1) Draw the structures of D-lysine and L-lysine and assign R/S configuration (showing your workings). 2) Draw the predominant ionisation forms of the free amino acid lysine, at pH 1.0, 8.0, and 11.0. pKa values: 2.2 (-COOH), 9.0 (α-NH3+), 10.5 (side-chain). 3) Calculate (showing your workings) the % of the different ionized species that are present in a 1.00 M solution of L-proline at pH = 10.0. pKa values: 1.95 (- COOH), 10.64 (α-NH3*). 4) a) Draw the tripeptide Tyr-Pro-Lys once with a trans peptide bond between Tyr and Pro and once with a cis peptide bond between Tyr and Pro. b) The electrospray ionization mass spectrum (ESI-MS) of the tripeptide you designed in part (a) shows peaks indicative of mono-protonation and di- protonation of the tripeptide. At what values of m/z would these peaks be expected (no fragmentation)? Briefly explain your answer (showing your workings). 5) How could the sequence of Ala-Met-Thr be distinguished from that of Thr-Ala- Met by tandem ESI-MS-MS? Explain in detail. 6) Draw the structures of products from a trypsin-catalysed reaction of Ser-Lys- Ala.

1) Draw the structures of D-lysine and L-lysine and assign R/S configuration (showing your workings). 2) Draw the predominant ionisation forms of the free amino acid lysine, at pH 1.0, 8.0, and 11.0. pKa values: 2.2 (-COOH), 9.0 (α-NH3+), 10.5 (side-chain). 3) Calculate (showing your workings) the % of the different ionized species that are present in a 1.00 M solution of L-proline at pH = 10.0. pKa values: 1.95 (- COOH), 10.64 (α-NH3*). 4) a) Draw the tripeptide Tyr-Pro-Lys once with a trans peptide bond between Tyr and Pro and once with a cis peptide bond between Tyr and Pro. b) The electrospray ionization mass spectrum (ESI-MS) of the tripeptide you designed in part (a) shows peaks indicative of mono-protonation and di- protonation of the tripeptide. At what values of m/z would these peaks be expected (no fragmentation)? Briefly explain your answer (showing your workings). 5) How could the sequence of Ala-Met-Thr be distinguished from that of Thr-Ala- Met by tandem ESI-MS-MS? Explain in detail. 6) Draw the structures of products from a trypsin-catalysed reaction of Ser-Lys- Ala.

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter27: Amino Acids And Proteins

Section: Chapter Questions

Problem 27.39P: A chemically modified guanidino group is present in cimetidine (Tagamet), a widely prescribed drug...

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A chemically modified guanidino group is present in cimetidine (Tagamet), a widely prescribed drug for the control of gastric acidity and peptic ulcers. Cimetidine reduces gastric acid secretion by inhibiting the interaction of histamine with gastric H2 receptors. In the development of this drug, a cyano group was added to the substituted guanidino group to alter its basicity. Do you expect this modified guanidino group to be more basic or less basic than the guanidino group of arginine? Explain.
(a) One amino acid that is likely to have a net negative charge at pH 8.(b) One amino acid that may be dehydrated with H2SO4.(c) One polar uncharged amino acid. (d) One nonpolar aromatic amino acid.(e) The nonpolar amino acid with the highest molar mass that was not previously selected.
3a) Consider a tripeptide (a peptide that's only 3 amino acidslong) composed of one molecule each of lysine, leucine, and thehypothetical amino acid lupine (which doesn't actually exist, sodon't try to look it up). Lupine has an ionizable side group with apa of 6.3. When this tripeptide is dissolved in an aqueoussolution at pH 5.0, the net charge on the molecule is +2. Givethe charge on the protonated form of the lupine side group, andthe charge on the deprotonated form of the lupine side group.show your work or explain how you determinedthe charge on each form of the lupine side groups
14. Identify one amino acid from each of the following categories: H2N CH- C-OH H,N CH-O HO- H,N -CH- C-OH I CH, II II CH, CH-OH C=O CH3 CH3 OH H2N -CH- OH H2N-CH- C OH CH2 H2N CH-C-OH CH2 CH2 CH2 CH2 CH3 CH3 IV VI
Shown below is the amino acid tyrosine in its protonated state, with the pK₂of each ionizable proton indicated. pK₂ = 10 HO COOH pk = 9 pK₂ = 2 Which best represents the predominant state of tyrosine at pH 7? a HO. O O OO a b U H3N P H₂N COOH b H₂N COO с НО. H₂N COO d HO. H₂N COO
What fraction of the side-chain amine on arginine is protonated at pH=10? At pH = 13? Express as a %. At pH = 10, 0% protonated. At pH = 13,76% protonated. At pH=10, 100% protonated. At pH-13, 76% protonated. At pH= 10, 0% protonated. At pH=13, 24% protonated. At pH-10, 100% protonated. At pH= 13, 24% protonated
The maximum number of amino acid side chains that can potentially form an ionic bond (+ll- interaction) with the side chain of His is _at pH 21;at pH 7 and at pH 11.5 andat pH 13.5. (assume no partial charges, only +/- whole number integers) 00: 2; 3:1 01:2:4:1 O 2;2;3,0 O 0: 2; 3;0 00:2; 4: 0 00: 0; 2; 2 none of these
the pKa values for phenylalanine are 1.83 (carboxyl group) and 9.13 (amino group). Use the Henderson-hasselbach equation to determine the ratio of the acidic and basic forms of each of the ionizing groups of phenylalanine at neutral pH. Based on this, draw the predominant structure of phenylalanine at neutral pH.
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Write the structure of all possible peptides containing these amino acids: Arg, Lys,Phe Use single letter abbreviations and capital letters only; i.e. GYR, not Gly-Tyr-Arg. If there are fewer than 6 peptides, leave an appropriate number of answer boxes empty.
Please consider the structural formula of the amino acid shown below when answering the following questions. Assume that the pKa values are as shown below. (A) draw the form of this amino acid that predominates at pH 8 (B) classify the amino acid as hydrophilic or hydrophobic (C) what is the net charge of this amino acid at pH 1?
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