Ligand Binding: Answer Sheet Example

Example Problem:

You are given a 4.0 mg/ml solution of a protein (M_r = 40,000 Da).
You do an equilibrium dialysis experiment at several concentrations of L_total.

a) Determine K_d and the stoichiometry of its binding to a ligand, L.

b) Submit your calculations and a graph of n/L. vs. n.

What we know from the problem:

1) Concentration of the protein = 4.0 mg/ml.

2) Protein M_r = 40,000 Da

What we found in the experiment:

 0.010
 0.020
 0.050
 0.075
 0.100
 0.150
 0.200
 0.400
 0.700
 1.000

0.005
0.011
0.029
0.045
0.061
0.103
0.142
0.333
0.625
0.901

0.005
0.009
0.021
0.030
0.039
0.047
0.058
0.067
0.075
0.099

0.05
0.09
0.21
0.30
0.39
0.47
0.58
0.67
0.75
0.99

10.00
 8.18
 7.24
 6.67
 6.39
 4.56
 4.08
 2.01
 1.20
 1.10

The above Scatchard plot was used as an example in the Lecture 12 handout, Ligand Binding Curves

Binding.xls is the Excel spreadsheet used to calculate and graph these results; it can be copied to your disk.