This set of Bioseparation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Precipitation using Anti-Chaotropic Salts”.

1. The increase in protein solubility with the increase in salt concentration is ___________

a) Salting in

b) Salting out

c) Chaotropic salt precipitation

d) Anti-chaotropic salts precipitation

View Answer

Explanation: The solubility of proteins in the presence of such salts depend on the salt concentration and the increase in protein solubility with increase in salt concentration is salting in effect and these salts provides a distinct electrostatic double layer surrounding the proteins. The presence of double layer provides the stability needs to keep the protein molecules in solution and increases the solubility.

2. What is the critical size of growth of particles for fluid motion?

a) 0.5 μm

b) 1.0 μm

c) 1.5 μm

d) 2.0 μm

View Answer

Explanation: 1.0 μm is the critical size of growth of particles for motion in fluid and such growth regime is responsible for the growth of particles by colliding and sticking together. This process of growth through collision is called flocculation and it is an enhanced process in which the electrostatic repulsion of particles is reduced in comparison to the attractive van der Waals force.

3. Which rate equation can describe the collision in particles for particles of uniform size in suspension?

a) Zero order reaction

b) First order reaction

c) Second order reaction

d) Pseudo first order reaction

View Answer

Explanation: The second order reaction is used to describe the collision of particles of uniform size in a suspension which leads to initial rate of decrease of particles number concentration. It favours raising the ionic strength and lowering the temperature to reduce the thickness of the electrical double layer or debye length around the particles.

4. What is the equation used to express the second order reaction for particles of uniform size?

a) \(\frac{dN}{dt}\) = \(\frac{2}{3}\) αL^{3} γN^{2}

b) –\(\frac{dN}{dt}\) = αL^{3} γN^{2}

c) –\(\frac{dN}{dt}\) = \(\frac{2}{3}\) αL^{3} γ

d) –\(\frac{dN}{dt}\) = \(\frac{2}{3}\) αL^{3} γN^{2}

View Answer

Explanation: –\(\frac{dN}{dt}\) = \(\frac{2}{3}\) αL

^{3}γN

^{2}is the equation for second order reaction which is derived by Smoluchowski where, α is collision effectiveness factor i.e. fraction of collisions that result in permanent aggregates, L is the diameter of the particles and γ is the shear rate i.e. velocity gradient.

5. What will be the modified second order rate reaction equation, if volume fraction of the particles is assumed to be constant?

a) \(\frac{N}{N_0}\) = exp\((\frac{-4\alpha \varphi \gamma t}{A})\)

b) –\(\frac{N}{N_0}\) = exp\((\frac{-4\alpha \varphi \gamma t}{A})\)

c) \(\frac{N}{N_0}\) = \((\frac{-4\alpha \varphi \gamma t}{A})\)

d) –\(\frac{N}{N_0}\) = \((\frac{-4\alpha \varphi \gamma t}{A})\)

View Answer

Explanation: When the volume fraction of the particles is constant during the particle growth is governed by fluid motion, the equation tends to be –\(\frac{dN}{dt}\) = \(\frac{4}{\pi}\)αφγN, after integration the final equation comes to –\(\frac{N}{N_0}\) = \((\frac{-4\alpha \varphi \gamma t}{A})\) where, N

_{0}is the particle number concentration at time t = 0 at which the particle growth starts to be governed by fluid motion, φ = πL

^{3}N/6, L is the diameter of the particle.

6. Who developed equation for turbulent flow with average rate of shear?

a) Flick

b) Camp and Stein

c) Kick

d) Smoluchowski

View Answer

Explanation: Camp and Stein developed equation for turbulent flow with average rate of shear is γ. The scientists assumed that the axial stretching can be eliminated by rotation of axes so that a differential volume element is in pure shear.

7. Which equation is known as Camp and stein equation?

a) γ = –\((\frac{P/V}{\rho v})^{1/2}\)

b) γ = \((\frac{P/V}{\rho v})^{1/3}\)

c) γ = \((\frac{\frac{P}{V}}{\rho v})^{\frac{1}{2}}\)

d) -γ = \((\frac{P/V}{\rho v})^{1/2}\)

View Answer

Explanation: γ = \((\frac{\frac{P}{V}}{\rho v})^{\frac{1}{2}}\) is known as Camp and Stein equation in which \(\frac{P}{V}\) is power dissipated per unit volume, ρ is density and v is kinematic viscosity of the liquid.

8. A salt was used for the process of precipitation of antibody having 20 l of media. The initial concentration of the antibody is 2 mg/ml meanwhile another salt was added to the solution which makes the salt concentration to 2.5 kg-mole/m^{3}. The precipitation of antibody becomes 80%. As soon as the concentration of first salt was raised to 2.75 kg-mole/m^{3} and the remaining precipitation is 68%, so find out the solubility of the antibody in the aqueous solution of first salt.

a) 3.5 × 10^{-21} kg – \(\frac{mole}{m^3}\)

b) 3.5 × 10^{21} kg – \(\frac{mole}{m^3}\)

c) 5.25 × 10^{-21} kg – \(\frac{mole}{m^3}\)

d) 7.5 × 10^{-21} kg – \(\frac{mole}{m^3}\)

View Answer

Explanation: The concentration of antibody after the 2.5 M of first salt precipitate is 0.4 mg/ml = 1.6 × 10

^{-6}kg – mole/m

^{3}and the concentration of antibody after 2.75 M ammonium sulphate precipitation is 0.128 mg/ml = 4.65 × 10

^{-5}kg – mole/m

^{3}. Using eq. ln(S) = B – K

_{s}C

_{s}, so ln(1.6 × 10

^{-6}) = B – K

_{s}× 2.5 and ln(4.65 × 10

^{-5}) = B – K

_{s}× 2.75 and B = -47.1. ln(B) = S ∴ S = 3.5 × 10

^{-21}kg – \(\frac{mole}{m^3}\).

9. Salt induced precipitation is usually carried out at low temperature.

a) True

b) False

View Answer

Explanation: Salt induced precipitation is usually carried out at low temperatures mainly 4°C and it primarily is due to the fact that the solubility of proteins decreases with the drop in temperatures and hence more proteins can be precipitated by such action.

10. Which approaches are applicable when ammonium sulphate is used as a precipitating agent?

a) addition of ammonium sulphate solution

b) addition of solid ammonium sulphate

c) addition of solid ammonium sulphate, addition of ammonium sulphate solution

d) addition of sample in ammonium sulphate

View Answer

Explanation: The two approaches used for precipitation when ammonium sulphate is used a s a precipitating agent are: direct addition of solid ammonium sulphate, addition of ammonium sulphate solution in the sample. The first approach is used in small scale applications and it suffers from the unevenness of ammonium sulphate concentration in the precipitating medium caused due to salt dissolution. The second approach is used in most of the protein precipitation processes.

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