Practice MT Ans

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Unformatted text preview: ndicate your reasoning. If your answer is illegible or if there is ANY doubt about your reasoning, “0” points will be awarded. A verbal clarification of your method following exam grading will NOT be considered. You may want to write out your answer in rough and then transfer it to the exam paper. UNFOLDED STATE # H-bonds between H 2O and peptide linkages = 33 x 2 = 66 Ignores groups at the ends of the a-helix which are assumed to maintain their H-bonds with water in the folded state FOLDED STATE # of H-bonds between H2O molecules = 66/2 = 33 # of H-bonds in the α-helix 33 a-helices have 4 less H-bonds than the number of residues Energy required to break H-bonds in the unfolded state Energy required to break H-bonds in the folded state = 66 x 12 = 792 kJ = (33 x 12) + (33 x 15) = 891 kJ Because it requires more energy to break the H-bonds in the final state, the final state is more strongly bonded thus ∆HH-bond ~ -99 kJ (b) Based on ∆HH-bond alone, should the protein fold in water? YES (YES/NO) Question #10 (TUTORIAL Content, 10 points) (a) In an effort to purify histone proteins from nuclear extracts, a biochemist applies a sample of nuclear proteins to a column containing a matrix composed of cellulose derivatized with DNA Following application of the sample in buffer at pH = 7, the column is washed with an NaCl gradient in buffer at pH = 7. What kind(s) of column chromatography is the biochemist using? (i) Cation exchange chromatography Recall that histones are +vely charged at pH =7. (ii) Anion exchange chromatography (iii) Affinity chromatography Histones bind to DNA. (iv) Size exclusion chromatography (b) You are investigating the properties of three monomeric proteins A, B and C, and find: When a mixture of the three proteins is subjected to native polyacrylamide gel electrophoresis, protein C lies nearest the bottom of the gel followed by A, and finally B which lies nearest the top of the gel (the point of sample application) Protein A binds to diethylaminoethylcellulose at pH 5.5 but not at pH 4.5. In 2-D gel e...
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This test prep was uploaded on 04/01/2014 for the course BIOL 201 taught by Professor Chowrira during the Winter '13 term at UBC.

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