Chem. 156 HW#5 5.1) Equilibrium Dialysis: A dialysis bag whose volume is 100 ml contains 10-4 moles of a monomeric protein. The dialysis bag is placed in a dialysis reservoir whose volume is 900 ml. Then 10-3 moles of a ligand, A, is added to the system and allowed to equilibrate between the inside and the outside of the bag. At equilibrium, the concentration of the ligand outside the bag is found to be 8.5 ·10-4M. Calculate the binding, v. [You may assume that there are no volume changes inside or outside the bag.] 5.2) Suppose you’re studying an octameric protein complex (with 8 identical and independent binding sites). You measure the binding when [A] = 0.1M and find that on average there are 7 ligands bound per octamer. What is the value of the association constant, K? [You can do this algebraically if you wish]. Include your units. 5.3) The following binding data are recorded for an oligomeric protein that binds some ligand: [ligand] (mM) 10 30 %saturation 20.0 64.4 a) Estimate the Hill coefficient. b) What does your answer to part a) tell you about the behavior of the protein? What does is suggest about the number of subunits present in the oligomer? 5.4) You are studying a trimeric enzyme that binds its ligand cooperatively according to the MWC model. Suppose the value of L is 1000, and the concentration of the ligand is such that K[A]=10. a) Prepare a table to show the values of the weights and degeneracies of the five possible states of the trimer (T, R0, R1, R2, and R3). b) Calculate the probabilities of finding a protein trimer in each of the five states. P(T)= P(R0)= P(R1)= P(R2)= P(R3)= Homework problem 5.5) These are a few of the protein structures determined in my lab in recent years. Determine the point group symmetries of the four structures. For the purposes of assigning symmetry, ignore differences in coloring between subunits. In the examples at the top right and bottom left, only the top half of the subunits are shown to avoid confusion. In these two cases, (A) name the symmetry of the group of subunits shown, and (B) the symmetry you expect for the complete assembly (including the other subunits that are not shown). A six subunit hexamer from the carboxysome shell. 5.6) Draw subunits (using the letter “5”) on the sides of the pentagonal prism below in a way that would obey D5 symmetry. You may choose to omit any subunits that would be hidden in the back. Draw in one of the two-fold axes of symmetry, making it clear where it would pass through the assembly.