Pair Distribution Function from Electron Diffraction in Cryogenic Electron Microscopy: Revealing Glassy Water Structure

• Published in: The journal of physical chemistry letters 2020-02, Vol.11 (4), p.1564-1569
• Main Authors: Souza Junior, João Batista, Schleder, Gabriel Ravanhani, Colombari, Felippe Mariano, de Farias, Marcelo Alexandre, Bettini, Jefferson, van Heel, Marin, Portugal, Rodrigo Villares, Fazzio, Adalberto, Leite, Edson Roberto
• Format: Article
• Language: English
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.0c00171

In recent years, cryogenic electron microscopy (Cryo-EM) has revolutionized the structure determination of wet samples and especially that of biological macromolecules. The glassy-water medium in which the molecules are embedded is considered an almost in vivo environment for biological samples. The local structure of amorphous ice is known from neutron- and X-ray-diffraction studies, techniques appropriate for much larger volumes than those used in cryo-EM. We here present a first study of the pair-distribution function g(r) of glassy water under cryo-EM conditions using electron diffraction data. We found g(r) to be between that of low-density amorphous ice and that of supercooled water. Under electron exposure, cubic-ice regions were found to nucleate in thicker glassy-water samples. Our work enables to obtain quantitative structural information using g(r) from cryo-EM.