Exam1-2006Key - _ Name (Last, First) BIO 361 _ SOLAR ID...

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__________________________________ _____________________________________ Name (Last, First) SOLAR ID 1 BIO 361 EXAM 1 FALL 2006 VERSION 1 NAME:_________________________________________________ ID:_____________________________________________________ 1. Write Your name and ID on all pages 2. Write all answers in pen only 3. Make sure your exam has six pages including this cover page Page 2 _______________ Page 3 _______________ Page 4 _______________ Page 5 _______________ Page 6 _______________ Extra Credit _______________ Total _______________ Maximum of 104 points + 5 points extra credit
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__________________________________ _____________________________________ Name (Last, First) SOLAR ID 2 A. You have been given four samples, one of which is pure phenylalanine (F), one of which is pure arginine (R), one of which is pure glutamic acid (E), and one of which is a pure tripeptide, lys-trp-asp (K- W-D). You are going to perform some tests on these samples. Indicate which of the three samples will give the result described with each test (you may use the single letter codes). The possible answers include one of the samples (identify by one-letter code), more than one of the samples (indicate which), or none of the samples (if none of the samples would give the result, write NONE). ____KWD__ 1. This sample emerges first from a column of highly crosslinked dextran gel beads (Sephadex beads). Sephadex (dextran beads) have channels into which low MW molecules penetrate, retarding their mobility on the column. The tripeptide is largest and emerges first. _____R____ 2. This sample emerges first from an anion-exchange column of DEAE-cellulose eluted with pH 8.0 buffer. This column contains fixed positive charges. The most positively charged molecule in the group is the amino acid arginine; it will not stick to the column. __F,KWD__ 3. This sample fails to move to the anode or cathode when electrophoresed at ~pH 6.5. Only molecules with an equal number of positive and negative charges will remain at the origin in an electrophoretic field. Both Phe (which has no ionizable side chain) and Lys-Trp-Asp- (which has one ionized ε -amino group and one ionized γ carboxyl group) have one ionized α -amino group and one ionized α - carboxyl group each. They will not move in the electrophoretic field. B. You have been given a synthetic peptide (not derived by proteolytic fragmentation of a protein) which is known to have activity against human mast cells, resulting in release of histamine. Your job is to sequence and characterize the peptide as much as possible. The amino acid composition of the peptide is: Gly 3 ,Arg 2 ,Leu 2 ,Met,Tyr, You find that reaction of the starting peptide with dansyl chloride followed by acid hydrolysis to individual amino acids yields DNS-Gly (the assay gives only qualitative information – not how much of each dansylated amino acid you obtain). You try to digest the peptide with
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Exam1-2006Key - _ Name (Last, First) BIO 361 _ SOLAR ID...

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