Question

How much protein will you need to make 100 microlitres of 15 micromolar solution of a 95 kDa protein?

• A. 0.1425 mg
• B. 1.425 mg
• C. 0.01425 mg
• D. 14.25 mg

Hint:

• Use: Mass = Molarity × Volume × Molecular weight
• Convert $\mu$M and $\mu$L carefully!

Answer 1

The Correct Option is A

Concept:
• Molarity \(M = \frac{\text{moles}}{\text{volume (L)}}\)
• Mass = Moles × Molecular weight

Step 1: Converting given values.

• Concentration = 15 $\mu$M = \(15 \times 10^{-6}\) mol/L
• Volume = 100 $\mu$L = \(100 \times 10^{-6}\) L = \(1 \times 10^{-4}\) L
• Molecular weight = 95 kDa = 95,000 g/mol

Step 2: Calculating number of moles.
\[ \text{Moles} = M \times V = (15 \times 10^{-6}) \times (1 \times 10^{-4}) = 1.5 \times 10^{-9} \text{ mol} \]

Step 3: Calculating mass.
\[ \text{Mass} = 1.5 \times 10^{-9} \times 95000 = 1.425 \times 10^{-4} \text{ g} \] \[ = 0.1425 \text{ mg} \]

Step 4: Selecting the correct answer.
Thus, required protein = 0.1425 mg.