Question

2. How much DL-Dithiothreitol (DTT), is needed to make 50 mL of a 0.5 M stock solution? 3. What volume of 2-mercaptoethanol is needed to prepare 100 mL of a 0.5 M stock solution? 4. Using the above stock solutions from questions #2 and #3, how would you prepare 250 mL of a solution that is 20 mM in DL-Dithiothreitol and 5 mM in 2-mercaptoethanol?

Answer 1

2) Molar mass of DL-Dithiotheritol (DTT) = 154.25 gm/mol

Molarity = Number of moles of solute/Volume of solution (L)

Number of moles of solute = 50/1000 * 0.5M = 0.025 moles

Mass of DTT required = number of moles * molar mass

=> 0.025 moles * 154.25 gm/mol

=> 3.85625 gm of DTT

3) Molar mass of Mercaptoethanol = 78.13 gm/mol

Molarity = Number of moles of solute/Volume of solution (L)

Number of moles of solute = 100/1000 * 0.5M = 0.050 moles

Mass of Mercaptoethanol required = number of moles * molar mass

=> 0.050 moles * 78.13 gm/mol

=> 3.9065 gm of mercaptoethanol

4) Volume of DTT = 0.02/0.025 * 50 = 40 ml of DTT

Volume of mercaptoethanol = 0.005/0.050 * 100 = 10 ml of mercaptoethanol

Hence the solution is prepared by 40 ml of DTT, 10 ml of mercaptoethanol and 200 ml of water