Electron Microscopy

Question 1

Compare light and electron microscopes

Answer 1

Question 2

What is the Rayleigh criteria

Answer 2

Question 3

What is the relationship between the resolution limit and wavelength

Answer 3

Question 4

What is meant by resolution

Answer 4

Question 5

What are the properties of electrons

Answer 5

Question 6

What could happen when an electron encounters an atom

Answer 6

Question 7

What different sources can be used in an electron microscope

Answer 7

Thermionic emission source
Field emission gun

Electrons emitted by source

Question 8

What is a thermionic source

Answer 8

Question 9

What is a field emission gun

Answer 9

Question 10

What does the electromagnetic lens do in an electron microscope

Answer 10

Question 11

What three types of lenses are there in an electron microscope

Answer 11

Question 12

What are apertures

Answer 12

Question 13

How were images recorded in the past

Answer 13

Question 14

What is a charged coupled device

Answer 14

Question 15

What is a direct electron detector

Answer 15

Question 16

Label the different parts of an electron microscope

Answer 16

Question 17

Describe the pathway of the e- beam in EM to generate an image

Answer 17

Question 18

What are the 2 types of contrast

Answer 18

Amplitude contrast
Phase contrast

Due to electron wave-particle duality

Question 19

What is amplitude contrast

Answer 19

Question 20

What are the 3 factors that contribute to amplitude contrast

Answer 20

Question 21

What is phase contrast

Answer 21

Question 22

How does a complex wave propagate

Answer 22

Question 23

Why is the amplitude of the scattered complex waves small

Answer 23

Question 24

What happens when the scattered and in scattered waves encounter the objective lens of an EM

Answer 24

Question 25

What are the threes ways in which the small amplitude of the scattered wave can contribute to the unscattered wave

Answer 25

Maximally in the opposite direction of the unscattered wave Minimally to the unscattered wave Maximally in the same direction of the scattered wave

Question 26

How can the small amplitude of the scattered wave can contribute to the unscattered wave maximally in the opposite direction

Answer 26

(Detector sees sum of scattered and unscattered wave)

Question 27

How can the small amplitude of the scattered wave can contribute to the unscattered wave minimally to the scattered wave (edit)

Answer 27

Question 28

How can the small amplitude of the scattered wave can contribute to the unscattered wave maximally in the same direction

Answer 28

Question 29

How can defocusing the objective lens create contrast

Answer 29

Question 30

What are spherical aberrations

Answer 30

Question 31

What is the CTF

Answer 31

Question 32

Why does the CTF need to be corrected

Answer 32

Question 33

How can a phase plate be used for defocus imaging

Answer 33

Question 34

What happens once images are obtained from EM

Answer 34

Question 35

What happens after negative staining imaging to obtain a model

Answer 35

Question 36

What happens in cryo-EM to obtain accurate models

Answer 36

Question 37

What is defocus estimation

Answer 37

Question 38

Why are particles selected in cryo EM

Answer 38

Question 39

How can selected particles be classified using 2D classification

Answer 39

Question 40

What 2D classification be used to do

Answer 40

Question 41

What is projection theorem used for

Answer 41

Question 42

How can orientation parameters be defined

Answer 42

Question 43

What can projection matching be used for

Answer 43

Question 44

What is meant by iterative refinement

Answer 44

Question 45

What is 3D classification What can classification be used for

Answer 45

Question 46

What are the downfalls of EM

Answer 46

Question 47

Why can noise in EM images result in inaccurate models

Answer 47

Question 48

Why my inaccurate structures still be obtained even after improving the signal to noise ratio What is model bias

Answer 48

Question 49

What could over refinement of particles lead to

Answer 49

Question 50

Give an overview of cryo-EM

Answer 50

Question 51

What does EM allow for in imageing of a sample

Answer 51

Size Range Quantity Environment Complexity and heterogeneity

Question 52

What does it mean when EM allows for imaging of sample in terms of size

Answer 52

Question 53

What does it mean when EM allows for imaging of sample in terms of range

Answer 53

Question 54

What does it mean when EM allows for imaging of sample in terms of quantity

Answer 54

Question 55

What does it mean when EM allows for imaging of sample in terms of environment

Answer 55

Question 56

What does it mean when EM allows for imaging of sample in terms of complexity and heterogeneity

Answer 56

Question 57

What is the goal of sample preparation

Answer 57

Question 58

What are the two sample prep techniques for the 2 types of EM

Answer 58

Question 59

What is the characteristics of the EM grid

Answer 59

Question 60

Explain the negative staining drop to drop method

Answer 60

Question 61

How is the sample loaded into the electron microscope in negative staining

Answer 61

Question 62

What are the advantages of negative staining

Answer 62

Question 63

What are the disadvantages of negative staining

Answer 63

Question 64

What is the first step of cryo-EM

Answer 64

Question 65

What is the second step of cryo-EM

Answer 65

Question 66

What are the different types of ice

Answer 66

Question 67

What is the major challenge for cryo-EM

Answer 67

Driving force for this difficulty is the air-water interface (where surface of suspended liquid meets air )

Question 68

What could happen at the air-water interface

Answer 68

Question 69

How can the effect of the air-water interface be reduced

Answer 69

Question 70

How is the sample loaded in cryo-EM + what factors need to be controlled

Answer 70

Question 71

Why is low dose imaging used to image the sample in cryo-EM

Answer 71

Question 72

What three modes does low-dose imaging cycle through in cryo-EM

Answer 72

Question 73

How do you calculate the amount of in elastic scattering through an electron microscope

Answer 73

10–20% of electrons undergo inelastic scattering, depending on the material and conditions. So do percentage of total e- suppled to calculate amount of e- inelastically scattered

Question 74

What factors can influence the orientation of particles in ice for cryo EM

Answer 74

The speed at which the sample is frozen pi of the protein