Tracking 3D picometer-scale motions of single nanoparticles with high-energy electron probes

Real-Time Observation of Polymer Fluctuations During Phase Transition Using Transmission Electron Microscope

Measuring molecular dynamics improves understanding of the structure-function relationships of materials. In this study, we present a novel technique for observing material dynamics using transmission electron microscopy (TEM), in which the gold nanoparticles are employed as motion probes for tracing the polymer dynamics in real space. A thin layer of polymer materials was generated on the 2 μm diameter holes of Quantifoil grids, and gold nanoparticles were dispersed on the membrane surface. By tracking the movement of gold nanoparticles from a series of TEM images taken under continuous temperature control, we obtained mean squared displacement (MSD) curves. The dynamics of poly{2-(perfluorooctyl)ethyl acrylate} (PC8FA) and poly(stearyl acrylate) (PSA) were analyzed. In the temperature-dependent analysis of the MSD, sharp peaks were observed for both PC8FA and PSA at positions corresponding to their melting and crystallization temperatures. These results demonstrate the capability of TEM to provide valuable insights into the dynamics of polymer materials, highlighting its potential for widespread application in materials sciences.

Diffracted X-ray Tracking for Observing the Internal Motions of Individual Protein Molecules and Its Extended Methodologies

In 1998, the diffracted X-ray tracking (DXT) method pioneered the attainment of molecular dynamics measurements within individual molecules. This breakthrough revolutionized the field by enabling unprecedented insights into the complex workings of molecular systems. Similar to the single-molecule fluorescence labeling technique used in the visible range, DXT uses a labeling method and a pink beam to closely track the diffraction pattern emitted from the labeled gold nanocrystals. Moreover, by utilizing X-rays with extremely short wavelengths, DXT has achieved unparalleled accuracy and sensitivity, exceeding initial expectations. As a result, this remarkable advance has facilitated the search for internal dynamics within many protein molecules. DXT has recently achieved remarkable success in elucidating the internal dynamics of membrane proteins in living cell membranes. This breakthrough has not only expanded our knowledge of these important biomolecules but also has immense potential to advance our understanding of cellular processes in their native environment.

Time-Resolved Measurement of the ATP-Dependent Motion of the Group II Chaperonin by Diffracted Electron Tracking

Previously, we demonstrated the ATP-dependent dynamics of a group II chaperonin at the single-molecule level by diffracted X-ray tracking (DXT). The disadvantage of DXT is that it requires a strong X-ray source and also perfect gold nano-crystals. To resolve this problem, we developed diffracted electron tracking (DET). Electron beams have scattering cross-sections that are approximately 1000 times larger than those of X-rays. Thus, DET enables us to perform super-accurate measurements of the time-resolved 3D motion of proteins labeled with commercially available gold nanorods using a scanning electron microscope. In this study, we compared DXT and DET using the group II chaperonin from Methanococcus maripaludis (MmCpn) as a model protein. In DET, the samples are prepared in an environmental cell (EC). To reduce the electron beam-induced protein damage, we immobilized MmCpn on the bottom of the EC to expose gold nanorods close to the carbon thin film. The sample setup worked well, and the motions of gold nanorods were clearly traced. Compared with the results of DXT, the mobility in DET was significantly higher, which is probably due to the difference in the method for immobilization. In DET, MmCpn was immobilized on a film of triacetyl cellulose. Whereas proteins are directly attached on the surface of solid support in DXT. Therefore, MmCpn could move relatively freely in DET. DET will be a state-of-the-art technology for analyzing protein dynamics.

An experimental viewpoint on the information depth of EBSD

This article contains a critical review of the literature concerning the information depth of electron backscatter diffraction (EBSD) and a viewpoint on the topic is formulated. EBSD is applied to a crystal partially covered by a wedge of amorphous glass. EBSD-patterns of decreasing quality are obtained from a crystal covered by an increasingly thick layer of glass. The location of the last indexable EBSD-patterns is compared to the last discernible contrast in SEM-micrographs obtained from the same crystal using accelerating voltages of 2-20 kV. It is concluded that the information depth of EBSD is at least as large as that of an SEM-micrograph obtained with a voltage of 4 kV from a non-tilted sample. Concepts of the information depth and experimental approaches are discussed.

Real time ligand-induced motion mappings of AChBP and nAChR using X-ray single molecule tracking

We observed the dynamic three-dimensional (3D) single molecule behaviour of acetylcholine-binding protein (AChBP) and nicotinic acetylcholine receptor (nAChR) using a single molecule tracking technique, diffracted X-ray tracking (DXT) with atomic scale and 100 μs time resolution. We found that the combined tilting and twisting motions of the proteins were enhanced upon acetylcholine (ACh) binding. We present the internal motion maps of AChBP and nAChR in the presence of either ACh or α-bungarotoxin (αBtx), with views from two rotational axes. Our findings indicate that specific motion patterns represented as biaxial angular motion maps are associated with channel function in real time and on an atomic scale.