Flashcards on Cryo-Electron Microscopy for Structural Biology
Cryo-Electron Microscopy for Structural Biology: A Student Guide
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Cryo-electron microscopy
34 cards
Card 1
Question: What is cryo-electron microscopy (cryo-EM) used for regarding biological samples?
Answer: Imaging biological samples in a hydrated, near-native state by rapid freezing into vitreous ice and observing them at low temperature in a TEM to acce
Card 2
Question: Why is rapid freezing into liquid ethane used in cryo-EM sample preparation?
Answer: Rapid freezing in liquid ethane forms vitreous (non-crystalline) ice that stabilizes the sample in a hydrated state and preserves native structure for
Card 3
Question: Name two reasons cryo-EM is preferred over harsh staining methods.
Answer: It avoids structural changes caused by stains and preserves the sample’s hydrated, native structure.
Card 4
Question: What is the main disadvantage of heavy-atom staining that cryo-EM avoids?
Answer: The stain’s size reduces achievable resolution (to about 20–30 Å) and may alter sample structure.
Card 5
Question: List three types of samples and the cryo-EM approaches used for each.
Answer: Periodic arrangements → 2D electron crystallography (small/membrane proteins <200 kDa); Random arrangements → single particle technique (macromolecula
Card 6
Question: What resolution can 2D electron crystallography typically achieve and what sample size is it suited for?
Answer: Resolution up to ~2.5 Å; suited for small or membrane proteins <200 kDa.
Card 7
Question: What type of samples and resolution range is single-particle cryo-EM aimed at?
Answer: Macromolecular complexes >200 kDa; can reach up to atomic resolution.
Card 8
Question: What is cryo-electron tomography used for and what is its typical resolution limit?
Answer: Imaging large organelles or whole cells (e.g., Golgi, ER); typical resolution is worse than ~4 Å.
Card 9
Question: Why are electrons used instead of visible light in cryo-EM?
Answer: Electrons have a much shorter wavelength (≈0.002–0.004 nm vs. 400–600 nm for visible light), allowing much higher resolution.
Card 10
Question: How does accelerating voltage affect electron wavelength in a TEM?
Answer: Higher accelerating voltage shortens the electron wavelength; typical wavelengths decrease as voltage increases (e.g., 100 kV → 0.037 Å, 1000 kV → 0.0