PracticeExam2_key - Name_KEY_ EID_ CH n339K Exam 2 17 June...

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Name_____________ KEY ____________________________ EID__________________________________________ 1 CH n339K Exam 2 17 June 2008 125 points total 15 pts. 1 . a . Draw the peptide ATLDAK + H 3 N N H H N O O O N H H N O O N H COO - CH 3 CH OH CH 3 CH 2 CH CH 3 CH 3 CH 2 COO - CH 3 CH 2 CH 2 CH 2 CH 2 NH 3 + Ala Thr Leu Asp Ala Lys 10 pts. b . What is the net charge of this peptide at pH = 7.0? 0 (as drawn above) 10 pts. c . On the isoelectric focusing gel shown below, estimate where you would expect this peptide to migrate (draw in the band on the gel): If you draw out the titration of this peptide to figure out the net charge after each of the 4 ionizations, you would find that the isoelectric species (neutral species) exists between the ionization of the Asp side chain (pK dn = 3.65 from Table 3-1) and the α -amino group of the first amino acid (Ala; pK dn = 9.69 from Table 3-1). Thus, pI = (3.65 + 9.69)/2 = 6.7 2 . You have two different ion exchange column chromatography matrixes in your laboratory, diethylaminoethyl (DEAE) and carboxymethyl (CM). The covalently bound groups on these two matrixes are : DEAE: —CH 2 —CH 2 —N + H(CH 2 —CH 3 ) 2 CM: —CH 2 —COO - 5 pts. a . In what order would the amino acids Arg, His, and Leu be eluted from the carboxymethyl column at pH 6? Leu, His, Arg
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This note was uploaded on 11/25/2009 for the course CH 53890 taught by Professor Raymonds during the Spring '09 term at University of Texas at Austin.

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PracticeExam2_key - Name_KEY_ EID_ CH n339K Exam 2 17 June...

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