DOI: 10.1101/494997Dec 13, 2018Paper

Cryo-EM sample preparation method for extremely low concentration liposomes

BioRxiv : the Preprint Server for Biology
Lige Tonggu, Liguo Wang

Abstract

Liposomes are widely used as delivery systems in pharmaceutical, cosmetics and food industries, as well as a system for structural and functional study of membrane proteins. To accurately characterize liposomes, cryo-Electron Microscopy (cryo-EM) has been employed as it is the most precise and direct method to determine liposome lamellarity, size, shape and ultrastructure. However, its use is limited by the number of liposomes that can be trapped in the thin layer of ice that spans holes in the perforated carbon film on EM grids. We report a long-incubation method for increasing the density of liposomes in holes. By increasing the incubation time, high liposome density was achieved even with extremely dilute (in the nanomolar range) liposome solutions. This long-incubation method has been successfully employed to study the structure of an ion channel reconstituted into liposomes. This method will also be useful for preparing other biological macromolecules / assemblies for structural studies using cryo-EM.

Related Concepts

Carbon
Pharmaceutical Preparations
Food
Ion Channel
Laboratory Procedures
Liposomes
Membrane Proteins
Electron Microscopy
Macromolecule
Lamellar Body

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