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Homework Help: Hill's equation and plot-Biochem

  1. Nov 23, 2008 #1
    1. The problem statement, all variables and given/known data

    The binding of a ligand B to a protein is studied. The protein concentration it 10^-3 M. The amounts bound,b, for each added is given as the following:

    (M) (b)(M)
    .001 5*10^-6
    .002 3.3*10^-3
    .005 3.78*10^-3
    .007 4.72*10^-3
    .01 4.95*10^-3
    .02 5*10^-3
    .05 5*10^-3

    Find if it is cooperative, the number of binding sites, and K_d

    2. Relevant equations

    The hills equation can be expressed as log Y/(1-Y) =n log [A] - log K_d

    3. The attempt at a solution

    So the y intercept is - log K_d and the slope is n when you plot the left side in respect to log [A]. Y is the fractions filled, so I think it would be (b)/(5*10^-3). But, plotting the graph.. it seems a little screwy.. the plot goes from slope of 10.9 to .5 then to ~5.. The graph is shown here.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Nov 24, 2008 #2


    User Avatar
    Homework Helper
    Gold Member

    If it were I could probably help, but I can't see it.:confused:

    Possible sources of confusion:
    1) [A] in your equation is concentration of free A in solution, did you calculate that?;
    2) That's enough possible sources of confusion till I see your graph. :tongue:

    And to make it easier for us and yourself put also the free A in a table with the other parameters.
    Last edited: Nov 24, 2008
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