# Concentration Ratio of protein

1. Jun 7, 2014

### mimocs

Myoglobin is a globular protein, with molar mass m ≈ 17,000g/mole. The buoyant correction typically reduces m to m' ≈ 0.25m. Calculate the concentration ratio of the protein at the top of a 4 cm test tube and that at the bottom.

Here, m' stands for effective mass.

I tried as below.

I used the equation of buyoancy so that the effective mass reduce into 0.25m.

m'g = (ρ-ρ')Vg = 0.25mg = 0.25ρVg
(ρ is the density of myoglobin, and ρ' is the density of water)
→ 0.75ρ = ρ'

So since ρ > ρ', I think the myoglobin should sink to the bottom of the test tube.

As a result, the concentration of myoglobin at the top is 0 and let the concentration of the bottom is M.

Then, concentration ratio of bottom and the top becomes 0 / M which gives me 0.

However, I don't think my answer is reasonable.
Why does the problem give me the molar mass?

I hope anyone could ever help me.

2. Jul 2, 2014

### Greg Bernhardt

I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?

3. Jul 2, 2014

### mimocs

sorry, I still couldn't find out anything more, wish I knew anything new.

deeply sorry.