MCB124_PROBLEM_SET3

MCB124_PROBLEM_SET3 - MCB 124 Protein Stability Enoch...

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Unformatted text preview: MCB 124 Protein Stability Enoch Baldwin PROBLEM SET III page 1 I. PROTEIN STABILITY 1. Stability Measurements and Calculations An enzyme, 100 residues was subjected to an equilibrium thermal unfolding experiment at pH 4.0. The following data were obtained. C Kfold 62 2.6343601 64 1.38607031 66 0.7189229 68 0.36773196 a) What is the T m ? (Hint: do a vant Hoff plot) b) What is H f at T m ?(Hint: do a ....) c) What is S f at T m ? (Hint: dont do a....) d) Using amazing biochemical tricks presently unknown to humans, you determine the cold unfolding transition. The cold T m is 41.8C. Calculate Cp for this protein? ( 4 pts ) 2. Amino Acids and Substitutions 1) Name six amino acid types that you might expect to find in the core of a protein. 2) Name six that you would more likely find on the surface. 3) Name two that would be reasonable in either place. 2. Mutational Effects on Stability Below is a list of substitutions made at various locations in the folded state of a protein a) predict their effects on the free energies of the folded (F) and unfolded state (U) (use "-" for a favorable change, "+" for an unfavorable change, and "o" for no change) b) for each state briefly explain why c) predict the overall change in stability (use same convention as for (a)) and why? 1) Surface Leu->Ala F_____ why?___________________________________________________________ U why?___________________________________________________________ Overall why?_________________________________________________ 2) Buried Leu->Ala F_____ why?___________________________________________________________ U why?___________________________________________________________ Overall why?_________________________________________________ MCB 124 Protein Stability Enoch Baldwin PROBLEM SET III page 2 3) Surface Lys->Leu F_____ why?___________________________________________________________ U why?___________________________________________________________ Overall why?_________________________________________________ 4) Buried Asp->His F_____ why?___________________________________________________________ U why?___________________________________________________________ Overall why?_________________________________________________ 5) Surface Helix Ala->Gly F_____ why?___________________________________________________________ F_____ why?...
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MCB124_PROBLEM_SET3 - MCB 124 Protein Stability Enoch...

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