Question

500µg of lyophilized Cas9 protein is given. A person needs to make a 1µM solution of Cas9 in buffer (20mM HEPES, 150mM KCl, pH7.5). The MW of Cas9 is 1.63x10⁵ g/mol. How much buffer do you have to add to the 500µg of Cas9 protein to make 1µM Cas9 solution?

Answer 1

The mass of the sample provided is 500ug and the concentration desired is 1uM. The MW of the sample is 1.63*10^5 g/mol.

Hence, the number of moles of sample given can be calculated as:

Now the relation between concentration and moles is:

where V is the volume of the buffer that should be added.

Substituting the values, we have:

Hence, 3.07mL of the buffer should be added to get the desired concentration of Cas9 protein.