1. Researchers isolated a monomeric protein from platelets that has 2 binding sites (A and B) for ADP; Site A's Ka is 157 μM, and Site B's Kd is 2.2 μM. 1.1. A) Which binding site has higher affinity for ADP? B) Briefly justify your answer. C) For this higher affinity site, calculate the standard free energy change for ADP binding. Show your work. 1.2. What concentration of ADP is required to get site A filled in 20% of the proteins? 1.3. Based on this information, sketch a graph of the fraction of site B filled as a function of [ADP].

2B. S. aureus hemolysin B attacks the RBC cell membrane by hydrolyzing the sphingomyelin headgroup: ОН HN .R hemolysin B cuts this bond i) Draw a plausible mechanism of hydrolysis for this lipid headgroup. Let B- and BH be general base and general acid. 00-P-O LOR2 OR, ii) Why is this damaging to the overall membrane architecture of the RBC?

8) A Leu > Ala mutation at a site buried in the core of the enzyme lysozyme ends up being destabilizing. Explain why in terms of AH", AS" (for both the protein and solvent), and AG".

6. Consider the following proteins to answer the questions below: Protein Size (kDa) pl ε at 280 nm 10 4 7000 50 4 14000 10 8 3000 50 8 50000 A B C C Red Colored? Yes No No No b. Describe a two-step purification procedure that could be used to purify/isolate protein A from the other proteins. In your response, describe the type of chromatography used, the pH of buffer needed, and a labeled chromatogram (include absorbances at both 280 and 400 nm). Make sure you note which "fraction/sample" is needed from the first step to proceed/use for the second step. Use another page if necessary.