1. You are making a potassium phosphate buffer that has 55 mM total phosphate (w

Question

1. You are making a potassium phosphate buffer that has 55 mM total phosphate (weighed out as KH2PO4), 183 mM KCl, and 8 mM dithiothreitol. You need 431 mL of buffer, which will be titrated to pH 55. What volume of a 2 M KH2PO4 stock solution should you add to the flask before diluting it to the final volume for your buffer? Report the volume in mL to the nearest 0.1 mL.

2. Which of the following is not a part of the protein denaturing step?

Heating, Denaturing agent, Reducing agent or cooling.

( I chose reducing agent and it was wrong the first time)

3. What role does sodium dodecyl sulfate play in the SDS-PAGE?

Reducing Agent, Denaturing Agent, Chelating agent or secret agent

Explanation / Answer

(1)

Stock conc = 2M

Desired buffer conc = 55mM = 0.055 M

So, dilution factor = 2/0.055 = 36.36

Assume volume of stock taken as 'x' mL

Final buffer volume = 431 mL

So, dilution factor = 431/x = 36.36

Solving we get:

x = 431/36.36 = 11.85 mL = 11.9 mL

(2)

Cooling is not a part of denaturing proteins. Rest all can denature proteins. Heating proteins to a high temperature causes denaturation. Chemicals such as SDS also act as denaturing agents. Dilsulfide bond reduction also causes denaturation.

(3)

SDS acts as the denaturing agent in SDS-PAGE

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