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Unformatted text preview: s a randomly ordered, non-alpha-helical conformation, under alkaline
conditions (pH > 10). A polymerized sample of the amino acid lysine, containing 100 lysine residues linked sequentially by peptide bonds, exhibits just
the opposite behavior (alpha-helical under alkaline conditions, and non-alpha-helical under acidic conditions). Let’s try to explain this behavior.
a) The side chains of glutamic acid and lysine are -CH2CH2CO2H and -(CH2)4NH2, respectively. How would the pKa’s of these side chains
compare to that of pure water (with a neutral pH of 7)? pKa for glutamic acid is lower than that of water (more acidic) (5 points) pKa for lysine is higher than that of water (more basic) (5 points) b) Under low and high pH conditions, what would be the charge state of these side groups for glutamic acid and lysine? Indicate your
answers in the table as +, – , or uncharged. Low pH Uncharged – + Glutamic acid High pH Uncharged Lysine (5 points per table entry)
c) From the structures of the amino acids and our discussion of forces influencing the conformation of polypeptides, you should now be able
to explain the pH dependent behaviors of the confor...
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This test prep was uploaded on 04/03/2014 for the course CHEM 1b taught by Professor Heath,rees during the Spring '13 term at Caltech.
- Spring '13
- Organic chemistry