Sample preparation for cryogenic electron microscopy (cryo-EM) is a demanding and often expensive process, requiring several purification and screening steps to obtain a suitable specimen. Negative stain electron microscopy (EM) is one of the widely accepted sample preparation techniques for the initial screening of purified samples, and specifically for the assessment of pathology, morphology, concentration and agglomeration. Traditionally, a conventional transmission electron microscope (TEM) is used for this purpose. With the introduction of the desktop scanning transmission electron microscope (STEM), an alternative solution for screening samples has been developed that is much faster and more cost-effective than traditional methods.
Sample preparation for Cryo-EM
Cryogenic electron microscopy (cryo-EM) has become an invaluable tool in the field of structural biology, allowing researchers to visualize three-dimensional structures from 2D images at different orientations using advanced computational techniques at near-atomic resolution.
Cryo-EM is a labour-intensive and time-consuming technique that requires highly specialized skills. A crucial tool in sample preparation for (3D) TEM is the ultramicrotome.
A typical exponent of this technology, the RMC Boeckeler ATUMtome (Automated Tape Collecting Ultramicrotome) is capable of fully automatically producing hundreds to thousands of slices of several tens of nanometers thickness. This responds to the clear evolution from 2D to 3D (cryo)- EM. An interesting application note related to this is the imaging of mitochondrial protrusions in neuronal cells.
Read the Application Note here
Good Cryo-EM results also depend on the very high quality of the purified samples. Before a sample is vitrified for high-resolution imaging, it is usually screened to ensure that it is suitable for imaging and contains the expected dimensions and morphologies.
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