Question

A lyophilized sample of 20 nanomoles of an oligonucleotide is dissolved in water and the volume of the solution is made up to 200 $\mu$L. The concentration (in $\mu$M) of the oligonucleotide in this solution is _______ (in integer).

Hint:

To find molar concentration: convert nanomoles to moles, divide by volume in liters, then convert molarity to $\mu$M by multiplying by $10^6$.

Answer 1

Step 1: Convert nanomoles to moles.
20 nanomoles = \(20 \times 10^{-9}\) moles. Step 2: Convert solution volume.
200 $\mu$L = \(200 \times 10^{-6}\) L = \(2 \times 10^{-4}\) L. Step 3: Concentration in mol/L.
\[ C = \frac{20 \times 10^{-9}}{2 \times 10^{-4}} = 1 \times 10^{-4}\, \text{mol/L}. \] Step 4: Convert to $\mu$M.
\(1 \times 10^{-4}\, \text{M} = 100\, \mu\text{M}\). But careful: check calculation again — \[ C = \frac{20 \times 10^{-9}}{2 \times 10^{-4}} = 1 \times 10^{-4}\, \text{M}. \] Since \(1\ \text{M} = 10^{6}\ \mu\text{M}\), \[ 1 \times 10^{-4}\, \text{M} = 100\, \mu\text{M}. \] Correction: The integer answer is \(100\ \mu\text{M}\).