Summary
Methods to determine atomic structures of biomolecules from diffraction or electron images.
In depth
Crystallography needs protein crystals and measures diffraction (DNA double helix, haemoglobin). Cryo-EM flash-freezes samples and images thousands of particles, resolving structures down to near 1.2 Å (Nobel 2017).
X-ray needs well-ordered crystals; cryo-EM can handle large, flexible complexes. Both give electron density maps into which atomic models are built. Resolution affects detail.
Key idea: structures reveal how drugs bind and how mutations alter function.
Structural biology determines the arrangement of atoms in biomolecules. In X-ray crystallography, a purified protein is crystallised and X-rays diffracted by the crystal form a pattern from which electron density and a model are calculated; it gave the structures of DNA, myoglobin and ribosomes.
In cryo-electron microscopy, samples are flash-frozen in thin ice and imaged with an electron microscope; thousands of particle images are averaged to give a 3D map, now at near-atomic resolution without crystals. Cryo-EM won the 2017 Nobel Prize and suits large complexes and membrane proteins. NMR is another method for small proteins in solution.
Example: cryo-EM showed the spike protein of SARS-CoV-2.
Frequently asked questions
What is X-ray Crystallography and Cryo-EM?
Methods to determine atomic structures of biomolecules from diffraction or electron images.
Which area of biology covers X-ray Crystallography and Cryo-EM, and how advanced is it?
X-ray Crystallography and Cryo-EM is one of the 56 topics in Biotechnology & Genomics. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Protein Structure Prediction, Machine Learning in Biology, CRISPR Base and Prime Editing.
Why does X-ray Crystallography and Cryo-EM matter?
Structures guide drug design.
Can you give an example of X-ray Crystallography and Cryo-EM?
Cryo-EM revealed the spike protein of SARS-CoV-2 early in the pandemic.
What should I learn before X-ray Crystallography and Cryo-EM?
Work through the Beginner topics in Biotechnology & Genomics first, such as Biotechnology, Genetic Engineering, Selective Breeding, then return to X-ray Crystallography and Cryo-EM. Advanced topics assume the Intermediate vocabulary.
What topics are related to X-ray Crystallography and Cryo-EM?
The closest topics to X-ray Crystallography and Cryo-EM are Protein Structure Prediction, Machine Learning in Biology, CRISPR Base and Prime Editing, Functional Genomics. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand X-ray Crystallography and Cryo-EM?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for X-ray Crystallography and Cryo-EM. To practise the whole of Biotechnology & Genomics, use the Biotechnology & Genomics quiz.
How is X-ray Crystallography and Cryo-EM different from Protein Structure Prediction?
X-ray Crystallography and Cryo-EM: Methods to determine atomic structures of biomolecules from diffraction or electron images. Protein Structure Prediction: Deep-learning systems like AlphaFold predict 3D protein structures from amino acid sequences. Read both side by side and note what each one explains.
How should I study X-ray Crystallography and Cryo-EM step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Protein Structure Prediction and explain the difference aloud. Finally, take the Biotechnology & Genomics quiz and come back to this page for any question you miss.