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Concentration Ratio of protein

  1. Jun 7, 2014 #1
    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. jcsd
  3. Jul 2, 2014 #2
    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?
  4. Jul 2, 2014 #3
    sorry, I still couldn't find out anything more, wish I knew anything new.

    deeply sorry.
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