Lecture 22 - Determination of protein structure

Question 1

Two most important techniques to elucidate the 3D structure of proteins

Answer 1

1. X-ray crystallography
2. Nuclear magnetic resonance (NMR) spectroscopy

Question 2

X-ray crystallography reveals

Answer 2

three-dimensional structure in atomic detail

Question 3

The three components in an x-ray crystallographic analysis are:

Answer 3

1. protein crystal
2. source of x-rays
3. detector

Question 4

X-rays can be produced in a ___________ by accelerating electrons in circular orbits at speeds close to the speed of light

Answer 4

synchrotron

Question 5

______ scatter x-rays

Answer 5

electrons

Question 6

The way in which scattered waves recombine depends only on

Answer 6

the atomic arrangement

Question 7

The image obtained in x-ray crystallography is referred to as the

Answer 7

electron-density map

Question 8

Critical to the interpretation of the electron-density map is its

Answer 8

resolution, which is the number of scattered intensities

Question 9

The basis of NMR is

Answer 9

nucleus spin

Question 10

One-dimensional NMR can resolve

Answer 10

most protons in many proteins

Question 11

Two-dimensional NMR spectrums can be obtained by

Answer 11

nuclear Overhauser enhancement spectroscopy (NOESY)

Question 12

The nuclear Overhauser effect is

Answer 12

an interaction between nuclei that is proportional to the inverse sixth power of the distance between them

Question 13

NMR in solution only works for _______ proteins

Answer 13

relatively small

Question 14

X-ray crystallography requires molecules form

Answer 14

well-organized crystals

Question 15

In a transmission electron microscope (TEM),

Answer 15

a beam of electrons interacts with the specimen to form an image

Question 16

In a scanning electron microscope (SEM),

Answer 16

a beam of electrons scans the sample surface to create an image

Question 17

_______ has been used to study low-contrast samples using the lowest possible electron intensity

Answer 17

Negative staining

Question 18

In negative staining, the sample is embedded in

Answer 18

a film of a heavy-metal salt

Question 19

Advantage of cryo-electron microscopy

Answer 19

Structure remains native and no dehydration is required

Question 20

Limitation of cryo-electron microscopy

Answer 20

Not possible to look at the sample for a long time due to beam damage

Question 21

Vitrification uses

Answer 21

rapid cooling to avoid the formation of ice

Question 22

In cryo-sectioning,

Answer 22

whole cells and tissues are cut into thin sections

Question 23

3D reconstruction process estimates

Answer 23

the unknown orientations and 3D structure at the same time