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University of Houston OO api Exam II Instructor Dr. Briggs Oct. 16,2012 Printed Name LAST, FIRST | (¢ Answer all questions; show all work; 100 points; 50 questions; 2 pts each question, no partial credit. & Multiple choice — Circle the single letter (i.e., a., b., c.,d., or e.) of the most correct answer on the EXAM, then mark it on the Scantron sheet with a #2 pencil. Mark BOTH the exam AND the Scantron sheet!! NOTE: A Ramachandran plot and a periodic table can be found at the end of the exam. 1). Why do antibodies raised against a native protein sometimes fail to bind to the corresponding denatured protein? a). The termini of the unfolded protein bind to antibodies b). The co-factors become unbound from the protein The antigens adopt non-native shapes that are not recognized by the antibodies. . The antigens adopt native shapes that are not recognized by the antibodies. €). The antigens cross-link with the antibodies causing them to precipitate and be unavailable for binding to the protein. 2). You are using ammonium sulfate to purify protein Q (p! =6.0) by salting out from a solution at pH 7.0. How should you adjust the pH of the mixture to maximize the amount of protein Q that precipitates? a). add 100 mL of 3M NaOH , add 100 mL of 3M NaCl 6) adjust it to pH 6 . adjust it to neutral pH. e). adjust it to pH 5 3). If tye.proteins are isoelectric at pH 7.6, they may be separated by PAGE (with NO SDS) if performed at Cpl #76. b). pH=7.6. c). a pH when the net charge on the protein is zero. d). pH 7.6 after denaturation of the protein to expose buried charges. €). none of the above 4). Below is a list of the first 10 residues of the B helix in myoglobin from different organisms. Based on this information, which positions exhibit only conservative substitutions/mutations? Position 2 5 6\7 8 #10 Human I HBQE ML Chicken I H eEgt Alligator J L H ePr Turtle L H EPI Tuna D K LW L Carp FEQGR ERY L Saeed be @,° Sams J (d).)5, 10 i 5). Proteins will normally exhibit minimum solubility in aqueous solutions at a). pH values above pl. b). pH values below pl. —¢). pH=pl d). low salt concentrations. e). pH=pK, 
