Electron cryomicroscopy (aka cryoelectron microscopy) is a developing method in structural biology. Biology material are preserved in a frozen-hydrated state by rapid freezing, usually in liquid ethane near liquid nitrogen temperature. By maintaining specimens at liquid nitrogen temperature or colder, they can be introduced into the high-vacuum of the electron microscope column. Most biological specimens are extremely radiation sensitive, so they must be imaged with low-dose techniques. Consequently, the images are extremely noisy. The low temperature of electron cryomicroscopy provides an additional protective factor against radiation damage.
For some biological systems it is possible to average images to increase the signal to noise ratio and retrieve high-resolution information about the specimen. This approach requires that the things being averaged are identical (e.g. ribosome particles). Analysis of ordered arrays of protein, such as 2-D crystals of membrane proteins or helical arrays of proteins, also allows a kind of averaging which can provide high-resolution information about the specimen.
Once scientists have access to sufficient quantities of proteins for their experiments, they can determine a protein's shape using standard methods involving X-rays, extremely powerful magnets, or specialized forms of microscopy such as cryoelectronmicroscopy.
The magnetized sample is blasted with a series of computer-generated radio pulses that disrupt the alignment in ways that permit scientists to deduce the protein's three-dimensional shape.
Cryoelectronmicroscopy uses electrons and magnets to magnify frozen protein samples, then combines thousands of images in a computer to generate a three-dimensional model of a protein.
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