diphenylalanine, FF) through directional elongation with LP-TEM pulsed imaging with a Protochips Poseidon Select Heating holder (SiN x membranes), and the TEM worked at 300 keV with the electron dose rate of 0.3 to 0.5 e – /Å 2 . This direct high temporal and spatial resolution videography revealing the growth of a single peptide fibril from monomers advances by addition to the end of the fibrils at a rate of around 22 nm s –1 .…”

“…(d) LP-TEM snapshots of FF nanotube growth captured by pulse imaging. Adapted from ref . Copyright 2021 American Chemical Society.…”

“…Meanwhile, new graphene liquid cell (GLC) electron microcopy is fabricated to attain a resolution similar to that of vacuum TEM (Figure c). − Thin SiN x membranes, the transparent windows based on SiO 2 , are perforated with apertures sealed with few-layer graphene . GLC achieved the observation in minimum resolution and contrast loss, with the electron beam damage minimized .…”

“…GLC achieved the observation in minimum resolution and contrast loss, with the electron beam damage minimized . Additionally, GLC-TEM has an advantage for elaborate chemical analysis with electron energy loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDS). , However, the uncontrollable liquid pocket and limit of liquid flow still prevent GLC from being used as a conventional imaging platform . To overcome these obstacles, the geometrical improvement has been proposed by fitting artificial cavities for a more stable liquid layer or a channel for liquid flow. , Although the liquid-flowing GLCs have been recently put into operation, the effectiveness of the GLCs needs further improvement .…”