Protein Structure Analysis | Protein Electron Microscopy

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Proteins serve as the primary molecular machinery of life, maintaining the functional order of our cells. As their structure informs their function, accurate determination of structural information is the basis of biological insights for any number of physiological, pharmaceutical, and biomaterial advances.

Cryo-electron microscopy (cryo-EM) is an established method for the determination of 3D structural information for a wide range of biomolecules, including proteins and protein complexes.
Until recently, proteins had to be crystallized to reconstruct and visualize them with X-ray crystallography. This information came with several stipulations; crystallization is time consuming and can typically only work on single purified protein (monomers or dimers); additionally, some proteins do not crystallize. Finally, the structure has to be determined outside of the cellular environment, removing vital contextual information.

Cryo-EM, which is comprised of several applications like single particle analysis (SPA), cryo-electron tomography (cryoET), and micro electron diffraction (MicroED), has revolutionized the study of proteins, their complexes, and their dynamics.

Single particle analysis (SPA) – Images and analyzes small (<250kDa) and intermediate sized proteins (>250kDa) as well as large protein complexes with high throughput and high resolution.
Cryo tomography (cryoET) – Ideal for the analysis of cellular components and fractions at intermediate resolutions. It provides cellular context to the macromolecular structures determined with single particle analysis.
Micro electron diffraction (MicroED) – Suited for structural determination of small sub-750-nm protein crystals, a unique class of crystals that cannot be analyzed by traditional X-ray crystallography.

GABA receptor protein within a lipid nanodisk, generated with cryo electron microscopy.

3D reconstructions of the GABA receptor membrane protein in a nanodisk, bound to the drug Ro-15-4513. Displayed resolution is 2.75 Å. Data collected on a Krios Cryo-TEM with the Falcon 4 Detector. Images Courtesy of Simonas Masiulis, Radu Aricescu, MRC-LMB Cambridge and Evgenia Pechnikova, Abhay Kotecha, Thermo Fisher Scientific.

Granulin protomer structure generated by micro electron diffraction.

Granulin protomer (29 kDa) structure generated by cryo electron microscopy (MicroED) with atomic-resolution detail visible.

Applications

Structural Biology Research

Cryo-electron microscopy enables the structural analysis of challenging biological targets such as large complexes, flexible species and membrane protein.

Infectious Disease Research

Cryo-EM techniques enable multiscale observations of 3D biological structures in their near-native states, informing faster, more efficient development of therapeutics.

Drug Discovery

Learn how to take advantage of rational drug design for many major drug target classes, leading to best-in-class drugs.

Techniques

Single Particle Analysis

Single particle analysis (SPA) is a cryo-electron microscopy technique that enables structural characterization at near-atomic resolutions, unraveling dynamic biological processes and the structure of biomolecular complexes/assemblies.

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Cryo-Tomography

Cryo-electron tomography (cryo-ET) delivers both structural information about individual proteins as well as their spatial arrangements within the cell. This makes it a truly unique technique and also explains why the method has such an enormous potential for cell biology. Cryo-ET can bridge the gap between light microscopy and near-atomic-resolution techniques like single-particle analysis.

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MicroED

MicroED is an exciting new technique with applications in the structural determination of small molecules and protein. With this method, atomic details can be extracted from individual nanocrystals (<200 nm in size), even in a heterogeneous mixture.

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Single Particle Analysis