Homework Problems #2 1. Draw the peptide KTQHV, write the sequence using 3-letter abbreviation for the amino acids, and identify: a. The N- and C-termini. b. Every a-carbon of the sequence, by labeling them with "a". c. All peptide bonds. d. Hydrogen bond donors and acceptors in the polar side chains. e. Covalent bonds that correspond to the backbone phi (D) and psi (4) angles f. Ionizable R-groups of amino acids in this sequence (circle them). i. Choose one ionizable group and draw it at pH 1, pH 7, and pH 14 and indicate the approximate net charge at each pH. ii. What fraction of His residues are charged at pH=5.8? 2. Use the table to answer the following questions about the peptide you drew in question 1. Amino PK1 Acid Lys 2.18 8.95 PK2 (-COOH) (NH3) (R-group) 10.53 PKR Thr 2.11 9.62 Gln 2.17 9.13 His 1.82 9.17 6.00 Val 2.32 9.62 a. Determine the net charge of the peptide at pH 0 and 14? b. Estimate the pl for this peptide. Is this an acidic or basic peptide?

Homework Problems #2 1. Draw the peptide KTQHV, write the sequence using 3-letter abbreviation for the amino acids, and identify: a. The N- and C-termini. b. Every a-carbon of the sequence, by labeling them with "a". c. All peptide bonds. d. Hydrogen bond donors and acceptors in the polar side chains. e. Covalent bonds that correspond to the backbone phi (D) and psi (4) angles f. Ionizable R-groups of amino acids in this sequence (circle them). i. Choose one ionizable group and draw it at pH 1, pH 7, and pH 14 and indicate the approximate net charge at each pH. ii. What fraction of His residues are charged at pH=5.8? 2. Use the table to answer the following questions about the peptide you drew in question 1. Amino PK1 Acid Lys 2.18 8.95 PK2 (-COOH) (NH3) (R-group) 10.53 PKR Thr 2.11 9.62 Gln 2.17 9.13 His 1.82 9.17 6.00 Val 2.32 9.62 a. Determine the net charge of the peptide at pH 0 and 14? b. Estimate the pl for this peptide. Is this an acidic or basic peptide?

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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1. Draw the appropriate titration curve for the tripeptide Met-Lys-Val starting at pH 1 and ending at pH 12. Label the pKas and the pI. Draw the two different forms of the molecule that is present at each buffering region. 2. Draw the structure of the peptide Arg-Met-His-Val-Glu and circle the coplanar atoms in one peptide bond. 3. Determine the pI for the peptide given in question 2 above.
K₁ = α [H+][A-] [HA] [A-] pH = pK+log [HA] 1-1 The Amino acid Arginine ionizes according to the scheme below. Calculate the isoelectric point of Arginine and the average charge on arginine when pH = 9.2. NH2 H C=N NH pka-2.17 -H' NH2 H C=N H NH PK-8.99 -H +H* H (CH2)3 H-N-C-COOH | H H +H* H (CH2)3 H-N-C-coo- H H Ans: 10.75; +0.38 NH2 NH2 H C=N C=N-H H NH PK-12.5 -H NH | +H* (CH2)3 H₂N-C-COO- | H III (CH2)3 H₂N-C COO- H IV
5. Refer to Model 2 for information relevant to this question. A sample of the peptide Lys-Glu-Ser has a net charge of zero between what two pH values? What is the pl of Lys-Glu-Ser? Model 2: The pl of a peptide is determined by examining the ionizable groups. The protonated and unprotonated forms of each ionizable group are in equilibrium. Consider the peptide Lys-Glu-Ser shown below at pH 7.2. The complete structure is on on the left and a stylized structure with just the ionizable groups is on the right. While the N-terminal is depicted as protonated, a sample of Lys-Glu-Ser is composed of a population of molecules and within that population some molecules contain a non-protonated N-terminal group at pH 7.2. may H3N* COO- H3N-CH-CIN-CH C N-CH C- H. pK 3.5 OH H. pK= 8.5 COO- CH2 CH2 CH2 NH, pK 10.0 pK 4.2 CH2 CH2 OH CH2 c=0
A mixture of Aspartic Acid (pl 2.98), Histidine (pl 7.59), Lysine (pl 9.74), Phenylalanine (pl 5.48) and Threonine (pl 6.53) are separated by cation exchange chromatography. What is the order of elution of these amino acids if you use gradient buffer system from pH 10 to pH 2. v First 1. Aspartic Acid v Second 2. Histidine v Third 3. Lysine 4. Phenylalanine v Fourth 5. Threonine v Fifth 6. No separation
1. Draw an approximate titration curve of the following amino acid. Label the approximate isoelectric point of arginine on the curve and be sure to label the axis of the graph appropriately. You DO NOT need to draw the structure of this amino acid here. Pk1= 1.92, pk2=8.99 and pk3=12.48. Show your work for determining the isoelectric point. You can draw out your curve within the text box or upload a drawing. A▾ B I - I B 7
What are the charges of the following amino acids peptides at ph 14? 1. GLAVV 2. RRKKQ
1. Which peptide would be more soluble at pH 7.0, (Val)₂₀ or (Asp)₂₀ ? at pH 3.0, (Gly-Glu-Val)
3
1. a. Draw the following pentapeptide: lysine-leucine-aspartate-threonine-phenylalanine b. Label the amino and carboxyl terminus of your peptide c. Label each amino acid residue with one and three letter abbreviations d. Label the alpha carbons e. Label the bonds around which phi and psi rotational angles occur f. Which amino acid in this chain is most likely to be phosphorylated? Which amino acid is most likely to be acetylated?
Please don't provid3e handwritten solution ....
Can you please help find the net charge?
29. Amino Acid Chemistry: Using the amino acid chart provided..Ala-Lys-Cys & give the isoelectric point for the tripeptide. Table 23.2 The pK, Values of Amino Acids pk, a-COOH a-NH3* Amino acid side chain Alanine 2.34 9.69 2.17 9.04 12.48 Arginine Asparagine 2.02 8.84 3.86 Aspartic acid Cysteine 2.09 9.82 1.92 10.46 8.35 Glutamic acid 2.19 9.67 4.25 Glutamine 2.17 9.13 Glycine 2.34 9.60 1.82 9.17 6.04 Histidine 2.36 9.68 Isoleucine Leucine 2.36 9.60 2.18 $ 95 10.79 Lysine 2.28 9.21 Methionine 16 9.18 Phenylalanine 1.99 10.60 Proline 2.21 9.15 Serine 2.63 9.10 Threonine 2.38 9.39 Tryptophan Tyrosine 9.11 10.07 2.20 2.32 9.62 Valine O something else! 5.14 O 8.65 something else! 5.81 9.02 9.57