Cryo-electron tomography Analytical chiral nano structure chitosan
In the latest \”ACS Nano\” magazine, from the University of British Columbia, Canada, Finland, Aalto University, Nanjing Forestry University researchers composed of an international team to achieve the chitin nanocrystals (chitin nanocrystal) has a straight rod-like structure of the novel the controlled preparation and freezing transmission electron microscope (Cryogenic-TEM, cryo-TEM) combined with electron tomography (electron tomography, ET) technique, finely resolved reconstructed its chiral structure. The study demonstrated the ultra-low temperature freezer electron microscopy and computer-aided simulation of natural renewable prospect structural characterization of polymer materials in fine, providing better help for the development of new green materials. Papers entitled \”Chirality from Cryo-Electron Tomograms of Nanocrystals Obtained by Lateral Disassembly and Surface Etching of Never-Dried Chitin\” 
It is well known cellulose nanocrystals (CNC) a rod having a spindle-shaped morphology. In a typical preparation of chitin nanocrystals acid hydrolysis process, the spindle and CNC similar appearance are also common. In this study, University of British Columbia Prof. Orlando J. Rajas group on the basis of a conventional method for preparing the acid hydrolysis, acetylation surface adjustment introduced before acid hydrolysis (FIG. 1), may be imparted to the ionizable hydrophobic amino chitin fiber tufts surface, positively charged surface of the fiber tufts with the acid hydrolysis characteristics. This fiber cluster structure with a charge spontaneously formed clusters with cluster and internal electrostatic repulsion cluster, therefore, easier to penetrate acid molecule into the interior of chitin clusters, so that the compact arrangement of the clusters can easily occur laterally off assembled (FIG. 2). Meanwhile, the enhanced surface cationized fiber surface hydrophilicity chitin certain extent, so that it can be more uniform etching acid molecules, facilitate the formation of a straight rod chitin nanocrystalline structure. As the University of British Columbia, the first author of the paper Dr. White Dragon said, \”requires only a simple pretreatment process, a huge change natural polymer chitosan nanoparticles on the morphology can be achieved, this is a very in-depth study to explore scientific phenomena.\”
In this study, the successful use of cryo-electron microscope provides a strong support for straight rod Morphological characterization chitin nanocrystals. As we all know, biomass materials are susceptible to damage from the electron beam in the electron microscope, it makes it difficult to direct observation. Finnish researchers after exploration Alto, mirror sample preparation process and the electrical parameters observed are optimized, to achieve a good in-situ observation of the natural polymer material. After cryo Chitin obtained nanocrystals in an electron beam at different angles, by electron tomography it is reconstructed three-dimensional model, which in turn can be finely resolved microstructure and the inherent structural features (FIG. 3). Studies have shown that the obtained nanocrystals straight rod having no significant chiral structure, i.e. it does not have a single nanocrystal torsional characteristics. This does not have a chiral structure having a straight rod chitin nanocrystals over the prospects in the development direction of the special purpose materials such as spun-type alignment, optical devices and the like. At the same time, the study also demonstrates the feasibility of cryo-electron tomography natural polymer materials in the field of biomass, to provide technical support for further analysis of the characteristics of biomass based nanomaterials, enrich their cognitive structure.
The full text link: https://pubs.acs.org/doi/abs/10.1021/acsnano.0c01327
