Draw a schematic of the chemical structure of the Leu-Tyr-Met-Lys tetrapeptide, with thecorrect ionization at neutral pH (pH 7). Also, give an estimate the pl of this tetrapeptide (youare given that the pKa of any acidic R group is 4, the pKa of any basic R group is 11.5, and thepKa of the α-COOH is 2, and the a-NH3 is 9.5). Provide rationale!

Structure of Leu-Tyr-Met-Lys at neutral pH (7) : At neutral pH (around 7), the ionization state of…

Answered: Draw a schematic of the chemical…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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1) (10 points) Draw a schematic of the chemical structure of the Leu-Tyr-Met-Lys tetrapeptide, with the correct ionization at neutral pH (pH 7). Also, give an estimate the pl of this tetrapeptide (you are given that the pKa of any acidic R group is 4, the pKa of any basic R group is 11.5, and the pKa of the a-COOH is 2, and the a-NH3 is 9.5). Provide rationale!
Draw the structure of the pentapeptide Gln-Trp-His-Glu-Tyr that would predominate in acqueous solution at pH=10.3. (Relevant pKa values are: 2.2,4.3,6.0,9.8 and 10.1)
80mL of a 0.3M solution of hexapeptide Leu-His-Cys-Glu-Asn-Arg is adjusted to pH=pl. The solution is then titrated with 0.2M HCI to a final pH of 2.1. Sketch the titration curve, labelling the pH and volume axes. Indicate the volume of HCl needed to reach each relevant pKa value and equivalence point(s). Relevant pka values are: 2.1, 4.3, 6.0, 8.3, 9.8, and 12.5.
Determine the net charge on the following pentapeptide "Lys-Ala-His-Asp-Ser" at: a. pH 1.0 b. pH 10.1
80mL of a 0.3M solution of hexapeptide Leu-His-Cys-Glu-Asn-Arg is adjusted to pH=pI. The solution is then titrated with 0.2M HCL to a final pH of 2.1. Sketch the titration curve, labelling the pH and volume axes. Indicate the volume of HCL needed to reach relevant pKa value and equivalence point(s)z Relevant pKa values are: 2.1, 4.3, 6.0, 8.3, 9.8, and 12.5.
The amino acid arginine ionizes according to the following scheme: (a) Calculate the isoelectric point of arginine. You can neglect contributionsfrom form I. Why?(b) Calculate the average charge on arginine when pH = 9.20.(c) Is the value of average charge you calculated in part b reasonable, giventhe pI you calculated in part a? Explain your answer.
The following amino acid is dissolved in solution at pH 7.4. HC H' + CH CH₂ H/ H+ HC a. Which amino acid is this? (all lower case) N- H CH CH₂ b. What is the pKa of its ionizable side chain? (Use the value from the textbook.) c. What is the ratio of the uncharged to the charged form at pH 7.4? (write answer as number with one decimal place, ex 2.5 or 0.2 or 50.0 with an implicit "to 1")
Draw dipeptide Arg-Thr at pH 6.0. Circle the six atoms that are restricted in one plane. Calculate its approximate pI assuming pKa for NH3+ is 10.0, pKa for COOH is 3.0, PKR for Arg is 12.0
Given the following Peptide: Q6 *H;N-Phe-Asp-Ala-Arg-Gy-His-Arg-Asp-Glu-His-Tyr-CO 6a. What is the peptide's net charge at pH 2.0, pH 6.0, pH 7.4, and pH 10.2? (show work) 6b. What is the approximate isoelectric point of this peptide?
For the following pentapeptides: Ser-Glu-Gly-His-Ala and Gly-His-Ala-Glu-Ser Draw the most protonated forms of the pentapeptides Illustrate the ionization of the pentapeptides from the most protonated to its deprotonated form. Label the ionization with its respective pK values. Compute their isoelectric pH (pI). Do these peptides with the same amino acid composition have different net charges at pH 7.0? Explain briefly. Would you expect the titration curves of the two peptides to differ? Why or Why not?
What is the Isoelectric point of Y-R-S (pH 7-11) What is the isoelectric point of N-G-L (pH 1-5) Please do the solutions like in the excel table indicated below and follow the pKa value in the table
Calculate the net charge on the following tripeptides at pH 5.0: (a) Leu-His-Asp [0] (b) Ala-Ile-Val [0] (c) Met-Lys-Arg [+2] (d) Which tripeptide will be retained the shortest on a cation-exchange chromatographic column in a pH 5.0 buffer? Why?

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