Protein Engineering Quiz on “Methods of Protein Crystallization – 2”.
1. Macromolecular crystals are temperature sensitive.
A. False
B. True
Answer: B
Clarification: The above statement is true. Macromolecular crystals are indeed temperature sensitive. They undergo extensive damage after prolonged exposure to radiation.
2. The extent of the diffraction pattern from a crystal is inversely correlated with its degree of internal order.
A. True
B. False
Answer: B
Clarification: The above statement is false. The extent of the diffraction pattern from a crystal is directly correlated with its degree of internal order. The vaster the pattern or the higher the resolution to which it extends, the more structurally uniform are the molecules in the crystal and the more precise is their periodic arrangement.
3. Crystallization of proteins proceeds in two distinct steps. Which are these steps?
A. Solidification and crystallization
B. Crystallization and expansion
C. Growth and solidification
D. Nucleation and growth
Answer: D
Clarification: Nucleation and growth are the two steps in which the crystallization of proteins proceeds. These steps are rather distinct but inseparable. Nucleation is the most difficult problem to address theoretically and experimentally.
4. Nucleation represents which order phase transition?
A. Zero-order
B. Third-order
C. Second-order
D. First-order
Answer: D
Clarification: Nucleation represents a first-order phase transition by which molecules pass from a completely disordered state to an ordered one. Therefore, it is the most difficult problem to address theoretically and experimentally.
5. Which of the following is not a method for creating supersaturation?
A. Salting in
B. Salting out
C. Evaporation
D. Dilution
Answer: D
Clarification: Dilution is not a method for creating supersaturation. It inhibits supersaturation. Salting in, salting out, and evaporation are methods for creating supersaturation.
6. Which of the following does not promote protein crystal formation?
A. Addition of organic solvents
B. Direct mixing of protein and precipitant solutions
C. Altering the temperature
D. Addition of a solubilizing agent
Answer: D
Clarification: The addition of a solubilizing agent does not promote protein crystal formation. The addition of organic solvents, direct mixing of protein and precipitant solutions, and altering the temperature promotes protein crystal formation.
7. Find the odd one out.
A. Removal of water through a membrane
B. Altering the dielectric of the medium
C. Altering the pH
D. Addition of detergent
Answer: D
Clarification: Removal of water through a membrane, Altering the dielectric of the medium, and Altering the pH promote the formation of crystals in protein crystallization. The addition of detergent does not promote protein crystallization. Hence, the addition of detergent is the odd one out.
8. Which of the following does not make the protein solution supersaturated?
A. Addition of salt
B. Change of pH
C. Addition of bridging ions
D. Addition of water
Answer: D
Clarification: The addition of salt, change of pH, and addition of bridging ions make the protein solution supersaturated. The addition of water does not make the protein solution supersaturated.
9. In the sitting drop vapour diffusion method the protein drop is suspended from a coverslip over the reservoir.
A. True
B. False